Catalytic Performance For Hydrogen Evolution Reaction Research Articles

CuS nanoparticles: An efficient electrocatalyst for hydrogen evolution reaction in a wide pH range

The design and fabrication of eco-friendly, highly sustainable and efficient, and non-noble metal-based electrodes are in high demand for the hydrogen evolution reaction (HER) in a wide pH range. Herein, we report the synthesis CuS nanoparticles and fabrication of paper-based electrodes. Robust and electrocatalytically active CuS nanoparticles shows the obvious hydrogen evolution reaction in broad pH range. Flexible, large area and binder free electrodes on paper substrate show the efficient catalytic performance in HER with small over potentials of 79, 258, 375 mV at 10 mA/cm2 in 0.5 M H2SO4, 0.5 M KOH, and 3 M NaCl, respectively. This result shows the highly active and stable electrocatalyst for HER in a wide pH range. Encouragingly, CuS/Ag/Paper electrodes advocates the significant technical development for industrial level hydrogen gas.

Construction of Glutinous Rice Potpourri-like MOTT−Schottky Ni/CeO2 Heterojunction Nanosheets for Robust Electrochemical Water Reduction

The development of efficient non-precious metal electrocatalysts through more economical and safe methods is consistent with the goals of sustainable development and accelerating the achievement of “carbon neutrality” in the 21st century but remains potentially challenging. Mott–Schottky heterojunction interfaces generated from metal/semiconductor have been a hot topic of recent research because of the unique built-in electric field effect which allows the preparation of more superior catalysts for water electrolysis. Herein, a glutinous rice potpourri-like Mott–Schottky two-dimensional (2D) nanosheet (abbreviated as Ni/CeO2 HJ-NSs) electrocatalyst composed of metal nickel (Ni) and cerium oxide (CeO2) hetero-nanoparticles was synthesized by a simple and scalable self-assembly and thermal reduction strategy. The experimental results and mechanistic analysis show that the Mott–Schottky heterojunction interface composed of metallic Ni and n-type semiconductor CeO2 with built-in electric field induces the electron redistribution at the interface to accelerate the dissociation of water and the binding of reaction intermediates, thus achieving lower water dissociation energy and more thermoneutral ΔGH* value to expedite the kinetics of the hydrogen evolution reaction (HER). Thus, the prepared Ni/CeO2 HJ-NSs exhibit excellent HER catalytic performance in 1 M KOH electrolyte with an overpotential of only 72 mV at 10 mA cm−2, as well as a moderate Tafel slope of 65 mV dec−1 and an extraordinary long-term stability over 50 h, laying a solid foundation for further in-depth investigation. The synthesis of splendid electrocatalysts by exploiting the metal/semiconductor interface effect provides an innovative way for the future generation of Mott–Schottky-based heterostructures with three or more heterocompositions with two or more heterojunction interfaces.

Controllably constructed carbide/oxide heterointerfaces of molybdenum for efficient hydrogen evolution

The dependence of cathodic hydrogen evolution reaction (HER) on noble metal catalysts is a critical challenge to realizing the industrial-scale application of hydrogen production from electrochemical water splitting. Due to the excellent water dissociation catalytic ability of Mo2C and the high HER catalytic activity of MoOx, Mo2C/MoOx heterointerfaces are controllably constructed via hydrogen peroxide oxidation of Mo2C to achieve improved HER catalytic performance. On the Mo2C/MoOx heterointerface, protons generated by the Mo2C sites via water dissociation can be immediately reduced by adjacent MoOx sites via the Volmer step to promote the overall HER kinetics. As a result, the rationally designed heterointerface-rich Mo2C-O catalyst exhibits great HER activity with a low overpotential of 115 mV to deliver 10 mA/cm2 current density. Along with great activity, the Mo2C-O catalyst also exhibits satisfying stability, confirming the promising application potential of the catalyst in industrial electrolysis systems.

