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Metal–organic frameworks (MOFs) derived nanostructures receive immense research focus due to its high porosity, conductivity, and structural tailrolability features. In this work, porous Zeolitic Imidazole Framework‐67 (ZIF‐67) to synthesize cobalt phosphide/carbon composite (ZCoPC) that serves as a positive electrode is utilized. Furthermore, porous and conductive office paper derived carbon (OPC) are utilized as a negative electrode to make a hybrid system. The metalloid characteristics, high conductivity, and good porosity of ZCoPC material makes it a high‐performance battery like electrode. ZCoPC electrode achieves maximum specific capacity of 192.6 mAh g−1 at 1 A g−1 using 1 m potassium hydroxide (KOH) electrolyte. Furthermore, surface and diffusion charge participation investigation are also undergone for ZCoPC electrode that helps in determining the actual charge dynamics occurring in the electrode. In addition, a supercapattery device is assembled using ZCoPC as battery electrode and OPC as supercapacitor electrode. The as fabricated OPC//ZCoPC hybrid supercapattery device delivers extraordinary energy density of 31.6 Wh kg−1 with a power density of 700 W kg−1 and also a long cycle life of 92.3% even after 10,000 charge–discharge cycles. Hence, these outcomes demonstrate that the synergy of porous MOF derived metal phosphide and OPC electrodes are beneficial for supercapattery devices. [ABSTRACT FROM AUTHOR]

Developing low‐cost and effective electrocatalysts for the hydrogen evolution reaction (HER) to replace Pt‐group metals is a continuous challenge. Recently, transition metal phosphides have received increasing attention owing to their high intrinsic activity in catalyzing HER in acidic media. Herein, we reported a novel hybrid nanostructure MoP/Co2P anchored on carbon fiber paper (CFP) (MoP/Co2P/CFP) which was achieved by a facile hydrothermal approach to obtain Co(CO3)0.35Cl0.20(OH)1.10 nanowires array (NA)/CFP, followed by deposition of MoO2 nanoparticles via chemical vapor deposition (CVD) in the presence of MoO3 and a subsequent in situ phosphorization process. It was worth noting that the catalyst exhibited higher catalytic activity for HER in 0.5 M H2SO4 solution, which afforded an overpotential of 140 mV at a current density of 10 mA cm−2, a Tafel slope of 80 mV dec−1, an exchange current density of 0.153 mA cm−2 and a high electrochemical double‐layer capacitance (Cdl) of 48.2 mF cm−2. Moreover, it also exhibited superior stability and durability in long‐term durability test. [ABSTRACT FROM AUTHOR]

• The carbon paper as the substrate was used to synthesize CEs in DSSC for the first time. • The CoP 3 /CP electrode exhibited low charge transfer resistance. • The DSSC with CoP 3 /CP electrode achieved the photoelectric conversion efficiency of 6.84%. The cobalt triphosphide (CoP 3) was grew on carbon paper (CP) by using a hydrothermal method and served as counter electrode (CE) catalyst in dye-sensitized solar cells (DSSCs). The morphology of the CoP 3 /CP CE exhibits a regular fibrous structure, which provides a guarantee for its good electrochemical performance of the CE made from the cyclic voltammetry, Tafel test, etc. Various photoelectric performance tests also show that the DSSCs with CoP 3 /CP CE achieves good photoelectric conversion efficiency of 6.84% under 100 mW·cm−2 illumination, which can compare to that of the DSSC assembled with the Pt (6.79%) CE. Metal phosphides are rarely used as CEs in DSSCs, and they will have a good promising alternative to the Pt electrode in the future. [ABSTRACT FROM AUTHOR]

Abstract: This study proposes a conformal surface coating of conducting polymer for protecting 1D nanostructured electrode material, thereby enabling a free‐standing electrode without binder for sodium ion batteries. Here, polypyrrole (PPy), which is one of the representative conducting polymers, encapsulated cobalt phosphide (CoP) nanowires (NWs) grown on carbon paper (CP), finally realizes 1D core–shell CoP@PPy NWs/CP. The CoP core is connected to the PPy shell via strong chemical bonding, which can maintain a Co–PPy framework during charge/discharge. It also possesses bifunctional features that enhances the charge transfer and buffers the volume expansion. Consequently, 1D core–shell CoP@PPy NWs/CP demonstrates superb electrochemical performance, delivering a high areal capacity of 0.521 mA h cm−2 at 0.15 mA cm−2 after 100 cycles, and 0.443 mA h cm−2 at 1.5 mA cm−2 even after 1000 cycles. Even at a high current density of 3 mA cm−2, a significant areal discharge capacity reaching 0.285 mA h cm−2 is still maintained. The outstanding performance of the CoP@PPy NWs/CP free‐standing anode provides not only a novel insight into the modulated volume expansion of anode materials but also one of the most effective strategies for binder‐free and free‐standing electrodes with decent mechanical endurance for future secondary batteries. [ABSTRACT FROM AUTHOR]

The rapid growth of environment pressures and fast depletion of fossil fuels compel public to pay more attention on developing affordable and efficient catalysts for renewable energy production. Metal (Co, Fe, Ni, etc.) phosphide nanoparticles uniformly encapsulated in porous N,P-codoped nanofibrous carbon coated on carbon paper (MeP@NPC/CP) are prepared through one-pot carbonization-phosphorization strategy, which are potential for effective electrocatalytic water reduction/oxidation reactions. The well-designed self-supported structure and the abundant accessible active centers together contribute to the high electrocatalytic performance for hydrogen and oxygen evolution. Remarkably, an alkaline electrolyzer assembled from CoP@NPC/CP as cathode and anode can afford the current density of 10 mA cm −2 at the voltage of 1.67 V for overall water splitting in alkaline media with excellent stability. The easily prepared route with suitable structural and textural properties endows this self-supported materials with versatile function as abundant metal catalysts for realistic energy conversion and storage systems. [ABSTRACT FROM AUTHOR]

Graphitic carbon nitride (gCN) has shown great potential in photocatalysis. Developing suitable cocatalysts is a critical way to enhance gCN's photocatalytic performance. In this paper cobalt–nickel bimetallic phosphide (CoNiP) was used as a cocatalyst to modify gCN. A gCN/CoNiP composite was successfully prepared by a simple hydrothermal method. XRD, XPS, SEM, UV-vis DRS, and PL characterization studies showed that a Schottky junction-like structure was constructed between gCN and CoNiP, which intensified the visible light response, enhanced the charge transfer rate and prohibited the recombination of photogenerated carriers, thus significantly improving gCN photocatalytic activity. Under simulated sunlight, the removal efficiency of methylene blue (10 mg L−1) was 97.8% by 120 min of irradiation, 44.6% higher than that of gCN. The quenching experiment showed that ˙O2−, ˙OH and h+ were the main active species. Based on the above points, the possible mechanism of photocatalysis was deduced. [ABSTRACT FROM AUTHOR]

