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As one of the effective methods for hydrogen production, water electrolysis has been widely studied. However, the high overpotential challenge faced by the anode and the limitation of the electron transfer rate in this process significantly inhibit the efficiency of hydrogen production, which has become the main obstacle to overcome in the current research. The use of thermodynamically more favorable organic compounds to oxidize at the anode instead of traditional water oxidation (OER) is an effective strategy to optimize the process of electrolytic hydrogen production. In this paper, Ni3S2 catalysts co-doped with non-noble metals Li and Mn were prepared on nickel foam and used for the glycerol oxidation reaction (GOR) coupled with the hydrogen evolution reaction (HER). In alkaline solution, Li, Mn–Ni3S2@NF exhibits good GOR and HER performance. Specifically, overpotentials of 1.58 V vs. RHE and 0.54 V vs. RHE are required to reach a current density of 200 mA cm−2, respectively, and the catalytic performance of the material remains good after a long-term test. Li, Mn–Ni3S2@NF as a bifunctional catalytic material oxidizes glycerol to formate, and its faradaic efficiency (FE) is as high as 91%, and the volume of hydrogen production is close to the theoretical value. In addition, the replacement of the OER by the GOR can reduce the energy consumption by about 17.44%. [ABSTRACT FROM AUTHOR]

In this work, Pd and Pt electrocatalysts were electrodeposited on three-dimensional carbon paper and carbon nanofoam with the purpose of increasing the catalytic area to improve the glycerol electro-oxidation. SEM and cross-sectional SEM micrographs showed that Pd and Pt particles were well-distributed over the entire three-dimensional electrode surfaces. Commercial Pd/C and Pt/C catalysts deposited by the spray method were used for comparison, showing lower surface area (SA) utilization than those electrodeposited. The electrodeposition effectiveness to cover the electrode surfaces was evaluated by changes in overall SA and through the calculation of electrochemically active surface area (EASA) and specific surface area (SSA). Despite the larger EASA values found for Pd and Pt on nanofoam, Pt on paper showed the highest utilization of the surface area, obtaining an SSA of 58.1 m2 g−1. Moreover, the electrodeposition of Pd and Pt dramatically increased the EASA versus the geometrical area, improving this ratio 16 (Pd on paper), 151 (Pt on paper), 158 (Pd on nanofoam) and 277-fold (Pt on nanofoam). The electrodeposited porous Pt electrodes showed good activity for glycerol oxidation, exhibiting a more negative potential than Pd-based materials. However, for fuel cell applications operated at intermediate temperatures, Pd on carbon paper is the optimal candidate to be used as an anode because of its high current density and excellent poisoning tolerance. [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]

The design of an efficient OER catalyst is significant for water splitting. Metal–organic frameworks (MOFs) are emerging as promising electrocatalysts due to their diversity of structure and tunability of function. In this paper, 2D FexCo1−x-MOF1/NF with an extended ligand (biphenyl-4,4′-dicarboxylic acid, BPDC) is constructed on nickel foam by a solvothermal method. Compared with the MOF2 synthesized by using BDC (1,4-bezenedicarboxylate), MOF1 shows excellent performance. Among MOF1, Fe0.5Co0.5-MOF1/NF exhibits outstanding performance with a low overpotential (217 mV) and a small Tafel slope (31.16 mV Dec−1) at 10 mA cm−2 and performs well at a high current density. In addition, the catalyst is remarkable in terms of durability both in alkaline solution and simulated seawater. The synergetic effect between Fe and Co and more active sites exposed play an important role in improving the OER activity. This work provides an effective strategy for the rational design of MOFs as inexpensive electrocatalysts. [ABSTRACT FROM AUTHOR]

To solve the problem of excessive energy consumption in the process of catalytic water splitting, it is quite essential to exploit high-activity and low-cost electro-catalysts. The present paper proposes a highly catalytically active Ni/Fe hydroxide electro-catalyst for the oxygen evolution reaction (OER), which is in situ formed on the surface of the stainless steel fiber felt using a sacrificial template by adding the oxidizing agent K2S2O8 to the alkaline solution under mild conditions. The electrode prepared using this simple one-step chemical oxidation method obviously shows enhanced catalytic activity for the OER. The overpotentials at 10 mA cm−2 are only 214 mV and 263 mV in KOH and Na2CO3/NaHCO3 solutions, respectively. In addition, the potential and morphology of the electrode remain stable for 180 h at 10 and 100 mA cm−2 in the Na2CO3/NaHCO3 system, demonstrating its ultra-high stability. This new route to prepare OER electrode materials has a promising bright application prospect for large-scale production. [ABSTRACT FROM AUTHOR]

In this paper, a facile and ultrafast two-step dipping process was developed to in situ form an electrocatalyst on a NiMo foam substrate without consuming extra energy. The obtained electrode showed a porous coral-like structure decorated with nanosheets and exhibited excellent overall water splitting properties in alkaline solution. This study provides a feasible strategy for developing an environmentally friendly and energy-efficient non-noble metal electrode for hydrogen production from water splitting. [ABSTRACT FROM AUTHOR]

Exploring active catalyst components is very important to develop high-performance and highly stable ORR electrocatalysts to replace costly Pt-based catalysts, though it remains an ongoing challenge. In this paper, three ORR catalysts with different active components were obtained by calcination of different proportions of mixed precursors simply and delicately. Among them, precursor 1 (bimetallic polymer Fe/Zn-ZIFs@ZnCO3) played the role of a self-sacrificing template, while precursor 2 (an N, P-co-doped polymer) played the role of a volatile atmosphere. Precursor 2 also embedded N and P heteroatoms into the carbon framework during high-temperature volatilization, which resulted in subtle changes in the active catalyst components. Finally, a hybrid of metal Fe and α-Fe2O3 nanoparticles embedded in N, P-codoped carbon nanotubes with many separated gullies (named α-Fe2O3/Fe@NPC) exhibited excellent ORR catalytic activity in an alkaline solution as compared to commercial Pt/C. This work provides a new strategy for designing controllable active components using volatile precursors. [ABSTRACT FROM AUTHOR]

A new indirect chemosensor for the detection of cyanide in blood is developed. 2-(5-Bromo-2-pyridylazo)-5-[N-n-propyl-N-(3-sulfopropyl)amino]phenol, a yellow dye, forms a blue-coloured complex with palladium ions. The yellow colour of this complex is regained upon reaction with cyanide ions. The complex shows high selectivity for the detection of cyanide over 16 other anions. The system was applied to two different methods for the detection of cyanide in human whole blood. As a quantitative absorbance method, blood samples were mixed with acid, and the resulting vaporised hydrogen cyanide was absorbed in an alkaline solution containing the complex in a Conway cell. The resulting absorbance response of the solution at 450 nm is linear over the range 4–40 μM (R2 = 1.000), and the limit of detection is 0.6 μM. Furthermore, the complex-soaked paper is applicable as a test strip for cyanide detection. When a test strip is used with 0.5 mL of blood, the limit of detection is 15 μM. The detection limits of these two methods are below the toxic blood cyanide concentration (19 μM). Therefore, both methods allow the quantification and screening of cyanide in blood samples. Furthermore, the test strip is low cost and enables on-site analysis. [ABSTRACT FROM AUTHOR]

