High-performance Electrocatalysts For Hydrogen Evolution Reaction Research Articles

Stacking Fault-Enriched MoNi4/MoO2 Enables High-Performance Hydrogen Evolution.

Producing green hydrogen in a cost-competitive manner via water electrolysis will make the long-held dream of hydrogen economy a reality. Although platinum (Pt)-based catalysts show good performance toward hydrogen evolution reaction (HER), the high cost and scarce abundance challenge their economic viability and sustainability. Here, a non-Pt, high-performance electrocatalyst for HER achieved by engineering high fractions of stacking fault (SF) defects for MoNi4/MoO2 nanosheets (d-MoNi) through a combined chemical and thermal reduction strategy is shown. The d-MoNi catalyst offers ultralow overpotentials of 78 and 121mV for HER at current densities of 500 and 1000mA cm-2 in 1M KOH, respectively. The defect-rich d-MoNi exhibits four times higher turnover frequency than the benchmark 20% Pt/C, together with its excellent durability (> 100 h), making it one of the best-performing non-Pt catalysts for HER. The experimental and theoretical results reveal that the abundant SFs in d-MoNi induce a compressive strain, decreasing the proton adsorption energy and promoting the associated combination of *H into hydrogen and molecular hydrogen desorption, enhancing the HER performance. This work provides a new synthetic route to engineer defective metal and metal alloy electrocatalysts for emerging electrochemical energy conversion and storage applications.

Synthesis of Stable and Efficient Electrocatalysts for Hydrogen Evolution: Hierarchical NiMo-Based Hollow Nanotubes

Large-scale development of low-cost, efficient, and stable powder electrocatalysts for the hydrogen evolution reaction (HER) in alkaline solutions is a key step toward commercial hydrogen production. Herein, a hierarchical NiMo-MoO3-x hollow nanotube (NiMo-MoO3-x-HNT) with bifunctional groups as an efficient HER electrocatalyst was strategically invented using an MoO3 nanorod (MoO3−NR) as the precursor. The synthesis mechanism of the NiMo-MoO3-x-HNT is established based on in-depth investigations using diffraction, spectral, and microscopy results. Experimental results suggest that the NiMo-MoO3-x-HNT exhibits excellent electrocatalytic HER performance in 1 M KOH, with a low overpotential of 26.5 mV@10.0 mA cm-2 and a small Tafel slope of 32.6 mV dec–1. These values are comparable to those of cutting-edge electrocatalysts based on platinum-group metals. Moreover, it exhibits an almost unaffected cyclic stability over 50,000 cycles and robust durability over 98 h. This remarkable performance is attributed to its bifunctional groups and the porous hierarchical hollow nanotubular morphology. In summary, this study proposes a novel, efficient, and cost-effective strategy for the development of noble metal-free, high-performance HER electrocatalysts.

Honeycomb-like hollow carbon loaded with ruthenium nanoparticles as high-performance HER electrocatalysts

A honeycomb-like N-doped hollow carbon material loaded with a low content of ruthenium nanoparticles was prepared as an efficient HER catalyst, and its performance is even superior to that of commercial Pt/C.

Synthesis of FeNi-based heterostructure on a nickel foam at room temperature for efficient catalyzing hydrogen evolution reaction

The FeNi-based heterostructure was synthesized on a nickel foam by a simple dip-coating method with zero-energy consumption at room temperature. The obtained heterostructure is flower-like and has high-performance for electrocatalyzing the hydrogen evolution reaction (HER). On the FeNi-based heterostructure, the overpotential was only 228 mV at a current density of 100 mA cm−2 in 1 M KOH, and can maintain 10 h stability with chronoamperometry test. The outstanding catalytic activity was attributed to the unique structure with a large electrochemical active surface area and the synergistic effect between different transition metal elements. This research afforded a new way to design low-cost and high-performance HER electrocatalyst.