Abstract: To maximize the activity and durability of transition metal sulfides for water oxidation is still a great challenge. Herein, we developed a new cobalt phosphosulfide nanosheet on carbon fiber paper (CFP) substrate electrocatalyst (Co2−xSP/CFP) following a simple two‐step electrodeposition method. The cobalt sulfide nanosheets were first deposited onto CFP by cyclic voltammetry. Then, the surface structure and P/S ratio as well as the Co3+/Co2+ ratio of the phosphosulfide nanosheets were well tuned by regulating the cycling numbers of the phosphorous electrodeposition. Benefiting from the hierarchical structure, distinct phosphosulfide species, as well as a high Co3+ content derived from partial S substitution with P and nonstoichiometric phase, the as‐synthesized Co2−xSP/CFP exhibits remarkable activity with an overpotential of 279 mV at a current density of 10 mA cm−2, a low Tafel slope of 54 mV dec−1 and excellent long‐term stability towards OER (overpotential increase of only 4.7 % within 60 h). Structural analysis after stability test indicates that cobalt oxide/hydroxide species are formed on the surface, which contribute to the high performance and excellent durability for oxygen evolution. This provides a simple and facile approach to rationally design and synthesize transition metal phosphosulfides for advanced electrochemical application. [ABSTRACT FROM AUTHOR]

In this paper, a novel Pt/CoP/C photo-electro synergistic catalyst was successfully synthesized by a hydrothermal method combined with phosphorus doping treatment. The addition of Vulcan XC-72R is in favor of effectively preventing agglomeration of active catalytic sites, resulting in more uniform and smaller Pt and CoP nanoparticles. The as-obtained Pt/CoP/C shows excellent photo-electro catalytic performance for the HER with simulated solar light irradiation. The optimal hydrogen production is 5384.18 mmol h−1 g−1, which is obviously higher than that of the commercial catalyst (20 wt% Pt/C: 4608.52 mmol h−1 g−1). The research results show that introducing cobalt phosphide into the Pt catalyst can improve the electrocatalytic activity and stability for the HER; in particular, the existence of Co3O4 in Pt/CoP/C leads to an efficient photo-electro catalysis under irradiation, which significantly improves the catalytic activity of Pt. The results above provide a novel strategy for the rational design of cost-effective Pt-based composites towards a fast HER. [ABSTRACT FROM AUTHOR]

A stable and highly active core‐shell heterostructure electrocatalyst is essential for catalyzing oxygen evolution reaction (OER). Here, a dual‐trimetallic core‐shell heterostructure OER electrocatalyst that consists of a NiFeWS2 inner core and an amorphous NiFeW(OH)z outer shell is designed and synthesized using in situ electrochemical tuning. The electrochemical measurements of different as‐synthesized catalysts with a similar mass loading suggest that the core‐shell Ni0.66Fe0.17W0.17S2@amorphous NiFeW(OH)z nanosheets exhibit the highest overall performance compared with that of other bimetallic reference catalysts for the OER. Additionally, the nanosheet arrays were in situ grown on hydrophilic‐treated carbon paper to fabricate an integrated three‐dimensional electrode that affords a current density of 10 mA cm−2 at a small overpotential of 182 mV and a low Tafel slope of 35 mV decade−1 in basic media. The Faradaic efficiency of core‐shell Ni0.66Fe0.17W0.17S2@amorphous NiFeW(OH)z is as high as 99.5% for OER. The scanning electron microscope, transmission electron microscope, and X‐ray photoelectron spectroscopy analyses confirm that this electrode has excellent stability in morphology and elementary composition after long‐term electrochemical measurements. Importantly, density functional theory calculations further indicate that the core‐shell heterojunction increased the conductivity of the catalyst, optimized the adsorption energy of the OER intermediates, and improved the OER activity. This study provides a universal strategy for designing more active core‐shell structure electrocatalysts based on the rule of coordinated regulation between electronic transport and active sites. [ABSTRACT FROM AUTHOR]

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In this paper, the structural characteristics and catalytic mechanism for hydrogen evolution of ammonia borane of non-metal (N, S) doped CoP catalysts were studied in detail by density functional theory (DFT) calculations. Specifically, we first investigated the structure of the cobalt phosphide catalyzed ammonia borane models. In addition, based on the most stable structures, the mechanism of the hydrogen evolution reaction of ammonia borane catalyzed by three catalysts was studied, and four feasible reaction paths for the hydrogen evolution reaction of ammonia borane catalyzed by three catalysts were discussed. By comparing the activation energies of the control steps of different reaction paths, the optimal reaction paths for the hydrogen evolution of ammonia borane catalyzed by three different catalysts were determined. The catalytic activities of the three catalysts for the hydrogen evolution of ammonia borane were compared. We found that the N-doped catalyst was beneficial to improve the catalytic activity of CoP for the catalytic hydrogen evolution of ammonia borane, while the catalytic activity of S-doped CoP for the catalytic hydrogen evolution of ammonia borane is relatively weak. These results reveal the relationship between the physical properties of CoP (and its non-metal-doped variants) and their catalytic activity. Finally, these findings can be used to explain the underlying mechanism reported in previous experimental studies from a microscopic perspective. [ABSTRACT FROM AUTHOR]

Summary: The cost of platinum group metal (PGM) catalysts is one of the major obstacles in commercializing proton exchange membrane water electrolyzers (PEMWEs). The non‐PGM substituents are often more financially beneficial but low in activity and durability in the acidic environment. In this study, cobalt phosphide catalysts, which are promising non‐PGM alternatives for the hydrogen evolution reaction (HER) and have enhanced durability and single‐cell performance, were fabricated directly on carbon paper using the pulse electrodeposition method. As the dissolution potential (reported as ‐x vs saturated calomel electrode) of the pulse electrodeposition shifted in the positive direction, the P/Co ratio of the Co‐P‐x catalysts increased because of severe Co dissolution. Among the catalysts, Co‐P‐0.6, Co‐P‐0.5, and Co‐P‐0.4 (where the number indicates the negative dissolution potential) were rapidly degraded in acid, whereas Co‐P‐0.3, Co‐P‐0.2, and Co‐P‐0.1 showed high stability because of the relative amounts of CoP and Co2P phases. The acid‐dissolved Co‐P‐0.3 catalyst showed the best half‐cell performance (an overpotential of 143.85 mV at 10 mA/cm2) and durability, and the P‐Co and Coδ+ surface states are critical for its performance. Single‐cell tests using the Co‐P‐0.3 cathode revealed its remarkable performance of 1.89 A/cm2 at 2.0 Vcell, indicating its promise as a non‐PGM cathode material for PEMWEs. [ABSTRACT FROM AUTHOR]