The development of earth-abundant and high-efficiency electrocatalysts for overall water splitting is highly fascinating and still presents a challenge caused by the low activity for both the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER) at the same time. In this paper, active cobalt-doped pyrite nanospheres with a porous structure are fabricated for the first time as advanced catalysts for water splitting in an alkaline solution. With the incorporation of cobalt atoms, the electronic structure of pyrite is well-tuned, with high conductivity as well as more active sites being obtained, which finally results in a superior bifunctional water splitting performance. Only 1.60 V is required to reach the current density of 10 mA cm−2, which is smaller than that of other transition metal sulfides. [ABSTRACT FROM AUTHOR]

Despite the significant importance of regenerating spent LiFePO4 (LFP) cathode materials to address resource shortages and environmental pollution, significant obstacles remain with ecologically friendly and cost-effective recycling processes. Herein, we propose a novel strategy to synthesize new high-performance nitrogen-doped carbon/graphene@LiFePO4 (N-DC/G@LFP) cathode materials by utilizing the spent LFP cathode material as raw materials. The regeneration strategy was performed in an alkaline solution, after repeated freezing and thawing, spray-drying, and subsequent thermal annealing under an Ar atmosphere. Benefiting from the synergistic effects that resulted from the tight contact between LiFePO4 and the high-conductivity nitrogen-doped carbon and graphene network, the refabricated N-DC/G@LFP cathodes delivered 124.8 mA h g−1 of excellent reversible discharge capacities at 2C, 117.5 mA h g−1 at 5C, and 149.7 mA h g−1 at 0.2C current rate. Furthermore, a 94.2% high-capacity retention ratio was observed over 500 cycles at 0.2C. This regeneration approach offers novel insight into the transformation from spent LFP cathodes to new cathode materials with efficient reutilization, which takes full advantage of the valuable components within the spent cathodes. Thus, this method enables the win–win situation of environmental protection and sustainable development of the LIB industry. [ABSTRACT FROM AUTHOR]

Developing low-cost high-efficient electrocatalysts for alkaline hydrogen evolution reaction (HER) is of critical significance in hydrogen production via alkaline electrolyzers. Herein, we prepared CeO2/Co4N heterostructure for the catalyst in alkaline HER, which introduced a synergistic effect within the CeO2 and Co4N catalytic sites that facilitates the two consecutive steps in alkaline HER reaction. More importantly, plasma treatment was further applied to the material to tune the electronic structure of the catalytic sites by creating multiple anion vacancies. The introduced O vacancies accelerated the H2O cleaving process on CeO2, while the N vacancies in Co4N optimized the H adsorption strength on the Co sites. The catalytic activity of the catalyst improved significantly after plasma treatment. It only required an overpotential of 36 mV@10 mA cm−2 for the HER operated in 1 M KOH electrolyte and provided one of the best precious metal-free catalysts ever reported. [ABSTRACT FROM AUTHOR]

Due to the very similar chemical and physical properties, D2O and H2O cannot be discriminated easily by convenient and cost-effective ways. Up to now, small organic molecules with active deprotonating ability in a very weak alkaline solution are proposed to deal with this fascinating yet challenging research. In this contribution, TPA-DP-COOH, a carboxylic acid group-substituted fluorescent substance, is demonstrated as a sensor to detect D2O and H2O with an external interference-free style, which not only displays a huge different signal output in D2O and H2O, but also very low limits of detection (LOD) as 49.08 ppm (D2O in H2O) and 0.23 ppm (H2O in D2O), respectively. Thus, these excellent sensing behaviors encourage us to fabricate TPA-DP-COOH and TPA-DP-COOK-absorbed filter papers as cost-effective and portable test strips, which are able to monitor the spoilage of Dimocarpus longan Lour and white leg shrimp in a non-contact mode during the storing process. [ABSTRACT FROM AUTHOR]

Efficient and stable oxygen evolution reaction (OER) electrocatalysts are essential for improving the overall efficiency of water electrolyzers. Iron-doped cobalt phosphide (CoFeP) nanowires are prepared via a one-step solvothermal process using a cobalt metal--organic framework (Co MOF), P4 and dissolved Fe2+. The ion-exchange between Fe2+ and the Co MOF occurs first, and then phosphides are formed. CoFeP exhibits the Co2P phase, and there exists an electronic interaction between Co and Fe. When supported on nickel foam (NF) to catalyze the OER in alkaline solutions, CoFeP/NF exhibits an overpotential of 240 mV at a 10 mA cm-2 OER current density, which is much lower than that of Co2P/NF. Kinetic analyses indicate that the lattice oxygen oxidation mechanism occurs at the CoFeP/NF surface, whereas the adsorbate evolution mechanism dominates at the Co2P/NF surface. The change in the mechanistic pathway is due to the increased acidity of the Co4+ site in CoFeP, which favors the decoupled proton--electron transfer process. Lower apparent activation energy, charge transfer resistance and Tafel slope values, and higher electron rate constants are observed on the CoFeP/NF surface, and the charge redistribution induced by Fe during the OER process alters the adsorption energy of the hydroxyl groups at the Co sites, leading to more facile OER kinetics, as proved by density functional theory calculations. CoFeP/ NF shows good long-term durability in alkaline solutions, and the conversion of surface phosphides to oxides and (oxy)hydroxides is observed. [ABSTRACT FROM AUTHOR]

The wide application of lithium-ion batteries (LIBs) for electric vehicles forebodes a future decommissioning tide of spent LIBs. Therefore, the recycling of spent LIBs has garnered significant attention, primarily due to the scarcity of resources and the detrimental effects of environmental pollution. However, traditional recycling technologies such as pyrometallurgy and hydrometallurgy methods are limited by their high energy consumption, high pollution, and complicated separation processes. Herein, we propose a novel and general approach to convert a series of spent LiNi1−x−yCoxMnyO2 (NCM) cathodes into Ni–Co–Mn hydroxide (NCM-OH) catalysts for the oxygen evolution reaction (OER) using deep eutectic solvents to extract valuable metals, followed by an in situ precipitation process using oxalic acid and a final self-templating process in an alkaline solution. The NCM-OH catalyst obtained from the spent LiNi0.33Co0.33Mn0.33O2 cathode is found to possess a nanoflake-assembled microrod structure with a large surface area (385.8 m2 g−1) and high porosity, which is endowed with abundant active sites and gas channels for the electrocatalytic reaction and mass transfer process. As a result, the NCM-OH catalyst for the oxygen evolution reaction exhibits a low overpotential of 273 mV at a current density of 10 mA cm−2 with a Tafel slope of 50.46 mV dec−1 as well as satisfactory stability. The effect of the composition on the catalytic performance is also evaluated by comparing different Ni1−x−yCoxMny hydroxide catalysts derived from commercially prevailing spent cathodes. This work provides a promising strategy for recycling spent LIBs into electrocatalyst materials for the OER. [ABSTRACT FROM AUTHOR]

