Electrocatalyst For Hydrogen Evolution Research Articles

Antimony-assisted controlled growth of PtSe2ribbon arrays for enhanced hydrogen evolution reaction.

In this study, we report the successful synthesis of few-layer parallel PtSe2ribbons on an Au foil employing a surface melting strategy via the chemical vapor deposition (CVD) growth method at 650℃. The controlled formation of parallel ribbons was directed by the Au steps generated through antimony treatment. These ribbons exhibit an average length of exceeding 100 μm and a width of approximately 100 nm across a substantial area. Electrocatalysis measurements showcase the catalytic performance of PtSe2ribbons grown on Au foil, which can be further augmented through subsequent oxidation treatment. This investigation introduces an effective growth method for few-layer ribbons at low temperatures and broadens the scope of employing the substrate-guided strategies for the synthesis of one-dimensional materials. Additionally, it underscores the potential of PtSe2ribbons as an electrocatalyst for hydrogen evolution.

Unsymmetric Co-Facial "Salixpyrrole" Hydrogen Evolution Catalysts: Two Metals are Better than One.

Designing ligand architectures that can mimic enzyme active sites is a promising approach for developing efficient small molecule activation catalysts for sustainable energy applications. Some key design features include chemically distinct binding pockets for multiple metal centers and a three-dimensional structure that controls the positioning of catalytic sites. With these principles in mind, mono- and bimetallic unsymmetric cofacial palladium complexes, 2 and 3, respectively, bearing ligands with calixpyrrole and salen coordination sites, or "salixpyrrole" ligands, are reported. These species were accessed in a straightforward Schiff-base reaction with appreciable yields. In addition, both 2 and 3 were found to be active hydrogen evolution electrocatalysts using para-toluenesulfonic acid monohydrate as the proton source. The two salixpyrrole species displayed different mechanisms of action, with 2 showing a second-order dependence on acid concentration, whereas 3 exhibited a first-order dependence. Moreover, the bimetallic catalyst was significantly more efficient, with higher turnover frequencies, 4640 s-1 vs 1680 s-1 for 2, and lower overpotentials, 0.39 V vs 0.69 V for 2. The results reported herein provide proof-of-concept that bimetallic catalysts with chemically distinct binding sites demonstrate enhanced catalytic properties in comparison to monometallic or symmetric analogues.

Construction of high activity electrocatalyst for alkaline hydrogen evolution by doping magnetic Fe3O4 with RuO2

Abstract The rational build of hydrogen evolution reaction (HER) electrocatalyst with low-cost, highly efficient, and excellent stability is the key to realizing the electrochemical decomposition of water. Herein, the optimal ratio between RuO2 and Fe3O4 for high-activity electrocatalysts (RuO2/Fe3O4 hybrid nanoparticles) was obtained by the microemulsion method. The morphology and structure characterization show uniform distribution (average particle size of ~35.0 ± 5.1 nm) and high crystallinity of the RuO2/Fe3O4 hybrid nanoparticles. Compared to RuO2/Fe3O4 (2:1) and RuO2/Fe3O4 (1:2) samples, electrochemical tests show that RuO2/Fe3O4 (1:1) exhibit favorable HER catalytic activity (overpotential: 181 mV at 10 mA cm-2; Tafel slope: 130 mV dec-1) and stability (no obvious activity attenuation during the 20 h) in an alkaline medium. The mechanism analysis implies that the doping of Fe3O4 accelerated the electron transfer rate and thus increased HER activity via the results of electrochemical impedance spectroscopy (EIS) tests. Blending the appropriate amount of Fe3O4 into RuO2 can not only reduce the cost of electrocatalyst but also improve the activity of electrocatalytic HER, which is expected to give guidance for the development of low-cost, highly stable nanostructured electrocatalysts for electrochemical HER in alkaline electrolytes.

