Search

Nowadays, the goal of carbon peaking and carbon neutrality has become a global consensus, and electrochemical CO2 reduction to provide high-value power fuel is one of the major technical approaches attracting significant research interests and application prospects. However, the inevitable hydrogen evolution reaction in water-based electrolyte systems crowds out the reactive sites of active metals, causing a low CO2 conversion efficiency. In this work, Zn nanosheets were prepared via electrodeposition on the surface of carbon paper and then modified with polytetrafluoroethylene (PTFE) to tune the wetting angle of the electrolyte. A CO faradaic efficiency of 90.2% was achieved for Zn NS-8% PTFE (contact angle: 136.8°) at the electrolytic voltage of −1.0 V vs. RHE along with an overall current density of −7.9 mA cm−2. Experimental results and molecular dynamics simulation revealed that PTFE weakened the aggregation of H2O molecules and was more beneficial for capturing and adsorbing CO2 molecules near the electrode surface. The active sites of hydrogen production were transformed into the reaction center for electrocatalytic CO2 reduction due to the hydrophobicity of the electrode, and the accumulation of the local CO2 concentration accelerated the kinetic activity for electrochemical conversion (CO2 to CO). This strategy of tuning the local environment offers an alternative approach for effective electrode manufacturing in liquid electrolytes. [ABSTRACT FROM AUTHOR]

The urea oxidation reaction (UOR), which possesses a low theoretical potential and superior kinetics, is an attractive substitute for the anodic oxygen evolution reaction (OER) in overall water splitting; however, the implementation of hydrogen production in overall urea splitting is impeded by the deficiency of highly efficient, durable and cost-effective catalysts. Herein, we fabricated an Ni2P–MoP2 heterostructure with a hierarchical structure grown on carbon paper (Ni–Mo–P/CP), which exhibited robust activity and outstanding durability for the electrocatalytic oxidation of urea. The Ni–Mo–P/CP catalyst possessed an ultralow potential of 1.39 V to obtain the current density of 100 mA cm−2, small Tafel slope (27 mV dec−1) and long-term durability with almost no decay within 15 h. The experimental characterization revealed that the optimized electronic structure and the synergistic effect of abundant exposed active sites in the Ni–Mo–P/CP catalyst contribute to the efficient UOR catalytic activity. This work enriches the candidate catalysts for the UOR and promotes the industrial development of hydrogen production. [ABSTRACT FROM AUTHOR]

Searching and developing earth-abundant electrocatalysts with predominant activity and favorable stability are significant to resolve increasing environmental pollution and serious energy crisis. In this paper, Mo-based nanowire arrays (NWAs) were synthesized on carbon fiber paper (CFP), and then Ru–MoP NWAs/CFP was successfully assembled through impregnation of Ru and phosphorization. The as-obtained Ru–MoP NWAs/CFP exhibited excellent performance over a broad pH range. As a result, overpotentials of 39.0, 49.9, and 67.1 mV were required to reach the current density of 10 mA cm−2 in 0.5 M H2SO4, 1 M KOH, and 1 M PBS, respectively. The outstanding performance of Ru–MoP NWAs/CFP is mainly related to the introduction of Ru and P atoms, which may enhance the conductivity of the catalyst and develop additional HER active sites. Our work may afford a novel designing approach to develop high performance HER electrocatalysts. [ABSTRACT FROM AUTHOR]

Efficient alkaline hydrogen evolution electrodes must be used for hydrogen production in anion exchange membrane water electrolyzers (AEMWEs). Therefore, we fabricated a NiMnS catalyst with a Mn-rich surface, which was self-supported on Ti paper through one-step electrodeposition. Mn doping endowed the catalyst with a unique hollow morphology and lattice-distorted structure. Consequently, the NiMnS/Ti electrode exhibited a large number of exposed electrochemical surfaces and effective active sites and a high hydrogen evolution reaction (HER) activity. Specifically, in half-cell measurements, the NiMnS/Ti electrode exhibited an overpotential of 65 mV at 10 mA cm−2, which was lower than that of NiS/Ti (102 mV) and indicated its superior HER activity. When the proposed cathode was applied in an AEMWE single cell, the device achieved a high current density of up to 0.9 A cm−2 at a cell potential of 2.0 V. [ABSTRACT FROM AUTHOR]

The use of a methanesulfonic acid (MSA) electrolytic system is recommended as a green method for hydrometallurgical recovery of metallic Pb from waste lead-acid batteries (LABs), contributing to the sustainable protection of the ecosystem. Nevertheless, the system's high energy consumption is a current issue due to the substantial overpotential of the oxygen evolution reaction (OER) and competitive anodic oxidation of Pb2+. Herein, we propose an IrFe/nitrogen-doped pyrolytic carbon black (IrFe/NCBp) composite as a novel OER catalyst for the MSA electrolytic system, which demonstrates advanced OER catalytic efficiency and selectivity for H2O oxidation. This can be ascribed to the catalyst's thoughtful design, which enhances the number and uniformity of Ir and Fe species via increasing the specific surface area and employing NCBp as a sustainable substrate. The optimized IrFe/NCBp composite exhibits superior OER performance, with a low 252 mV@10 mA cm−2 overpotential and a 62 mV dec−1 Tafel slope, and excellent durability in a 1 M MSA electrolyte for 30 h operation compared to commercial Ir/C. In contrast to carbon paper (CP) and commercial Ir/C anodes, the anodic reaction of IrFe/NCBp is primarily OER-driven (97%) in 1 M MSA and 0.2 M Pb2+ electrolyte for Pb recovery. This effectively circumvents the high potential oxidation of Pb2+ into PbO2, reducing the electrolytic voltage to 488 kWh for the recovery of 1 ton Pb metal. This work provides a green, low-carbon footprint solution for the MSA electrolytic system, thereby promoting the commercialization of the hydrometallurgical Pb recovery. [ABSTRACT FROM AUTHOR]

Platinum-based catalysts exhibit outstanding electrocatalytic performance in the hydrogen evolution reaction (HER). However, platinum-based catalysts face significant challenges due to their rarity and high cost. This paper endeavors to shed light on a promising alternative: polyoxometalate (POM)-based catalysts, which possess significant potential for the synthesis of non-noble metal-based catalysts for the HER. Utilizing POMs as raw materials to assemble POM-derived materials, including POM-derived crystalline materials, metal sulfides, phosphides, carbides, nitrides, and so on, has emerged as an effective approach for the synthesis of hydrogen evolution electrocatalysts. This approach offers advantages in both stability and electrocatalytic performance. This comprehensive review navigates through latest progress in the assembly strategy and HER performance of POM-based crystal materials, alongside discussion on transition metal compounds derived from POMs, such as carbides, phosphides, and sulfides. Besides, future developments in POM-derived electrocatalyst regulation of the electrochemical HER are prospected. [ABSTRACT FROM AUTHOR]

The shortage of freshwater resources in the world today has limited the development of water splitting, and our eyes have turned to the abundant seawater. The development of relatively low-toxicity and high-efficiency catalysts is the most important area in seawater electrolysis. In this paper, the preparation of NiS2@Co4S3@FeS via a hydrothermal method on nickel foam has been studied for the first time. In the process of vulcanization, Fe will first generate FeS by virtue of its high affinity for vulcanization. Once Fe is vulcanized, the residual sulfur will be used to generate NiS2, while the vulcanization of Co requires a higher sulfur concentration and reaction temperature; thus, Co4S3 will be generated last. NiS2@Co4S3@FeS is confirmed to have excellent hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) catalytic properties in alkaline seawater. Its unique structure allows it to expose more reaction centres, and the synergies between the multiple metals optimize the charge distribution of the material and accelerate the OER and HER kinetics. NiS2@Co4S3@FeS requires overpotentials of only 122 mV and 68 mV for the OER and HER when reaching 10 mA cm−2, which is superior to most catalysts reported to date for seawater electrolysis, and the material displays acceptable stability. In an electrolytic cell composed of both positive and negative electrodes, when the current density is 10 mA cm−2, the NiS2@Co4S3@FeS material displays a low overpotential of only 357 mV for seawater splitting. Density functional theory shows that the FeS electrode has the optimum Gibbs free energy of H to accelerate reaction kinetics, and the synergistic catalysis of the NiS2, Co4S3 and FeS materials promotes the hydrogen production activity of the NiS2@Co4S3@FeS electrode. This work proposes a novel idea for designing environmentally friendly seawater splitting catalysts. [ABSTRACT FROM AUTHOR]