Efficient hydrogen evolution enabled by in-situ synthesis of biphasic Mo2C/Mo16N7 nitrogen-doped carbon nanorods as catalysts

Molybdenum carbide (Mo2C) has gained significant recognition as a cutting-edge, non-precious transition metal catalysts for efficiently driving the hydrogen evolution reaction (HER). However, the desorption of Mo-H bonds on the pristine Mo2C surface are difficult, resulting in a slow Heyrovsky/Tafel step. Herein, biphasic Mo2C/Mo16N7 nitrogen doped carbon nanorods (Mo2C/Mo16N7@NRs) is synthesized as the high-performance HER electrocatalyst by using a one-step in-situ pyrolysis growth method. It is found that a suitable pyrolysis temperature can simultaneously tune the morphology of the catalyst and form abundant heterointerface. Benefit from abundant porous nanostructure and more electron-rich Mo active sites at the Mo2C-Mo16N7 interfaces, the optimized Mo2C/Mo16N7@NRs demonstrates exceptional catalytic activity. It achieves low overpotentials (η10) of 63.62 and 117.43 mV at 10 mA cm−2, accompanied by Tafel scopes of 49.73 and 64.44 mV dec−1 in both alkaline and acidic electrolytes. Also, Mo2C/Mo16N7@NRs shows long-lasting stability for 24 h in the different electrolytes. The experimental and theoretical findings explain the synergistic effects of unique morphology control and interface engineering on electrocatalyst activity. The one-step in-situ pyrolysis growth method is expected to produce non-precious metal catalysts with distinct morphology and heterointerfaces.

Machine learning assisted screening of doped metals phosphides electrocatalyst towards efficient hydrogen evolution reaction

Transition metals (TM) doped metal phosphides usually exhibits promising reactivity towards acidic hydrogen evolution reaction (HER). However, the experimental screening of highly active TM-doped metal phosphides catalyst is time-consuming and challenging. In this study, a density functional theory combined machine learning (DFT-ML) framework is proposed to accelerate the screening and predicting TM-doped metal phosphides-based HER electrocatalysts. In this framework, the ML database is constructed using critical catalyst features and DFT-calculated adsorption energy of HER intermediates. Also, local average electronegativity of the adsorption site and the surrounding atoms as catalyst feature is proposed to describe the reaction sites in this ML model. Using the HER energetics on the state-of-art highly active Pt (111) as benchmark catalyst model, a set of 10 potential active HER catalysts is predicted. By performing the H* adsorption Gibbs free energy change analysis on these ML-predicted catalysts, six promising TM-doped metal phosphides HER catalysts are determined in the sample space. This study provides a facile and effective approach for the quick screening of high-performance HER electrocatalysts.

Effective electrocatalytic hydrogen evolution of carbon paste electrode modified by Fe (II) and Ni (II) phenylimidazole‐dicarboxylate complexes

The structure determined is helpful to explore the reaction mechanism and provide a design strategy for the synthesis of high‐performance hydrogen evolution reaction (HER) electricity catalysts. Therefore, two structurally tunable and deterministic metal complexes, [Fe(m‐H2MOPhIDC)2(H2O)2]·2H2O (1) and [Ni(m‐HMOPhIDC)(H2O)2)]n (2) (m‐H3MOPhIDC = 2‐[3‐methoxyphenyl]‐1H‐imidazole‐4,5‐dicarboxylic acid), were synthesized under solvothermal conditions and used to assemble modified carbon paste electrodes (CPE 1–2) to explore the relationship between structure and catalytic performance. Structural analysis revealed that complexes 1 and 2 had a mononuclear structure and 1D linear structure, respectively, and that the central ions of the two complexes had the same coordination environment of the octahedral spatial configuration. In 0.5 M H2SO4 and 293 K, linear sweep voltammetry and Tafel curve indicate that the η10 (overpotential, 10 mA cm−2) of two modified carbon paste electrodes are −574 and −539 mV and Tafel slopes are 161 and 128 mV dec−1. Comparing the overpotential of CPE 1–2 with that of unmodified solid carbon paste electrode (sCPE, −976 mV), it was found that the overpotential of CPE1–2 shifted positively and the Tafel slopes are obviously reduced compared to sCPE (221 mV dec−1), which proves that the CPE 1–2 has effective electrocatalytic hydrogen evolution activity. The controlled potential electrolysis and impedance spectroscopy further validated the above conclusions. The higher HER activity of the CPE 2 than CPE 1 can be attributed to the fact that complex 2 is a one‐dimensional polymer, which can efficiently disperse the catalytic active site. The use of metal complexes as HER electrocatalysts provides a new idea for an effective method for converting electric energy into hydrogen energy and is beneficial to the development of the HER research field.

