Improved Hydrogen Evolution Reaction Activity Research Articles

One-step synthesis of self-supporting porous Cu81(Ni,Co)19 intermetallic catalysts for hydrogen evolution reaction

The development of hydrogen evolution reaction (HER) catalysts with excellent performance is the key to the wide-scale application of hydrogen energy. Herein, this work facilely synthesizes the self-supporting porous Cu81(Ni,Co)19 electrocatalysts by dealloying ZrNiCoCuAl amorphous alloy in HF solution. By regulating the composition of ZrNiCoCuAl amorphous alloy dealloying precursor, the porous Cu81(Ni,Co)19 composite synthesized by dealloying Zr60Ni8Co8Cu16Al8 amorphous alloy demonstrates the great HER performance with an overpotential of 35mV at 10mAcm-2 and a Tafel slope of 73.3mV dec-1. The outstanding catalytic performance of porous Cu81(Ni,Co)19 is attributed to the hierarchical porous structure, low charge transfer resistance as well as the synergistic interactions among the Cu, Ni and Co elements. Moreover, the theoretical calculations indicate that the constituent Cu, Co and Ni elements in the Cu81(Ni,Co)19 intermetallic alloy can act synergistically to optimize the free energy of hydrogen adsorption, therefore improve HER activity.

Nonmetal-modification 2D molybdenum carbide (MXene) for enhanced activity in hydrogen evolution reaction: A DFT study

Two-dimensional (2D) transition metal carbides/nitrides (MXenes) materials exhibit potential as catalysts for the hydrogen evolution reaction (HER) due to their large surface area, excellent conductivity, and notable electrical properties. Despite these advantages, pristine MXenes often display insufficient catalytic activity compared to noble metal electrocatalysts. Enhancing the HER performance of MXenes by introducing nonmetal atoms on the surface has proven effective. However, understanding the precise regulation of the HER performance by nonmetal atoms remains challenging. In this study, we utilized density functional theory calculations to explore how the introduction of fourteen distinct nonmetal atoms into Mo2CO2 catalysts (NM-Mo2CO2) influences the catalytic behavior in HER. The results indicated that nonmetal atom doping significantly activates oxygen atoms, substantially enhancing catalytic activity. Notably, the addition of nonmetal atoms like chlorine (Cl), bromine (Br), and iodine (I) onto the Mo2CO2 surface effectively improved HER activity, showcasing their potential as HER catalysts. Our study proved that nonmetal atom doping not only causes localized structural distortions but also charge redistribution, influencing the HER performance of NM-Mo2CO2. Furthermore, we developed two descriptors to quantify the regulation mechanism of nonmetal atoms, successfully predicting the HER activity of NM-Mo2CO2 and extending these insights to NM-Cr2CO2 and NM-V2CO2. These findings offer a comprehensive understanding of how nonmetal atom doping enhances HER activity, providing valuable insights for innovative catalyst design.

Electrodeposition of PdPt Nanoparticles on Edges and S-Vacancies in Exfoliated MoS2 Nanosheets for Enhanced Hydrogen Evolution Activity.

Deposition of metal nanoparticles onto the molybdenum disulfide (MoS2 ) nanosheets is an efficient method to tune the electronic structure of the MoS2 and maximize its catalytic performance towards the hydrogen evolution reaction (HER). Herein, we report the electrodeposition of Pd and Pt nanoparticles onto desulfurized MoS2 nanosheets (MoS2-x ) to achieve an improved HER activity in an acidic electrolyte. The initial MoS2 powder was exfoliated and isolated through centrifugation, followed by electrochemical desulfurization to create defect sites. Subsequently, Pt and Pd nanoparticles were electrodeposited onto the S-vacancies of MoS2-x nanosheets. The resulting PdPt nanoparticles, with a diameter of 3.3 ±1.7 nm, were distributed across the surfaces of the nanosheets. A preferential deposition was evident at the edges of the nanosheets, particularly when Pd was deposited first followed by Pt. Owing to this preferential deposition of Pd and Pt and the synergistic interaction of MoS2-x with Pd and Pt, the prepared catalyst exhibited a low overpotential of 30 mV at 10 mA cm-2 , which is 2.7× lower than the MoS2-x alone. The prepared catalyst exhibited a 1.7× increase in the mass activity at 20 mV overpotential, relative to that of a commercial Pt/C nanocatalyst, showcasing its promising potential as an alternative catalyst.