Ruthenium nanoparticles loaded on N/P co-doped carbon sphere derived from sphere cross-linked hydrogel for highly improved hydrogen evolution reaction

Developing efficient and stable catalysts for hydrogen evolution reaction (HER) in electrolysis water is crucially significant but challenging. With enhanced hydrogen bonding energy as well as a reasonable price, ruthenium-based catalysts are one of the promising catalytic materials to replace Pt for HER. In this work, nitrogen and phosphorus co-doped carbon materials supporting ruthenium nanoparticles (Ru/NPC) are prepared by two pyrolysis processes and then used as a HER efficient catalyst. In alkaline media, Ru/NPC-2 requires only a low overpotential of 64 mV to achieve the current density of 10 mA cm−2, and shows a small Tafel slope of about 76 mV dec-1 and long-lasting stability. The introduction of Ru effectively increases the electrochemical active area of the catalytic material as well as promotes sufficient contact between the surface of the catalyst and the electrolyte, thereby exposing more active sites. In addition, the normalized results show that the synergistic effect among phosphorus, nitrogen, and ruthenium effectively enhances the intrinsic activity of active sites. Therefore, Ru/NPC exhibits outstanding HER catalytic performance. This work fully demonstrates the advantages of non-metallic element-doped carbon supports in enhancing the activity of ruthenium, and has an important reference for the subsequent development of carbon-supported high-efficiency electrocatalysts.

Facile colloidal synthesis of transition metal (Co, Fe, and Ni)-added Ir-W NPs for HER in acidic electrolyte

Alloying earth-abundant transition metals with iridium, one of the promising catalysts for the hydrogen evolution reaction (HER), is an effective way to reduce the usage of precious metal without sacrificing its catalytic activity. In particular, tungsten and early transition metals (Co, Fe, and Ni) are known to promote the inherent HER activity by modulating surface adsorption energy, but ternary alloy nanoparticles (NPs) of those elements and their universal synthetic strategy are not well-established yet. In this study, we synthesized a new iridium-based ternary alloy NP with tungsten and transition metals of cobalt, iron, and nickel (Ir-M-W, M = Co, Fe, and Ni) through colloidal synthesis. All the constituent metal elements were uniformly distributed over the particle, forming a homogeneous solid solution. The Ir-M-W NPs showed excellent catalytic activity and mass activity toward HER in an acidic electrolyte compared with the binary Ir-W NPs. In particular, the Ir-Co-W NPs exhibited the lowest overpotential (35.82 mV of overpotential to drive −10 mA cm−2) and the highest mass activity (3.98 A/mgIr) with 40 µg cm−2 of catalyst loading. Such superior catalytic HER performance could be achieved by the modulation of the surface electronic structure induced by the inclusion of transition metal.

1T’ RexMo1−xS2–2H MoS2 Lateral Heterojunction for Enhanced Hydrogen Evolution Reaction Performance

AbstractThe imperfect interfaces between 2D transition metal dichalcogenides (TMDs) are suitable for boosting the hydrogen evolution reaction (HER) during water electrolysis. Here, the improved catalytic activity at the spatial heterojunction between 1T’ RexMo1−xS2 and 2H MoS2 is reported. Atomic‐scale electron microscopy confirms that the heterojunction is constructed by an in‐situ two‐step growth process through chemical vapor deposition. Electrochemical microcell measurements demonstrate that the 1T’ RexMo1−xS2–2H MoS2 lateral heterojunction exhibits the best HER catalytic performance among all TMD catalysts with an overpotential of ≈84 mV at 10 mA cm−2 current density and 58 mV dec−1 Tafel slope. Kelvin probe force microscopy shows ≈40 meV as the work function difference between 2H MoS2 and 1T’ RexMo1−xS2, facilitating the electron transfer from 2H MoS2 to 1T’ RexMo1−xS2 at the heterojunction. First‐principles calculations reveal that Mo‐rich heterojunctions with high structural stability are formed, and the HER performance is improved with the combination of increased density of states near the Fermi level and optimal ΔGH* as low as 0.07 eV. Those synergetic effects with many electrons and active sites with optimal ΔGH* improve HER performance at the heterojunction. These results provide new insights into understanding the role of the heterojunction for HER.

