Tunable cation vacancy engineering of FeP toward efficient hydrogen evolution reaction.

The development of efficient and robust hydrogen evolution reaction (HER) catalysts that operate across a wide pH range is critical for advancing sustainable hydrogen production. Previously, a series of molecular complexes have been immobilized on solid supports to achieve efficient HER activity. However, achieving HER activity with molecular complexes across a universal pH range still remains challenging. Herein, we demonstrated two Ru(II) complexes and systematically characterized them using spectroscopic techniques. The (MeTBEN)Ru(II) complex (2) exhibited outstanding hydrogen evolution activity across a wide pH range, specifically in alkaline, neutral, and acidic electrolytes, with the highest performance observed in acidic electrolytes compared to the (BnTBEN)Ru(II) complex (1). 2 demonstrates outstanding electrocatalytic performance with a low overpotential of 115 mV at 10 mA cm-2 in 0.5 M H2SO4, along with an excellent turnover frequency. Furthermore, 2 demonstrated excellent electrochemical stability, sustaining its activity for up to 8 hours under acidic conditions.

Surface restructuring Prussian blue analog-derived bimetallic CoFe phosphides by N-doped graphene quantum dots for electroactive hydrogen evolving catalyst

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.

Regulating the structural and interfacial properties of transition metal phosphides (TMPs) by coupling carbon-based materials with large surface areas to enhance hydrogen evolution reaction (HER) performance presents significant progress for water splitting technology. Herein, we constructed a composite substrate of a three-dimensional porous graphene oxide matrix (3D-GO) embedded in nickel foam (NF) to grow a Co2P electrocatalyst. Well-defined gladiolus-like Co2P nanowire arrays tightly anchored on the substrate show enhanced electrochemical characteristics for the hydrogen evolution reaction (HER) based on the promoting roles of 3D porous reduced GO (3D-rGO) derived from 3D-GO, which promotes the dispersion of active components, improves the rate of electron transfer, and facilitates the transport of water molecules. As a result, the obtained Co2P@3D-rGO/NF electrode exhibits superior HER activity in 1.0 M KOH media, achieving overpotentials of 36.5 and 264.7 mV at current densities of 10 and 100 mA cm-2, respectively. The electrode also has a low Tafel slope of 55.5 mV dec-1, a large electrochemical surface area, and small charge-transfer resistance, further revealing its mechanism of high intrinsic activity. Moreover, the electrode exhibits excellent HER stability and durability without surface morphology and chemical state changes.

Simultaneously achieving enhanced water adsorption and rapid adsorbed hydroxyl transfer toward MXene-based materials for highly efficient alkaline electrocatalytic hydrogen evolution

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

Novel ternary metals-based telluride electrocatalyst with synergistic effects of high valence non-3d metal and oxophilic Te for pH-universal hydrogen evolution reaction

Efficient etching of oxygen-incorporated molybdenum disulfide nanosheet arrays for excellent electrocatalytic hydrogen evolution

Enhanced electrocatalysis of NiMnIn Heusler alloy films for hydrogen evolution reaction by magnetic field

Transition metal phosphides (MPs) are emerging earth-abundant catalysts for hydrogen evolution reaction (HER) due to their promising activity and stability. Even though further development is needed to meet real-world application needs, fundamental understanding of how MP catalysts can be improved is low. In this work, we present several different approaches to uncover the relationships of bulk (electronic structure) and surface (active sites) of the catalysts with HER activity and stability. We studied well-ordered crystalline materials as model systems to elucidate the aforementioned relationships. Anionic Si/P substitution in NiSi1-xPx compounds showed that the density of the states (DOS) at EF could be one of the key determinants on HER activity. The impact of DOS was further investigated by studying two polymorphs of Fe2P where upward shift of the d-band position was shown to enhance HER activity. Several surface termination effects were demonstrated on the mm-sized single crystals of Ni2P, Co2P, and Fe2P upon facet-dependent HER activity studies. Lastly, operando X-ray absorption spectroscopy of Ni and P K-edges of Ni-P catalysts clearly demonstrated that during the HER process, reduction occurred on the catalyst surface, but reduced state was only stable under applied reductive bias and quickly oxidized after turning off the potential, and this oxidized species did not appear to return to its original state.