Ru-doping W4.6N4 nanoparticles anchored on N-doped graphene tubes as efficient hydrogen evolution electrocatalyst

Designing efficient electrocatalysts for hydrogen evolution reaction (HER) is essential to facilitate hydrogen energy applications. Herein, efficient strategies of doping with metal atoms (Ru) and incorporating with conductive carbon-based material (N-doping graphene tubes) have been developed to construct the hybrid electrocatalyst RuW4.6N4@N-GTs, in which, Ru-doped W4.6N4 nanoparticles integrated on the surface of N-doped graphene tubes. RuW4.6N4@N-GTs reveals superior HER activity and good stability, with a low overpotential of 29 mV to deliver the current density of 10 mA cm−2 and a low Tafel slope of 57 mV dec−1. The unique 3D nano-structure morphology of abundant homogeneous RuW4.6N4 nanoparticles supported on conductive N-GTs network carrier contributes to expose more electrochemical active sites, promoting electrolyte transport and gas emission. At the same time, the N-GTs skeleton could prevent the RuW4.6N4 particles from agglomerating and collapsing, thus leading to the superior stability during HER process. The in situ Ru heteroatom doping could cause the directional electron transfer and more nitrogen vacancies, thus modulating the electron structure of catalysts and optimizing the hydrogen adsorption free energy. The synergistic effect of the above merits endows RuW4.6N4@N-GTs with outstanding HER performance for potential applications in the hydrogen production field.

Ru-doping W4.6N4 nanoparticles anchored on N-doped graphene tubes as efficient hydrogen evolution electrocatalyst

Designing efficient electrocatalysts for hydrogen evolution reaction (HER) is essential to facilitate hydrogen energy applications. Herein, efficient strategies of doping with metal atoms (Ru) and incorporating with conductive carbon-based material (N-doping graphene tubes) have been developed to construct the hybrid electrocatalyst RuW4.6N4@N-GTs, in which, Ru-doped W4.6N4 nanoparticles integrated on the surface of N-doped graphene tubes. RuW4.6N4@N-GTs reveals superior HER activity and good stability, with a low overpotential of 29 mV to deliver the current density of 10 mA cm−2 and a low Tafel slope of 57 mV dec−1. The unique 3D nano-structure morphology of abundant homogeneous RuW4.6N4 nanoparticles supported on conductive N-GTs network carrier contributes to expose more electrochemical active sites, promoting electrolyte transport and gas emission. At the same time, the N-GTs skeleton could prevent the RuW4.6N4 particles from agglomerating and collapsing, thus leading to the superior stability during HER process. The in situ Ru heteroatom doping could cause the directional electron transfer and more nitrogen vacancies, thus modulating the electron structure of catalysts and optimizing the hydrogen adsorption free energy. The synergistic effect of the above merits endows RuW4.6N4@N-GTs with outstanding HER performance for potential applications in the hydrogen production field.

Electronic-Structure-Modulated Cu,Co-Coanchored N-Doped Nanocarbon as a Difunctional Electrocatalyst for Hydrogen Evolution and Oxygen Reduction Reactions.

To alleviate the problems of environmental pollution and energy crisis, aggressive development of clean and alternative energy technologies, in particular, water splitting, metal-air batteries, and fuel cells involving two key half reactions comprising hydrogen evolution reaction (HER) and oxygen reduction (ORR), is crucial. In this work, an innovative hybrid comprising heterogeneous Cu/Co bimetallic nanoparticles homogeneously dispersed on a nitrogen-doped carbon layer (Cu/Co/NC) was constructed as a bifunctional electrocatalyst toward HER and ORR via a hydrothermal reaction along with post-solid-phase sintering technique. Thanks to the interfacial coupling and electronic synergism between the Cu and Co bimetallic nanoparticles, the Cu/Co/NC catalyst showed improved catalytic ORR activity with a half-wave potential of 0.865 V and an excellent stability of more than 30 h, even compared to 20 wt% Pt/C. The Cu/Co/NC catalyst also exhibited excellent HER catalytic performance with an overpotential of below 149 mV at 10 mA/cm2 and long-term operation for over 30 h.

Transition Metals Co, Ni, Mn Based Bimetallic Sulfides as an Efficient Electrocatalyst for Hydrogen Evolution Using Graphite Counter Electrode Extracted from Spent Battery

The clean and green hydrogen energy production by electrochemical process is gaining great attention in recent years. For this, designing an efficient and cost-effective electrocatalyst for the hydrogen evolution reaction (HER) is highly desirable. Herein, Co-Ni-Mn based bimetallic sulfides electrocatalysts are developed for HER in 1 M KOH. Owing to the presence of abundant electrochemical active sites and micro flower-like morphology, the fabricated Co-Ni-S, Ni-Mn-S, Co-Mn-S electrodes deliver the small overpotential of 136, 112, 75 mV to reach the current density of 10 mA cm−2. For practical applications, the commercially available 1.6 V battery is used to drive the overall water splitting process of the device fabricated with the two-electrode system (symmetric device). In addition to this, in this research work, a graphite rod extracted from a spent battery is directly used as a counter electrode for the entire electrochemical study to substitute platinum (Pt) counter electrode. This approach is sustainable as well as eco-friendly.