Role of introduced Se element and induced anion vacancies in Mo(SSe)2-x/G van der Waals heterostructure for enhanced hydrogen evolution reaction

The Gibbs free energy of hydrogen adsorption at the edge of molybdenum disulfide (MoS2) is close to that of Pt, meaning that MoS2 is the best candidate to replace Pt-based materials. However, easy agglomeration between layers to mask active sites, lack of catalytic activity in the basal planes, and poor electronic conductivity make MoS2 exhibit dissatisfactory hydrogen evolution reaction (HER) catalytic performance. Here, we successfully construct a van der Waals heterostructure stacked alternately with Mo(SSe)2-x and graphene (Mo(SSe)2-x/G) to enhance its catalytic ability. The introduction of Se into MoS2 and the thermal treatment induce the sample to generate more anion vacancies. Theoretical and experimental results demonstrate the constructed van der Waals heterostructure, the introduced Se element, and the increased anion vacancies are in favor of promoting the number of active sites and improving the electronic conductivity of the catalyst. Therefore, Mo(SSe)2-x/G exhibits superior HER catalytic performance (the overpotentials of 137 mV and 136 mV at a current of 10 mA cm−2) and long-term stabilities (>90 h and 140 h at a current density of 20 mA cm−2) in both acidic and alkaline media.

Recent Advances in Ni‐Based Electrocatalysts for Hydrogen Evolution Reaction

Electrochemical water splitting driven by the electricity generated from renewable energy is an ideal sustainable approach for hydrogen production, where an efficient hydrogen evolution reaction (HER) electrocatalyst is indispensable. Ni‐based electrocatalysts are widely investigated for HER in different electrolytes due to their advantages of high Earth abundance, remarkable corrosion resistance, efficient electrocatalytic performance, and high electrical conductivity. Although several Ni‐based electrocatalysts exhibit catalytic HER performance comparable to that of state‐of‐the‐art Pt catalysts, it is still lack of practical applications possibly due to the duration limitation. In order to promote the next‐step intensive studies and applications, it is important to systematically summarize the progress of Ni‐based electrocatalysts for HER. Accordingly, this review article focuses on the recent advances in Ni‐based electrocatalysts toward HER, which includes the mechanism of the electrocatalytic HER in different electrolytes and progresses in the Ni‐based electrocatalysts toward HER. The preparation approaches, electrocatalytic activities, and overall performance comparison of the Ni‐based electrocatalysts are systemically summarized based on Ni‐based compounds, that is, phosphides, chalcogenides, nitrides, carbides, borides, alloys, and (hydro)oxides. The improvement modulation strategies including morphological/phase control, heterostructures/heterointerfaces, defect engineering, composite engineering, and heteroatom doping are thoroughly discussed. Finally, corresponding challenges and perspectives are proposed.

Hydrothermal preparation of MoX2 (X = S, Se, Te)/TaS2 hybrid materials on carbon cloth as efficient electrocatalyst for hydrogen evolution reaction

The prominent features-based two-dimensional (2D) materials have proven themselves as efficient as well as robust electrocatalysts for the hydrogen evolution reaction (HER) owing to their low-cost, abundance and predominant conductivity. In this work, we report the synthesis of series of molybdenum chalcogenide nanostructures MoX2 (X = S, Se, Te), hybridized with TaS2 nanosheets, via a facile hydrothermal method, on self-supported carbon cloth electrode. Used as an electrocatalyst for HER, hybrid phase MoSe2/TaS2/CC electrode with a Mo/Se ratio of 1:1.5 exhibits the best HER performance, which could afford the benchmark current densities of 10 mA/cm2 at the overpotentials of 75 mV with the measured Tafel slope values of 54.7 mV/dec. In addition, the presented molybdenum dichalcogenides in this work are also complimented with robustness as determined from durability and air stability measurements. The unique aspects of these unique hybrids, such as 1T and 2H phases hybridized MoS2 and MoSe2, semimetallic nature 1T′-MoTe2 petal clusters and strong interface interaction between MoX2 (X = S, Se, Te) and conductive TaS2 nanosheets, cause superior HER catalytic performance.

