N-doped Mo2C nanoblock for efficient hydrogen evolution reaction

Electrocatalysts for hydrogen evolution reaction (HER) from water splitting have been widely studied as one of the efficient energy storage methods by producing hydrogen (H2), the important clean energy resource. The best-known electrocatalyst for HER is platinum (Pt) that is expensive and scarce on earth. Molybdenum disulfide (MoS2) has attracted great attentions as one of promising catalysts for replacing Pt not only because of the relatively low cost and earth abundancy but also great HER activity, selectivity and stability as a great catalyst. Since the edge site of MoS2 was proved as an active site for HER, a great number of efforts on maximally exposing edge site have contributed to the studies about MoS2 based catalysts for HER. The basal plane of MoS2 is catalytically inert for HER since the free energy of adsorbed hydrogen (delGH*) known to a great descriptor for activation energy is thermodynamically uphill (~1.92eV) compared with that of active edge site (~0.06eV). However, sulfur (S) vacancy in the basal plane was very recently investigated as a new active site for HER demonstrating the basal plane that composes the majority part of MoS2 can be utilized for HER. Diverse methods to generate S-vacancy to make a use of the basal plane of MoS2 for efficient HER catalysts have been investigated such as Ar plasma treatment, hydrogen annealing and electrochemical desulfurization. However, HER activity of desulfurized MoS2-x still needs to be improved to be competitive with the HER activities of platinum. Cobalt is one of the non-precious metal promotors for MoS2 based catalysts for hydrogen evolution reaction, water gas shift reaction and oxygen reduction reaction. In very recently, Co was doped in the basal plane of S-vacancy rich MoS2 and Co-SMoS2 achieved a great catalytic activity for the hydrodeoxygenation (HDO) reaction. Since S-vacancy site is coordinatively unsaturated and has a high surface free energy like edge site, it is expected to provide a great nucleation site for doping or anchoring transition metal atoms or clusters. Thus, Co promotor can be employed for enhancing the catalytic activity of the basal plane of MoS2 based catalysts. Herein we report the great HER activity enhancement of the catalytically inert basal plane of MoS2 by combining the catalytic effects of S-vacancy and Co cluster addition as a non-precious metal oxide promotor. We use both density functional theory (DFT) calculations and experiments to support the claim. The polycrystalline 2H phase MoS2 multilayer whose basal plane is dominantly exposed was synthesized on fluorine-doped tin oxide (FTO) and carbon foam electrodes through thermolysis in the tube furnace. S-vacancy was generated on the basal plane of MoS2 through the same electrochemical desulfurization method. On top of that, Co cluster was electrodeposited to further promote the HER activity of the basal plane under different desulfurization conditions. Consequently, we demonstrate S-vacancy plays a critical role for Co nucleation during electrodeposition and thus both electrochemically active surface area and the intrinsic catalytic activity increased. Especially, the overpotential at -10 mA/cm2 was reduced around 300mV making the inert basal plane of MoS2 have comparable overpotential about -0.21 V vs. RHE at -10 mA/cm2 with the state of the art non-precious MoS2 based catalysts.

Water electrolysis, a key enabler of hydrogen energy production, presents significant potential as a strategy for achieving net‐zero emissions. However, the widespread deployment of water electrolysis is currently limited by the high‐cost and scarce noble metal electrocatalysts in hydrogen evolution reaction (HER). Given this challenge, design and synthesis of cost‐effective and high‐performance alternative catalysts have become a research focus, which necessitates insightful understandings of HER fundamentals and material engineering strategies. Distinct from typical reviews that concentrate only on the summary of recent catalyst materials, this review article shifts focus to material engineering strategies for developing efficient HER catalysts. In‐depth analysis of key material design approaches for HER catalysts, such as doping, vacancy defect creation, phase engineering, and metal‐support engineering, are illustrated along with typical research cases. A special emphasis is placed on designing noble metal‐free catalysts with a brief discussion on recent advancements in electrocatalytic water‐splitting technology. The article also delves into important descriptors, reliable evaluation parameters and characterization techniques, aiming to link the fundamental mechanisms of HER with its catalytic performance. In conclusion, it explores future trends in HER catalysts by integrating theoretical, experimental and industrial perspectives, while acknowledging the challenges that remain.