Electrodes composited by bisbenzimidazole silver(I) coordination polymers as electrocatalysts for hydrogen evolution and H2O2-sensing

Two new silver(Ⅰ) coordination polymers (CPs) {[Ag2(p-HMOPhIDC)(BBP)](H2O)}n (1), {[Ag2(m-HMOPhIDC)(BBP)](H2O)}n (2) (BBP = 1,3-[bis(2,2′-benzimidazole)] propane, p-H3MOPHIDC = 2-(4-methoxyphenyl)–2H-imidazole-4,5-dicarboxylic acid, m-H3MOPHIDC = 2-(3-methoxyphenyl)–2H-imidazole-4,5-dicarboxylic acid), were prepared under hydrothermal condition and structurally characterized. The CPs 1–2 both exhibit binuclear 1D “square waveform” chain structures. Structural analysis shows that the two silver ions in CP 1 are crystallographically independent but chemically identical; whereas the two silver ions in CP 2 are crystallographically independent and chemically different. Electrocatalytic hydrogen evolution reaction (HER) of carbon paste composite electrodes (CPCEs 1–2) prepared by mixing graphite powder with coordination polymers was investigated by variable temperature linear sweep voltammetry (VT-LSV), controlled potential electrolysis (CPE) and electrochemical impedance spectroscopy (EIS) in 0.5 M H2SO4 electrolyte. It was found that the overpotential η10293K of CPCEs 1–2 positively shifted 449 and 172 mV compared with sCPCE (−966 mV), and the Tafel slope of sCPCE and CPCE 1–2 were 276, 160 and 226 mV dec-1, respectively. The results proved that CPCEs 1–2 could effectively catalyze and accelerate the HER behavior. The higher HER activity of the CPCE 1 than CPCE 2 can be attributed to the fact that CP 1 contains more three-coordinated silver ions. Moreover, the recognition performance of CPCEs 1–2 for H2O2 was further studied by chronoamperometry in 0.2 M phosphate buffer solution (PBS, pH = 6). The two sensors can detect H2O2 in a linear range from 0.5 μM to 4 mM with a detection limit of 128 µM for CPCE 1 and 27.1 µM for CPCE 2 at a signal-to-noise ratio of 3, and also revealed long-term stability and good selectivity.

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.

Charge Redistribution of Lattice-Mismatched Co─Cu3P Boosting pH-Universal Water/Seawater Hydrogen Evolution.

Practical applications of the hydrogen evolution reaction (HER) rely on the development of highly efficient, stable, and low-cost catalysts. Tuning the electronic structure, morphology, and architecture of catalysts is an important way to realize efficient and stable HER electrocatalysts. Herein, Co-doped Cu3P-based sugar-gourd structures (Co─Cu3P/CF) are prepared on copper foam as active electrocatalysts for hydrogen evolution. This hierarchical structure facilitates fast mass transport during electrocatalysis. Notably, the introduction of Co not only induces a charge redistribution but also leads to lattice-mismatch on the atomic scale, which creates defects and performs as additional active sites. Therefore, Co─Cu3P/CF requires an overpotential of only 81, 111, 185, and 230mV to reach currents of 50, 100, 500, and 1000mA cm-2 in alkaline media and remains stable after 10 000 CV cycles in a row and up to 110h i-t stability tests. In addition, it also shows excellent HER performance in water/seawater electrolytes of different pH values. Experimental and DFT show that the introduction of Co modulates the electronic and energy level structures of the catalyst, optimizes the adsorption and desorption behavior of the intermediate, reduces the water dissociation energy barrier during the reaction, accelerates the Volmer step reaction, and thus improves the HER performance.