Effect of plasma process on hydrogen evolution reaction of ternary MoS2(1−x)Se2x alloys

Transition metal chalcogenides (TMDs) have shown excellent catalytic performance for hydrogen evolution reaction (HER). Recent studies have demonstrated that plasma treatment in binary TMDs can efficiently improve the catalytic performance for HER. The influence of the plasma treatment for HER of the ternary TMD alloys has not been reported. In this work, MoS2(1−x)Se2x ternary alloys were synthesized on the conductive base carbon cloth by APCVD method successfully for HER applications. The effects of the plasma parameters such as the energy power and processing time on the HER activity have been investigated. Compared with the pristine MoS2(1−x)Se2x alloy, the performance of the sample treated with plasma has been improved. And the MoS2(1−x)Se2x ternary alloy treated with plasma power of 10 W for 10 min presents a superior HER activity characterized by a low overpotential of 217 mV @ 10 mA/cm2, a low Tafel slope of 65.8 mV/dec, a low impedance of 6 Ω, and a high Cdl of 18.68 mF/cm2 with good durability. Therefore, similar with the binary TMD alloys, the plasma treatment has been demonstrated an effective technique to significantly enhanced HER performance of ternary TMD alloys.

Study on Nickel-induced 1T/2H MoS2 nanostructures in realizing efficient electrocatalysts for hydrogen evolution reaction

• Rational design and successfully prepared Ni-induced 1T/2H MoS 2 . • Ni-induced 1T/2H MoS 2 exhibits efficient HER catalytic performance. • The Ni-ions are favorable for enhancing the HER performance. Two-dimensional (2D) molybdenum disulfide (MoS 2 ) catalysts have gained great attention in several applications due to their unique properties as well as their tunable electronic structures. Fabrication of cost-effective and highly efficient electrocatalysts is vital for water splitting. Herein, we have synthesized nickel (Ni) induced mixed-phase (1T/2H) MoS 2 by solvothermal method and have studied its characteristics to be used for hydrogen evolution reaction (HER). The doping of Ni in MoS 2 is aimed at increasing the efficiency of HER performance and it has been proved to be a highly effective HER catalyst in an acidic medium. Ni-doped (9%) MoS 2 achieved the lowest overpotential of 127 mV for the HER at 10 mA cm −2 and a Tafel slope of 86 mV dec -1 among the other concentrations of Ni-doping studied. This work demonstrates the constructive outcome of doping the catalyst for HER and provides a pragmatic way for obtaining earth-abundant electrocatalysts.

Improving the HER Activity and Stability of Pt Nanoparticles by Titanium Oxynitride Support.

Water electrolysis powered by renewables is regarded as the feasible route for the production of hydrogen, obtained at the cathode side through electrochemical hydrogen evolution reaction (HER). Herein, we present a rational strategy to improve the overall HER catalytic performance of Pt, which is known as the best monometallic catalyst for this reaction, by supporting it on a conductive titanium oxynitride (TiONx) dispersed over reduced graphene oxide nanoribbons. Characterization of the Pt/TiONx composite revealed the presence of small Pt particles with diameters between 2 and 3 nm, which are well dispersed over the TiONx support. The Pt/TiONx nanocomposite exhibited improved HER activity and stability with respect to the Pt/C benchmark in an acid electrolyte, which was ascribed to the strong metal–support interaction (SMSI) triggered between the TiONx support and grafted Pt nanoparticles. SMSI between TiONx and Pt was evidenced by X-ray photoelectron spectroscopy (XPS) through a shift of the binding energies of the characteristic Pt 4f photoelectron lines with respect to Pt/C. Density functional theory (DFT) calculations confirmed the strong interaction between Pt nanoparticles and the TiONx support. This strong interaction improves the stability of Pt nanoparticles and weakens the binding of chemisorbed H atoms thereon. Both of these effects may result in enhanced HER activity.