Modulating Electronic Structures of Bimetallic Co-Fe Sulfide Ultrathin Nanosheet Supported on g-C3N4 Promoting Electrocatalytic Hydrogen Evolution Performance

Heteroatom doping is a possible way to regulate the catalytic capability of electrocatalysts for hydrogen evolution reaction (HER). This work focuses on the development of bimetallic Cobalt-Iron sulfide ultrathin nanosheets supported on the graphitic carbon nitride (g-C3N4) catalyst as efficient HER electrocatalysts (CoS2/FeS2/CN) with good stability at wide pH value. The ultrathin nanosheet exposes more active sites and enhances the catalyst activity. Electrochemical experiments demonstrate that adding g-C3N4 and Fe to CoS2 increases its catalytic activity and stability. Furthermore, g-C3N4 and Fe co-doped with CoS2 can modulate electronic structures on the interface. The CoS2/FeS2/CN exhibits outstanding HER performance, reaching a current density of 10 mA cm−2 with overpotentials of only 76.5 mV in an acidic solution and 175.6 mV in an alkaline solution. It also demonstrates exceptional durability, superior to commercial platinum/carbon catalysts. This work introduces a promising approach for designing low-cost, high-performance HER electrocatalysts with a wide pH range.

Wet chemical synthesis of rhodium nanoparticles anchored on cobalt/nitrogen-doped carbon nanofibers for high-performance alkaline and acidic hydrogen evolution

Constructing high-activity electrocatalysts towards hydrogen evolution reaction (HER) is an essential way to achieve efficient, green and sustainable energy from water electrolysis. In this work, rhodium (Rh) nanoparticles anchored on cobalt (Co)/nitrogen (N)-doped carbon nanofibers (NCNFs) catalyst is prepared by the electrospinning-pyrolysis-reduction method. The synergy effect between Co-NCNFs and Rh nanoparticles contributes to the superior HER activity and favorable durability. The optimized 0.15Co-NCNFs-5Rh sample exhibits ultralow overpotentials of 13 and 18 mV to reach 10 mA cm−2 in an alkaline and acidic electrolyte, surpassing many Rh-based or Co-based electrocatalysts reported in the literature. Additionally, the Co-NCNFs-Rh sample shows a better HER activity than benchmark Pt/C catalyst in an alkaline medium at all current densities and in an acidic condition at higher current densities, offering its promising practical applications. Thus, this work provides an efficient methodology to construct high-performance HER electrocatalysts.

D-Band Center Optimization of Edge-Rich Ultrathin RuZn Nanosheets With Moiré Superlattices for pH-Universal Hydrogen Evolution Reaction.

Electrocatalytic hydrogen evolution reaction (HER) is a promising way to produce pure and clean hydrogen. However, the preparation of efficient and economical catalysts for pH-universal HER remains a challenging but rewarding task. Herein, ultrathin RuZn nanosheets (NSs) with moiré superlattices and abundant edges are synthesized. The RuZn NSs with unique structure exhibit superb HER performance with overpotentials of 11, 13, and 29mV to achieve 10mA cm-2 in 1M KOH, 1M PBS, and 0.5M H2 SO4 , respectively, which is substantially lower than those of Ru NSs and RuZn NSs without moiré superlattices. Density functional theory investigations reveal that the charge transfer from Zn to Ru will lead the appropriate downshift of the d-band center of surface Ru atoms, thus accelerating hydrogen desorption from the Ru sites, lowering the dissociation energy barrier of water and greatly improving the HER performance. This work provides an effective design scheme for high-performance HER electrocatalysts over a wide pH range, and propose a general route to prepare Ru-based bimetallic nanosheets with moiré superlattices.