Catalytic conversion of CO2 to produce fuels and chemicals is of great importance, and the electrocatalytic CO2 reduction reaction (eCO2RR) is considered one of the most attractive pathways. Multi-carbon (C2+) products are more desirable in many cases. To date, Cu-based catalysts, especially Cu+ sites, have been found to be the most efficient for the production of C2+ products. However, the retention of Cu+ sites at high cathodic potentials in the eCO2RR remains a great challenge. In this study, we designed and synthesized CuAl-oxide-derived (CuxAly-OD, x and y are the mass percentages of Cu and Al) catalysts for the eCO2RR to C2+ products. During the eCO2RR process, the predominant Cu species changed to Cu+, and the resulting electrocatalyst showed a high faradaic efficiency (FE) of 81.6% for C2+ products in alkaline aqueous solutions. Experimental studies showed that the presence of a stable amorphous Al2O3 phase stabilized the Cu+ sites by oxidation state control, leading to high selectivity and activity for the production of C2+ products. This work provides a strategy for improving the stability of Cu+ in the catalyst to enhance the performance of the eCO2RR. [ABSTRACT FROM AUTHOR]

The hydrogen oxidation reaction is an important process in anion exchange membrane fuel cells with alkaline solutions. The pursuit of efficient catalysts for alkaline hydrogen oxidation has attracted considerable attention. In this study, we present a precursor route for the synthesis of a new Ir-based catalyst (Ir–Ni/NiO/C), in which Ir nanoclusters were immobilized on the generated Ni/NiO/C support derived from a metal–organic framework. The small size of Ir clusters facilitates the exposure of catalytically active sites. The electronic interplay between the Ir nanoclusters and the Ni/NiO/C support optimized the hydrogen binding energy (HBE) and hydroxide binding energy (OHBE) on the surface, which is unattainable on the contrasting Ir–C, Ir–Ni/C, and Ir–NiO/C products. The optimized catalyst shows excellent mass activity for alkaline hydrogen oxidation, which is 3.1 times that of the Pt/C catalyst. This study presents a promising pathway for the development of advanced HOR catalysts. [ABSTRACT FROM AUTHOR]

A new atomically precise, single-ion catalyst (MWCNT-LPd) for ORR (oxygen reduction reaction), consisting of a Pd(II) complex of a tetraazacycloalkane anchored on multiwalled carbon nanotubes, has been prepared through a supramolecular approach ensuring a uniform distribution of catalytic centres on the support surface. A tetraazacycloalkane was chosen to saturate the four coordination sites of the typical square planar coordination geometry of Pd(II) with the aim of ascertaining whether the metal ion must have free coordination sites to function effectively in the ORR or whether, as predicted by quantum mechanical calculations, the catalytic effect can be originated from an interaction of O2 in the fifth coordinative position. The results clearly demonstrated that tetracoordination of Pd(II) does not influence its catalytic capacity in the ORR. Electrodes based on this catalyst show ORR performance very close to that of commercial Pt electrodes, despite the low Pd(II) content (1.72% by weight) in the catalyst. The onset potential (Eon) value and the half-wave potential (E1/2) of the catalyst are, respectively, only 53 mV and 24 mV less positive than those observed for the Pt electrode and direct conversion of O2 to H2O reaches 85.0%, compared to 89% of the Pt electrode. Furthermore, a preliminary galvanostatic test (simulating a working fuel cell at a fixed potential) showed that the catalyst maintains its efficiency continuing to produce water throughout the process (the average number of electrons exchanged over time per O2 molecule remains close to 4). [ABSTRACT FROM AUTHOR]

Au nanoparticle-embellished metal–organic framework UiO-66 on reduced graphene oxide (Au/UiO-66/rGO) was synthesized. Au/UiO-66/rGO displayed strong electrocatalytic activity for oxidation of glucose in alkaline solution at a remarkably low oxidation potential of +0.20 V vs. Ag/AgCl. Au nanoparticles played a paramount role in the catalytic oxidation of glucose at the electrode, while both rGO and UiO-66 can significantly enhance the current responses to glucose. The resulting non-enzymatic glucose sensor exhibited a wide range of linear response, high sensitivity and selectivity for the determination of glucose. The sensor was successfully applied for the determination of glucose in honey products. [ABSTRACT FROM AUTHOR]

Developing efficient and economical catalysts is essential for water splitting. The application of MOF catalysts in water splitting is limited by poor conductivity; however, the introduction of conductive TMS could enhance their activity. Herein, novel composite Fe9S10/Fe-MOF/NF-2 was constructed by introducing dendritic Fe9S10 onto the surface of a 2D ultrathin Fe-MOF. Composite catalysts elaborately utilize the structural and chemical advantages of MOF and TMS while improving the deficiencies of monomers through the combination. Owing to the optimal structure, the hybrid catalyst Fe9S10/Fe-MOF/NF-2 displayed better catalytic performance than bare Fe-MOFs and Fe9S10, with low overpotentials of 202 and 216 mV at 10 mA cm−2 in alkaline solution and simulated seawater, respectively. This work provides an innovative approach to modify MOFs as electrocatalysts for OER. [ABSTRACT FROM AUTHOR]

Controlling the ratio of metals in bimetallic organic frameworks (MOFs) can not only alter the structures but also tailor the properties of MOFs. Herein, we report a series of electrocatalytically active CoxNiy-based bimetallic MOFs that are synthesized with the 3,5-pyridinedicarboxylic acid (3,5-H2pdc) ligand (where x : y = 20 : 1, 15 : 1, 10 : 1, 5 : 1, 1 : 1, and 1 : 20) and a facile, scalable, low temperature synthetic route. The materials have one-dimensional (1D), rod-like microstructures with different aspect ratios. While they all electrocatalyze the oxygen evolution reaction (OER) in alkaline solution (1 M KOH), their electrocatalytic performances vary substantially depending on their compositions. The CoxNiy-MOF with an optimal ratio of x : y = 15 : 1 (Co15Ni1-MOF) electrocatalyzes the OER with the highest maximum current density (92.2 mA cm−2 at 1.75 V vs. RHE) and the smallest overpotential (384 mV vs. RHE at 10 mA cm−2) in a 1 M KOH solution. It is also stable under constant current application during the electrocatalytic OER. This work demonstrates the application of bimetallic MOFs that are synthesized following a simple, low temperature synthetic route for the OER and their tailorable electrocatalytic properties for the OER by varying the ratio of two metals and the synthetic conditions used to produce them. [ABSTRACT FROM AUTHOR]

We used sodium hydroxide-mediated approach and tannic acid etching to prepare hollow structured trimetallic MOF-derived CoFeNi/Z-P NC nanocomposites. Remarkably, the resulting CoFeNi/Z-P NC nanocomposites have large specific surface area and mesoporous structure, making their active sites more accessible and mass transfer more effective. More complex trimetallic components provide greater possibilities for further improving electrocatalytic performance. The CoFeNi/Z-P NC nanocomposites demonstrate notable enhancements for the OER, and 10 mA cm−2 current density is achieved at a low overpotential of 244 mV, with a low Tafel slope of 66.2 mV dec−1 and have good stability in alkaline solutions. In addition, as a cathode material for overall alkaline water splitting, CoFeNi/Z-P NC is better than RuO2 with longer cycling stability. [ABSTRACT FROM AUTHOR]