Urea electrolysis can be used to treat wastewater containing urea and alleviate the energy crisis, so it is one of the best ways to solve environmental and energy problems. This paper reports the synthesis of M doped NiVS (M = Co, Ce and Cr) composites by a simple hydrothermal process for the first time. What is noteworthy is that the Ce-NiVS material as a catalytic electrode requires only 141 mV overpotential for the hydrogen evolution reaction (HER) and 1.291 V potential for the urea oxidation reaction (UOR) at a current density of 10 mA cm−2 in 1.0 M KOH and 0.5 M urea mixed alkaline solution. Using Ce-NiVS/NF as both the anode and cathode for urea electrolysis, a current density of 10 mA cm−2 is driven by a voltage of only 1.55 V, which is better than most previous catalysts. Experimental results demonstrate that the excellent catalytic activity of Ce-NiVS materials is due to the formation of a large number of active sites and the improvement of conductivity due to doping with Ce. Density functional theory calculation shows that the VS4 material has a small Gibbs free energy of hydrogen adsorption, which plays a major role in the hydrogen production process, and Ce-NiS has a higher density of states (DOS) near the Fermi level, indicating that Ce-NiS has better electronic conductivity. The synergistic catalysis of VS4 and Ce-NiS promoted the hydrogen production performance of the Ce-NiVS material. This work provides guidance for the optimization and design of low-cost electrocatalysts to replace expensive precious metal-based electrocatalysts for overall urea electrolysis. [ABSTRACT FROM AUTHOR]

Electrocatalytic water splitting is considered to be one of the most promising technologies for large-scale sustained production of H2. Developing non-noble metal-based electrocatalytic materials with low cost, high activity and long life is the key to electrolysis of water. Transition metal sulfides (TMSs) with good electrical conductivity and a tunable electronic structure are potential candidates that are expected to replace noble metal electrocatalysts. In addition, self-supported electrodes have fast electron transfer and mass transport, resulting in enhanced kinetics and stability. In this paper, TMS self-supported electrocatalysts are taken as examples and their recent progress as hydrogen evolution reaction (HER) electrocatalysts is reviewed. The HER mechanism is first introduced. Then, based on optimizing the active sites, electrical conductivity, electronic structure and adsorption/dissociation energies of water and intermediates of the electrocatalysts, the article focuses on summarizing five modulation strategies to improve the activity and stability of TMS self-supported electrode electrocatalysts in recent years. Finally, the challenges and opportunities for the future development of TMS self-supported electrodes in the field of electrocatalytic water splitting are presented. [ABSTRACT FROM AUTHOR]

Electrochemical water splitting offers the potential for environmentally friendly hydrogen and oxygen gas generation. Here, we present the synthesis, characterization, and electrochemical analyses of four organic polymers where metalloporphyrins are the active center nodes. These materials were obtained from the polymerization reaction of poly(p-phenylene terephtalamide) (PPTA) with the respective amino-functionalized metalloporphyrins, where M = Fe, 1; Co, 2; Ni, 3; Cu, 4. Scanning and transmission electron microscopy images (SEM and TEM) show that these polymers exhibit a layer-type morphology, which is attributed to hydrogen bonding and π–π stacking between the metalloporphyrin nodes. The synthesized materials were characterized by X-ray photoelectron spectroscopy (XPS), X-ray powder diffraction (XRD), energy-dispersive X-ray spectroscopy (EDX), UV-Vis spectroscopy, and Fourier-transform infrared spectroscopy (FT-IR). Among the materials studied, the cobalt-based polymer, 2, demonstrates a bifunctional electrocatalytic activity for oxygen (OER) and hydrogen (HER) evolution reactions with overpotentials (η10) of 337 mV and 435 mV, respectively. The Fe, 1, and Ni, 2, polymers are less active for HER with maximum current densities (jmax) of 12.6 and 19.1 mA cm−2 and η10 678 mV, 644 mV. Polymer 2 achieves a jmax of 37.7 mA cm−2 for HER and 133 mA cm−2 for OER. The copper-based material, 4, on the other hand, shows selectivity towards HER with an overpotential (η) of 436 mV and a maximum current density (j) of 45.5 mA cm−2. The bifunctional electrocatalytic performance was tested in the overall water-splitting setup, where polymer 2 requires a cell voltage of 1.64 V at 10 mA cm−2. This work presents a novel approach to heterogenized molecular systems, providing materials with exceptional structural characteristics and enhanced electrocatalytic capabilities. [ABSTRACT FROM AUTHOR]

Herein, an A3-type and an A2B-type meso-thiophene-substituted CoIIIcorrole are prepared and their electronic structures are investigated. Interestingly, these two CoIIIcorroles are facilely polymerized under electrochemical conditions and rationally controlled by polymerizing cycles, speed, molecular structure as well as co-polymerizations. In addition, these conductive CoIIIcorrole–polymers exhibit a significant increase and tunable electrochemically catalyzed hydrogen evolution behaviours with the best overpotential E = 0.091 V (j = 10 mA cm−2) in aqueous media. [ABSTRACT FROM AUTHOR]

In recent years, as a green renewable energy production technology, electrochemical water splitting has demonstrated high development potential. Many materials have been reported as successful catalysts in the water-splitting field. However, it is still a huge challenge to produce bifunctional electrocatalysts for the efficient and sustainable generation of hydrogen and oxygen simultaneously. Herein, we successfully developed oxygen vacancies abundant CuCo layered double oxide (Ov-CuCo-LDO) hollow nanotube arrays (HNTAs) loaded on nickel foam as advanced electrocatalysts for total water splitting. When the current density was 10 mA cm−2, the Ov-CuCo-LDO HNTAs exhibited outstanding onset overpotentials of 53.9 and 72.5 mV for the hydrogen evolution and oxygen evolution reactions (HER and OER) in alkaline medium, respectively, because of the bimetallic synergistic effect between the cobalt and copper and the unique hollow porous structure. In addition, an as-assembled Ov-CuCo-LDO‖‖Ov-CuCo-LDO electrolytic cell showed a small potential of 1.55 V to deliver a current density of 10 mA cm−2. Moreover, it also showed remarkable durability after long-term overall water splitting for more than 20 h. The research results in this paper are of great interest to practical applications of the water decomposition process, providing clear and in-depth insights into preliminary robust and efficient multifunctional electrocatalysts for overall water splitting. [ABSTRACT FROM AUTHOR]

Constructing a suitable heterojunction structure while maintaining a tight interface to promote the separation of photogenerated electrons is of great significance for improving the photocatalytic activity. In this paper, a new PANI/NH2-MIL-101(Fe) II-scheme heterojunction was prepared by a hydrothermal method. PANI with a porous structure was firstly obtained by the template method, and then PANI fragments were loaded on the surface of NH2-MIL-101(Fe) crystals under hydrothermal conditions to obtain a PANI/NH2-MIL-101(Fe) photocatalyst. The photocatalytic degradation of TC under simulated sunlight can reach 90% within an hour, and the maximum hydrogen evolution rate is 7040 μmol g−1 h−1 under visible light. The enhanced catalytic performance of PANI/NH2-MIL-101(Fe) was attributed to the appropriate matching of the VB and CB of PANI and NH2-MIL-101(Fe), and secondly, the coordination bonds formed between PANI and NH2-MIL-101(Fe) provided a channel for charge separation and transfer. Finally, a possible mechanism of the photocatalytic system was proposed through a free radical capture experiment and characterization analysis. More importantly, the experiment proved that the heterojunction formed by PANI and NH2-MIL-101(Fe) can achieve the effect of complementing each other, which provides a feasible idea and method for the design of efficient heterojunction photocatalysts. [ABSTRACT FROM AUTHOR]