Synthesis of M/Mo LDH@P-rGO (M = Ni, Co, Fe, Cu, Zn, Mn, W, and V) as a new electrocatalyst for efficient hydrogen evolution reaction in alkaline media

The design of non-precious electrocatalysts with high performance is essential for developing green and renewable energy sources. Here, we presented a facile method for the synthesis of three-dimensional (3D) phosphorus-doped reduced graphene oxide (P-rGO) assembled by metal/molybdenum layered double hydroxide (M/Mo LDH), where M is Ni, Co, Fe, Cu, Zn, Mn, W, and V. The 3D structure of P-rGO provides abundant active sites for the hydrogen evolution reaction (HER). Among the mentioned metals, nickel shows the best HER performance, presenting a low overpotential of 91 mV at 10 mA cm−2 with a Tafel slope of 56 mV dec−1 in alkaline media. The Ni/Mo LDH@P-rGO electrocatalyst delivers excellent stability after 1000 consecutive cycles and after long-term testing over 12 h. The satisfactory HER activity of Ni/Mo LDH@P-rGO is due to its high electrochemically active surface area and synergistic effects between Ni and Mo atoms. This study will present a simple and efficient strategy to fabricate a high-performance electrocatalyst for HER.

Zr-MOF/NiS2 hybrids on nickel foam as advanced electrocatalysts for efficient hydrogen evolution

As a typical transition-metal sulfides (TMS), nickel disulfide (NiS2) has attracted great attention in terms of hydrogen evolution reaction (HER). Howbeit, owing to the poor conductivity, slow reaction kinetics and instability of NiS2, its HER activity is still necessary to be improved. In this work, we designed hybrid structures consisting of the nickel foam (NF) as a self-supporting electrode, NiS2 derived from the sulfuration of NF and Zr-MOF grown on the surface of NiS2@NF (Zr-MOF/NiS2@NF). Due to the synergistic effect between the different constituents, the obtained Zr-MOF/NiS2@NF demonstrates ideal electrochemical hydrogen evolution ability in acidic and alkalescent environment, reaching a standard current density of 10 mA cm−2 at overpotentials of 110 and 72 mV in 0.5 M H2SO4 and 1 M KOH electrolytes, respectively. What is more, it also maintains excellent electrocatalytic durability for 10 h in both electrolytes. This work could provide a useful guidance on effectively combining metal sulfide with MOF for high-performance HER electrocatalysts.

Synthesis and study of electrochemical properties of Ni-Co-V@PrGO to enhance hydrogen evolution reaction

Hydrogen evolution reaction (HER) is kinetically slow as a necessary half-reaction in water-splitting. It requires high-efficiency electrocatalysts to reduce the overpotential and improve energy conversion efficiency. Transition-metal electrode materials with high stability and efficiency have become the frontiers of energy conversion and storage fields. The present work involves the investigation of transition metals as electrocatalysts for HER. On the other hand, various carbon nanomaterials, including carbon nanotubes, activated carbon, and graphene for high-performance electrocatalysts, have been successfully shown. Still, their performances must be improved (using phosphorus-doped graphene) for wider and more challenging applications. The Ni-Co-V@PrGO was synthesized through a simple method with an amorphous structure that enhanced catalytic activity toward hydrogen evolution reaction with a Tafel slope of 80 and 58 mV dec−1 (counter electrode: Pt) and 85 and 118 mV dec−1 (counter electrode: graphite) in alkaline and acidic media, respectively. Hereupon this research presents a simple and efficient high-performance electrocatalyst for HER.