Transition‐metal phosphides have stimulated great interest as catalysts to drive the hydrogen evolution reaction (HER), but their use as bifunctional catalytic electrodes that enable efficient neutral‐pH water splitting has rarely been achieved. Herein, we report the synthesis of ternary Ni0.1Co0.9P porous nanosheets onto conductive carbon fiber paper that can efficiently and robustly catalyze both the HER and water oxidation in 1 m phosphate buffer (PBS; pH 7) electrolyte under ambient conditions. A water electrolysis cell comprising the Ni0.1Co0.9P electrodes demonstrates remarkable activity and stability for the electrochemical splitting of neutral‐pH water. We attribute this performance to the new ternary Ni0.1Co0.9P structure with porous surfaces and favorable electronic states resulting from the synergistic interplay between nickel and cobalt. Ternary metal phosphides hold promise as efficient and low‐cost catalysts for neutral‐pH water splitting devices. Sheets and paper: Ternary Ni0.1Co0.9P porous nanosheets anchored onto conductive carbon fiber paper, can be used as a bifunctional catalytic material for driving both water reduction and oxidation reactions efficiently in neutral‐pH electrolyte under ambient conditions. [ABSTRACT FROM AUTHOR]

Transition metal phosphides (TMPs) have attracted extensive interest to catalyze the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER). However, the development of TMPs with high conductivity is a great challenge. Herein, we report hybrids of cobalt phosphide (CoP) and copper phosphide (CuP) strongly coupled with ZIF-67 derived carbon as bifunctional ORR/OER electrocatalysts (CoP/CuP@NC). The as-prepared CoP/CuP@NC catalysts exhibit delightful activity and stability toward the ORR (E1/2 = 0.86 V) and the OER (E10 = 1.61 V). Moreover, the assembled Zn-air battery exhibits a small charge-discharge voltage gap and excellent stability. These remarkable electrocatalytic capabilities stem from the combined impact of active CoP/CuP components and the structural framework derived from ZIF-derived materials. This work provides a meaningful strategy for constructing high-performance bifunctional electrocatalysts for commercial Zn-air batteries. [ABSTRACT FROM AUTHOR]

New heteroleptic dppe appended Co(III)-dithiocarbamate (dtc) complex cations with compositions [Co(S2CNEt2)2(dppe)](PF6) (Co-Et), [Co(S2CNPri2)2(dppe)](PF6) (Co-Pr) and [Co(S2CNBun2)2(dppe)](PF6) (Co-Bu) have been synthesized and characterized by microanalysis, spectroscopic methods and crystallographic analysis. The single crystal X-ray diffraction results indicated that in all three complexes, the coordination environment around Co(III) is distorted octahedral and Co(III) is coordinated to four sulfur centers of the two dtc ligands and the two phosphorus centers of the dppe ligand. These complexes serve as precursors to yield cobalt sulfide/cobalt phosphide nano-composites dCo-Et, dCo-Pr and dCo-Bu by solvothermal decomposition of Co-Et, Co-Pr and Co-Bu, respectively. The decomposed materials have been characterized by PXRD and SEM-EDAX and explored as potential electrocatalysts for both oxygen evolution and hydrogen evolution reactions in basic and acidic media, respectively. Catalytic activity is dependent on the precursor complex and best OER and HER activities are observed for dCo-Bu with an η10 of 230 mV and a Tafel slope of 192.11 mV dec−1 for the OER and an η10 of 470 mV and a Tafel slope of 126.21 mV dec−1 for the HER. [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]

In this paper, using density functional theory (DFT) methods, we meticulously investigated the structural properties of cobalt phosphide (CoP) and its Cu‐ and Ni‐doped counterpart. Then, on the surfaces of three catalysts, the hydrogen evolution reaction mechanism of ammonia borane (NH3BH3) was examined in turn, and four possible hydrogen evolution reaction paths of NH3BH3 on the catalyst surface were reviewed. The optimal reaction channel for each catalyst was found by comparing the activation energies of the control steps for several reaction paths, and activation energies of the optimal reaction for CoP, Cu, and Ni‐doped CoP were 31.4, 30.4, and 30.8 kcal/mol, respectively. Cu‐ and Ni‐ doped were beneficial to improve the hydrogen evolution reaction activity of NH3BH3. At the same time, the band structures and density of states of the stable catalysts were calculated. The results showed that near the fermi level, the electron cloud density of Cu and Ni‐doped CoP catalysts increased. The energy gap values of the three catalysts are 43.8, 41.0, and 41.7 kcal/mol, respectively, and the energy gap values of Cu and Ni doped CoP catalysts decrease. The energy gap values of the three catalysts are inversely proportional to their catalytic activities. We believe that these two factors together contribute to the increased catalytic activity of the doped CoP. Our results revealed the correlation between the physical properties of CoP and its metal‐doped catalysts and their catalytic activity. [ABSTRACT FROM AUTHOR]

The decomposition of ammonia borane (NH3BH3) to produce hydrogen has developed a promising technology to alleviate the energy crisis. In this paper, metal and non-metal diatom-doped CoP as catalyst was applied to study hydrogen evolution from NH3BH3 by density functional theory (DFT) calculations. Herein, five catalysts were investigated in detail: pristine CoP, Ni- and N-doped CoP (CoPNi-N), Ga- and N-doped CoP (CoPGa-N), Ni- and S-doped CoP (CoPNi-S), and Zn- and S-doped CoP (CoPZn-S). Firstly, the stable adsorption structure and adsorption energy of NH3BH3 on each catalytic slab were obtained. Additionally, the charge density differences (CDD) between NH3BH3 and the five different catalysts were calculated, which revealed the interaction between the NH3BH3 and the catalytic slab. Then, four different reaction pathways were designed for the five catalysts to discuss the catalytic mechanism of hydrogen evolution. By calculating the activation energies of the control steps of the four reaction pathways, the optimal reaction pathways of each catalyst were found. For the five catalysts, the optimal reaction pathways and activation energies are different from each other. Compared with undoped CoP, it can be seen that CoPGa-N, CoPNi-S, and CoPZn-S can better contribute hydrogen evolution from NH3BH3. Finally, the band structures and density of states of the five catalysts were obtained, which manifests that CoPGa-N, CoPNi-S, and CoPZn-S have high-achieving catalytic activity and further verifies our conclusions. These results can provide theoretical references for the future study of highly active CoP catalytic materials. [ABSTRACT FROM AUTHOR]