An NiMo alloy bonded with sulfur (NiMoS) exhibits enhanced surface affinity toward water and organic molecules, thereby enhancing electrocatalytic hydrogenation (ECH) reactions through synergistic effects. In industrial processes, indigo, an ancient dye employed in the denim industry, is typically chemically reduced using sodium dithionite. However, this process generates an excess of toxic sulfide, which heavily contaminates the environment. ECH is a sustainable alternative for indigo reduction due to its reduced reliance on chemicals and energy consumption. In this study, carbon-felt (CF)-supported NiMoS was synthesized in a two-step process. First, the NiMo alloy was electrodeposited onto the CF surface, followed by sulfidation in an oven at 600 °C. NiMoS exhibits a larger electrochemically active surface area and a smaller charge transfer resistance compared to pure Ni and NiMo. Furthermore, NiMoS demonstrates excellent thermodynamic and kinetic properties for water splitting in strong alkaline solutions (1.0 M KOH). Additionally, optimal reaction conditions for the ECH of indigo were explored. Under the conditions of a 1.0 M KOH hydroxide medium with 10% methanol (v/v), an indigo concentration of 5 g L−1, a reaction temperature of 70 °C, and a current density of 10 mA cm−2, NiMoS/CF achieved remarkable improvements in both conversion (99.2%) and Faraday efficiency (38.1%). The results of this experimental work offer valuable insights into the design and application of novel catalytic materials for the ECH of vat dyes, opening up new possibilities for sustainable and environmentally friendly processes in the dye industry. [ABSTRACT FROM AUTHOR]

It is crucial to develop cost-effective novel non-noble metal catalysts with high activity and durability for large-scale industrial hydrogen production via water splitting. Here, based on a facile powder metallurgy method, Ni3Fe intermetallic electrodes with porous structures and controllable phases have been designed and fabricated by sintering mixed Ni and Fe powders under an Ar atmosphere. The effects of sintering temperature on the morphology, porous structure and phase composition of the intermetallic were studied. The resultant Ni3Fe-900 intermetallic electrode exhibits promising HER activity in alkaline electrolytes with an overpotential of 112 mV to drive a current density of 10 mA cm−2. Additionally, the Ni3Fe-900 intermetallic electrode shows good alkali corrosion resistance and stability in the HER process at a current density as high as 500 mA cm−2 for 24 h with no significant changes of the surface morphology, porous structure and phases. The efficient HER performance of the Ni3Fe-900 electrode is attributed to the unique intrinsic activity of the intermetallic electrode, increased accessible active sites originating from the porous structure and accelerated charge transfer. This work provides new insights into the design of electrocatalysts for industrial large-scale hydrogen production by water splitting. [ABSTRACT FROM AUTHOR]

Conductive self-healing hydrogels (CSHs) are a class of materials that possess both electrical conductivity and the ability to autonomously repair mechanical damage. These materials have potential for use in various applications, such as flexible electronics, soft robotics, and biomedical devices. However, the majority of CSHs currently rely on doped conductive media to achieve conductivity, which often leads to dopant agglomeration and limits their mechanical properties. This study presents a facile approach for synthesizing a reduced graphene oxide/polyvinyl alcohol CSH hydrogel with superior dispersibility (PVA/Agar-rGO). We synthesize rGO directly in the polymer solution using an alkaline heat-reduction technique to improve its dispersibility, which results in superior conductivity. PVA/Agar-rGO is structured through a double network gel system of PVA and agarose, which also enables excellent self-healing properties. The PVA/Agar-rGO gel demonstrates potential as an ECG electrode, producing clear waveforms with good signal strength and low baseline noise. Additionally, it can function as a printable motion sensor, capable of resolving spatial signals in two directions. This work highlights a novel and promising approach for developing CSHs with potential biomedical and wearable electronics applications. [ABSTRACT FROM AUTHOR]

To achieve sustainable economic growth, it is essential to have a resource recycling system that uses energy and resources efficiently, eliminates waste, and maximizes their value. In particular, efficient recovery and recycling technology for scarce resources is extremely important because it leads to a stable supply of resources, environmental conservation, and reduction of mining energy. In this study, we demonstrate the one-pot and selective recovery of platinum (Pt) ions from aqueous media containing various coexisting ions using a two-dimensional silicon material. Specifically, Pt ions dissolved in artificial seawater were recovered using layered polysilane (SiH)n (LpSi), which is a stacking of hydrogen-terminated monatomic silicon layers. Hydrosilyl groups (≡Si–H) in LpSi selectively reduced Pt ions to form Pt nanoparticles (Pt-NPs) on LpSi with a particle size less than 200 nm. The selective recovery of Pt ions using LpSi is effective even for low concentrations of Pt ions around 10 ppm, and Pt-NPs with sizes of less than 1 nm were recovered on LpSi. The formed Pt-NPs can be isolated from LpSi by simple treatment with an alkaline solution. Moreover, the resulting Pt-NP-loaded LpSi catalysed the hydrogen evolution reaction in water splitting as an electrocatalyst, and hydrogen evolution proceeded quantitatively for the supplied charges. [ABSTRACT FROM AUTHOR]

Developing low-cost and highly efficient electrocatalysts for the hydrogen evolution reaction (HER) has stimulated extensive interest. Molybdenum carbide materials have been proposed as promising alternatives to noble platinum-based catalysts due to their earth abundance and tunable physicochemical characteristics. Here, we report Mo2C@NC/Mo2C hollow microspheres composed of a β-Mo2C core and small β-Mo2C particles embedded within a nitrogen-doped carbon shell and prepared using guanosine and hexaammonium molybdate as precursors via a hydrothermal self-assembly process, which results in outstanding catalytic activity and fast kinetics in hydrogen evolution in both acidic and alkaline solutions. The significant activity improvement of Mo2C@NC/Mo2C can be attributed to the large ratio of exposed active sites and abundant interfacial structures. This work provides a new template-free strategy for the design of a highly active Mo2C@NC/Mo2C hollow microsphere HER catalyst. [ABSTRACT FROM AUTHOR]

As a non-noble metal material, molybdenum carbide is considered to be an electrocatalyst with the most potential for the hydrogen evolution reaction (HER) due to its similar electron structure to platinum. However, its high preparation temperature easily leads to aggregations of nanoparticles (NPs) that affect the properties of Mo2C. For this purpose, we synthesized ultrafine molybdenum carbide anchored on nanocarbon (MCC) by designing an Mo-precursor to engineer micro/nanostructures. The results show that as-prepared MCC materials consist of 3D laminated 2D lamellar structures that are self-assembled from Mo2C NPs anchored on nanocarbon. Electrocatalytic tests indicate that the 3D/2D MCC materials exhibit excellent activity and stability in alkaline solution. Notably, a low overpotential of 123 mV is achieved to drive a current density of 10 mA cm−2 for HER, which implies the 3D/2D structures are conducive to molecules accessing active sites, transport and diffusion, and this structural MCC has promising application as an alternative non-noble metal electrocatalyst for hydrogen evolution and other catalysis. [ABSTRACT FROM AUTHOR]