Facile and rapid synthesis of ultrafine RuPd alloy anchored in N-doped porous carbon for superior HER electrocatalysis in both alkaline and acidic media

Searching for preeminent electrocatalysts toward hydrogen evolution reaction (HER) is significantly important in transforming renewable electricity to clean hydrogen energy by electrochemical water splitting. Herein, ultrafine RuPd alloy nanoparticles anchored in MOFs-derived N-doped porous carbon dodecahedrons (Ru x Pd 1−x @NPC) were synthesized by microwave-assisted ethylene glycol reduction method. Due to the synergistic promotion by modulating the composition and structure, excellent HER catalytic performance was achieved in both alkaline and acidic media for the as-prepared Ru x Pd 1−x @NPC electrocatalysts with low noble metal loading. In which, Ru 0.7 Pd 0.3 @NPC exhibited significantly enhanced alkaline HER activity with a low overpotential of only 20 mV to reach a current density of 10 mA cm −2 . Meanwhile, Ru 0.3 Pd 0.7 @NPC showed admirable HER activity in acidic media, which delivered an overpotential of 36 mV at 10 mA cm −2 . Additionally, the proposed catalysts demonstrated high mass activity and good long-term stability in both alkaline and acidic condition, remarkably surpassing the commercial Pt/C catalyst. The superior activity of the Ru x Pd 1−x @NPC catalysts is attributed to improved intrinsic activity, fast charge transfer kinetics and distinct electrochemical active surface areas after alloying. This work provides a rapid and facile synthesis of highly efficient, durable and affordable alloy electrocatalysts for hydrogen evolution. With low noble metal loading, the alloying Ru x Pd 1−x @NPC electrocatalysts synthesized by facile and rapid microwave-assisted reduction method exhibit dramatically enhanced performance for sustainable hydrogen evolution. • Series of ultrafine alloying RuPd nanoparticles are dispersedly encapsulated in N-doped porous carbon dodecahedrons. • A facile and rapid microwave-assisted reduction method is proposed to synthesize RuPd alloy catalysts. • Enhanced HER electrocatalytic performance is realized in both alkaline and acidic media .

Preparation of Au/MoS2‐CNT@CNF Composite Electrocatalyst for High‐Efficiency Hydrogen Evolution Reaction

AbstractBy virtue of excellent ion storage and fast ion‐diffusion rates, molybdenum disulfide (MoS2) has been regarded as a promising electrocatalyst for hydrogen evolution reaction (HER). however, it is inherently inert to HER, its electrochemical activity is usually improved by enhancing electrical conductivity or increasing exposed active sites. To improve the conductivity and adsorption of MoS2, we prepared the MoS4‐Ppy intermediate by oxidative polymerization. Taking advantage of the adsorption properties of MoS4‐Ppy to combine with Au(III), Au(III) was simultaneously reduced to Au nanoparticles(Au NPs). Combining the Au/MoS4‐Ppy with BC and converting it into a catalyst Au/MoS2‐CNT@CNF by calcination, the catalyst activity was improved by optimizing the concentration of Au(III). Combining MoS2 with Polypyrrole (Ppy) and Bacterial cellulose (BC) not only improves the conductivity of MoS2, but also increases the exposed active sites. Notably, the obtained 50 ppm Au/MoS2‐CNT@CNFs exhibited good HER catalytic performance in an acidic electrolyte (0.5 M H2SO4) with a low overpotential of only 108 mV at a current density of 10 mA ⋅ cm−2, a low Tafel slope of 52.1 mV ⋅ dec−1, and along with outstanding stability. The improvement of electrocatalytic activity is mainly attributed to the larger electrochemical specific surface area of the composites after adsorption of Au(III) and loaded BC. The low load Au NPs can provide dense active sites. Moreover, and synergistic effect among Au NPs, MoS2, and Ppy can greatly enhance the charge transfer efficiency and lead to excellent electron transfer ability, thus significantly improving the HER performance.

