Modulation of Phosphorene for Optimal 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.

Doping regulation holds promise to modulate electrocatalytic performance, yet it remains largely unexplored for ferroelectric (FE) BaTiO3 (BTO). By jointly employing first-principles calculations and machine learning (ML) analysis, we examine the effect of a broad range of transition metal (TM) doping in FE BTO on the electrocatalytic hydrogen evolution reaction (HER) activity and screen out the optimal TM dopants. We unveil that some early-to-middle group TM (V, Cr, Mo, Ta, Ru)-doped BTO surfaces feature higher synthesizability, which also exhibit noticeable HER activity with |ΔGH*| < 0.2 eV owing to intermediate hydrogen adsorption strength. Among all doped surfaces, the Mo-doped one shows optimal HER activity under both out-of-plane and in-plane polarization states. We reveal an intense interplay between the hydrogen adsorption configuration and the corresponding hydrogen bonding interaction, which relies more on the TM group than the polarization state. Most importantly, we propose a physically informed descriptor of the surface oxygen p band, which better describes HER activity trends of TM-doped surfaces than conventional band descriptors.This indicates the significance of the fractional filling and bandwidth of occupied oxygen p-band states. Moreover, we establish a robust ML model that can well predict HER activity with surface-independent input parameters alone with R2 value above 0.93. From these parameters, we identify the inherent outer electron number of the TM dopant as the dominant feature, while the second ionization energy of the TM dopant and the initial polarization state show non-negligible feature importance. These findings could enlighten understanding, rational design, and accelerated discovery of element doping of FE materials for catalysis and other implications.

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

Using first-principles calculations, we systematically investigated the hydrogen evolution reaction (HER) potential of 27 types of homogeneous dual-atom M₂-N₆-graphene catalysts. Shared nitrogen atoms between dual metal atoms were identified as crucial adsorption sites for hydrogen atoms. Notably, we found that relying solely on the free energy of hydrogen adsorption (<inline-formula id="M1"> <math id="mathml_M1" display="inline" overflow="scroll"><msub><mrow class="MJX-TeXAtom-ORD"><mi mathvariant="normal">Δ</mi><mi>G</mi></mrow><mrow class="MJX-TeXAtom-ORD"><msup><mrow class="MJX-TeXAtom-ORD"><mrow class="MJX-TeXAtom-ORD"><mi mathvariant="normal">H</mi></mrow></mrow><mrow class="MJX-TeXAtom-ORD"><mo>∗</mo></mrow></msup></mrow></msub></math></inline-formula>) could exclude the extremely unfavorable substrates, but may lead to misleading assessments of HER activation for substrates with modest <inline-formula id="M2"> <math id="mathml_M2" display="inline" overflow="scroll"><msub><mrow class="MJX-TeXAtom-ORD"><mi mathvariant="normal">Δ</mi><mi>G</mi></mrow><mrow class="MJX-TeXAtom-ORD"><msup><mrow class="MJX-TeXAtom-ORD"><mrow class="MJX-TeXAtom-ORD"><mi mathvariant="normal">H</mi></mrow></mrow><mrow class="MJX-TeXAtom-ORD"><mo>∗</mo></mrow></msup></mrow></msub></math></inline-formula>. Thermodynamic activity evaluation reveals that M₂-N₆-graphene (M = Cr, Co, Ni, Cu, Os, Pt) models exhibit promising HER activities. Kinetic analysis, based on the Volmer–Tafel mechanism, determined that the hydrogen coverage and relative distance between the adsorbed hydrogen atoms in the Tafel step affect the reaction energy barrier significantly. The coverage limits depend on the reaction free energy of the non-spontaneous third hydrogen adsorption step. By integrating the kinetic metric with thermodynamic assessments, we propose that the Co₂-N₆-graphene model displays superior HER activity. We further recommend selecting one of the metal positions in M_<i>a</i>M_<i>b</i>-N₆-graphene to be Cr and excluding Cu and Ni elements during the selection of the second metal atom when designing heterogeneous M_<i>a</i>M_<i>b</i>-N₆-graphene for alkaline HER catalyst. This study establishes a convenient workflow and provides valuable insights for the rational design of efficient HER catalysts.