Compared with the noble metal Pt, the non-noble metal Cu as a cocatalyst exhibits a low hydrogen-evolution activity owing to its weak Cu–H bond (11 kcal mol−1), which inhibits hydrogen adsorption on Cu atoms for the hydrogen-evolution reaction of photocatalysts. Considering that the introduction of Ni with a strong Ni–H bond into Cu is beneficial for strengthening the H-adsorption ability of Cu, in this paper, the low-cost transition-metal Ni was directly introduced into Cu to form CuNi alloy nanodots as photocatalytic cocatalysts to enhance the hydrogen-evolution rate of TiO2. The CuNi alloy nanodots (2–3 nm) were photodeposited on the surface of a reduced graphene oxide (rGO)-modified TiO2 photocatalyst to generate CuNi-rGO/TiO2 by the pre-adsorption of Cu2+ and Ni2+ ions on graphene oxide (GO). Photocatalytic hydrogen-production data manifested that the CuNi-rGO/TiO2 photocatalyst achieved the highest hydrogen-production rate (10 411 μmol h−1 g−1), which was 53.7, 38.7, 1.8, and 2.2 times higher than that of pure TiO2, rGO/TiO2, Cu-rGO/TiO2, and Ni-rGO/TiO2, respectively. Density-functional-theory (DFT) calculations and mechanistic investigation showed that the introduction of Ni into Cu to form CuNi alloy nanodots improved the H-adsorption ability of Cu and optimized the H-adsorption free energy close to zero (0.046 eV) for boosting the hydrogen production rate of TiO2. This research presents a promising design of bimetallic alloy structures as H2-production cocatalysts for efficient photocatalysts. [ABSTRACT FROM AUTHOR]

While Pt is considered the best catalyst for the electrocatalytic hydrogen evolution reaction (HER), it is evident that non-noble metal alternatives must be explored. In this regard, it is well known that the binding sites for non-noble metals play a pivotal role in facilitating efficient catalysis. Herein, we studied Fe(II) complexes with bidentate 2-(2'-pyridyl)benzoxazole (LO), 2-(2'-pyridyl)benzthiazole (LS), 2-(2'-pyridyl)benzimidazole (LNH), and 2-2'-bipyridyl (Lpy) ligands - by adding trifluoroacetic acid (TFA) to their acetonitrile solution - in order to examine how their reactivity towards protons under reductive conditions could be impacted by the non-coordinating heteroatoms (S, O, N, or none). By applying this ligand series, we found that the reduction potentials relevant for HER correlate with ligand basicity in the presence of TFA. Moreover, DFT calculations underlined the importance of charge distribution in the ligand-based LUMO and LUMO+1 orbitals of the complexes, dependent on the heterocycle. Kinetic studies and controlled potential electrolysis - using TFA as a proton source - revealed HER activities for the complexes with LNH, LO, and LS of kobs = 0.03, 1.1, and 10.8 s-1 at overpotentials of 0.81, 0.76, and 0.79 V, respectively, and pointed towards a correlation between the kinetics of the reaction and the noncoordinating heteroatoms of the ligands. In particular, the activity was associated with the [Fe(LS/O/NH)2(S)2]2+ form (S = solvent or substrate molecule), and the rate-determining step involved the formation of [Fe(H-H)]+, during the weakening of Fe-H and CF3CO2-H bonds, according to the experimental and DFT results. [ABSTRACT FROM AUTHOR]

Electrocatalytic hydrogen generation in alkaline medium has become widely used in a variety of sectors. However, the possibility for additional performance improvement is hampered by slow kinetics. Because of this restriction, careful control over processes such as water dissociation, hydroxyl desorption and hydrogen recombination is required. Covalent organic frameworks (COFs) based on porphyrin and polyoxometalates (POMs) show encouraging electrocatalytic performance, offering a viable route for effective and sustainable hydrogen generation. Their specific architectures lead to increased electrocatalytic activity, which makes them excellent choices for developing water electrolysis as a clean energy conversion method in the alkaline medium. In this regard, TTris@ZnPor and Lindqvist POM were coordinated to create a new eco-friendly and highly active covalent organic framework (TP@VL-COF). In order to describe TP@VL-COF, extensive structural and morphological investigations were carried out through FTIR, 1H NMR, elemental analysis, SEM, fluorescence, UV-visible, PXRD, CV, N2-adsorption isotherm, TGA and DSC analyses. In an alkaline medium, the electrocatalytic capability of 20%C/Pt, TTris@ZnPor, Lindqvist POM and TP@VL-COF was explored and compared for the hydrogen evolution reaction (HER). The TP@VL-COF showed the best catalytic efficiency for HER in an alkaline electrolyte, requiring just a 75 mV overpotential to drive 10 mA cm−2 and outperforming 20%C/Pt, TTris@ZnPor, Lindqvist POM and other reported catalysts. The Tafel slope value also indicates faster kinetics for TP@VL-COF (114 mV dec−1) than for 20%C/Pt (182 mV dec−1) TTris@ZnPor (116 mV dec−1) and Lindqvist POM (125 mV dec−1). [ABSTRACT FROM AUTHOR]

Lithium is thought to be an excellent anode material for next-generation Li metal batteries (LMBs). However, some problems with lithium anodes often lead to serious safety concerns and catastrophic failures due to the huge volume change, Li dendritic growth, and related side reactions. Therefore, in order to manufacture stable rechargeable batteries, the abovementioned serious problems must be effectively solved. In this paper, a three-dimensional N,P-doped silicon-containing lithium anode is designed and prepared by in situ metallurgy using low-cost Si3N4. The 3D stable composite anode (DLi/LiSix CA) was prepared by adding a small amount of Si3N4 to molten lithium to form N-doped silicon-containing lithium metal which was supported on a polyaniline modified carbon cloth (PMCC). The results show that the DLi/LiSix CA not only has high Li affinity but can also effectively inhibit lithium nucleation and lithium dendritic growth, so as to maintain good structural stability in the process of Li plating/stripping. The new lithium metal anode based on doping and 3D carbon cloth shows good cycling stability and low polarizability in both symmetrical and full cells. [ABSTRACT FROM AUTHOR]

In this paper, we present a MoP/P–Mn0.5Cd0.5S photocatalytic material (PMOMCS-Px). A novel catalyst can efficiently split water into hydrogen without precious metals. In the sacrificial agent environment, the HER (hydrogen evolution rate) of PMOMCS-P5 was 4368.25 μmol g−1 h−1 which was 11.4 times greater than the HER of Mn0.5Cd0.5S (383.19 μmol g−1 h−1), and its hydrogen production performance was better than that of Pt/Mn0.5Cd0.5S (2.0 wt% Pt). Furthermore, the hydrogen evolution performance of PMOMCS-P5 under pure water conditions was also examined, and the HER of PMOMCS-P5 was 209.76 μmol g−1 h−1, which was 20.4 times that of Mn0.5Cd0.5S (10.29 μmol g−1 h−1). Its characterization proved that the introduction of the co-catalyst MoP and P doping inhibited the recombination of e− and h+, enhanced the reduction capacity, and reduced the hydrogen precipitation reaction overpotential of PMOMCS-Px, thus enhancing the hydrogen production performance of PMOMCS-Px. Therefore, an efficient and economical photocatalyst was prepared. [ABSTRACT FROM AUTHOR]