Ultrafast Preparation of Metal/Carbon Nanocomposite Electrocatalysts by Magnetic Induction Heating toward Efficient Hydrogen Evolution Reaction

Hydrogen, which can be readily produced by electrochemical water splitting, has been hailed as one of the most promising green energy sources. In a water electrolyzer, catalysts are needed for the hydrogen evolution reaction (HER) at the cathode, which are traditionally based on platinum-based materials. Recently, carbon-based nanocomposites have emerged as viable alternatives, which are mostly prepared by pyrolysis or wet chemistry methods, which are time- and energy-consuming. We have exploited magnetic induction heating (MIH) for ultrafast and green preparation of high-performance HER electrocatalysts. A novel MIH method was developed for the ultrafast and green preparation of carbon-supported Ru NPs toward HER in alkaline media, where the size and morphology of the Ru NPs can be readily manipulated by the heating current and duration. It is expected that MIH can be exploited for the design and engineering of high-performance nanocomposite catalysts for important electrochemical energy technologies.

Unveiling the synergy of polymorph heterointerface and sulfur vacancy in NiS/Ni3S2 electrocatalyst to promote alkaline hydrogen evolution reaction

Efficient transition metal sulfide electrocatalysts for alkaline hydrogen evolution reaction (HER) are desired but restricted by their sluggish kinetics. Herein, we report a hydrothermal sulfurization-acid assisted etching strategy for the controllable fabrication of Mo doped NiS/Ni3S2 polymorph heterostructure with rich sulfur vacancies (Mo-NiS/Ni3S2-rich Sv). Direct spectroscopic evidence, together with theoretical analysis, demonstrate that the S centers on the Ni3S2 side of the nickel sulfide polymorphs are identified as the H2-evolving sites, while the Ni sites on the Mo-NiS side are beneficial for cleaving the HO-H bond. Importantly, in situ Raman spectroscopy further reveals that the presence of rich Sv can expedite the evolution of H* to molecular H2, promoting the HER kinetics. As expected, the optimal Mo-NiS/Ni3S2-rich Sv electrocatalyst exhibits the outstanding HER activity and excellent durability in alkaline solution. Understanding the synergy of polymorph heterostructure and element defect is crucial for the rational design of high-performance HER electrocatalysts.

Strategies for Designing High-Performance Hydrogen Evolution Reaction Electrocatalysts at Large Current Densities above 1000 mA cm-2.

The depletion of fossil fuels and rapidly increasing environmental concerns have urgently called for the utilization of clean and sustainable sources for future energy supplies. Hydrogen (H2) is recognized as a prioritized green resource with little environmental impact to replace traditional fossil fuels. Electrochemical water splitting has become an important method for large-scale green production of hydrogen. The hydrogen evolution reaction (HER) is the cathodic half-reaction of water splitting that can be promoted to produce pure H2 in large quantities by active electrocatalysts. However, the unsatisfactory performance of HER electrocatalysts cannot follow the extensive requirements of industrial-scale applications, including working efficiently and stably over long periods of time at high current densities (⩾1000 mA cm-2). In this review, we study the crucial issues when electrocatalysts work at high current densities and summarize several categories of strategies for the design of high-performance HER electrocatalysts. We also discuss the future challenges and opportunities for the development of HER catalysts.

Plasma-assisted highly dispersed Pt single atoms on Ru nanoclusters electrocatalyst for pH-universal hydrogen evolution

Exploring highly active and stable electrocatalyst using trace noble metals for hydrogen evolution reaction (HER) is urgently needed but still challenging. Here, atomically dispersed Pt on ultrafine Ru nanoclusters (∼1.46 nm) loaded by the commercial acetylene black (Acet) support is fabricated by a facile one-step cold-plasma technique. The Pt single atoms on Ru nanoclusters electrocatalyst (Pt0.47-Ru/Acet) with 0.47 wt% content of Pt exhibit an excellent HER activity in all pH, achieving ultralow overpotential of only 17, 28, and 8 mV at 10 mA·cm−2 in 1 M KOH, 0.5 M H2SO4, and 1 M PBS, respectively. And the mass activity of Pt0.47-Ru/Acet catalyst in alkaline is about 5.54 and 2.15 times that of commercial Ru/C and Pt/C catalyst at an overpotential of 100 mV, respectively. Meanwhile, after 8000 CV cycles, there is barely performance decrease for Pt0.47-Ru/Acet, displaying good stability. DFT calculation reveals that the Pt single atoms could effectively regulate the electronic structure of Ru clusters, and reduce the energy barriers of water dissociation (Volmer step) as well as subsequent hydrogen evolution (Heyrovsky step), thus enhancing the alkaline HER performance effectively. This work provides an effective approach to designing a high-performance HER electrocatalyst with the atomic-dimension Pt surface modification.