Fe-B alloy coupled with Fe clusters as an efficient cocatalyst for photocatalytic hydrogen evolution

Exploring highly effective electrocatalysts with heterostructures is significant for sustainable hydrogen production by the hydrogen evolution reaction (HER). However, there are still challenges in improving the HER activities of the heterostructures to achieve efficient hydrogen production. Here, nitrogen-decorated dual transition metal sulphide heterostructures (N-NiS/MoS2) were constructed with an enhanced HER performance in alkaline electrolytes. These novel N-NiS/MoS2 heterostructures exhibited a low overpotential of 71 mV (10 mA cm-2), small Tafel slope of 79 mV dec-1 and favorable stability. In particular, the experimental and theoretical calculation results consistently demonstrated that the introduction of nitrogen can effectively tune the electronic structure of the heterostructures. Furthermore, the synergistic effect between dual-active components N-NiS and N-MoS2 in the N-NiS/MoS2 heterostructures effectively promoted water dissociation and hydrogen formation, leading to remarkable increase in the HER performance in an alkaline medium. This work provides a valuable avenue for the rational modulation of the electronic structure of heterostructures by hetero-atoms for highly efficient HER catalysts.

Defect engineered Janus MoSiGeN4 as highly efficient electrocatalyst for hydrogen evolution reaction

Molybdenum disulfide (MoS2) has been gathered attention as a non-precious metal catalyst for hydrogen evolution reaction (HER); however, pristine MoS2 (bulk mineral) is known to be a poor catalyst. The fundamental challenge to improving the catalytic performance of MoS2 is to increase the density of active reaction sites on the surface of MoS2. Usually, the crystalline plane (0001) is inert to the HER whereas the edges of MoS2 are active. In this presentation, we will show how our thermal texturization method improves the HER performance of MoS2 using a simple annealing procedure in forming gas (hydrogen and nitrogen mixture). The annealed bulk MoS2 shows a roughened surface including a higher density of edge sites. As a result, the catalytic performance of the annealed MoS2 shows more 100 mV reduction of overpotential to obtain 10 mA/cm2 of HER current density. We show that this treatment is generally applicable to many morphologies, including bulk, microflake, and nanoflakes of MoS2 to use as an efficient HER catalyst. The simplicity of this procedure suggests this method would be scalable, and furthermore could be applicable for other chalcogenide-based 2D materials.

The study of efficient, robust, and earth-abundant electrocatalysts for the hydrogen evolution reaction (HER) is essential for hydrogen-based energy technologies. Previous works have demonstrated that pyrite-structure materials (e.g., CoS2, NiSe2) are efficient HER catalysts. Here, we first systematically investigate the nanostructure synthesis of a series of pyrite-phase nickel phosphoselenide materials—NiP2, Se-doped NiP2 (NiP1.93Se0.07), P-doped NiSe2 (NiP0.09Se1.91), and NiSe2—through a facile thermal conversion of Ni(OH)2 nanoflakes. The similar nanostructures enable a systematic and fair comparison of their structural properties and catalytic activities for HER. We found that NiP1.93Se0.07 shows the best HER performance, followed by NiP2, NiP0.09Se1.91, and NiSe2. Se-doped NiP2 grown on carbon fiber paper can achieve an electrocatalytic current density of 10 mA cm–2 at an overpotential as low as 84 mV and a small Tafel slope of 41 mV decade–1. This study not only estabilishes Se-doped NiP2 as a comp...