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

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

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

As a Pt-group element, Pd has been regarded as one of the alternatives to Pt-based catalysts for the hydrogen evolution reaction (HER). Herein, we performed density functional theory (DFT) computations to explore the most stable structures of PdxBy (x = 6, 19, 44), revealed the in situ structural reconstruction of these clusters under acidic conditions, and evaluated their HER activity. We found that the presence of B can prevent underpotential hydrogen adsorption and activate the H atoms on the cluster surface for the HER. The theoretical calculations show that the reaction barrier for the HER on ~1 nm sized Pd44B4 can be as low as 0.36 eV, which is even lower than for the same-sized Pt and Pd2B nanoparticles. The ultra-high HER activity of sub-nanosized PdxBy clusters makes them a potential new and efficient HER electro-catalyst. This study provides new ideas for evaluating and designing novel nanocatalysts based on the structural reconstruction of small-sized nanoparticles in the future.

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.

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

Exploring high-performance catalysts for the hydrogen evolution reaction (HER) is essential for the development of clean hydrogen energy. Single atom catalysts (SACs) have garnered significant attention due to their maximum atomic efficiency, high catalytic performance and excellent selectivity. In this work, we systematically investigated the HER activity of Ru and Fe SACs on nitrogen-doped graphene using density functional theory (DFT) calculations. Various nitrogen defect configurations (N to 4N) were examined to access their impact on structural stability and catalytic performance. The results indicate that lower N-coordinated moieties, particularly N_pyrrolic and 2N, exhibit superior HER activity, while high N-coordinated moieties (4N) demonstrate greater stability. Volcano plot analysis reveals that catalytic performance is highly sensitive to metal-support interactions, which can be effectively described using binding energy and metal charge state. Ru SACs@N_pyrrolic and Fe SACs@2N achieve the most favorable performance, with additional active sites and low overpotentials of approximately 0.26 V and 0.23 V, respectively. Bader charge analysis further confirms that moderate positive charge states enhance electronic metal-support interactions, optimizing hydrogen adsorption and desorption. These findings highlight the critical role of nitrogen coordination in tuning the electronic and energetic properties of SACs on N doped graphene, providing valuable insights into the rational design of Pt-free SACs for highly efficient HER catalysis.

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

Three-dimensional reduced graphene oxide/carbon nanotube nanocomposites anchoring of amorphous and crystalline molybdenum sulfide: Physicochemical characteristics and electrocatalytic hydrogen evolution performances

Transition metal phosphides (TMPs) have emerged as promising and cost-effective electrocatalysts for the hydrogen evolution reaction (HER). However, their practical applications are hindered by insufficient catalytic performance. Herein, we develop a tunable cation vacancy engineering strategy to enhance the HER activity of FeP, one of the most inexpensive TMPs, via facile phosphidation and acid etching of zinc iron hexacyanoferrate (ZnFeHCF) with controllable Zn sacrificial agents. The non-exclusive incorporation of Zn2+ into the ZnFeHCF precursor ensures a uniform distribution of vacancies, while the adjustable Zn2+ content enables precise control of vacancy concentrations over a broad range (0.3-33.6%). Systematic investigations reveal that an optimal level of cation vacancies elevates the d-band center and strengthens hydrogen adsorption, thereby boosting the HER activity of FeP. Conversely, excessive cation vacancies induce severe lattice distortion and surface oxidation, resulting in deteriorated catalytic performance. At the optimized cation vacancy concentration of 16.2%, FeP exhibits the best HER activity, showing a small overpotential of 119 mV at 10 mA cm-2, a low Tafel slope of 59.2 mV dec-1, and excellent stability. This study demonstrates not only an efficient catalyst for the HER but also an effective methodology for cation vacancy engineering of TMPs toward diverse applications.

Hydrogen evolution reaction efficiency of carbon nanohorn incorporating molybdenum sulfide and polydopamine/palladium nanoparticles