An insight to catalytic synergic effect of Pd-MoS2 nanorods for highly efficient hydrogen evolution reaction

The electrocatalytic hydrogen evolution reaction (HER) is a sustainable energy production route using green chemistry. Transition metal dichalcogenides' application in catalytic hydrogen production is limited due to a lack of solutions that simultaneously address intrinsic activity, increased surface area, electrical conductivity, and stability problems. Herein we address these issues simultaneously by modifying the electronic structure of molybdenum disulfide (MoS2) nanorods using a low content of Pd (1 wt% and 2 wt%) dopant via a facile colloidal solvothermal route. The resulting MoS2 nanorods doped with (1 and 2 wt%) palladium demonstrate current density of 100 mA/cm2 at quit lower over-potentials of 137 mV and 119 mV than 273 mV for pure MoS2 nanorods, accompanied by high stability. This research proposes a strategy for designing high-performance HER electrocatalysts that work in acidic medium. In addition, the Tafel slop calculated for MoS2 is 112 mV/dec whereas for 1 and 2 wt% Pd-MoS2, the Tafel slopes are 70 mV/dec and 46 mV/dec.

NiMo@C3N5 heterostructures with multiple electronic transmission channels for highly efficient hydrogen evolution from alkaline electrolytes and seawater

Designing highly efficient and stable electrocatalysts for hydrogen evolution reaction (HER), particularly in seawater, still remains a challenging task. Herein, the unique heterostructures composed of 1D NiMo cores and 2D C3N5 shells (NiMo@C3N5) are rationally designed and demonstrated as the robust HER catalysts in both alkaline electrolytes and natural seawater, where the carbon-based shell can effectively protect the catalyst core from seawater poisoning. Based on the experimental investigation and density functional theory calculation, multiple electronic transmission channels were found to establish at the interface between NiMo cores and C3N5 shells, thus providing efficiently optimized HER pathways to achieve minimized overpotential with a reduced energy barrier of the rate-determining step. More importantly, the NiMo@C3N5 hybrids exhibit stable HER performance with a high Faradaic efficiency of 94.8% in seawater, which is superior to that of commercial Pt/C. All these results can evidently highlight a feasible strategy to develop high-performance HER electrocatalysts via interface engineering.

Excellent Electrocatalytic Hydrogen Evolution Reaction Performances of Partially Graphitized Activated-Carbon Nanobundles Derived from Biomass Human Hair Wastes.

Carbonaceous materials play a vital role as an appropriate catalyst for electrocatalytic hydrogen production. Aiming at realizing the highly efficient hydrogen evolution reaction (HER), the partially graphitized activated-carbon nanobundles were synthesized as a high-performance HER electrocatalyst by using biomass human hair ashes through the high-temperature KOH activation at two different temperatures of 600 and 700 °C. Due to the partial graphitization, the 700 °C KOH-activated partially graphitized activated-carbon nanobundles exhibited higher electrical conductivity as well as higher textural porosity than those of the amorphous activated-carbon nanobundles that had been prepared by the KOH activation at 600 °C. As a consequence, the 700 °C-activated partially graphitized activated-carbon nanobundles showed the extraordinarily high HER activity with the very low overpotential (≈16 mV at 10 mA/cm2 in 0.5 M H2SO4) and the small Tafel slope (≈51 mV/dec). These results suggest that the human hair-derived partially graphitized activated-carbon nanobundles can be effectively utilized as a high-performance HER electrocatalyst in future hydrogen-energy technology.