Interfacial Strain-Modulated Nanospherical Ni2 P by Heteronuclei-Mediated Growth on Ti3 C2 Tx MXene for Efficient Hydrogen Evolution.

Interface modulation of nickel phosphide (Ni2 P) to produce an optimal catalytic activation barrier has been considered a promising approach to enhance the hydrogen production activity via water splitting. Herein, heteronuclei-mediated in situ growth of hollow Ni2 P nanospheres on a surface defect-engineered titanium carbide (Ti3 C2 Tx ) MXene showing high electrochemical activity for the hydrogen evolution reaction (HER) is demonstrated. The heteronucleation drives intrinsic strain in hexagonal Ni2 P with an observable distortion at the Ni2 P@Ti3 C2 Tx MXene heterointerface, which leads to charge redistribution and improved charge transfer at the interface between the two components. The strain at the Ni2 P@Ti3 C2 Tx MXene heterointerface significantly boosts the electrochemical catalytic activities and stability toward HER in an acidic medium via a combination between experimental results and theoretical calculations. In a 0.5m H2 SO4 electrolyte, the Ni2 P@Ti3 C2 Tx MXene hybrid shows excellent HER catalytic performance, requiring an overpotential of 123.6mV to achieve 10mA cm-2 with a Tafel slope of 39mV dec-1 and impressive durability over 24h operation. This approach presents a significant potential to rationally design advanced catalysts coupled with 2D materials and transition metal-based compounds for state-of-the-art high efficiency energy conversions.

Co(OH)2 promoting the catalytic activity of CoP/Ni2P heterojunction for hydrogen evolution in both alkaline and acid media

Developing non-precious metal catalysts to replace commercial Pt for hydrogen evolution reaction (HER) is extremely significant for practical application of water splitting. Here, we synthesized a composite CoP/Ni2P@Co(OH)2 catalyst via the sequential phase growth strategy. Owing to the cooperative effect between CoP/Ni2P and Co(OH)2, the CoP/Ni2P@Co(OH)2 catalyst presents excellent HER catalytic performance with 39 mV overpotential in 1 M KOH and 68 mV overpotential in 0.5 M H2SO4 to deliver the current density of 10 mA cm−2. By designing a control experiment, we found that the Co(OH)2 may promote water dissociation effectively in alkaline media and accelerate the generation of M-H∗ in acidic media, while CoP/Ni2P can serve as the active sites for the adsorption and desorption of hydrogen. The synergistic effects of CoP/Ni2P and Co(OH)2 greatly boost its HER catalytic performance in both alkaline and acid media. In short, the new finding of introducing Co(OH)2 into the CoP/Ni2P can accelerate the development of high-performance HER catalysts.

Heterojunction engineering of Ni3S2/NiS nanowire for electrochemical hydrogen evolution

Hydrogen evolution reaction (HER) over the non-noble metal-based electrocatalysts is a promising approach to realize future clean energy economy. Herein, to achieve effective interface construction, epitaxial growth of NiS on the surface of one-dimensional (1D) Ni3S2 nanowire on nickel foam (NF) was performed, to construct a Ni3S2/NiS electrocatalyst with a heterojunction structure via a solid-state phase transformation. Benefiting from the strong charge transfer at the Ni3S2/NiS heterojunction interface, the d-band center was downshifted compared to the single component (Ni3S2 or NiS), which effectively optimized the valence state and the H adsorption of Ni, thus improved the HER activity. The obtained Ni3S2@NiS-250/NF showed the robust HER catalytic performance with a low overpotential of 129 mV to deliver the current density of 10 mA cm−2 with a small Tafel slope (75.5 mV dec-1) in 1 M KOH media. Moreover, it exhibited superior durability for at least 50 h. This work provides a novel strategy for designing nickel sulfide-based catalysts for HER with high performance.