Improving the efficiency of the anodic oxygen evolution reaction (OER) is important to solve the global energy crisis and greenhouse gas emission problems. In this paper, a preparation method for a MIL-53(Fe)@ZIF-67(Co) composite electrode is proposed. The hierarchical structure formed by the combination of MIL-53(Fe) and ZIF-67(Co) provides a rich channel for the transport of electrons and mass in the OER process. XPS analysis and DFT calculations revealed that Fe electrons in MIL-53(Fe) were transferred to Co in ZIF-67(Co) through O, which confirmed the rapid charge transfer effect of this transport channel. The MIL-53(Fe)@ZIF-67(Co) electrode has significant OER performance. When the current density reaches 10 mA cm−2, the overpotential is only 193 mV. This study inaugurates a new way for the rational design of a multiphase interface and the construction of new MOF channel structures. [ABSTRACT FROM AUTHOR]

The electrolysis of water, particularly proton exchange membrane (PEM) water electrolysis, holds great promise for hydrogen production in industry. However, the catalyst used in this process is prone to dissolution in acidic environments, making it imperative to develop cost-effective, highly efficient, and acid-stable electrocatalytic materials to overcome this challenge and enable large-scale application of PEM water electrolysis technology. Herein, we prepared ruthenium oxide (RuO2)/graphitic carbon nitride (g-C3N4) composites (RuO2/C3N4) via a combination of sol–gel and annealing methods. The g-C3N4 provides a large surface area, while RuO2 is uniformly deposited on the g-C3N4 surface. The interaction between g-C3N4 and RuO2 stabilizes the RuO2 nanoparticles and enhances long-term water oxidation stability. This unique structure and the combined advantages of RuO2 and g-C3N4 yield exceptional electrocatalytic activity toward both the oxygen evolution reaction (OER, 240 mV@10 mA cm−2) and the hydrogen evolution reaction (HER, 109 mV@10 mA cm−2), with excellent durability (over 28 h), and a cell voltage of 1.607 V at 10 mA cm−2 when used in an RuO2/C3N4‖‖RuO2/C3N4 electrolyzer. This study highlights the efficacy of the g-C3N4 support method in designing highly stable Ru-based OER electrocatalysts for efficient acidic water splitting. [ABSTRACT FROM AUTHOR]

Due to the slow reaction kinetics of the oxygen evolution reaction (OER), the electrolysis rate of water is greatly limited. Therefore, it is of great significance to study stable and efficient non-noble metal based electrocatalysts. In this paper, three-dimensional (3D) spherical V-NiFe LDH@Ni3S2 was developed by exquisitely decorating ultra-thin V-doped NiFe layered dihydroxide (NiFe-LDH) on Ni3S2 nanosheets supported by nickel foam (NF). It is worth mentioning that V-NiFe LDH@Ni3S2 exhibits an excellent electrocatalytic performance and only 178 mV overpotential is required in 1 M KOH to achieve a current density of 10 mA cm−2. Long-term chronoamperometry manifests its superior electrochemical stability. The combination of NiFe LDH and conductive substrate coupling can drastically afford abundant active sites and accelerate charge transfer, and V doping can markedly regulate the electronic structure. Therefore, the activity and durability of the electrocatalysts are greatly improved. This study may provide a new strategy for the preparation of efficient OER electrocatalysts. [ABSTRACT FROM AUTHOR]

A two-step simple and efficient ion-exchange chemical strategy is proposed to obtain nanostructured Bi2S3 electrodes of different surface morphologies from the Bi2O3. In the first step, nanoplates of the Bi2O3 are obtained on nickel-foam using successive ionic layer adsorption and reaction method at room-temperature (25 °C). In the second phase, as-obtained nanoplates of the Bi2O3 are transferred to the Bi2S3 using four autoclaves containing different sulfur precursor solutions at 120 °C for 8 h for phase change, structural conversion and surface morphological modification (i.e., walnuts, network-type, nanowires, and nanoflowers). Due to higher surface area and conductivity, lower charge transfer resistance, and reduced band gap caused by ionic and phase conversion, the Bi2S3 surpasses the Bi2O3 in hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) activities. The overpotential of 112–370 mV for the Bi2S3 network is much lower than that of the nanoplates of the Bi2O3 (275–543 mV), and walnuts (134–464 mV), nanowires (125–500 mV), and nanoflowers (194–520 mV) of the Bi2S3. The Bi2S3 network-type Bi2S3 electrode shows considerable chemical stability through cycling measurement, suggesting the importance of the present study in obtaining metal sulfides from metal oxide with better water splitting activities. [ABSTRACT FROM AUTHOR]

The synthesis, characterization and photocatalytic hydrogen evolution reaction (HER) performance of a series of metal–organic gels (MOGs) constructed from titanium(IV)-oxo clusters and dicarboxylato linkers (benzene-1,4-dicarboxylato and 2-aminobenzene-1,4-dicarboxylato) are described. All the MOGs exhibit a microstructure comprised of metal–organic nanoparticles intertwined into a highly meso-/macroporous structure, as demonstrated by cryogenic transmission electron microscopy and gas adsorption isotherms. Comprehensive chemical characterization enabled the estimation of the complex formula for these defective materials, which exhibit low crystallinity and linker vacancies. To gain deeper insights into the local structure, X-ray absorption fine structure (XAFS) spectroscopy experiments were performed and compared to that of the analogous crystalline metal–organic framework. Additionally, the ultraviolet–visible absorption properties and optical band gaps were determined from diffuse reflectance spectroscopy data. The MOGs were studied as light absorbers for the sacrificial photocatalytic HER under simulated solar light irradiation using a platinum co-catalyst by either (1) in situ photodeposition or (2) ex situ doping process, through a post-synthetic metalation of the MOG structure. The chemical analysis of the metalation, along with high-angle annular dark-field scanning transmission electron microscopy, revealed that although the in situ addition of the co-catalyst led to greater HER rates (227 vs. 110 μmolH2 gMOG−1 h−1 for in situ and ex situ, respectively), the ex situ modification provided a finer distribution of platinum nanoparticles along the porous microstructure and, as a result, it led to a more efficient utilization of the co-catalyst (45 vs. 110 mmolH2 gPt−1 h−1). [ABSTRACT FROM AUTHOR]

To develop hydrogen energy production and address the issues of global warming, inexpensive, effective, and long-lasting transition metal-based electrocatalysts for the synthesis of hydrogen are crucial. Herein, a porous electrocatalyst NiMo/Ni/NF was successfully constructed by a two-step electrodeposition process, and was used in the hydrogen evolution reaction (HER) of electrocatalytic water decomposition. NiMo nanoparticles were coated on porous Ni/NF grown on nickel foam (NF), leading to a resilient porous structure with enhanced conductivity for efficient charge transfer, as well as distinctive threedimensional channels for quick electrolyte diffusion and gas release. Notably, the low overpotential (42 mV) and fast kinetics (Tafel slope of 44 mV dec-1) at a current density of 10 mA cm-2 in 1.0 M KOH solution demonstrate the excellent HER activity of the electrode, which was superior to that of recently reported non-noble metal-based catalysts. Additionally, NiMo/Ni/NF showed extraordinary catalytic durability in stability tests at a current density of 10 mA cm-2 for 70 h. The porous structure catalyst and the electrodeposition-electrocatalysis technique examined in this study offer new approaches for the advancement of the electrocatalysis field because of these benefits. [ABSTRACT FROM AUTHOR]