One-step hydrothermal synthesis of nanowire-like W/Mo-Ni3S2/NF electrocatalysts for highly efficient hydrogen evolution reactions

The design of nanostructures and the adjustment of components are very important to improve the performance of hydrogen evolution electrocatalysts. In this paper, Ni, W and Mo trimetallic catalysts are studied from the aspects of morphology, structure and electronic transfer, and a better combination of hydrogen reaction efficiency is obtained. The W/Mo co-doped nickel sulfide electrocatalyst was synthesized on Ni foam by one-step hydrothermal method. As anticipated, the individual incorporation of either tungsten (W) or molybdenum (Mo) into the electrocatalyst did not yield satisfactory enhancements in hydrogen evolution reaction (HER) performance. However, when both W and Mo were co-doped onto the electrocatalyst, a significant improvement in catalyst material performance was observed. Hence, the coexistence of W and Mo is the key to improve HER electrocatalytic activity. In 1 M KOH solution, the W/Mo-Ni3S2/NF electrocatalyst exhibited exceptional HER activity with an overpotential of only 136 mV at a current density of 10 mA·cm−2 and demonstrated excellent cycle stability exceeding 20 hours. In this paper, the strategy of bimental co-doping composite is adopted to adjust the structure of nickel sulfide, which provides reference value for the design of reasonable and efficient HER electrocatalyst.

Metal-support interface engineering for stable and enhanced hydrogen evolution reaction

Hydrogen has emerged as a green and sustainable pathway towards achieving global decarbonization and net-zero emissions, intensely driving the need for efficient hydrogen production protocols. Electrocatalytic hydrogen evolution reaction (HER) holds great potential as a scalable, eco-friendly and safe avenue for efficient hydrogen production. However, the large-scale implementation of electrocatalytic HER is substantially challenged by the high-cost and unstable materials that are mainly fabricated from noble metals, e.g., Pt and Pd. Given this challenge, we adopted an interface engineering strategy to immobilize nanoscale Pt particles within the framework of nitrogen-doped CNTs, namely Pt@N-CNTs, where electronic metal-support interaction (EMSI) plays an important role in enabling orbital rehybridization and regulating the charge transfer through the metal-support interface, thereby considerably improving the electrocatalytic activity. With limited content of noble metals, our developed Pt@N-CNTs delivered superior HER performance with an ultralow overpotential of 5.8 mV at 10 mA cm−2 and demonstrated a high mass activity of 12.72 A mgPt−1 at an overpotential of 50 mV as well as excellent stability under harsh acidic conditions. At 500 mA cm−2, Pt@N-CNTs surprisingly exhibited an overpotential of 55.2 mV, outperforming that of commercial 20 wt% Pt/C catalysts (131.5 mV). Importantly, we established a straightforward, scalable, and time-saving microwave reduction strategy, alluding to its promising commercial viability. This work therefore sheds light on the development of high-performance electrocatalysts for hydrogen evolution and water electrolysis.

Integration of biocompatible hydrogen evolution catalyst developed from metal-mix solutions with microbial electrosynthesis

Microbial conversion of CO2 to multi-carbon compounds such as acetate and butyrate is a promising valorisation technique. For those reactions, the electrochemical supply of hydrogen to the biocatalyst is a viable approach. Earlier we have shown that trace metals from microbial growth media spontaneously form in situ electro-catalysts for hydrogen evolution. Here, we show biocompatibility with the successful integration of such metal mix-based HER catalyst for immediate start-up of microbial acetogenesis (CO2 to acetate). Also, n-butyrate formation started fast (after twenty days). Hydrogen was always produced in excess, although productivity decreased over the 36 to 50 days, possibly due to metal leaching from the cathode. The HER catalyst boosted microbial productivity in a two-step microbial community bioprocess: acetogenesis by a BRH-c20a strain and acetate elongation to n-butyrate by Clostridium sensu stricto 12 (related) species. These findings provide new routes to integrate electro-catalysts and micro-organisms showing respectively bio and electrochemical compatibility.