Tailoring Binding Abilities By Incorporating Oxophilic Transition Metals on 3D Nanostructured Ni Arrays for Accelerated Alkaline Hydrogen Evolution Reaction

Developing efficient and inexpensive electrocatalysts for the hydrogen evolution reaction (HER) in alkaline water electrolysis plays a key role for renewable hydrogen energy technology. The slow reaction kinetics of HER in alkaline solutions, however, has hampered advances in high-performance hydrogen production. Herein, we investigated the trends in HER activity with respect to the binding energies of Ni-based thin film catalysts by incorporating a series of oxophilic transition metal atoms. It was found that the doping of oxophilic atoms enables the modulation of binding abilities of hydrogen and hydroxyl ions on the Ni surfaces, leading to the first establishment of a volcano relation between OH-binding energies and alkaline HER activities. In particular, Cr-incorporated Ni catalyst shows optimized OH-binding as well as H-binding energies for facilitating water dissociation and improving HER activity in alkaline media. Further enhancement of catalytic performance was achieved by introducing an array of three-dimensional (3D) Ni nanohelixes (NHs) that provide abundant surface active sites and effective channels for charge transfer and mass transport. The Cr dopants incorporated into the Ni NHs accelerate the dissociative adsorption process of water, resulting in remarkably enhanced catalytic activities in alkaline medium. Our approach can provide a rational design strategy and experimental methodology toward efficient bimetallic electrocatalysts for alkaline HER using earth-abundant elements.Reference Journal of the American Chemical Society 3, 1399-1408 (2021) [Front Cover]

Improving hydrogen evolution catalytic activity of 2D carbon allotrope biphenylene with B, N, P doping: Density functional theory investigations

Using a first principles approach, we studied the hydrogen evolution reaction activity of newly synthesized biphenylene and B, N, P decorated biphenylene sheet. Hydrogen evolution reaction activity of pristine biphenylene sheet is not encouraging, as it is similar to pristine graphene. The Gibbs free energy and overpotential of P(N) doped on biphenylene sheet are 0.022 (−0.092) eV and 22 (92) mV, respectively. The reported Gibbs free energy and overpotential of Pt are 0.9 eV and 90 mV. Hence doping of P(N) atom on top of biphenylene sheet improves hydrogen evolution reaction activity much better (near to) Pt metal. We analyzed the adsorption mechanism of dopants (B, N, P) and hydrogen with Bader charge analysis and density of states analysis. P and N-decoration on biphenylene sheet change its electronic structure so that one obtains improved hydrogen evolution reaction activity for P and N-doped biphenylene sheet. Furthermore, the stability of N, P decorated biphenylene at room temperature with ab-initio molecular dynamics and formation energy near that of biphenylene indicate experimental feasibility. We have compared all our best hydrogen evolution reaction activity results in the reaction coordinate and volcano plots of pristine, B, N, and P-doped BPh sheets. They indicate that P-doped biphenylene is a metal-free, powerful catalyst for hydrogen evolution reaction activities.

Constructing built-in electric field via ruthenium/cerium dioxide Mott-Schottky heterojunction for highly efficient electrocatalytic hydrogen production

Ensuring the consumption rate of noble metals while guaranteeing satisfactory hydrogen evolution reaction (HER) performance at different pH values is imperative to the development of Ru-based catalysts. Herein, we design a Mott-Schottky electrocatalyst (Ru/CeO2) with a built-in electric field (BEF) based on density functional theory (DFT). The Ru/CeO2 achieves the criterion current density of 10 mA cm−2 at overpotentials of 55 mV, 80 mV, and 120 mV in alkaline, acidic and neutral media, respectively. Both theoretical calculations and experimental analysis confirm that the improved HER activity in the Ru/CeO2 catalyst could be due to the successful construction of BEF at the interface between the prepared Ru clusters and CeO2. Under the action of BEF, the electron-deficient Ru atoms can optimize the adsorption energy of H* and H2O and thus promote HER kinetics. Furthermore, the Ru/CeO2 catalyst delivers a power density of approximately 94.5 mW cm−2 in alkaline-acidic Zn-H2O cell applications while maintaining good H2 production stability. In this work, we optimize the electrocatalytic performance of the Ru/CeO2 catalyst through examination of the interfacial BEF electrical charge, which combines hydrogen production with power generation and provides a promising method for sustainable energy conversion.