Nickel-based nanosheets array as a binder free and highly efficient catalyst for electrochemical hydrogen evolution reaction

Hydrogen technology through water electrolyzer systems has attracted a great attention to overcome the energy crisis. So, rationally designed non-noble metal based-electrocatalysts with high activity and durability can lead to high performance water electrolyzer systems and high purity hydrogen generation. Herein, a facile two-step method: hydrothermal and electrodeposition, respectively, are developed to decorate highly porous three-dimensional binder-free structure NiFeO/NiO nanosheets array on Ni foam (NiFeO/NiO/NF) with robust adhesion as a high-performance electrode for Hydrogen Evolution Reaction (HER).The electrodeposition process applied after the initial hydrothermal process provides a stable structure and, in addition, enhances the sluggish hydrogen evolution efficiency. In alkaline media, the developed electrode needs an overpotential of 48 and 188 mV to drive current densities (j) of 10 and 100 mA cm−2, respectively. After continuous 110 h electrochemical stability test under j = 150 mA cm−2 conditions, demonstrates an excellent stability with ignorable activity decrease. Such superior HER catalytic performance can be derived from the synergistic effect between Ni and Fe atoms, also exposure to a high number of active sites on the nanosheets, and good dynamic with effective electron transport along the nanosheets. The present work provides a promising route for the design and fabrication of cost-effective and highly efficient HER electrocatalysts.

Inorganic doped libethenite nanoparticle clusters show high catalytic activity in hydrogen evolution reaction

A noble metal-free Na Al Si doped libethenite nanoparticle clusters were obtained by applying the method of hydrothermal synthesis. The Linear Sweep Voltammetry (LSV) curve of this nanoparticle cluster electrode shows that there is no noble metal in the hydrogen evolution reaction (HER), and it still exhibits good catalytic activity. The catalytic activity of the libethenite nanoparticle cluster is further enhanced after reduction by the amperometric i-t curve method (A i-t C). The electrochemical performance and catalytic mechanism were investigated by the cyclic voltammetry (CV) method. The characterization analysis by XRD, SEM, TEM, EDS, and XPS found that the catalyst was isomorphous with the natural mineral libethenite, but different from the minerals with Cu and P as the main components in nature when the crystal synthesized under hydrothermal conditions was doped. The heterogenous libethenite nanoparticle cluster framework is replaced by more additional Na, Al, and Si elements. Cu and P elements in the libethenite nanoparticle cluster structure are connected through the mineral framework and uniformly distributed in the crystal structure. This structure increases the electrochemical activity of its HER. Due to the interaction of Cu and P, the catalyst exhibits good catalytic performance for HER under acidic conditions. The reduction by the electrochemical i-t curve reduces the consumption of Cu and enhances the stability of the mineral framework.

Enhanced electrocatalytic performance of Ni-based phosphides via dual regulation of Co-introducing and graphene-support for hydrogen evolution

Ni-based phosphides are a kind of promising electrocatalyst for the hydrogen evolution reaction (HER). However, the catalytic activity of phosphides still needs further improvement. Herein, with the incorporation of Co, highly dispersed spherical NiCoP supported on graphene nanosheets (NiCoP/GR) as HER catalyst was successfully prepared by the simple impregnation and phosphorization method. The highly-dispersed morphology and the synergetic interaction between NiCo bimetal endow the as-prepared NiCoP/GR with high catalytic performance for HER. When the current density is 10 mA cm−2 in 0.5 M H2SO4, the as-prepared NiCoP/GR exhibited a low overpotential of 195 mV, and the Tafel slope was only 66.4 mV dec−1. Furthermore, the density functional theory (DFT) calculations reveal that the low activation barrier of NiCoP/GR can be ascribed to the adjustment of electronic structure. As a result, the HER catalytic performance of NiCoP/GR is significantly enhanced by electronic structure adjustment. This work provides a new approach for introducing multiple metal elements and graphene support material with unique properties to boost the catalytic performance of transition metal phosphide catalysts.