Herein, three new coordination polymers (CPs), namely {Ni (4,4′-abpt)(2,5-fdca)H2O]n (1), [Co(4,4′-abpt)(2,5-fdca)H2O]n (2) and [Co(4,4′-abpt)(1,3-abc)]n (3) {4,4′-abpt = 3,5-di-4-pyridinyl-4H-1,2,4-triazol-4-amine, 2,5-fdca2− (the fully deprotonated forms of 2,5-furandicarboxylic acid), 1,3-abc2− (the fully deprotonated forms of 1,3-adamantanedicarboxylic acid)} were synthesized under solvothermal conditions and were characterized by elemental analysis, thermogravimetric analysis, powder X-ray diffraction, and single crystal X-ray diffraction (1 and 3) techniques. Structural analyses revealed that 1 is a two-dimensional structure with quadrilateral holes, while 3 is a two-dimensional rhombus network configuration with a binuclear metal center. Three as-prepared compounds exhibited efficient photocatalytic performance for the degradation of organic dyes of crystal violet (CV), methylene blue (MB), and rhodamine B (Rh-B) under UV irradiation, among which, 1 exhibited the best photocatalytic activity with a percentage degradation of more than 96% for the three dyes in 30 min. In addition, in the free radical capture experiment involving 3, it was found that both, the hydroxyl radical OH˙ and superoxide radical (˙O2−) were involved in the degradation process of dyes, among which, the OH˙ radical is the main species to trigger the photocatalytic degradation experiment. Finally, the electrocatalytic performance of the catalysts was investigated in 1 M alkaline KOH solution, and the results showed that all three catalysts had certain electrocatalytic performance, and the catalytic performance of 1 was slightly better than that of 2 and 3. It exhibited a low overpotential of 367 mV at a current density of mA cm−2. [ABSTRACT FROM AUTHOR]

It is of great significance for sustainable development to produce degradable, thiol–ene networks obtained from bio-based monomers using environment-friendly processes. Hence, we have prepared tunable and degradable thiol–ene crosslinked networks from renewable vanillin and multifunctional thiols. Vanillin was converted into an α,ω-diene monomer (1a) with degradable ester group via Williamson and Tishchenko reactions. UV-thermally induced thiol–ene click polymerizations between 1a and thiols with various functionalities were performed to prepare thiol–ene networks. 1,2-Ethanedithiol and 2,4,6,8-tetramethyl-2,4,6,8-tetravinylcyclotetrasiloxane were also incorporated into the networks to further regulate their properties. The curing behaviours were studied by FT-IR and DSC to determine the optimal curing conditions. The thermomechanical, thermal and mechanical characteristics of the networks were investigated by DMA, DSC, TGA, and tensile strength tests to understand the influence of different crosslinkers on the material's properties. By varying the amount of co-monomer, the networks exhibited glass transition temperature, tensile strength, and elongations at break in the ranges of 14.5–43.3 °C, 2.6–24.8 MPa, and 29.1–510.2%, respectively. All the thiol–ene networks had good transparency with transmittance between 85 and 90% at 600 nm. Moreover, the networks could be degraded in mild alkaline aqueous solution owing to their inherent ester groups. [ABSTRACT FROM AUTHOR]

As the most abundant natural aromatic polymer on the Earth, lignin is expected to replace fossil resources for the preparation of high-performance thermosetting polymers. Numerous studies have been devoted to utilizing lignin through depolymerization and chemical modification; nevertheless, the green and facile valorization of lignin to high value products is still a challenge. Herein, we developed a straightforward approach to directly use lignin to prepare thermosetting polymers combining high performance and excellent degradability. In a green acetone–water–acetic acid component solvent system, lignin-based thermosets were facilely prepared via cross-linking reactions between lignin and glycidoxypropyltrimethoxysilane (KH560). The thermosets exhibited outstanding thermal and mechanical properties with a glass transition temperature of ∼214 °C, a tensile strength of ∼45 MPa and a Young's modulus of ∼2274 MPa, and these properties can be easily manipulated by adjusting the ratio of lignin to KH560. The presence of Si–O–C bonds and ester bonds in the network structure imparts excellent degradability to the thermosets in alkaline aqueous solution. This work provides a green and facile strategy to directly integrate lignin into cross-linked networks, which discloses a new idea for the valorization of lignin to value-added materials. [ABSTRACT FROM AUTHOR]

The excellent motion performance of gallium-based liquid metals (LMs) upon the application of a modest electric field has provided a new opportunity for the development of autonomous soft robots. However, the locomotion of LMs often appears in an alkaline solution, which hampers the application under other different conditions. In this work, a novel robot arm is designed to transfer the motion of the LM from an alkaline solution in a synchronous drive mode. The liquid metal droplet (LMD) at the bottom of the robot arm is actuated using a DC voltage to provide the driving force for the system. By introducing an end effector at the center of the robot arm, the synchronous motion of the system is replicated and can be applied to different situations. The theoretical understanding of continuous electrowetting (CEW) at the LM interface is explained, and then the motion performance of the robot arm against the function of the applied voltage and driving direction is investigated. Moreover, several applications using this robot arm, such as pattern drawing, cargo transportation, and drug concentration detection, are demonstrated. The presented robot arm has the potential to observably expand the application fields of the LM. [ABSTRACT FROM AUTHOR]

Lignin nanoparticles have emerged during the past decade as well-defined and renewable nanomaterials for fundamental and applied research. However, the presently known methods for the preparation of lignin nanoparticles rely on the use of organic solvents and energy intensive water evaporation processes. Here we present organic solvent-free production of spherical lignin nanoparticles by neutralization of alkaline solution of poorly water-soluble lignins in the presence of sodium lignosulfonate. We show that by combining these two predominant technical lignins it is possible to achieve colloidally stable lignin nanoparticle dispersions at concentrations exceeding 30 wt%. We further demonstrate versatility of the process by using ethanol organosolv lignin, soda lignin, and lignosulfonates from different sources. The lignin nanoparticle dispersions exhibit shear-thinning behaviour and undergo gelation within well-defined pH and concentration regions. Such flowable lignin dispersions mark a breaktrough towards scalable processing of lignin towards sustainable bio-based chemicals and materials. [ABSTRACT FROM AUTHOR]

Developing high-performance and earth-abundant electrocatalysts for hydrogen production by electrolysis of freshwater/seawater is desirable but remains a huge challenge, especially in seawater solution. Herein, we report an efficient catalyst for a cathode consisting of three-dimensional standing arrays of Mo-Ni2P/CC nanosheets uniformly grown on carbon cloth, in which the Mo doping improved the HER properties of Ni2P by providing applicable morphology, electronic properties and active sites. It is found that the as-obtained catalyst shows superior HER activity with a low overpotential of 113 and 154 mV at 10 mA cm−2 in 1 M KOH and simulated alkaline seawater solution, respectively. Moreover, the Mo–Ni2P/CC catalyst exhibits favorable stability in 5000 CV cycles in 1 M KOH and reasonable stability in a 20 h stability test in alkaline, simulated seawater and alkaline seawater solution. This work may provide a feasible insight into the construction and development of high-efficiency HER electrocatalysts for freshwater/seawater electrolysis. [ABSTRACT FROM AUTHOR]