Ru-promoted NiFe oxyhydroxide anchored on the hierarchical porous N-doped carbon aerogel: Electronic structures modulation for much enhanced OER/HER dual-functional characteristics

Herein, we have demonstrated a novel Ru-promoted NiFe oxyhydroxide anchored on N-doped carbon aerogel (RuNi7FeOx(OH)y @NCA) aerogel electrocatalyst via a facile sol-gel process, combined with a supercritical drying technique. The optimal RuNi7FeOx(OH)y @NCA shows a typical "pearl-like" aerogel nanostructure with a three-dimensional network, showing a large specific surface area of 227.7 m2·g−1. The achieved RuNi7FeOx(OH)y @NCA exhibits high OER activity with a low overpotential of 278.0 mV at 10 mA·cm−2 and a high TOF of 0.107 s−1. Moreover, the RuNi7FeOx(OH)y @NCA aerogel displays excellent hydrogen evolution reaction (HER) activity under alkaline conditions, with a small overpotential of 99.0 mV at a current density of 10 mA·cm−2, and a small Tafel slope of 61.1 mV·dec−1. DFT calculations show that the enhanced OER activity is attributed to the improved binding strength of *OOH intermediate on the catalyst surface, and the introduced Ru with larger electron density and weaker spin density leads to the improved HER activity.

Carbon nanotubes encapsulating Pt/MoN heterostructures for superior hydrogen evolution

Achieving efficient hydrogen evolution reaction (HER) catalysts to scale up electrochemical water splitting is desirable but remains a major challenge. Here, nitrogen-doped carbon nanotubes (NCNTs) loaded with PtNi/MoN electrocatalyst (PtNi/MoN@C) is synthesized by a simple strategy to obtain stronger interphase effects and significantly improve HER activity. The surface morphology of the materials is altered by Pt doping and the electronic structure of MoN is changed, which optimizing the electronic environment of the materials, shifting the binding energy and giving the materials a higher electrical conductivity, this ultimately leads to faster proton and electron transfer processes. The synergistic effect of Pt nanoparticles, MoN and the good combination with carbon leads to a high HER activity of 18 mV to reach 10 mA cm−2 in alkaline solution, outperforming that of the commercial Pt/C. Theoretical studies show that the heterostructures can efficiently enhance the electron transport and reduce the △GH*.

Amorphous nickel hydroxide shell tailors local chemical environment on platinum surface for alkaline hydrogen evolution reaction.

In analogy to natural enzymes, an elaborated design of catalytic systems with a specifically tailored local chemical environment could substantially improve reaction kinetics, effectively combat catalyst poisoning effect and boost catalyst lifetime under unfavourable reaction conditions. Here we report a unique design of 'Ni(OH)2-clothed Pt-tetrapods' with an amorphous Ni(OH)2 shell as a water dissociation catalyst and a proton conductive encapsulation layer to isolate the Pt core from bulk alkaline electrolyte while ensuring efficient proton supply to the active Pt sites. This design creates a favourable local chemical environment to result in acidic-like hydrogen evolution reaction kinetics with a lowest Tafel slope of 27 mV per decade and a record-high specific activity and mass activity in alkaline electrolyte. The proton conductive Ni(OH)2 shell can also effectively reject impurity ions and retard the Oswald ripening, endowing a high tolerance to solution impurities and exceptional long-term durability that is difficult to achieve in the naked Pt catalysts. The markedly improved hydrogen evolution reaction activity and durability in an alkaline medium promise an attractive catalyst material for alkaline water electrolysers and renewable chemical fuel generation.

Engineering Superaerophobic Electrodes Using Hydrophilic PEDOT and Colloidal Lithography for Enhanced Bubble Release and Efficient Hydrogen Evolution Reaction.

The efficient removal of gas bubbles is essential to reduce the reaction overpotential and improve the electrode stability in the hydrogen evolution reaction (HER). To address this challenge, the current study combines hydrophilic functionalized poly(3,4-ethylenedioxythiophene) (PEDOT) with colloidal lithography to create superaerophobic electrode surfaces. The fabrication process involves the use of polystyrene (PS) beads with varying sizes (100, 200, and 500 nm) as hard templates and the electropolymerization of EDOTs with hydroxymethyl (EDOT-OH) and sulfonate (EDOT-SuNa) functional groups. The surface properties and HER performances of the electrodes are investigated. The electrode modified with poly(EDOT-SuNa) and 200 nm PS beads (SuNa/Ni/Au-200) exhibits the best hydrophilicity with a water contact angle of 37°. Moreover, the overpotential required at -10 mA cm-2 is substantially reduced from -388 mV (flat Ni/Au) to -273 mV (SuNa/Ni/Au-200). This approach is further applied to commercially available nickel foam electrodes, showing improved HER activity and electrode stability. These results highlight the potential for promoting catalytic efficiency by constructing a superaerophobic electrode surface.