Hydrogen (H2) is a new type of renewable energy that can meet people's growing energy needs and is environmentally friendly. In order to improve the industrial application prospects and electrochemical performance of hydrogen evolution catalysts, extensive research on transition metal materials has been carried out. Among the many catalytic materials, cobalt is an element with potential for the hydrogen evolution reaction (HER) due to its abundant reserves, low cost, and small energy barrier for H adsorption. This review classifies the latest research on cobalt-based catalysts according to the types of compound, including cobalt-based sulfides, phosphides, carbides, borides, oxides, etc., and summarizes the latest research progress of cobalt-based compound catalysts in acidic and alkaline media. Strategies to tune the properties of cobalt-based compound catalysts for high catalytic activity for HER are focused on, including structural engineering, defect engineering, and doping, etc. The advantages and limitations of each modified approach are reviewed. Not only that, but also the catalytic activity and advantages of the catalyst are evaluated by using density functional theory (DFT) calculation-related descriptors, activity evaluation parameters, etc. Finally, limitations and challenges of cobalt-based materials for HER are presented, as well as prospects for future research. This paper aims to understand the chemical and physical factors that affect cobalt-based catalysts, and to find directions for future research on cobalt-based catalysts. [ABSTRACT FROM AUTHOR]

The hydrogen evolution reaction (HER) plays a vital role for the production of pure hydrogen with zero carbon release. Developing high efficiency non-noble metal electrocatalysts could reduce its cost. Here, vanadium doped cobalt phosphide grown on carbon cloth (CC) was synthesized by the low temperature electrodeposition–phosphorization method. The influence of V dopants on the structural, morphological, and electrocatalytic performance of Vx–Co1−x–P composites was also investigated in-depth. Impressively, the optimized amorphous V0.1–Co0.9–P nano-electrocatalyst exhibits outstanding catalytic activity with a low overpotential of 50 mV at a current density of 10 mA cm−2 and a small Tafel value of 48.5 mV dec−1 in alkaline media. The results showed that V dopants in the composite change its crystal structure from the crystalline phase to the amorphous phase, resulting in the introduction of V–O sites, which regulate the electron density of the active sites and the exposure of surface active sites and thus promote the electrocatalytic HER process. This work provides a novel idea for the fabrication of high-efficiency metal phosphide based electrocatalysts. [ABSTRACT FROM AUTHOR]

The oxygen evolution reaction (OER) is involved in various renewable energy systems, such as water-splitting cells and metal–air batteries. Cobalt phosphide nanomaterials have been reported as promising OER electrocatalysts. Herein, the rational design of advanced nanostructures for nitrogen doped and carbon coated cobalt phosphide hollow nanospheres (CoP@NC HNS) was highly desirable to optimize their electrocatalytic performance. SiO2 nanospheres were used as a sacrificial template for the synthesis of hollow nanospheres composed of ultrathin CoP@NC nanosheet arrays. The hollow nanostructure CoP@NC was coated with a layer of carbon material and the thickness of the shell was about 40 nm. The resultant CoP@NC HNS manifested high electrocatalytic activity towards the OER with low overpotential (320 mV, 10 mA cm−2), small Tafel slope (68 mV dec−1), and remarkable stability in alkaline electrolyte. Remarkably, the CoP@NC HNS still maintained an outstanding performance for the OER at 60 °C. [ABSTRACT FROM AUTHOR]

The high overpotential of the oxygen evolution reaction (OER) and the undesirable chlorine evolution reaction (ClER) severely limit the hydrogen production efficiency of seawater electrolysis. The organic electrooxidation reactions, involving C–H bond oxidation with low bond dissociation energy in the rate-limiting step, can possess lower oxidation potential than the OER as well as prevent the ClER. Herein, we demonstrate a strategy for replacing the sluggish OER by thermodynamically favorable biomass oxidation for scaling up the electrolysis of alkaline seawater. A xylose electrooxidation reaction (XOR) holds great promise for superseding the OER in seawater electrolysis, which not only simultaneously produces valuable formic acid and hydrogen, but also improves energy utilization. By utilizing NiCoP metal phosphide as the bifunctional electrode, the XOR shows an apparent overpotential reduction of 290 mV at 100 mA cm−2 as compared with the OER in the alkaline seawater electrolyte. Furthermore, the xylose-assisted seawater electrolysis exhibits a high formic acid selectivity of at least 94.6% and a high hydrogen production rate of 150 mL cm−2. This work provides a universal and an effective pathway for hydrogen production from seawater and biomass upgrading. [ABSTRACT FROM AUTHOR]

In this paper, using density functional theory (DFT) methods, we meticulously investigated the structural properties of cobalt phosphide (CoP) and its Cu‐ and Ni‐doped counterpart. Then, on the surfaces of three catalysts, the hydrogen evolution reaction mechanism of ammonia borane (NH3BH3) was examined in turn, and four possible hydrogen evolution reaction paths of NH3BH3 on the catalyst surface were reviewed. The optimal reaction channel for each catalyst was found by comparing the activation energies of the control steps for several reaction paths, and activation energies of the optimal reaction for CoP, Cu, and Ni‐doped CoP were 31.4, 30.4, and 30.8 kcal/mol, respectively. Cu‐ and Ni‐ doped were beneficial to improve the hydrogen evolution reaction activity of NH3BH3. At the same time, the band structures and density of states of the stable catalysts were calculated. The results showed that near the fermi level, the electron cloud density of Cu and Ni‐doped CoP catalysts increased. The energy gap values of the three catalysts are 43.8, 41.0, and 41.7 kcal/mol, respectively, and the energy gap values of Cu and Ni doped CoP catalysts decrease. The energy gap values of the three catalysts are inversely proportional to their catalytic activities. We believe that these two factors together contribute to the increased catalytic activity of the doped CoP. Our results revealed the correlation between the physical properties of CoP and its metal‐doped catalysts and their catalytic activity. [ABSTRACT FROM AUTHOR]