Biphenylene nanoribbon as a promising electrocatalyst for hydrogen evolution

Biphenylene nanoribbon as a promising electrocatalyst for hydrogen evolution

Vertical graphene nanowalls supported hybrid W2C/WOx composite material as an efficient non-noble metal electrocatalyst for hydrogen evolution

Research for the development of noble metal-free electrodes for hydrogen evolution has blossomed in recent years. Transition metal carbides compounds, such as W2C, have been considered as a promising alternative to replace Pt-family metals as electrocatalysts towards hydrogen evolution reaction (HER). Moreover, hybridization of TMCs with graphene nanostructures has emerged as a reliable strategy for the preparation of compounds with high surface to volume ratio and abundant active sites. The present study focuses in the preparation of tungsten carbide/oxide compounds deposited in a three-dimensional vertical graphene nanowalls (VGNW) substrate via chemical vapor deposition, magnetron sputtering and thermal annealing processes. Structural and chemical characterization reveals the partial carburization and oxidation of the W film sputtered on the VGNWs, due to C and O migration from VGNWs towards W during the high temperature annealing process. Electrochemical characterization shows the enhanced performance of the nanostructured hybrid W2C/WOx on VGNW compound towards HER, when compared with planar W2C/WOx films. The W2C/WOx nanoparticles on VGNWs require an overpotential of −252 mV for the generation of 10 mA cm−2. Chronoamperometry tests in high overpotentials reveal the compounds stability while sustaining high currents, in the order of hundreds of mA. Post-chronoamperometry test XPS characterization unveils the formation of a W hydroxide layer which favours hydrogen evolution in acidic electrolytes. We aspire that the presented insights can be valuable for those working on the preparation of hybrid electrodes for electrochemical processes.

Allotrope-dependent activity-stability relationships of molybdenum sulfide hydrogen evolution electrocatalysts

Molybdenum disulfide (MoS2) is widely regarded as a competitive hydrogen evolution reaction (HER) catalyst to replace platinum in proton exchange membrane water electrolysers (PEMWEs). Despite the extensive knowledge of its HER activity, stability insights under HER operation are scarce. This is paramount to ensure long-term operation of Pt-free PEMWEs, and gain full understanding on the electrocatalytically-induced processes responsible for HER active site generation. The latter are highly dependent on the MoS2 allotropic phase, and still under debate. We rigorously assess these by simultaneously monitoring Mo and S dissolution products using a dedicated scanning flow cell coupled with downstream analytics (ICP-MS), besides an electrochemical mass spectrometry setup for volatile species analysis. We observe that MoS2 stability is allotrope-dependent: lamellar-like MoS2 is highly unstable under open circuit conditions, whereas cluster-like amorphous MoS3-x instability is induced by a severe S loss during the HER and undercoordinated Mo site generation. Guidelines to operate non-noble PEMWEs are therefore provided based on the stability number metrics, and an HER mechanism which accounts for Mo and S dissolution pathways is proposed.

L-arginine-etched nickel-silver electrocatalyst for low-potential hydrogen evolution

The oxidation of formaldehyde at low potentials to achieve anodic hydrogen production is a crucial focus of current research. Copper-based alloys are prominent electrocatalysts in these reactions but face long-term stability challenges and are susceptible to CO intermediate poisoning. A novel approach that utilizes L-arginine in the surface modification of nickel foam substrates has been developed, enabling the highly dispersed deposition of silver catalysts on the substrates as sub-nanometer particles. This modified electrocatalyst allows formaldehyde oxidation and water electrolysis at a minimal potential of 0.32 VRHE and bipolar hydrogen production with near 100% Faradaic efficiency. This surface modification of substrate material provides a new approach to the design of electrodes.

Electrocatalyst for hydrogen evolution and H2O2 recognition on composite carbon paste electrodes with three new Ag(I) MOFs