Efficient Hydrogen Evolution Catalysts Based on Hierarchical Flowerlike NixCo9–xS8 Nanosheets

In terms of the need for a low-carbon economy and alleviating the need for energy security, hydrogen (H2) plays a key role in promoting a sustainable economy because it is clean and efficient. The bottleneck of the hydrogen evolution reaction (HER) can be overcome by developing high-efficiency electrocatalysts. Using a simple solvothermal method, p-NixCo9–xS8 with polyvinylpyrrolidone (PVP) compounds are successfully prepared with synergistic effects between bimetallic sulfides. The resulting p-NixCo9–xS8 catalyst shows a hierarchical flowerlike nanosheet shape based on physical representations. An ultrathin and porous nanosheet surface facilitates rapid electrolyte injection and provides abundant active sites for H+ adsorption, thus giving p-NixCo9–xS8 nanosheets outstanding HER performance. Furthermore, the synergistic effect of a bimetallic electrocatalyst is helpful to improve HER activity. In comparison to NixCo9–xS8 nanosheets without PVP, individual Co9S8 particles, and individual Ni9S8 nanosheets, p-NixCo9–xS8 nanosheets have a lower overpotential (137 mV to 10 mA cm–2), Tafel slope (109 mV dec–1), and 95.7% retention of current after 1000 cycles in the HER process.

Nanosized amorphous nickel-boron alloy electrocatalysts for hydrogen evolution reaction under alkaline conditions

Hydrogen production from electrolyzed water driven by sustainable energy is an effective way to achieve the hydrogen economy with zero carbon emission. Alkaline electrocatalytic hydrogen evolution reaction (HER) is one of the main energy transforming processes in the field of electrolytic water technology. The development of active and cost-effective nonprecious catalytic electrodes is of great importance to alkaline hydrogen evolution reaction. Amorphous nanosized nickel-boron alloy particles (NiB-COS) have been obtained by using chitosan oligosaccharides (COS) as a stabilizer via chemical reduction method. The as-prepared electrocatalysts have been used for the hydrogen evolution reaction (HER). The electrocatalysts have been characterized by using X-ray diffraction (XRD), transmission electron microscopy (TEM), inductively coupled plasma analysis (ICP) and X-ray photoelectron spectroscopy (XPS). NiB-COS displays a significant increase in hydrogen evolution reaction properties in alkaline media, affording low overpotentials of 49.4 mV at 10 mA/cm2 and 15.1 mV onset overpotential for the hydrogen evolution reaction. Tafel slope of NiB-COS is 86.1 mV/dec. Remarkably, the formation of a nickel-boron alloyed phase and the decrease of particle size are helpful to improve HER activity of NiB-COS. The experimental data indicated that the NiB-COS showed excellent long-term stability as a very active electrocatalyst.

Synergistic Coupling of Hierarchical Heterostructured Ni3P/Ni/VN Microflower Electrocatalyst for Enhanced Hydrogen Evolution Reaction

AbstractThe exploration of economical and highly efficient electrocatalysts for hydrogen evolution reaction (HER) is paramount for the development of sustainable hydrogen economy. Herein, a novel three‐dimensional (3D) hierarchical microflower electrocatalyst comprised of N‐doped carbon‐armored Ni3P/Ni/VN heterogeneous nanoparticles (Ni3P/Ni/VN@NC) is developed by combining a hydrothermal method with in‐situ carbonization‐phosphating strategy. The unique robust hierarchical structure derived from 3D NiV layered double hydroxide (NiV‐LDH) skeleton as precursor provides multidimensional mass and charge transport channels as well as numerous active sites for HER, leading to the improved HER activity. More importantly, the possible electron transfer route of Ni3P→Ni→VN is demonstrated due to the charge pumping capability of VN during interfacial electron intercoupling among the tri‐component, which endows Ni3P/Ni/VN with the favorable absorption of hydrogen‐intermediates and thus upgraded HER kinetics over such heterostructure. The resulting Ni3P/Ni/VN@NC catalyst exhibits extremely low overpotentials of 81 mV and 134 mV to deliver a current density of 10 mA cm−2 without iR‐compensation in alkaline and acidic media, respectively, and maintains continuous operation for over 90 h. This work enlightens the rational design of hierarchical multi‐component heterostructured catalysts for efficient hydrogen production.