Cobalt phosphide has excellent electrical conductivity, metallic properties, and thermal stability. However, its application is limited due to the few active sites exposed in electrochemical reactions and poor structural stability. Herein, we adopt the strategies of material compounding and structural design to construct CoP@Ni(OH)2 bilayer nanosheets. The bilayer nanosheet structure can provide abundant transport paths for electrons and ions while also exposing more electroactive sites. In addition, the close contact and mutual support of the bilayer nanosheet structure can significantly alleviate material morphological collapse during charging/discharging processes, improving the cycle stability. The advantages of multiple components were combined in CoP@Ni(OH)2 to provide multiple valances for the faradaic redox reactions. The CoP@Ni(OH)2 manifested a specific capacity of 1697.8 C g−1 at 1 A g−1 and maintained a high rate capability of 35.0% even at 20 A g−1. Moreover, the electrode, had great cycling stability, retaining 83.9% of its capacity at 6 A g−1 after 7000 cycles. The asymmetric supercapacitor made of CoP@Ni(OH)2//activated carbon delivered 53.2 W h kg−1 at 800 W kg−1. [ABSTRACT FROM AUTHOR]

Efficient and low‐cost bifunctional OER/HER electrocatalysts are important for overall water splitting. Herein, three‐dimensional self‐supported Fe‐doped NiCo‐based phosphide nanosheets arrays are in‐situ grown on carbon fiber paper. The catalyst shows superior bifunctional activity, with an OER overpotential of 230 mV and an HER overpotential of 95 mV at 10 mA cm−2 in alkaline electrolyte. It is evidenced that the Fe doping facilitates electron transfer from Co/Ni to P, thus optimizing the electronic structures of both Ni and Co active sites, in turn greatly enhancing intrinsic OER and HER activities. The OER and HER turnover frequency are largely improved after Fe doping. When used as both anode and cathode for water splitting, the catalyst enables the electrolyzer to achieve 10 mV cm−2 at a low cell voltage of 1.59 V with a long‐term stability up to 35 h. This work highlights the synergy effect of multi‐metal‐based phosphides for efficient water electrocatalysis. [ABSTRACT FROM AUTHOR]

Developing high-performance and low-cost self-supporting electrodes as pH-universal electrocatalysts for the hydrogen-evolution reaction (HER) and realizing high-quality hydrogen production at a high current density are highly desirable, but are hugely challenging. We created a self-supporting electrode with a coupled hierarchical heterostructure by simple electrodeposition followed by sulfurization. It comprised oxygen-deficient molybdenum oxide (MoO3−x) and cobalt phosphide (CoP) on nickel foam (NF), which represented a highly active pH-universal electrocatalyst for the HER at a high current density. Benefiting from a plethora of catalytic active sites, improved interfacial charge transfer, and strong electronic interaction, this type of MoO3−x@CoP/NF electrode delivered a superior catalytic performance. Overpotentials of only 100 mV, 135 mV, and 400 mV were needed to realize a high current density of 1 A cm−2 in alkaline, acid and neutral media, respectively, which were superior to those of most other well-developed materials based on non-noble metals. Our experimental work demonstrates the synergistic advantages of a MoO3−x@CoP heterostructure for improving the intrinsic catalytic performance but also paves a new path for the rational design of advanced electrodes for hydrogen generation in a wide range of pH conditions. [ABSTRACT FROM AUTHOR]

The development of efficient, durable and economical catalysts based on non-precious metals for the controllable and fast hydrogen evolution from chemical hydrogen storage materials is highly desirable for the hydrogen economy. Herein, we introduce an advanced catalytic system by in situ encapsulating cobalt phosphide (CoP) nanoparticles into a quasi-metal–organic framework (quasi-Co-MOF-74) through a smart pyrolysis method. The designed synergic structure of CoP@quasi-Co-MOF-74 facilitates the efficient adsorption and activation of reactants, and achieves superior catalytic activity for the dehydrogenation of ammonia borane (AB). The extremely high hydrogen generation rate (HGR) of 9790 mL min−1 gcat−1 achieved by this catalytic system is 13.1, 4.4, and 46.5 times higher than that of quasi-Co-MOF-74, CoP, and CoP@C counterparts, respectively. Furthermore, CoP@quasi-Co-MOF-74 also delivers a high turnover frequency (TOF) of 55.9 min−1 and a low activation energy of 38.22 kJ mol−1 for the catalytic hydrolysis of AB, which compares favorably to most of the previously reported transition metal phosphide and cobalt-based catalysts. [ABSTRACT FROM AUTHOR]

Photocatalytic H2O-to-H2(g) and –H2O2(aq) (2H2O(l) → H2(g) + H2O2(aq)) by a two-electron reaction is kinetically feasible. The proton-coupled two-electron transfer induced a photocatalytic oxygen reduction reaction (ORR) from oxygen and water is also an accessible path for the safe production of H2O2. It is thus desirable to synthesize effective photocatalysts that yield H2O2 by the coupling of two-electron transfer water oxidation (+1.23 VNHE) and ORR (+0.68 VNHE). In this work, new g-C3N4/BiOI S-scheme heterojunctions with co-catalyst cobalt phosphide (CoP) (BiOI/g-C3N4/CoP) were prepared for the photocatalytic H2O-to-H2O2 reactions. The BiOI/g-C3N4/CoP heterojunctions can enhance visible light absorption and reduce electron–hole pair recombination rates. Because of the water splitting by two-electrons and reduction of oxygen, the BiOI/g-C3N4/CoP heterojunctions have a better photocatalytic H2O-to-H2O2 yield than with the BiOI/g-C3N4 heterojunction by 3.0–8.4 times. With more CoP (i.e., 19 wt%) on the BiOI/g-C3N4, the BiOI/g-C3N4/(CoP)0.19 heterojunction generates more photocatalytic H2O2 with higher formation rate constant (kf), equilbrium constant (K), and a lower decomposition rate constant (kd). This new, low-cost and ready-prepared BiOI/g-C3N4/CoP S-scheme heterojunction has a high efficiency for the reversible photocatalytic H2O-to-H2O2 reaction, which could be feasibly used for applications in H2O2-fuel cells for electricity using solar energy. [ABSTRACT FROM AUTHOR]

Highly active, durable, and inexpensive nanostructured catalysts are crucial for achieving efficiently and economically electrochemical water splitting. In recent years, the introduction of cerium (Ce) into electrocatalysts is an effective way to improve the performance of oxygen evolution reaction (OER). Herein, we report a cerium oxide deposited nickel iron carbonate hydroxide hydrate (NiFeCH(Ce)) on the carbon fiber paper through two-step hydrothermal/electrodeposition approach. The NiFeCH(Ce) not only exhibits a remarkably improved OER performance with an overpotential of 252 mV at a current density of 100 mA cm−2, but also possesses a small Tafel slope of 59 mV dec−1, the both values superior to the most non-noblemetal-based OER electrocatalysts reported. X-ray photoelectron spectroscopy analysis shows that the super OER electrocatalysis performance of the NiFeCH(Ce) was related intensely with the introduction of Ce ions, which not only richer surface defects and higher oxygen adsorption capacity, but also provide more effective charge and mass transfer between intermediates and catalysts, making a great contribution to the OER enhancement. [ABSTRACT FROM AUTHOR]