Objectives It would be essential for solving the global warming problem to use renewable energy as well as increase the efficiency of energy production. One of the renewable and efficient energy sources is hydrogen energy, and the electrochemical hydrogen evolution reaction (HER) is the most important reaction in the hydrogen energy production. For HER, inexpensive catalyst development is indispensible because the precious metal Pt is being used as the most efficient catalyst for HER. Methods Density functional theory (DFT) calculations were performed using the Vienna ab initio simulation package (VASP) to calculate atomic and electronic structures and total energies using the projector-augmented wave (PAW) method. Results and Discussion The HER efficiencies of Pt(111), Pt nanoclusters, and Pt-based core-shell nanoclusters were examined based on the hydrogen adsorption energies (Eads) by using the density functional theory (DFT) calculations. The DFT results demonstrate that Pt nanoclusters (0.5 ~ 2.1 nm in diameter) showed stronger hydrogen adsorption (Eads = -0.65 ~ -1.25 eV) than that of Pt(111) (Eads = -0.61 eV), implying a lower HER efficiency of Pt nanoclusters than Pt(111). On the other hand, a Rucore-Ptshell nanocluster (Eads = -0.48 eV) showed weaker hydrogen adsorption than Pt(111), indicating an increase in the HER efficiency. The weaker hydrogen adsorption on Rucore-Ptshell was attributed to the d;-band shift of Pt atoms further away from the Fermi level in negative direction due to the core Ru atoms. Conclusion By evaluating the HER efficiency using a descriptor of the hydrogen atom adsorption strength, a Ru-Pt core-shell (Rucore-Ptshell) nanocluster was expected to exhibit the highest HER efficiency among Pt(111), Pt55 nanocluster, and Mcore-Ptshell (M = Ni, Co, Mn, Cu, Ru, Ir and Au) nanoclusters. Key words: Hydrogen Evolution Reaction (HER), Platinum (Pt) Catalysts, Nanocluster, Core-shell, Density Functional Theory (DFT), d-Band Center Theory

Unravelling the role of work function difference on supported Ru nanoclusters for alkaline hydrogen evolution reaction

RuMo nanoalloy confined on N-doped carbon toward efficient alkaline and acidic hydrogen evolution reaction

Facile synthesis of interlaced flower-like layered double hydroxides grown on porous CoMoP as a highly efficient electrocatalyst for hydrogen evolution reaction

Transformation of Fe-B@Fe into Fe-B@Ni for efficient photocatalytic hydrogen evolution

Engineering FeP4/CoFe2O4 heterostructure with balanced proton adsorption ability for efficient hydrogen evolution reaction

The electrocatalytic hydrogen evolution reaction (HER) is an efficient and economic pathway to generate clean hydrogen energy in a sustainable manner. To improve the HER activity of Earth-abundant catalysts, reducing the dimension of materials is an effective strategy, and in this context two-dimensional (2D) materials have received substantial research attention owing to their large surface area and 2D charge transport channels. However, the thermodynamically stable basal surface of 2D catalysts is usually inactive in catalysis, which significantly impedes further optimization of the 2D HER catalysts. In this Minireview, we highlight in detail that defect engineering in 2D catalysts could bring multiple benefits in improving the HER activity. From the point of view of kinetics, defect sites could serve as active sites for catalyzing the HER process directly, and the introduction of defect structures may result in the optimization of electronic structures of the catalysts, thereby facilitating the HER process. Besides, for catalytically inert substrate materials, the defect sites could act as anchoring sites for catalyst loading, thus realizing efficient HER performance with the aid of enhanced electric conductivity. We anticipated that this Minireview could provide useful guidance for designing advanced HER catalysts in the future.

Molybdenum phosphide (MoP) nanomaterials are of great promise as electrochemical hydrogen evolution reaction (HER) catalysts, but the catalytic performance suffers from insufficient active sites and poor material stability. To address these challenges, we employed cerium and nitrogen elements to regulate the electronic structure of MoP in this study, where Ce and N doped MoP (Ce, N‐MoP) was synthesized by one‐pot high‐temperature pyrolysis of the uniform mixture of (NH 4 ) 6 Mo 7 O 24 •4H 2 O, NH 4 H 2 PO 4 , Ce(Ac) 3 and melamine. Compared with the bare MoP and N‐doped MoP (N‐MoP), Ce, N‐MoP only requires 102.6 mV to obtain the current density of 10 mA cm −2 in alkaline electrolyte, and exhibits excellent electrochemical and material long‐term durability. From experimental results, Ce and N co‐doping effectively modulate electronic structure of MoP, alters binding strength of Mo‐P bonds and enriches Mo‐P active species, which not only promotes the HER performance but also prevent MoP oxidation and improve its material stability. Theoretical calculation results show that Ce and N co‐doping can effectively promote the desorption of *OH in alkaline HER, thus promoting the dissociation of water and improving overall HER efficiency. This work gives useful guidance for constructing advanced HER catalysts by rare‐earth metal and nonmetal co‐doped transition metal phosphides.