In situ modulation of Pt-Ni heterocatalysts on highly graphitized wood-derived carbon platform to boost hydrogen production

Although Pt is an ideal electrocatalyst for hydrogen evolution reaction (HER), in addition to high cost and scarcity, Pt nanocatalysts suffer from low water dissociation rates and poor stability. Herein, we used graphitized wood-derived carbon (GWC) as a platform to construct dual-active catalytic sites via Pt-Ni recombination and modulate interactions of heterointerface atoms through in situ phase transition to improve HER activity and durability of Pt nanocatalysts. Specifically, Ni(OH)2 nanosheets were grown on GWC; then, Pt nanoparticles were introduced and converted in situ into Pt-Ni(PO3)2-GWC. As expected, the catalyst exhibited excellent HER activity, requiring only 10 mV (overpotential) to reach a current density of 10 mA cm–2 and excellent durability over 120 h. DFT calculations further revealed that in situ converted Pt and Ni(PO3)2 heterointerface tuned the electronic structure of interface atoms and synergistically promoted water dissociation and hydrogen adsorption. Notably, Pt-Ni(PO3)2-GWC can be used as a bifunctional catalyst for overall urea electrolysis, and the assembled electrolytic cell exhibited high-efficiency hydrogen production performance, requiring a cell voltage of only 1.39 V to reach a current density of 10 mA cm–2. These findings will provide new insights into the development of highly efficient, stable catalysts for energy-saving hydrogen production.

Bimetallic FeCo phosphide nanoparticles anchored on N-doped carbon foam for wide pH hydrogen evolution reaction

Transition metal phosphides (TMPs) have considered as excellent electrocatalysts with high reactivity for hydrogen evolution reaction (HER). While electro-catalytic properties of TMPs are restricted by uneven dispersion, small surface area, poor conductivity, and unsatisfied stability. Herein, a facile procedure was proposed to prepare a hierarchical structure of FeCoP nanoparticles anchored on N-doped carbon/multi-walled carbon nanotubes (NC/CNT) nanocomposites. With the increased porosity and conductive network of NC/CNT substrate, the as-synthesized NC/CNT-FeCoP provided abundant active sites for HER. Meanwhile, due to the synergistic effect between the dual metal centers and uniform distribution of bimetallic composites, the synthesized electrocatalyst can provide enhanced intrinsic activity. Therefore, the optimized NC/CNT-FeCoP delivered excellent HER activity in 1.0 M KOH and 0.5 M H2SO4 with overpotentials of 182 mV and 150 mV at 10 mA cm−2, respectively. Moreover, NC/CNT-FeCoP coupled two-electrode system needs a low cell potential of 1.68 V at 10 mA cm−2 for overall water splitting. First-principle calculations indicated that N-doped graphene substrate can adjust the electronic properties of surface metal site and consequently affect the H adsorption strength to yield an improved HER activity. Our work demonstrated that the combination of mesoporous conductive matrices with bimetallic phosphides could greatly improve the HER efficiency for electrocatalysis.

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.

Interface engineering of snow-like Ru/RuO2 nanosheets for boosting hydrogen electrocatalysis

Ru has recently been regarded as a promising catalyst for hydrogen oxidation reaction (HOR) and hydrogen evolution reaction (HER) due to its similar binding energy towards *H but lower price compared to Pt. Nevertheless, the quest of high-efficiency Ru-based catalysts for HOR and HER is driven by the current disadvantages including low activity and unsatisfactory stability. Herein, we have fabricated and engineered two-dimensional (2D) Ru-based snow-like nanosheets with Ru/RuO2 interface (Ru/RuO2 SNSs) via a post-annealing treatment. Detailed characterizations and theoretical calculations indicate that the interfacial synergy, which is dependent on the temperature for annealing, can alter the hydrogen binding energy (HBE) and hydroxide binding energy (OHBE), as a result of the enhanced HOR and HER performance. Impressively, the optimal Ru/RuO2 SNSs display a mass activity of 9.13 A mgRu–1 at an overpotential of 50 mV in 0.1 mol L–1 KOH for HOR, which is 65, 304, and 21 times higher than those of Ru SNSs (0.14 A mgRu–1), RuO2 SNSs (0.03 A mgRu–1), and commercial Pt/C (0.43 A mgRu–1), respectively. Moreover, Ru/RuO2 SNSs display improved HER activity with a low overpotential of 20.2 mV for achieving 10 mA cm−2 in 1 mol L–1 KOH. This work not only provides an efficient catalyst for HOR and HER, but also promotes fundamental research on the fabrication and modification of catalysts in heterogeneous catalysis.