At present, the electrocatalytic hydrogen evolution reaction (HER) has been widely studied in the field of energy and resource conversion. Herein, a metal-free sulfur-containing covalent organic framework material (JLNU-300) was designed and synthesized using thieno[3,2-b]thiophene-2,5-dicarboxaldehyde (TTDC) as an efficient electrocatalyst for the hydrogen evolution reaction in alkaline solution. The test analysis results showed that JLNU-300 had high crystallinity and specific surface area (298.99 m2 g−1). In addition, the material has high electrocatalytic hydrogen evolution reaction (HER) activity, with an overpotential value of 290 mV and a Tafel slope of 99 mv dec−1 at a current density of 10 mA cm−2. The introduction of thiophene groups effectively changed the electronic structure and chemical properties of the COF framework, and the high crystallinity and specific surface area of the COF itself increased the effective contact area between reactants and active points, thus promoting the HER process. The results show that the reasonable structure design of COFs can further promote their wide application in the field of electrocatalysis. [ABSTRACT FROM AUTHOR]

Aqueous two-phase system (ATPS) extraction combined with a natural deep eutectic solvent (NADES) is an environmentally friendly separation process. In this work, ATPSs were constructed for the first time using NADESs, inorganic salts, and water to extract gold thiosulfate from alkaline solutions. The crucial parameters were optimized, including the types of NADESs and salts, equilibrium pH, contact time, and the initial concentration of Au(I). Thermodynamics studies showed that Au(S2O3)23− was effectively extracted into a NADES-rich phase, and this was mainly driven by an increase in entropy. Studies on the extraction mechanism indicated that the anion Au(S2O3)23− replaces the anion Cl− in NADES molecules to generate stable ion pairs with N+ through electrostatic interaction; simultaneously, new hydrogen bonds form with the acidic component. Also, amorphous MoS2 was used directly for the photocatalytic reduction of gold in the NADES-rich phase. The results showed that MoS2 can be used for efficient recovery of Au(I) and it simultaneously regenerates the NADES without destroying the structure of the extractant. Finally, a continuous cyclic experimental model is constructed. After three cycles, the extraction rate of Au(S2O3)23− by NADES–ATPS is slightly reduced from 96.2% to 93.0%, and the reduction rate of Au(S2O3)23− by MoS2 is decreased from 100.0% to 95.0%; this indicates that NADES–ATPS had excellent cycling performance. The strategy of coupling NADES–ATPSs with photocatalytic reduction with amorphous MoS2 to recover gold from thiosulfate solution is expected to contribute to the sustainable and green industrial processes of gold. [ABSTRACT FROM AUTHOR]

A novel two-dimensional Co-MOF material {[Co(dptz)2(oba)2]·(DMF)2}n is prepared using mixed organic ligands, which exhibits both OER (oxygen evolution reaction) and HER (hydrogen evolution reaction) catalytic performance. The integration of an Fe dopant and amorphous interface into Co-MOF to improving the electrocatalytic performance of pristine MOFs (metal–organic frameworks) is demonstrated and the origin of the remarkable electrocatalytic performance of the catalyst is elucidated. The comprehensive characterization data of Fe@Co-MOFs illustrate that there is a crystallinity transition during the doping of Co-MOF, which increases the electron transfer rate of the material and ensures increased exposure of the ligand unsaturated active site on the surface, and modulates the electronic structure of the Co center in a synergistic manner. As a result, the optimized catalytic Fe@Co-MOF-3 with an amorphous structure exhibits outstanding electrocatalytic performance for the OER, with only 248 mV at a current density of 50 mA cm−2 and excellent stability after 11 h of testing in alkaline solution. Not only that, the HER was achieved with a low overpotential of 150 mV at 10 mA cm−2. The present work indicates that the as-synthesized Co-MOF and Fe@Co-MOFs offer prospects in developing electrocatalysts for water splitting. [ABSTRACT FROM AUTHOR]

Preparing low-cost and highly efficient electrocatalysts for the hydrogen evolution reaction using a simple strategy still faces challenges. In this work, we proposed a facile phosphating process to successfully transform CoFe-BTC (BTC = 1,3,5-benzenetricarboxylate) precursors into carbon-incorporated bimetallic phosphide (CoFe-P/C) nanospheres. Due to the synergistic effect between bimetals and uniformly covered carbon shells outside, the as-synthesized porous bimetallic phosphide nanospheres exhibit superior HER activity, enhanced kinetics, and excellent cycle durability in both acidic and alkaline solutions. The optimized material could afford a current density of 10 mA cm−2 with overpotentials of 138 and 193 mV for the HER in acidic and alkaline solutions, respectively. Meanwhile, it delivered small Tafel slopes of 84 and 78 mV dec−1 for the HER in 0.5 M H2SO4 and 1.0 M KOH, respectively. Moreover, an assembled alkaline electrolyzer enabled a low voltage of 1.62 V to drive a current density of 10 mA cm−2 for overall water splitting. DFT calculations indicate that the CoP–Fe2P composite is supposed to exhibit better HER performance than each component, revealing the vital role of the interfacial site in catalyzing the HER. [ABSTRACT FROM AUTHOR]

Graphene oxide (GO) membranes with doorman characteristic, tunable nanochannel microenvironment and high interfacial adhesion were fabricated. Herein, polyethyleneimine (PEI) molecules were selected for bridging, reducing and intercalating the GO nanosheets in GO-PEI membranes. Moreover, the optimal amount of PEI molecules facilitated the expansion and alignment of the transfer channels with the spacing of 0.93 nm to 1.52 nm. In particular, the GO nanosheets undertook deoxidations twice under the action of a strong alkaline NaOH solution and PEI molecules, which led to more structural defects and certain wrinkles for providing extra water transfer channels. On this basis, PEI molecules exhibited doorman characteristics at different pH values. As the state-of-the-art technology, the nano-scratch tests showed that the interfacial adhesion of the GO-PEI membrane (18.62 μN) bridged by PEI was nearly 9 times stronger than that of the pure GO membrane (2.15 μN). [ABSTRACT FROM AUTHOR]

Four new functionalized Ni(II) dithiocarbamate complexes of the formula [Ni(L x )2] (1–4) (L1 = N-methylthiophene-N-3-pyridylmethyl dithiocarbamate, L2 = N-methylthiophene-N-4-pyridylmethyl dithiocarbamate, L3 = N-benzyl-N-3-pyridylmethyl dithiocarbamate, and L4 = N-benzyl-N-4-pyridylmethyl dithiocarbamate) have been synthesized and characterized by IR, UV–vis, and 1H and 13C{1H} NMR spectroscopic techniques. The solid-state structure of complex 1 has also been determined by single crystal X-ray crystallography. Single crystal X-ray analysis revealed a monomeric centrosymmetric structure for complex 1 in which two dithiocarbamate ligands are bonded to the Ni(II) metal ion in a S^S chelating mode resulting in a square planar geometry around the nickel center. These complexes are immobilized on activated carbon cloth (CC) and their electrocatalytic performances for the oxygen evolution reaction (OER) have been investigated in aqueous alkaline solution. All the complexes act as pre-catalysts for the OER and undergo electrochemical anodic activation to form Ni(O)OH active catalysts. Spectroscopic and electrochemical characterization revealed the existence of the interface of molecular complex/Ni(O)OH, which acts as the real catalyst for the OER. The active catalyst obtained from complex 2 showed the best OER activity achieving 10 mA cm−2 current density at an overpotential of 330 mV in 1.0 M aqueous KOH solution. [ABSTRACT FROM AUTHOR]