Zinc-doped cobalt nickel sulfides coupled with polypyrrole hollow nanospheres grown on carbon paper (Zn-CoNiS/PHS/CP) were developed by unipolar pulse electrodeposition (UPED) method as efficient and stable electrocatalysts for hydrogen evolution reaction (HER), oxygen evolution reaction (OER) and overall water splitting in neutral media for the first time. With abundant active sites intrigued by moderate Zn doping, the optimized Zn 10 -CoNiS delivers improved catalytic performance with small overpotentials of 213 mV and 414 mV to achieve the current densities of 10 mA cm−2 for HER and OER respectively, and outstanding long-term stability. The water electrolyzer device with Zn 10 -CoNiS as both anode and cathode delivers a current density of 10 mA cm−2 at a cell voltage of 1.896 V in neutral media. The low charge transfer resistance of Zn-CoNiS and confinement effect of 2D Ni 9 S 8 /Co 9 S 8 nanosheets on 0D ZnS nanodots endow the bifunctional electrocatalysts with efficient activity and high stability, providing a competitive candidate for green hydrogen production. [Display omitted] • Unipolar pulse electrodeposition is used to construct cation-doped bimetallic sulfide. • Zn-CoNiS shows advanced catalytic activity and high stability for both HER and OER. • Doping of Zn optimizes electronic structure and enhances conductivity of Ni 9 S 8 /Co 9 S 8. • 0D/2D confinement effect promotes long-term stability of Zn-CoNiS in neutral media. • Zn 10 -CoNiS bifunctional catalyst delivers superb overall water splitting performance. [ABSTRACT FROM AUTHOR]

• The heterostructures were synthesized via electrospinning, sulfuration and subsequent hydrothermal process. • Low overpotential of 52–93 mV at the current density of 10 mA/cm2 and small Tafel slope of 61–86 mV/dec were achieved. • More active sites and synergistic effect contributed to the enhanced HER performance. Transition metal sulfides have attracted much attraction in electrochemical water splitting owing to their low cost and unlimited availability. The formation of heterostructures has been demonstrated to be an effective manner to enhance the electrocatalytic performance. In this paper, hierarchical nanowires of MoS 2 @transition metal sulfide (FeS, CuS, CoS 2 and SnS 2) heterostructures were fabricated via simple electrospinning, sulfuration and subsequent hydrothermal process. X-ray diffraction and X-ray photoelectron spectroscopy were utilized to character the crystal structures and chemical compositions of as-prepared electrocatalysts. Scanning electron microscope and transmission electron microscope characterization results confirmed the existence of heterostructures in the MoS 2 @transition metal sulfide hybrid nanowires. Benefitting from the synergistic effect and the increased active sites, the as-prepared MoS 2 @transition metal sulfide (FeS, CuS, CoS 2 and SnS 2) heterostructures exhibited superior electrocatalytic HER performance. The MoS 2 @transition metal sulfides (FeS, CuS, CoS 2 and SnS 2) delivered the overpotential of 52 mV, 62 mV, 88 mV and 93 mV at the current density of 10 mA/cm2, and the Tafel slope of 64 mV/dec, 82 mV/dec, 73 mV/dec and 70 mV/dec in acid media. This work provides a novel way to optimize the HER activity of nanostructured MoS 2. [ABSTRACT FROM AUTHOR]

Under the gravity of future socio-economic development, the viability of water electrolysis still hinges on the accessibility of stable earth-abundant electrocatalysts and net energy efficiency. This work emphasizes the design and synthesis of two newly developed cobalt(II) complexes, [Co(HL)2(NCS)2] (Comono) and [Co2(L)3(CH3OH)]ClO4 (Codi), with a (N,O)-donor ligand, HL (2-methoxy-6-(((2-methoxyphenyl)imino)methyl)phenol). The study delves into understanding their structural, morphological, magnetic, and charge transport characteristics. Moreover, the study explores the potential of these complexes in catalyzing hydrogen production through heterogeneous electrocatalysis. The X-ray crystal structure of Comono reveals the octahedral geometry of the Co(II) ion, adopting two HL units and two NCS− units. The Codi complex exhibits a doubly-phenoxo-O-bridged (μ1,1) dinuclear complex, forming a typical octahedral geometry for both the Co(II) centres in coupling with three units of L−. Temperature-dependent magnetic susceptibility measurements showed that all of the Co(II) ion in Comono shows a typical paramagnetic behaviour for high spin octahedral Co(II) ions while the Co(II) centres in Codi are coupled with doubly-phenoxo-bridges bearing weak ferromagnetic characteristics at low temperature. Electron transport properties of the Co(II) complex-mediated Schottky device address the superior carrier mobility (μ) for Codi (9.21 × 10−5) over Comono (2.02 × 10−5 m2 v−1 s−1) with respective transit times of 1.70 × 10−9 and 7.77 × 10−9 s. Additionally, electron impedance spectral analysis supports the lower electrical transport resistance of Codi relative to Comono. The heterogeneous electrocatalytic HER activity of Codi and Comono in 0.1 M KOH shows excellent electrocatalytic efficiency in terms of the various electrochemical parameters. Constant potential electrolysis, multi-cycle CVs, and post-HER analysis reveal the pre-catalytic nature of the complexes, which in turn delivers Co3O4 nanoparticles as the active catalysts for efficient hydrogen evolution. [ABSTRACT FROM AUTHOR]

Transition metal phosphides have been widely used as electrocatalysts for water splitting. In particular, cobalt phosphide electrocatalysts play an important part in the oxygen evolution reaction. Here, two kinds of CoP with different nanostructures, CoP-MA and CoP-GC (MA = methylamine and GC = guanidine carbonate), were successfully prepared by a two-step method, including calcination of the corresponding Co-based metal formate frameworks, [Amine][Co(HCOO)3] (Amine = CH3NH3 and C(NH2)3), in air and the subsequent low temperature phosphating process. As OER catalysts, the CoP nanostructures show strong electrochemical structure-dependent properties. Electrochemical tests show that nanoparticle based CoP-MA micro-cubes required an overpotential of 340 mV at a current density of 10 mA cm−2, while nanosheet based CoP-GC micro-cubes only required an overpotential of 310 mV at the same current density. Importantly, the two CoP micro-cubes have a similar morphology but different structures, providing a direct side-by-side evaluation of their OER activities. The comparisons of the same metal phosphide OER catalysts with the same morphology but different structures are of great significance in identifying the key material characteristics that lead to high activity. [ABSTRACT FROM AUTHOR]