Electrocatalytic performance of MoS2 nanosheets grown on a carbon nanotubes/carbon cloth substrate for the hydrogen evolution reaction

Two dimensional (2D) layered molybdenum sulfide (MoS2) exhibit unique advantages as electrocatalyst for the hydrogen evolution reaction (HER). However, the low conductivity of MoS2 itself still limit the overall HER rate. In this work, MoS2 nanosheets grown on a carbon nanotubes (CNTs)/carbon cloth (CC) were used as a cathode electrode for HER under alkaline electrolysis. A MoS2/CNTs/CC were prepared by a hydrothermal method using a precursor solution of sodium molybdate (Na2MoO4·2H2O), thiourea (SC(NH2)2), oxalic acid (C2H2O4·2H2O) and deionized water. The oxalic acid is used as a reducing agent and its concentration plays a significant role in controlling the size and the HER performance of MoS2 nanosheets. The MoS2/CNTs/CC catalyst prepared with the oxalic acid concentration of 5.625 mM shows the optimal HER activity, exhibiting the overpotential of 134 mV at a current density of 10 mA cm-2, Tafel plots of 45.7 mV dec-1, electrochemical double layer capacitance of 123.9 mF cm-2, electrochemical surface area of 3097.5 cm2 and very high durability. The improved HER activity is attributed to the more exposed active sites for the smaller size MoS2 nanosheets and improved conductivity of MoS2 nanosheets by CNTs.

Protrusion-Rich Cu@NiRu Core@shell Nanotubes for Efficient Alkaline Hydrogen Evolution Electrocatalysis.

The development of highly efficient and durable water electrolysis catalysts plays an important role in the large-scale applications of hydrogen energy. In this work, protrusion-rich Cu@NiRu core@shell nanotubes are prepared by a facile wet chemistry method and used for catalyzing hydrogen evolution reaction (HER) in an alkaline environment. The protrusion-like RuNi alloy shells with accessible channels and abundant defects possess a large surface area and can optimize the surface electronic structure through the electron transfer from Ni to Ru. Moreover, the unique 1D hollow structure can effectively stabilize RuNi alloy shell through preventing the aggregation of nanoparticles. The synthesized catalyst can achieve a current density of 10mA cm-2 in 1.0 m KOH with an overpotential of only 22mV and show excellent stability after 5000 cycles, which is superior to most reported Ru-based catalysts. Density functional theory calculations illustrate that the weakened hydrogen adsorption on Ru sites induced by the alloying with Ni and active electron transfer between Ru and Ni/Cu are the keys to the much improved HER activity.

Boosting Hydrogen Evolution Electrocatalysis via Regulating the Electronic Structure in a Crystalline-Amorphous CoP/CeOx p-n Heterojunction.

The modulation of the electronic structure is the effective access to achieve highly active electrocatalysts for the hydrogen evolution reaction (HER). Transition-metal phosphide-based heterostructures are very promising in enhancing HER performance but the facile fabrication and an in-depth study of the catalytic mechanisms still remain a challenge. In this work, the catalytically inactive n-type CeOx is successfully combined with p-type CoP to form the CoP/CeOx heterojunction. The crystalline-amorphous CoP/CeOx heterojunction is fabricated by the phosphorization of predesigned Co(OH)2/CeOx via the as-developed reduction-hydrolysis strategy. The p-n CoP/CeOx heterojunction with a strong built-in potential of 1.38 V enables the regulation of the electronic structure of active CoP within the space-charge region to enhance its intrinsic activity and facilitate the electron transfer. The functional CeOx entity and the negatively charged CoP can promote the water dissociation and optimize H adsorption, synergistically boosting the electrocatalytic HER output. As expected, the heterostructured CoP/CeOx-20:1 with the optimal ratio of Co/Ce shows significantly improved HER activity and favorable kinetics (overpotential of 118 mV at a current density of 10 mA cm-2 and Tafel slope of 77.26 mV dec-1). The present study may provide new insight into the integration of crystalline and amorphous entities into the p-n heterojunction as a highly efficient electrocatalyst for energy storage and conversion.