Developing non-noble metal-based electrocatalysts with high catalytic activity is an urgent task for overall electrocatalytic water decomposition. In this study, carbon-incorporated porous honeycomb NiCoFe phosphide (labelled NiCoFeP/C) was successfully developed from a metal–organic framework (MOF) precursor for the first time. Benefitting from a unique structure and compositional advantages, NiCoFeP/C exhibits excellent bifunctional electrocatalytic activity for the oxygen evolution reaction/hydrogen evolution reaction (OER/HER) in alkaline solution, showing low OER and HER overpotentials of 270 and 149 mV at 10 mA cm−2, respectively. This work successfully developed a MOF-derived novel multi-component transition metal phosphide with a unique structure, which shed some light on the development of promising catalysts for the OER/HER. [ABSTRACT FROM AUTHOR]

Engineering a porous membrane with an amphiphilic zwitterionic surface is effective for the improvement of the permeability and antifouling performance of sterilization filtration. Here, we prepared a zwitterionic EVOH nanofibrous membrane (NFM) through nanofiber suspension coating (nanofiber coverage density of 6 g m−2), alkaline solution activation and a simple one-step addition reaction with isocyanate-sulfopropylbetaine (NCO-SB). As indicated by experimental analysis, the nanofibrous membrane possesses a thin nanofiber active layer (about 8 μm), narrow pore size distribution and high hydrophilicity, which is beneficial for the absolute interception of Escherichia coli, Staphylococcus aureus and Brevundimonas diminuta as well as a relatively high and stable permeability (11032.3 L m−2 h−1, 0.2 MPa). The dynamic fouling experiments and protein adsorption experiments illustrated that the modified membrane exhibited strong antifouling properties and excellent permeation recovery abilities mainly due to the grafting of zwitterions on the membrane surface. Specifically, the higher flux and flux recovery ratio (65.1%) after three sequential cross-flow filtration cycles were still obtained compared to the nascent NFM. The ameliorated physical–chemical performance of the membrane can be attributed to the synergistic effect between the uniformly distributed small pore size and the zwitterionic surface of the modified NFM. This work provides a valuable approach for manufacturing high-performance sterilization membranes in bio-separation applications. [ABSTRACT FROM AUTHOR]

The main objective of the current work is to develop a luminol-based chemiluminescence (CL) system with the help of a reactive functional polymer of azothiacalix[4]arene-modified carboxymethyl cellulose (ACCMC) for the trace analysis of copper(II) ions. ACCMC was synthesized by linking water-soluble deoxy-azido carboxymethyl cellulose to monopropargyl-tetradiazothiacalix[4]arene through a [2+3] dipolar cycloaddition click reaction for the first time. The obtained materials were characterized by FT-IR, 1H, and 13C NMR spectroscopies, TGA, and FE-SEM. Under optimal conditions, AC and ACCMC quenched the CL intensity of luminol and 1,2-dihydro-3,6-pyridazinedione through hydrogen peroxide-assisted oxidation in an alkaline solution, which was evaluated for the detection of copper(II) ions based on the enhancement effect of Cu(II). According to the CL spectra in the presence of Cu2+, the CL intensities of the luminol-H2O2, luminol-AC-H2O2, and luminol-ACCMC-H2O2 increased to about 2, 6.5, and 3-fold, respectively. The introduced systems provide luminescence in a wide range, with the advantage of analyzing or measuring analytes in the CL system. The prepared AC and ACCMC exhibited suitable figures of merit for copper(II) with linear calibration curves in the low levels of copper(II) ions ranging from 0.01 to 100 μM, with detection limits of 1.36 nM and 2.2 nM, and relative standard deviations (RSDs) of 5.41% and 4.82% in determining 0.1 μM Cu2+ using luminol-AC-H2O2 and luminol-ACCMC-H2O2 systems, respectively. The recovery values were in the range of 92–112% and RSDs were less than 5.3%. [ABSTRACT FROM AUTHOR]

Water electrolysis is one of the most capable processes for supplying clean fuel. Herein, two novel ionic Ru(II)–Fe(II) complexes, [Ru(tmphen)3]2[Fe(CN)6] and [Ru(phen)3][Fe(CN)5(NO)], where tmphen = 3,4,7,8-tetramethyl-1,10-phenanthroline and phen = 1,10-phenanthroline, were synthesized and characterized by UV-Vis spectroscopy, elemental analysis, FT-IR, and single-crystal X-ray structural analysis. By thermally decomposing the [Ru(tmphen)3]2[Fe(CN)6] complex at 600 °C for 4 h, a heterostructured RuO2–Fe2O3 nanocomposite was fabricated through a facile one-pot treatment and then characterized by FT-IR, XRD, FT-Raman, UV-Vis (DRS), ICP-OES, FE-SEM, TEM, TGA/DTG, BET, and XPS analyses, which revealed the formation of highly crystalline RuO2–Fe2O3 nanoparticles with an average size of 8–12 nm. The prepared nanocomposite was an efficient heterostructured electrocatalyst for performing water-splitting redox reaction processes, including hydrogen and oxygen evolution reactions (HER and OER) in alkaline solutions. In this regard, RuO2 and Fe2O3 samples were also prepared through thermal decomposition of [Ru(tmphen)3](NO3)2 and K4[Fe(CN)6] precursors, respectively, as control experiments to compare their HER and OER electrocatalytic activity with that of the RuO2–Fe2O3 nanocomposite. Specifically, the RuO2–Fe2O3 nanocomposite exhibited significant electrocatalytic performance, generating 10 mA cm−2 current density at −148 and 292 mV overpotentials, and the Tafel slope results from fitting the LSV curves to the Tafel equation were −43 and 56.08 mV dec−1 for the HER and OER, respectively. Therefore, the heterostructured RuO2–Fe2O3 nanocomposite can be viewed as a bi-functional electrocatalyst for HER and OER because it exploits the synergistic effects of heterostructures and active sites at its interface. [ABSTRACT FROM AUTHOR]