Designing an efficient electrocatalyst for facile oxygen reduction reaction (ORR) is essential to achieve higher fuel cell performance. Herein, we demonstrate a simple in situ process to synthesize cobalt sulfide-decorated N and S co-doped mesoporous carbon (Co9S8/N,S-MC) and evaluated its electrocatalytic activity for ORR in alkaline media. Porous carbon has great potential as a support material due to its well-defined porous architecture, which facilitates the mass transport. Here, the Co9S8/N,S-MC electrocatalyst was designed through a soft template route using pluoronic-F127 as a structure-directing agent, phloroglucinol-formaldehyde resin as a carbon source, and thiourea and cobalt acetate as N, S and Co sources, respectively. The combined effects of cobalt sulfide, heteroatoms and the well-defined porous architecture of mesoporous carbon resulted in the excellent ORR performance of the Co9S8/N,S-MC catalyst. Consequently, the optimized Co9S8/N,S-MC catalyst exhibited an onset potential and limiting current density of 0.87 V vs. RHE, and 3.40 mA cm−2, respectively. These values were very close to those of the commercial Pt–C catalyst with only a difference of 50 mV and 80 mA cm−2, but the Co9S8/N,S-MC catalyst also showed a 30 mV higher half-wave potential and excellent long-term stability compared to those of the commercial Pt/C catalyst. These interesting results suggested the good potential application of Co9S8/N,S-MC as ORR electrocatalysts with longer stability in fuel cells. [ABSTRACT FROM AUTHOR]

Metal phosphides have been proved to be potential theranostic agents of tumors. However, the limitations of single-modal imaging or the treatment effect of such materials need to be further improved. Here, we successfully prepared polyvinylpyrrolidone-modified bimetallic nickel cobalt phosphide (NiCoP/PVP) nanoparticles as a theranostic agent of tumors. Owing to the different types of magnetic properties of Ni and Co components, T1- and T2-weighted magnetic resonance imaging (MRI) could be simultaneously achieved to compensate the low accuracy brought about by single-modal MRI. In addition, NiCoP/PVP possesses excellent photothermal properties owing to its obvious absorption in the near-infrared (NIR) region, which endows NiCoP/PVP with high photothermal conversion efficiency (PCE) to serve as a photothermal agent for tumor ablation. Therefore, NiCoP/PVP is a promising theranostic agent for accurate diagnosis and effective treatment of tumors. [ABSTRACT FROM AUTHOR]

Materials containing cobalt phosphide nanoparticles are among the most promising electrocatalysts for the hydrogen evolution reaction in terms of compromise between activity, cost, and durability. A simple and effective approach to fabricating a nanocomposite of graphene–phosphorene structures decorated with CoP nanoparticles 2–5 nm in size is proposed. The nanocomposite was fabricated by the electrochemical exfoliation of black phosphorus followed by the solvothermal synthesis. The synthesis was carried out in the presence of few-layer graphene structures doped with nitrogen atoms in the solution containing Co2+ ions. The electrocatalyst exhibited high activity and stability towards hydrogen evolution reaction in the acidic medium. In order to achieve a current density of 10 mA cm–2, an overpotential of ~220 mV was required, and the Tafel slope was ~63 mV dec–1. It is suggested that this result is due to both the synergistic effect of the interaction between graphene and phosphorene structures and the electrocatalytic activity of CoP nanoparticles, which are located at the edges of phosphorene structures. [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]

The exploration of highly active bifunctional electrocatalysts for acidic electrochemical water splitting has attracted wide attention due to their importance in polymer electrolyte membrane (PEM) electrolyzers. However, existing catalysts normally suffer from low catalytic efficiency under acidic conditions. Herein, we developed a series of Ir-doped CoP nanowires arrays on carbon cloth (Ir-CoP/CC) materials, realizing prominently improved bifunctional catalytic activity for overall water splitting in an acidic medium. The optimized Ir4-CoP/CC catalyst exhibits the smallest overpotential of 38 mV and 237 mV to reach 10 mA cm−2 for HER and OER, respectively. Through systematic experimental research, we find the best intrinsic activity belongs to Ir3-CoP/CC catalyst, which presents superior bifunctional performance with the most economical usage of Ir. As a result, the best acidic water splitting electrolyzer displays a very low voltage of 1.50 V at 10 mA cm−2. This work provides a novel strategy to develop highly active bifunctional catalysts for acidic electrochemical water splitting. [ABSTRACT FROM AUTHOR]

Rational structural and compositional modulation endows electrode materials with unique physicochemical characteristics due to their adjustable electronic properties. Herein, a phosphate-modified hierarchical nanoarray consisting of a heterojunction with a well-aligned cobalt phosphide nanowire core and nickel phosphide nanosheet shell on flexible carbon cloth (denoted as CoP@Ni2P-CC) is engineered. The phosphate-modulated heterogeneous phosphide with a tuned electronic structure, additional heterojunction interfaces, and high degree of covalency in the chemical bonds accelerates the reaction kinetics and enhances the energy storage performance. Due to these reasons, the as-obtained phosphide-based heterostructured CoP@Ni2P-CC electrode delivers a capacity of 475.9 C g−1 at 0.5 A g−1 with a satisfying rate capability, which is greatly superior to that of its transition metal counterparts (sulfide, selenide, and oxide). After being assembled into a flexible hybrid supercapacitor (FHSC), a wide operating voltage (1.8 V), high energy/power densities (49.8 W h kg−1/8.6 kW kg−1), and long-term stability (85.1% capacity retention after 10 000 cycles) were achieved. This work may provide a general method from multiple strategies for designing reliable pseudocapacitive materials for flexible electronics. [ABSTRACT FROM AUTHOR]

The controllable and safe hydrogen storage technologies are widely recognized as the main bottleneck for the accomplishment of sustainable hydrogen energy. Ammonia borane (AB) has regarded as a competitive candidate for chemical hydrogen storage. However, developing efficient yet high-performance catalysts towards hydrogen evolution from AB hydrolysis remains an enormous challenge. Herein, cobalt phosphide nanosheets are synthesized by a facile salt-assisted along with low-temperature phosphidation strategy for simultaneously modulating its morphology and electronic structure, and function as hydrogen evolution photocatalysts. Impressively, the Co2P nanosheets display extraordinary performance with a record high turnover frequency of 44.9 min-1, outperforming most of the noble-metal-free catalysts reported to date. This remarkable performance is attributed to its desired nanosheets structure, featuring with high specific surface area, abundant exposed active sites, and short charge diffusion paths. Our findings provide a novel strategy for regulating metal phosphides with desired phase structure and morphology for energy-related applications and beyond. [ABSTRACT FROM AUTHOR]