Three new Ag(I) metal-organic frameworks (Ag-MOFs) containing bisbenzimidazole-derived ligand, namely, {[Ag2(L)(TP)](H2O)}n (1), {[Ag2(L)(HBTC))(H2O)](CH3CH2OH)(H2O)}n (2) and {[Ag4(L)2(IP)2](CH3CN)3(H2O)16}n (3) (L = bis(1-(pyridin-4-ylmethyl)-benzimidazol-2-yl methyl) ether, TP = Terephthalate, BTC = Benzenetricarboxylate, IP = Isophthalate), have been synthesized by volatilization method and systematic adjustment of solvent and aromatic polyacid co-ligand. Single crystal structural analysis showed that although three Ag-MOFs have a three-dimensional (3D) network backbone structure, their topological structures are different. Electrocatalytic hydrogen evolution reaction (HER) of carbon paste composite electrodes (Ag-MOF-1∼3@CPE) prepared by mixing graphite powder with Ag-MOFs were investigated in 0.5 M H2SO4 electrolyte. The HER measurements show that the overpotential η10293K of Ag-MOF-1∼3@CPE are -634, -533 and -615 mV compared with sCPCE (blank electrode, -966 mV), and the Tafel slope of sCPCE and Ag-MOF-1∼3@CPE were 276, 251, 123 and 220 mV dec−1, respectively. The results prove that Ag-MOF-1∼3@CPE could effectively catalyze and accelerate the HER behavior, with electrocatalytic activity order being Ag-MOF-2@CPE > Ag-MOF-3@CPE > Ag-MOF-1@CPE > sCPE. The highest HER activity of Ag-MOF-2@CPE can be attributed to the fact that Ag-MOF-2 contains coordination water molecule, while the higher activity of Ag-MOF-3@CPE than Ag-MOF-1@CPE is due to steric hindrance. Furthermore, the recognition performance of Ag-MOF-1∼3@CPE for H2O2 was further studied by chronoamperometry in 0.2 M phosphate buffer solution (PBS, pH = 6). The three sensors can detect H2O2 in a linear range from 0.5 μM to 4 mM with sensitivities of 103, 34.5 and 138 μA·mM−1·cm−2, and also revealed long-term stability and good selectivity. Our study provides a new approach for designing efficient, non-precious metal electrochemical catalysts.

Enhancing Ni/Co Activity by Neighboring Pt Atoms in NiCoP/MXene Electrocatalyst for Alkaline Hydrogen Evolution

AbstractDensity functional theory (DFT) calculations demonstrate neighboring Pt atoms can enhance the metal activity of NiCoP for hydrogen evolution reaction (HER). However, it remains a great challenge to link Pt and NiCoP. Herein, we introduced curvature of bowl‐like structure to construct Pt/NiCoP interface by adding a minimal 1 ‰‐molar‐ratio Pt. The as‐prepared sample only requires an overpotential of 26.5 and 181.6 mV to accordingly achieve the current density of 10 and 500 mA cm−2 in 1 M KOH. The water dissociation energy barrier (Ea) has a ~43 % decrease compared with NiCoP counterpart. It also shows an ultrahigh stability with a small degradation rate of 10.6 μV h−1 at harsh conditions (500 mA cm−2 and 50 °C) after 3000 hrs. X‐ray photoelectron spectroscopy (XPS), soft X‐ray absorption spectroscopy (sXAS), and X‐ray absorption fine structure (XAFS) verify the interface electron transfer lowers the valence state of Co/Ni and activates them. DFT calculations also confirm the catalytic transition step of NiCoP can change from Heyrovsky (2.71 eV) to Tafel step (0.51 eV) in the neighborhood of Pt, in accord with the result of the improved Hads at the interface disclosed by in situ electrochemical impedance spectroscopy (EIS) and scanning electrochemical microscopy (SECM) tests.

Enhancing Ni/Co Activity by Neighboring Pt Atoms in NiCoP/MXene Electrocatalyst for Alkaline Hydrogen Evolution.

Density functional theory (DFT) calculations demonstrate neighboring Pt atoms can enhance the metal activity of NiCoP for hydrogen evolution reaction (HER). However, it remains a great challenge to link Pt and NiCoP. Herein, we introduced curvature of bowl-like structure to construct Pt/NiCoP interface by adding a minimal 1 ‰-molar-ratio Pt. The as-prepared sample only requires an overpotential of 26.5 and 181.6 mV to accordingly achieve the current density of 10 and 500 mA cm-2 in 1 M KOH. The water dissociation energy barrier (Ea) has a ~43 % decrease compared with NiCoP counterpart. It also shows an ultrahigh stability with a small degradation rate of 10.6 μV h-1 at harsh conditions (500 mA cm-2 and 50 °C) after 3000 hrs. X-ray photoelectron spectroscopy (XPS), soft X-ray absorption spectroscopy (sXAS), and X-ray absorption fine structure (XAFS) verify the interface electron transfer lowers the valence state of Co/Ni and activates them. DFT calculations also confirm the catalytic transition step of NiCoP can change from Heyrovsky (2.71 eV) to Tafel step (0.51 eV) in the neighborhood of Pt, in accord with the result of the improved Hads at the interface disclosed by in situ electrochemical impedance spectroscopy (EIS) and scanning electrochemical microscopy (SECM) tests.