Vanadium and cesium were recovered from spent sulfuric acid catalysts, generated during a sulfuric acid manufacturing process, by an environmentally friendly hydrometallurgical process. This process consisted of water leaching to recover valuable metals, a solvent extraction process to recover vanadium selectively, and a precipitation process to recover cesium selectively. More than 99% of vanadium was leached from the spent sulfuric acid catalysts using water only at room temperature. The leachate obtained was employed in the solvent extraction process to recover vanadium selectively. The solvent extraction experiments were conducted by varying the concentration of the extractant, the equilibrium pH, the organic/aqueous (O/A) phase ratio, and the saponification ratio using di-2-ethylhexyl phosphoric acid (D2EHPA). As a result, more than 99% of the vanadium was separated from cesium in the leachate in three stages of counter-current extraction at an O/A ratio of 1.5. However, impurities such as iron and titanium were found to be present in the loaded organic phase. Therefore, vanadium was stripped selectively from the latter using an alkaline solution. The concentration of the alkaline solution and the O/A phase ratio affected emulsion formation during the stripping process. Cesium present in the raffinate was precipitated as a cesium alum by adding aluminum sulfate, with a precipitation efficiency of more than 98% and with greater than 99% purity. The process developed in this study provides an efficient method for recovering vanadium and cesium from spent sulfuric acid catalysts using an eco-friendly and economical metallurgical process. [ABSTRACT FROM AUTHOR]

The design and synthesis of hybrid core–shell catalysts is of great significance for obtaining an excellent performance of hydrogen evolution reaction (HER). However, it remains a challenge to explore the exact active sites and research the catalytic mechanism for HER. Here, a series of Ni3S2@MOOH/NF (M = Fe, Ni, Cu, Mn and Co) hybrid structures is firstly in-site grown on Ni foam by the typical hydrothermal and electrodeposition methods. The Ni3S2@NiOOH/NF catalyst with a core–shell structure exhibits a relatively low overpotential of 79 mV for HER at a current density of 10 mA cm−2, which is one of the best catalytic activities reported so far. Moreover, it also shows good stability in the long-term durability test. Various spectral analysis and density functional theory calculations demonstrate that NiOOH is favorable for the adsorption of water molecules, and the S atom at the interface between Ni3S2 and NiOOH is favorable for the adsorption of H intermediates, which strongly accelerates the HER process in alkaline solution. This work provides a general strategy for the synthesis of electrocatalytic materials, which can be used for efficient electrocatalytic water splitting reactions. [ABSTRACT FROM AUTHOR]

Research on highly efficient nitrogen and sulfur co-doped carbon materials is crucial for the development of Fe-based non-noble metal electrocatalysts (NNMEs) as alternatives to platinum-group metal-based electrocatalysts for the oxygen reduction reaction (ORR) in fuel cells. In this work, complexes were derived from iron salt and biomass ligands, subsequently mixed with active carbon nanoparticles (NPs) and pyrolyzed at 800 °C to obtain the resulting electrocatalysts Fe/NSC (800) and Fe/NC (800). Through screening the synthetic parameters, it was found that the N and S co-decorated Fe-based electrocatalyst of Fe/NSC (800) displays better ORR performances in terms of the onset potential (Eonset) and the half-wave potential (E1/2) than those of the Fe-free electrocatalyst of NSC (800) and the N-doped electrocatalyst of Fe/NC (800). The improved ORR activity can be mainly ascribed to the FeN4 active sites, as well as the additional S-doping within the carbon matrixes. Additionally, Fe/NSC (800) displays good durability superior to that of 20 wt% Pt/C in 0.1 M KOH solution. This synthetic approach is beneficial for the synthesis of NNMEs with biomass ligands for boosting the ORR performances in an alkaline solution. [ABSTRACT FROM AUTHOR]

Studying the speciation of Pu(IV) in very alkaline and silicate ion rich reactive media allowed identification of the formation of plutonium(IV)-silicate colloidal suspensions which were stable for months. These colloids were stabilized in aqueous solution for pH > 13 and for concentrations around 10−2 mol L−1. Successive filtration processes allowed evaluation of their size, which was found to be smaller than 6 nm. Their structural characterization by XAS evidenced that their structure was similar to those identified for the other tetravalent actinide-silicate colloidal systems like thorium, uranium and neptunium. Their formation could explain the increase of plutonium solubility usually observed in alkaline silicate-rich solutions and could affect the plutonium mobility as a result in contaminated sites or in other environmental permeable media. [ABSTRACT FROM AUTHOR]

Replacing the sluggish oxygen evolution reaction (OER) by the sulfide electro-oxidation reaction (SOR) could be a promising way to decrease the energy consumption for the hydrogen evolution reaction (HER) and to treat the waste H2S simultaneously. However, promoting the catalyst activity and stability in sulfide solution remains a great challenge. In this work, a sulfur-tolerable bifunctional Cu2S micro-flake catalyst supported on nickel foam (Cu2S/NF) was fabricated for catalyzing the SOR-assisted electrochemical water splitting. The Cu2S/NF electrode exhibited good activity and stability for both the SOR (0.26 V vs. RHE) and HER (−0.18 V vs. RHE) at 10 mA cm−2. The anodic product obeyed the chain-growing mechanism of HS− → Sn2− (polysulfides) in alkaline solutions. Moreover, for a two-electrode SOR-assisted water splitting system, a current density of 100 mA cm−2 was successfully obtained at a cell voltage of only 0.64 V. Compared to the normal water splitting (OER + HER), our system (SOR + HER) can save 74% energy consumption when producing the same amount of H2, close to the theoretic energy-saving value of 86%. This work proposed a new way for not only generating highly efficient hydrogen but also reusing the toxic sulfide waste, which shed light on the low-cost and scaling-up hydrogen production using waste resources. [ABSTRACT FROM AUTHOR]

The design and development of robust and environmentally friendly electrocatalytic materials are of great significance to the hydrogen production industry for the electrolysis of water. A series of P-Co3O4@NiCo-LDH/NF materials was firstly successfully synthesized by a hydrothermal method, high temperature calcination and an electrochemical deposition approach when sodium hypophosphite was used as the source of P and Ni(NO3)2·6H2O as the source of nickel and introduced cobalt at the same time. The structure, composition, morphology and electrochemical performance of the P-Co3O4@NiCo-LDH/NF electrocatalytic material were determined by X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy and electrochemical performance testing. It is worth noting that the P-Co3O4@NiCo-LDH-2/NF material presents excellent hydrogen evolution reaction performance in 1 M KOH alkaline solution. It only needs an overpotential of 181 mV to drive a current density of 100 mA cm−2, which is one of the best catalytic activities reported so far. The experimental results and theoretical calculations demonstrate that the electrocatalytic activity of the P-Co3O4@NiCo-LDH-2/NF material is attributed to the faster electron transfer rate, exposure of more active sites, optimal water adsorption energy and better electrical conductivity. [ABSTRACT FROM AUTHOR]

Transition metal oxides with spinel structures prepared using the traditional method have defects, including a small specific surface area, large particle size and poor conductivity. These defects considerably limit their catalytic activity in oxygen evolution reactions (OERs). This study involves the preparation of manganese iron oxide modified using flaky cobalt phosphide. The obtained product exhibits good OER catalytic performance in a 1 M alkaline solution, which shows a low overpotential of 320 mV for the OER at 50 mA cm−2. Furthermore, modified manganese iron oxide exhibits a low Tafel slope of 65.58 mVdec−1. After the introduction of flaky cobalt phosphide, the increase of the active area and conductivity of manganese iron oxide significantly improves the OER performance of the sample. The OER performance of transition metal oxides with spinel structures can be further improved using the proposed method. [ABSTRACT FROM AUTHOR]