Interfacial engineering emerges as a potent strategy for regulating the catalytic reactivity of metal phosphides. Developing a facile and cost-effective method to construct bifunctional metal phosphides for highly efficient electrochemical overall water splitting remains an essential and challenging issue. Here, a multiphase transition metal phosphide is constructed through the direct phosphorization of a Ni–Co metal–organic framework grown on nickel foam (Ni–Co-MOF/NF), which is prepared by utilizing nickel foam as conductive substrate and nickel source. The resulting transition metal phosphide manifests a pillar-layered morphology, wherein CoP, Ni2P, and Ni5P4 nanoparticles are embedded within each carbon sheet and these carbon sheets assemble into a pillar-shaped structure on the nickel foam (Ni2P–Ni5P4–CoP–C/NF). The heterogeneous Ni2P-Ni5P4–CoP–C/NF with multiple interfaces serves as a highly efficient bifunctional electrocatalyst with overpotentials of −100 mV and 293 mV in the hydrogen evolution reaction and oxygen evolution reaction, respectively, at 50 mA cm−2 in alkaline media. This superior catalytic performance should mainly be ascribed to its enriched active centers and multiphase synergy. When directly applied for alkaline overall water splitting, the Ni2P–Ni5P4–CoP–C/NF couple demonstrates satisfactory activity (1.55 V @10 mA cm−2) along with sustained durability over 18 hours. This method brings fresh enlightenment to the economical and controllable preparation of multi-metal phosphides for energy conversion. [ABSTRACT FROM AUTHOR]

Heteroatomic anion doping represents a powerful approach for manipulating the electronic configuration of the active metal locus in electrocatalysts, resulting in enhanced multifunctional electrocatalytic properties in hydrogen/oxygen evolution reactions (HER/OER). Here, fluorine-tailored Ni2P-F3 nanosheets were synthesized and evaluated as a robust multifunctional electrocatalyst for HER, OER, and UOR. Our comprehensive experimental and theoretical investigations reveal that the anionic F effectively tailored the electronic states of the Ni2P-F3 nanosheets, resulting in an elevated d-band center and optimizing the sorption capacity of intermediates. In addition to thermodynamically and kinetically favoured redox reactions, F doping facilitates the reconstruction and generation of active γ-NiOOH. Resulting from the optimized electronic configuration and nanosheet architecture, outstanding catalytic activities are demonstrated by Ni2P-F3 with low overpotentials to reach 100 mA cm−2 for HER (177 mV) and OER (293 mV), surpassing Ni2P by 234 and 205 mV, respectively. Notably, 1.618 V is required for full-water-diversion to reach 10 mA cm−2, while 1.414 V is required with urea oxidation for 100 mA cm−2. [ABSTRACT FROM AUTHOR]

Leveraging solar energy through photocatalytic hydrogen production from water stands out as one of the most promising approaches to address the energy and environmental challenges. The choice of catalyst profoundly influences the outcomes of photocatalytic reactions, and constructing heterojunctions has emerged as a widely applied strategy to overcome the limitations associated with single-phase photocatalysts. MoO3, renowned for its high chemical stability, encounters issues such as low photocatalytic efficiency and fast recombination of photogenerated electrons and holes. To tackle these challenges, the morphology of MoO3 has been controlled to form nanorods, simultaneously suppressing the aggregation of the catalyst and increasing the number of surface-active sites. Moreover, to facilitate the separation of photogenerated charge carriers, Cd0.9Zn0.1S nanoparticles with a twin crystal structure are deposited on the surface of MoO3, establishing an S-scheme heterojunction. Experimental findings demonstrate that the synergistic effects arising from the well-defined morphology and interface interactions extend the absorption range to visible light response, improve charge transfer activity, and prolong the lifetime of charge carriers. Consequently, Cd0.9Zn0.1S/MoO3 S-scheme heterojunctions exhibit outstanding photocatalytic hydrogen production performance (3909.79 μmol g−1 h−1) under visible light irradiation, surpassing that of MoO3 by nearly nine fold. [ABSTRACT FROM AUTHOR]

To date, researchers in chase of economic cost-efficiency are faced with the problem of developing effective catalysts for water splitting without the use of platinoids. Herein, catalytic properties of hexanuclear rhenium cluster complexes are investigated in application to the hydrogen evolution reaction (HER). A paste composite electrode containing the cluster complexes was obtained, producing a current density of 10 mA cm−2 at an extraordinarily low overpotential of 90 mV (RHE). The {Re6Se8}-based complexes have shown very favorable reaction kinetics via 102 mV dec−1 value of the Tafel slope for HER reaction within the composition of the paste electrode. Model calculations of kinetic parameters using density functional theory also support the experimental findings. This work underscores the perspectivity of rhenium cluster compounds in HER and opens a promising avenue toward the practical implementation of hydrogen production through electrochemical water splitting. [ABSTRACT FROM AUTHOR]

In contrast to the energy-consuming Haber–Bosch process, ammonia synthesis by electrocatalysis under ambient conditions is an efficient and environmentally friendly method. In this work, through first principles calculations, the potential of four dual-atom FeTM (TM = Fe, Mo, Co, and V) anchored graphyne (FeTM@GY) as efficient nitrogen reduction reaction (NRR) catalysts is systematically investigated. Among them, FeMo@GY is the most promising, with excellent NRR catalytic activity, high ability to suppress the competing hydrogen evolution reaction (HER), and good stability. Moreover, NRR prefers the maximum pathway with the calculated onset potentials of −0.27 V for FeMo@GY. This work not only suggests that FeMo@GY holds great promise as an efficient, low-cost, and stable dual-atom catalyst for NRR but also further provides a guiding idea for the design of efficient NRR catalysts. [ABSTRACT FROM AUTHOR]

Mn-doped Bi3O4Br has been synthesized using a solvothermal route. The undoped Bi3O4Br and Mn–Bi3O4Br materials possess orthorhombic unit cells with two distinct Bi sites forming a layered atomic arrangement. The shift in the (020) plane in the powder X-ray diffraction (PXRD) pattern confirms Mn-doping in the Bi3O4Br lattice. Elemental mapping indicated 7% Mn doping in the Bi3O4Br lattice structure. A core-level X-ray photoelectron study (XPS) indicates the presence of BiIII and MnII valence-states in Mn–Bi3O4Br. Doping with a cation (MnII) containing a different charge and ionic radius resulted in vacancy/defects in Mn–Bi3O4Br which further altered its electronic structure by reducing the indirect band gap, beneficial for electron conduction and electrocatalysis. The irreversible MnII to MnIII transformation at a potential of 1.48 V (vs. RHE) precedes the electrochemical oxygen evolution reaction (OER). The Mn-doped electrocatalyst achieved 10 mA cm−2 current density at 337 mV overpotential, while the pristine Bi3O4Br required 385 mV overpotential to reach the same activity. The pronounced OER activity of the Mn–Bi3O4Br sample over the pristine Bi3O4Br highlights the necessity of MnII doping. The superior activity of the Mn–Bi3O4Br catalyst over that of Bi3O4Br is due to a low Tafel slope, better double-layer capacitance (Cdl), and small charge-transfer resistance (Rct). The chronoamperometry (CA) study depicts long-term stability for 12 h at 20 mA cm−2. An electrolyzer fabricated as Pt(−)/(+)Mn–Bi3O4Br can deliver 10 mA cm−2 at a cell potential of 2.05 V. The post-CA-OER analyses of the anode confirmed the leaching of [Br−] followed by in situ formation of Mn-doped Bi2O3 as the electrocatalytically active species. Herein, an ultra-low Mn-doping into Bi3O4Br leads to an improvement in the electrocatalytic performance of the inactive Bi3O4Br material. [ABSTRACT FROM AUTHOR]

In this study, a trimetallic catalyst, NiWRu@NF, is electrodeposited onto nickel foam using chronoamperometry to enhance the hydrogen evolution reaction (HER) in alkaline water electrolysis. The catalyst combines nickel, tungsten, and ruthenium components, strategically designed for efficiency and cost-effectiveness, hydroxyl transfer and water dissociation, and acceleration of hydrogen combination, respectively. Evaluation of NiWRu@NF reveals exceptional performance, with a low overpotential of -50 mV and high current density of -10 mA cm-2, signifying its efficiency in promoting HER. Tafel values further corroborate the catalyst's effectiveness, indicating a rapid reaction rate of hydrogen evolution in such a highly alkaline medium compared to other controls studied along with it. This study underscores the significance of NiWRu@NF in advancing alkaline HER kinetics, paving the way for more efficient electrolysis processes. [ABSTRACT FROM AUTHOR]