In this study, the successful synthesis of bimetallic nickel/cobalt phosphide nanosheets (Ni-Co-P NSs) via the hydrothermal method and the subsequent high-temperature phosphorization process were both confirmed. Ni-Co-P NSs exhibited excellent electrocatalytic activity for the electrochemical non-enzymatic DA sensing. The surface morphologies and physicochemical properties of Ni-Co-P NSs were characterized by atomic force microscopy (AFM), field-emission scanning (FESEM), field-emission transmission electron microscopy (FETEM), and X-ray diffraction (XRD). Further, the electrochemical performance was evaluated by cyclic voltammetry (CV) and differential pulse voltammetry (DPV). The metallic nature of phosphide and the synergistic effect of Ni/Co atoms in Ni-Co-P NSs provided abundant catalytic active sites for the electrochemical redox reaction of DA, which exhibited a remarkable consequence with a wide linear range from 0.3~50 μM, a high sensitivity of 2.033 µA µM−1 cm−2, a low limit of detection of 0.016 µM, and anti-interference ability. As a result, the proposed Ni-Co-P NSs can be considered an ideal electrode material for the electrochemical non-enzymatic DA sensing. [ABSTRACT FROM AUTHOR]

A rapid microwave-assisted preparation of Co2P nanowires (NWs) is reported here, comparing with the CoP NWs. The characterizations and theoretical calculations indicate that Co2P exhibits metallic properties with improved conductivity. The electrocatalytic hydrogen and oxygen evolution activities are then measured and discussed in the paper, which show the advanced efficiency of Co2P NWs for the overall water-splitting. [ABSTRACT FROM AUTHOR]

Four A2B type cobalt triaryl corrole complexes (1–4) bearing aldehyde and pyridyl substituents at the 10-meso-phenyl group with different spatial configurations have been synthesized and thoroughly characterized using high-resolution mass spectrometry, nuclear magnetic resonance spectroscopy (NMR), X-ray photoelectron spectroscopy, and single-crystal X-ray diffractometry. These complexes all exhibited good activity in the electrocatalytic hydrogen evolution reaction (HER) when acetic acid, trifluoroacetic acid (TFA) or p-toluenesulfonic acid (TsOH) was used as the proton source. The Tafel catalytic plot revealed the intrinsic characteristics of the catalytic activity. The HER followed the EECEC pathway when acetic acid was used as a proton source, while it proceeded through the EECC or EECEC pathway when using TFA or TsOH as the proton source, depending on the acid concentration. The presence of CoIII–H was detected by 1H NMR, which provided evidence for the catalytic mechanism. The amide pyridyl may function as the proton relay group since the meta-substituted cobalt corroles 3 and 4 exhibited significantly higher turnover frequency (TOF)max values than corroles 1 and 2 in an organic medium. [ABSTRACT FROM AUTHOR]

The synthesis of low-cost and efficient electrocatalysts for the hydrogen evolution reaction (HER) is highly challenging. And apart from the intrinsic activity, the structure of the electrocatalysts also plays a vital role in the highly efficient catalysis for the hydrogen evolution reaction. Herein, the H2 bubbling-assisted electroplating method was employed to construct a coralline-like structure of Cu on the copper plate. And then, cobalt phosphide (CoP3) was successfully electrodeposited on the structure to form a CoP3@Cu/Cu electrode. Benefitting from this unique structure, the optimized CoP3@Cu/Cu exhibited an excellent electrocatalytic activity for the HER with Tafel slopes of 44 and 82 mV dec−1 in 0.5 M H2SO4 and 1 M KOH electrolytes, respectively. To reach a current density of 10 mA cm−2, an overpotential of 101 and 92 mV was required for the HER under acidic and alkaline conditions, respectively. Moreover, the CoP3@Cu/Cu electrode exhibited a long-term stability for the HER, indicating a promising prospect in the application. [ABSTRACT FROM AUTHOR]

• A self-standing, non-noble metal and 3D-networked ultrathin nanosheet array (Cu-CoP NAs/CP) is fabricated. • The optimized Cu-CoP NAs/CP exhibits excellent HER and OER activities in neutral media. • DFT investigation corroborated that Cu doping effectively tailor the electronic structures of CoP. • This electrolyzer can be powered by a single AA battery for neutral-pH water splitting. We report here, an effective strategy to optimize the electronic structure of CoP using copper doping, for greatly enhancing the intrinsic activity and conductivity of CoP in neutral-pH water splitting. As a result, the as-synthesized 3D self-supported Cu-doped CoP nanosheet arrays on carbon paper (Cu-CoP NAs/CP) exhibits admirable electrocatalytic performance toward both the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER) with overpotentials of 81 and 411 mV at 10 mA cm−2 in 1.0 M PBS (Phosphate Buffer Solution) , respectively. Moreover, a neutral electrolyzer, using Cu-CoP NAs/CP as both the anode and cathode, achieves a low cell voltage of 1.72 V at 10 mA cm−2, superior to that of the typical Pt/C||IrO 2 couple (1.81 V) and of most of the state-of-the-art bifunctional electrocatalysts. Impressively, the electrolyzer can be driven by a single AA battery (∼1.5 V), indicating its practicality in neutral water or seawater splitting. Experimental and density functional theory (DFT) calculations results reveal that the incorporation of Cu into CoP can effectively improve the conductivity and optimize the electronic structure to facilitate the H* adsorption and desorption and the formation of O* intermediates (generated CoOOH active species), thus yielding superior HER and OER catalytic activities. This study opens up a promising way to rationally design highly efficient and low-cost electrocatalysts for electrocatalysis applications. [ABSTRACT FROM AUTHOR]

Novel crystalline covalent organic polymers (COPs) were constructed by reacting 1,4-diaminoanthraquinone with 1,3,5-triformylphloroglucinol or tris(4-formylphenyl)amine (TPDA or TADA). After they were covalently bonded to amine-functionalized graphene oxides, the resulting mesoporous COPs@graphene composites demonstrated efficient capacitance storage performance in both alkaline and acidic media. In particular, the as-synthesized TPDA@graphene displayed a reversible specific capacitance of 522 F g−1 in a 6.0 mol L−1 aqueous KOH electrolyte, superior to the previously reported COPs with inconspicuous capacitance storage properties in alkaline media. Its specific capacitance also reached 390 F g−1 in 2.0 mol L−1 H2SO4. The impressive capacitance storage properties of this composite can be ascribed to its unique structure with abundant pendulous anthraquinone redox groups and better electrical conductivity enhanced by the coupled graphenes. [ABSTRACT FROM AUTHOR]