Asymmetrical radial strain energy strategy of M–N–SWCNT single atom catalysts for highly efficient hydrogen evolution: A high-throughput DFT study

The pursuit of sustainable energy solutions has driven extensive research into efficient and cost-effective water-splitting techniques. This study introduces a straightforward method employing nickel molybdenum oxide NiMoO4 (NMO) nanorods integrated with graphitic carbon nitride (g-CN) sheets as promising catalysts for water splitting. The integrated coupling between NMO nanorods and g-CN leverages the distinctive properties of both materials to boost robustness as well as effectiveness in catalysis for the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). We systematically optimized the nanostructure by adjusting the reduction annealing temperature during calcination to improve HER and OER activities. The NMO@g-CN-600 nanostructured catalyst demonstrates exceptional electrochemical HER activity in acidic media, with an overpotential of 148 mV at 10 mA cm-2 current density, which is approximately 2.72 times lower than that of bare NMO and 2.97 times lower than pristine g-CN catalysts. Under alkaline conditions, the NMO@g-CN-600 nanostructured catalyst exhibited superior OER activity with an overpotential of 252 mV to reach a current density of 10 mA cm-2, outperforming bare NMO and pristine g-CN catalysts. Additionally, the nanostructured catalyst demonstrated excellent long-term electrochemical stability with chronoamperometric testing over 50 h in both basic and acidic environments, showing low Tafel slopes for the OER and HER of 97 and 98 mV dec-1, respectively. Various analytical methods confirmed the successful synthesis and structural stability of prepared catalysts. The outstanding electrocatalytic properties of the NMO@g-CN-600 nanostructured catalyst position it as a feasible choice to platinum-group-based catalysts for overall water electrolysis.

Economical and highly effective catalysts are crucial to the electrocatalytic hydrogen evolution reaction (HER), and few-layer black phosphorus (phosphorene) is a promising candidate because of the high carrier mobility, large specific surface area, and tunable physicochemical characteristics. However, the HER activity of phosphorene is limited by the weak hydrogen adsorption ability on the basal plane. In this work, optimal active sites are created to modulate the electronic structure of phosphorene to improve the HER activity and the effectiveness is investigated theoretically by density-functional theory calculation and verified experimentally. The edges and defects affect the electronic density of states, and a linear relationship between the HER activity and lowest unoccupied states (εLUS) is discovered. The medium εLUS value corresponds to the suitable hydrogen adsorption strength. Experiments are designed and performed to verify the prediction, and our results show that a smaller phosphorene moiety with more edges and defects exhibits better HER activity and surface doping with metal adatoms improves the catalytic performance. The results suggest that modified phosphorene has large potential in efficient HER and provides a convenient standard to explore ideal electrocatalysts.

Tuning surface strain is a new strategy for boosting catalytic activity to achieve sustainable energy supplies; however, correlating the surface strain with catalytic performance is scarce because such mechanistic studies strongly require the capability of tailoring surface strain on catalysts as precisely as possible. Herein, a conceptual strategy of precisely tuning tensile surface strain on Co9 S8 /MoS2 core/shell nanocrystals for boosting the hydrogen evolution reaction (HER) activity by controlling the MoS2 shell numbers is demonstrated. It is found that the tensile surface strain of Co9 S8 /MoS2 core/shell nanocrystals can be precisely tuned from 3.5% to 0% by changing the MoS2 shell layer from 5L to 1L, in which the strained Co9 S8 /1L MoS2 (3.5%) exhibits the best HER performance with an overpotential of only 97 mV (10 mA cm-2 ) and a Tafel slope of 71 mV dec-1 . The density functional theory calculation reveals that the Co9 S8 /1L MoS2 core/shell nanostructure yields the lowest hydrogen adsorption energy (∆EH ) of -1.03 eV and transition state energy barrier (∆E2H* ) of 0.29 eV (MoS2 , ∆EH = -0.86 eV and ∆E2H* = 0.49 eV), which are the key in boosting HER activity by stabilizing the HER intermediate, seizing H ions, and releasing H2 gas.

The production of hydrogen through electrochemical water splitting driven by clean energy becomes a sustainable route for utilization of hydrogen energy, while an efficient hydrogen evolution reaction (HER) electrocatalyst is required to achieve a high energy conversion efficiency. Nickel phosphides have been widely explored for electrocatalytic HER due to their unique electronic properties, efficient electrocatalytic performance, and a superior anti-corrosion feature. However, the HER activities of nickel phosphide electrocatalysts are still low for practical applications in electrolyzers, and further studies are necessary. Therefore, at the current stage, a specific comprehensive review is necessary to focus on the progresses of the nickel phosphide electrocatalysts. This review focuses on the developments of preparation approaches of nickel phosphides for HER, including a mechanism of HER, properties of nickel phosphides, and preparation and electrocatalytic HER performances of nickel phosphides. The progresses of the preparation and HER activities of the nickel phosphide electrocatalysts are mainly discussed by classification of the preparation method. The comparative surveys of their HER activities are made in terms of experimental metrics of overpotential at a certain current density and Tafel slope together with the preparation method. The remaining challenges and perspectives of the future development of nickel phosphide electrocatalysts for HER are also proposed.