A new polyoxometalate (POM)-based hybrid nanomaterial (denoted as PMo11-Cr-mGO) was designed via covalent interaction between the Cr(acac)3 complex and [PMo11O39]7− followed by immobilization on the surface of modified graphene oxide (mGO). The prepared nanomaterial was characterized using a series of physicochemical techniques. X-ray diffraction (XRD), Raman analysis, transmission electron microscopy (TEM), and FE-SEM-EDS revealed the preservation of layered GO during the formation of the desired hybrid nanomaterial. Fourier transform infrared (FT-IR), X-ray photoelectron spectroscopy (XPS), and elemental analysis confirmed the immobilization of POM (PMo11-Cr) on the surface of mGO and the formation of PMo11-Cr-mGO. In order to evaluate the performance of PMo11-Cr-mGO in the hydrogen evolution reaction (HER), electrochemical measurements were also performed. The resulting PMo11-Cr-mGO exhibited excellent HER activities with a low overpotential of 153 mV at 10 mA cm−2 and good durability in acidic media, thus emerging as one of the most efficient POM-based electrocatalysts. [ABSTRACT FROM AUTHOR]

The designing of efficient electrocatalysts for hydrogen generation is essential for the practical application of water-splitting devices. With numerous electrochemical advantages, transition metal sulphides are regarded as the most promising candidates for catalysing the hydrogen evolution reaction (HER) in acidic media. In the present study, Ru-doped cobalt sulphide nanosheets, termed Co9S8/Ru@t (t = 24 h, 48 h, and 72 h), were obtained by varying the reaction time from 24 h to 72 h from a RuCo-PBA precursor. The role of the time period for the synthesis of Co9S8/Ru@48h is vital in increasing the number of electroactive sites and optimising the hydrogen adsorption–desorption phenomena leading to an increment in the HER activity. The electrochemical outcomes demonstrate that the optimized Co9S8/Ru@48h requires a low overpotential of just 94 mV to produce 10 mA cm−2 current density, and also exhibits a lower Tafel slope value of 84 mV dec−1 defining its faster reaction kinetics. The as-synthesized Co9S8/Ru@48h was stable for up to 20 h of constant electrolysis signifying its outstanding durability. The optimized synthetic approach and impressive electrochemical results make Co9S8/Ru@48h a suitable alternative to noble-metal-based electrocatalysts for the HER. [ABSTRACT FROM AUTHOR]

In aqueous pH 7 phosphate buffer, during controlled potential electrolysis (CPE) at -1.10 V vs. Ag|AgCl the literature square planar copper complex, [CuIILEt]BF4 (1), forms a heterogeneous deposit on the glassy carbon working electrode (GCWE) that is a stable and effective hydrogen evolution reaction (HER) electrocatalyst. Specifically, CPE for 20 hours using a small GCWE (A = 0.071 cm²) gave a turnover number (TON) of 364, with ongoing activity. During CPE the brownish-yellow colour of the working solution fades, and a deposit is observed on the small GCWE. Repeating this CPE experiment in a larger cell with a larger GCWE (A = 2.7 cm²), connected to a gas chromatograph, resulted in a TON of 2628 after 2.6 days, with FE = 93%, and with activity ongoing. After this CPE, the working solution had faded to nearly colourless, and visual inspection of the large GCWE showed a material had deposited on the surface. In a 'rinse and repeat test', this heterogeneous deposit was used for further CPE, in a freshly prepared working solution minus fresh catalyst, which resulted in similar ongoing HER activity to before, consistent with the surface deposited material being the active HER catalyst. EDS, PXRD and SEM analysis of this deposit shows that copper and oxygen are the main components present, most likely comprising copper and copper(I) oxide ((Cu2O)n) formed from 1. The use of 1 leads to a deposit that is more catalytically active than that formed when starting with a simple copper salt (control), likely due to it forming a more robustly attached deposit, which also enables the observed long-lived catalytic activity. [ABSTRACT FROM AUTHOR]

Molybdenum disulfide (MoS2)-based electrocatalysts have been considered as promising alternatives to platinum for use in the hydrogen evolution reaction (HER). Developing MoS2 electrocatalysts with more active sites has been recognized as an efficient way to enhance the HER activity. Moreover, phase transition and heteroatom doping show great influence on the HER performance. In this work, we develop a vapor-phase hydrothermal (VPH) approach to introduce phosphorus (P) atoms into a MoS2 nanosheet array on carbon fiber cloth, which presents enhanced HER activity compared with MoS2 without P-doping. The improved performance is due to the synergistic effects of the new active sites formed by the P dopants and the sulfur (S) vacancies in the MoS2 nanosheets generated by the doping of P atoms, which increases the number of active sites. In general, the obtained P-doped MoS2/CFC exhibits a lower onset potential of 80 mV and an overpotential of 162 mV at 10 mA cm−2 than MoS2 without P-doping in 0.5 M H2SO4, accompanied by extremely large cathodic current density and excellent stability. This strategy may open up opportunities for heteroatom doping of electrocatalysts for various applications and provide a new method for material synthesis. [ABSTRACT FROM AUTHOR]

The hydrogen evolution reaction is an important process for energy storage. The six-coordinate cobalt complex [CoIII(L1−)(LH)]2+ (LH = N-(4-amino-6-(pyridin-2-yl)-1,3,5-triazin-2-yl)benzamidine) was found to catalyze photocatalytic hydrogen evolution. In this work, we performed density functional calculations to obtain the reduction potentials and the proton-transfer free energy of possible intermediates to determine the preferred pathways for proton reduction. The mechanism involves the metal-based reduction of Co(III) to Co(II) before the protonation at the amidinate N on the pyridinyl-substituted diaminotriazine benzamidinate ligand L1− to form [CoII(LH)(LH)]2+. Essentially, the subsequent electron transfer is not metal-based reduction, but rather ligand-based reduction to form [CoII(LH)(LH˙1−)]1+. Through a proton-coupled electron transfer process, the cobalt hydride [CoIIH(LH)(LH2˙)]1+ is formed as the key intermediate for hydrogen evolution. As the cobalt hydride complex is coordinatively saturated, a structural change is required when the hydride on Co is coupled with the proton on pyridine. Notably, the redox-active nature of the ligand results in the low acidity of the protonated pyridine moiety of LH2˙, which impedes its function as a proton relay. Our findings suggest that separating the proton relay fragment from the electron reservoir fragment of the redox-active ligand is preferred for fully utilizing both features in catalytic H2 evolution. [ABSTRACT FROM AUTHOR]

Noble metal-based catalysts such as RuO2 and IrO2 are widely used in the catalysis of the OER. However, because of their high price and poor stability, it is urgent to develop transition metal-based electrocatalysts with low precious metal doping as an alternative. Layered double hydroxides (LDHs) grown on 3D metal–organic frameworks (MOFs) are ideal for doping precious metals owing to abundant defects at the heterointerface, large surface area, and intrinsic oxygen evolution activity. In this study, a novel FeNi LDH/MOF heterostructure was prepared via a two-step solvothermal method using Fe-soc-MOFs as the substrate. Subsequently, Ru was introduced through a hydrothermal process. The as-synthesized Ru@FeNi LDH/MOF has an overpotential of only 242 mV at a current density of 10 mA cm−2 and can be used in continuous electrolysis for 48 h. Its unique nanocubic core–shell structure and flower-like LDHs on its surface provide a large number of active sites, which become the key to ensuring high activity and stability. With the doping of Ru, the electronic structure was adjusted and electron transfer was accelerated, further improving electrochemical activity. This study provides a new idea for developing transition metal-based catalysts with low noble metal loading. [ABSTRACT FROM AUTHOR]

The development of low-cost, high-efficiency, and stable electrocatalysts for the alkaline hydrogen evolution reaction (HER) is a key challenge because the alkaline HER kinetics is slowed by an additional water dissociation step. Herein, we report an interfacial engineering strategy for polyoxometalate (POM)-stabilized nickel (Ni) quantum dots decorated on the surface of porous titanium mesh (POMs–Ni@PTM) for high-rate and stable alkaline hydrogen production. Benefiting from the strong interfacial interactions among POMs, Ni atoms, and PTM substrates, as well as unique POM–Ni quantum dot structures, the optimized POMs–Ni@PTM electrocatalyst exhibits a remarkable alkaline HER performance with an overpotential (η10) of 30.1 mV to reach a current density of 10 mA cm−2, which is much better than those of bare Ni decorated porous titanium mesh (Ni@PTM) (η10 = 171.1 mV) and POM decorated porous titanium mesh (POMs@PTM) electrocatalysts (η10 = 493.6 mV), comparable to that of the commercial 20 wt% platinum/carbon (20% Pt/C) electrocatalyst (η10 = 20 mV). Moreover, the optimized POMs–Ni@PTM electrocatalyst demonstrates excellent stability under continuous alkaline water-splitting at a current density of ∼100 mA cm−2 for 100 h, demonstrating great potential for its practical application. [ABSTRACT FROM AUTHOR]

A newly synthesized series of bimetallic CPM-37(Ni,Fe) metal–organic frameworks with different iron content (Ni/Fe ≈ 2, 1, 0.5, named CPM-37(Ni2Fe), CPM-37(NiFe) and CPM-37(NiFe2)) demonstrated high N2-based specific SBET surface areas of 2039, 1955, and 2378 m2 g−1 for CPM-37(Ni2Fe), CPM-37(NiFe), and CPM-37(NiFe2), having much higher values compared to the monometallic CPM-37(Ni) and CPM-37(Fe) with 87 and 368 m2 g−1 only. It is rationalized that the mixed-metal nature of the materials increases the structural robustness due to the better charge balance at the coordination bonded cluster, which opens interesting application-oriented possibilities for mixed-metal CPM-37 and other less-stable MOFs. In this work, the CPM-37-derived α,β-Ni(OH)2, γ-NiO(OH), and, plausibly, γ-FeO(OH) phases obtained via decomposition in the alkaline medium demonstrated a potent electrocatalytic activity in the oxygen evolution reaction (OER). The ratio Ni : Fe ≈ 2 from CPM-37(Ni2Fe) showed the best OER activity with a small overpotential of 290 mV at 50 mA cm−2, low Tafel slope of 39 mV dec−1, and more stable OER performance compared to RuO2 after 20 h chronopotentiometry at 50 mA cm−2. [ABSTRACT FROM AUTHOR]

Using electrochemical water splitting to generate hydrogen is considered a desirable approach, which is greatly impeded by the sluggish dissociation of H2O and adsorption and desorption of H*. Effective hydrogen production can be achieved by speeding up the chemical process with a suitable electrocatalyst. In this work, we designed and synthesized a rare earth element cerium (Ce) regulated iron–nickel bimetallic phosphide Ce-NiFeP@NF (here NiFeP represents Fe2P/NiP2) nanoarray with nanoflowers. For the hydrogen evolution reaction (HER), Ce-NiFeP@NF only needs an overpotential of 106 mV to provide a current density of 10 mA cm−2, compared to NiFeP@NF (175 mV@10 mA cm−2). This self-supported electrocatalyst Ce-NiFeP@NF with a composite morphology exhibits excellent performance in the HER. Specifically, the introduction of Ce promotes the electron transfer process at the Fe2P/NiP2 heterojunction interface and the Ce-NiFeP@NF nanocomposite structure with nanoflowers has a larger electrochemically active specific surface area, which is more conducive to improving the intrinsic catalytic activity. Also, a dual-electrode alkaline electrolytic cell (Ce-NiFeP@NF functions as both the anode and the cathode) operates with a cell voltage of only 1.56 V to achieve a current density of 10 mA cm−2. The synergistic effect of rare earth element doping and heterojunction engineering can improve the morphology of intrinsic catalysts to achieve more efficient electrochemical water splitting for hydrogen production. [ABSTRACT FROM AUTHOR]

Oxygen evolution reaction (OER) electrocatalysts are frequently made from noble metal-based oxides like ruthenium/iridium oxides. However, because of their scarcity and high price, researchers are now focusing on creating innovative OER catalysts based on affordable transition metals that have improved electrical conductivity and accessibility to active sites. Metal–organic frameworks (MOFs), a unique class of inorganic materials with excellent physical and chemical properties, have witnessed significant progress in promising green energy systems. In this work, a novel mixed-ligand metal–organic framework [Co(μ-1κN,2κN′-BDP)(μ3-1κoo′,2κo′′2κo′′′-BTC)]n·nH2O (BDP = boron-dipyrromethene or BODIPY; BTC = benzene tricarboxylate) denoted as CoBDPMOF has been synthesized, and its composites with different carbon materials have been designed. Compared to the pristine MOF, the composites showed enhanced electrocatalytic activity toward the oxygen evolution reaction (OER) in alkaline media. In addition, the CoBDPMOF with activated carbon showed the highest OER performance with a low Tafel slope (82 mV dec−1) and the highest j600 (59.8 mA cm−2), outperforming noble metal IrO2, the OER benchmark electrocatalyst. This study presents new insights into the design and application of CoBDPMOF-based materials for energy conversion and suggests promising avenues for further research and development in electrocatalysis. [ABSTRACT FROM AUTHOR]

Hydrazine-assisted electrochemical water splitting is an important avenue toward low cost and sustainable hydrogen production, which can significantly reduce the voltage of electrochemical water splitting. Herein, we took a simple approach to fabricate NiFeP nanosheet arrays on nickel foam (NiFeP/NF), which exhibit superior electrocatalytic activity for the hydrogen evolution reaction (HER) and the hydrazine oxidation reaction (HzOR). Our investigations revealed that the excellent electrocatalytic activity of NiFeP/NF mainly arises from the bimetallic synergistic effect, abundant electrocatalytically active sites facilitated by the porous nanosheet morphology, high intrinsic conductivity of NiFeP/NF and strong NiFeP–NF adhesion. We assembled a hydrazine-boosted electrochemical water splitting cell using NiFeP/NF as a bifunctional catalyst for both electrodes, and the overall hydrazine splitting (OHzS) exhibits a considerably low overpotential (100 mV at 10 mA cm−2), and is stable for 40 h continuous electrolysis in a 1 M KOH + 0.5 M N2H4 electrolyte. When it is applied to hydrogen production by seawater electrolysis, its catalytic activity shows strong tolerance. This work provides a promising approach for low cost, high-efficiency and stable hydrogen production based on hydrazine-assisted electrolytic seawater splitting for future applications. [ABSTRACT FROM AUTHOR]

The development of photocatalysts plays a pivotal role in facilitating the production of green hydrogen energy through water splitting. In this study, one-dimensional (1D) organic–inorganic ZnCdS(EDA)/Ni@NiO (EDA: ethylenediamine) nanorods were prepared by combining organic molecules of EDA into ZnCdS. The EDA molecule possesses two amino functional groups with strong electron-donating capacity, thereby facilitating electron transfer to ZnCdS(EDA)/Ni@NiO and enabling efficient hydrogen evolution through photocatalytic water splitting. The H2 evolution rate of ZnCdS(EDA)/Ni@NiO was 159 μmol g−1 h−1 in the absence of sacrificial agents, and its H2 evolution rate in the system with EDA as the sacrificial agent can reach 5760 μmol g−1 h−1. The combination of EDA, a S vacancy, and heterojunction was proved to be the main factor for improving the separation and transfer rate of photogenerated carriers. The incorporation of ZnCdS(EDA)/Ni@NiO enhances the participation of photogenerated electrons in the photocatalytic hydrogen evolution reaction, thereby improving the overall photocatalytic activity. The synthesis of this one-dimensional composite catalyst holds great potential for advancing the development of efficient photocatalytic materials. [ABSTRACT FROM AUTHOR]

A bifunctional catalyst used for urea oxidation-assisted hydrogen production can efficiently catalyze the urea oxidation reaction (UOR) and hydrogen evolution reaction (HER) simultaneously, thus simplifying electrolytic cell installation and reducing the cost. Constructing the heterointerface of two components or species and doping heteroatom are effective strategies to improve the performance of electrocatalysts, which could regulate the local electronic structure of the catalysts at their interface region, adjust their orbital overlap, and achieve enhanced catalytic performance. In this study, a simple hydrothermal method was studied for the preparation of B-doped Ni5P4/Ni2P heterostructures on nickel foam (B-Ni5P4/Ni2P@NF). Under 1 M KOH at a current density of 10 mA cm−2, an overpotential of 76 mV was obtained for the HER. When 0.3 M urea was added to 1 M KOH, the performance of the prepared catalyst was greatly improved. When the current density reached 10 mA cm−2, the potential was only 1.35 V. In addition, urea-assisted overall water splitting voltage was only 1.41 V. Thus, the B-Ni5P4/Ni2P catalyst possess excellent electrocatalytic activity. The main reason for the excellent properties of the electrocatalyst is the construction of heterostructure, which regulates the electronic structure of the catalyst at its interface and generates a new efficient active site. In addition, the doping of B atoms further promotes the charge transfer rate, thus strengthening the interaction between two phases and improving the catalytic performance. This study provides a simple, environmentally friendly, and rapid design method to prepare an active bi-functional electrocatalyst that has a positive effect on urea-assisted overall water splitting. [ABSTRACT FROM AUTHOR]

Infiltration of the mesoporous structure of SBA-15 silica as a hard template with phenanthroline complexes of Fe3+ and Co2+ allowed the simultaneous dispersion of nitrogen, iron and cobalt species on the surface of the obtained carbonaceous CMK-3 silica replica, with potential as bifunctional heterogeneous catalysts for the cathodic oxygen reduction and evolution reactions (ORR and OER). The textural properties and mesopore structure depended on the composition of the material. The carbonaceous FeCoNCMK-3 (1/1), obtained with an Fe/Co molar ratio of 1/1, exhibited an ordered cylindrical mesoporous structure with a high mesopore volume, a rather homogeneous composition in terms of total and surface concentrations of iron and cobalt, and a balanced presence of pyridinic-, pyrrolic- and graphitic-N species. FeCoNCMK-3 (1/1) could improve the ORR kinetics by adsorption and reduction of O2 through the 4-electron mechanism with a current density of −17.37 mA cm−2, Eonset of 1.13 V vs. RHE and E1/2 of 0.75 V when compared to metal-free, monometallic or bimetallic electrocatalysts with a higher amount of cobalt than that of iron. In addition, FeCoNCMK-3 (1/1) exhibited activity for the OER, presenting lower values of Eonset (1.52 V), Ej10 (1.78 V) and the Tafel slope (76.3 mV dec−1) with respect to other catalysts. When evaluated as a cathode in a prototype of a Zn–air battery, FeCoNCMK-3 (1/1) exhibited a high open circuit voltage of 1.41 V, a peak power density of 66.84 mW cm−2, a large specific capacity of 818.88 mA h gZn−1, and cycling for 20 h but with deactivation upon cycling. [ABSTRACT FROM AUTHOR]

Advances in the hydrogen evolution reaction (HER) are intricately connected with addressing the current energy crisis and quest for sustainable energy sources. The necessity of catalysts that are efficient and inexpensive to perform the hydrogen evolution reaction is key to this. Following the ground-breaking discovery of graphene, metal thio/seleno phosphates (MPX3: M – transition metal, P – phosphorus and X – S/Se), two dimensional (2D) materials, exhibit excellent tunable physicochemical, electronic and optical properties, and are expected to be key to the energy industry for years to come. Taking this into account, a facile time-effective electrostatic restacking synthesis procedure has been followed to synthesize a 2D/2D heterostructure (FePS3@BCN) involving FePS3, one of the prominent MPX3 materials, with borocarbonitride (BCN), for hydrogen evolution reaction (HER). The piled up nanosheets of FePS3 and BCN are held together by an electrostatic force, and display extreme robustness under the harsh conditions of HER application. The amalgamated electrocatalyst achieved an overpotential of 187 mV at a current density of 10 mA cm−2 with a shallow Tafel slope of 41 mV dec−1, following the Volmer–Heyrovsky mechanism. The resilience of the electrocatalyst has been examined through chronoamperometric testing for long term stability, and it is stable for more than 14 hours, which shows the excellent electrocatalytic activity for hydrogen evolution reaction owing to the strategic approach to the catalyst design, the use of numerous electrochemically active sites, large surface area and a barrier-free channel for quick ion transfer. [ABSTRACT FROM AUTHOR]

Aqueous zinc-ion batteries (ZIBs) are one of the most promising candidates for electric energy storage devices due to their merits of low cost and high safety. However, the notorious side reactions and dendrite formation on zinc anodes impede the commercialization of ZIBs. In this work, a cheap and edible electrolyte additive sucrose is applied to address the above issues. Sucrose with hydroxyl groups can react as zincophilic sites to adsorb Zn2+. As verified by Raman and FT-IR spectroscopy, the solvation structure of Zn2+ and the hydrogen bonds can be regulated by the sucrose molecule. The weakened solvated structure of Zn2+ and lowered coupling degree between Zn2+ and SO42− can inhibit the hydrogen evolution reaction (HER) and the generation of the sulfate by-product. Furthermore, a solid electrolyte interphase (SEI)-like ion buffer layer is formed because of the preferentially adsorbed sucrose, which can increase the nucleation overpotential and equalize the ion distribution. The enriched Zn nucleation sites and inhibited 2D diffusion of Zn2+ resulting from the sucrose additive enable uniform Zn deposition. Thus, improved performances of symmetric Zn‖‖Zn, asymmetric Zn‖‖Cu and Zn‖‖VO2 cells are realized. The Zn‖‖Zn cell exhibits a highly reversible cycling performance for 1200 h and 400 h at 5 mA cm−2/1 mA h cm−2 and 10 mA cm−2/5 mA h cm−2, respectively. This work provides a readily available and edible additive to improve the performance of ZIBs. [ABSTRACT FROM AUTHOR]

Designing photocatalysts with efficient charge separation and electron transport capabilities to achieve efficient visible-driven hydrogen production remains a challenge. Herein, 2D–2D conductive metal–organic framework/g-C3N4 heterojunctions were successfully prepared by an in situ assembly. Compared to pristine g-C3N4, the ratio-optimized Ni-CAT-1/g-C3N4 exhibits approximately 3.6 times higher visible-light H2 production activity, reaching 14 mmol g−1. Through investigations using time-resolved photoluminescence, surface photovoltage, and wavelength-dependent photocurrent action spectroscopies, it is determined that the improved photocatalytic performance is attributed to enhanced charge transfer and separation, specifically the efficient transfer of excited high-energy-level electrons from g-C3N4 to Ni-CAT in the heterojunctions. Furthermore, the high electrical conductivity of Ni-CAT enables rapid electron transport, contributing to the overall enhanced performance. This work provides a feasible strategy to construct efficient dimension-matched g-C3N4-based heterojunction photocatalysts with high-efficiency charge separation for solar-driven H2 production. [ABSTRACT FROM AUTHOR]