Atomic-Scale Core/Shell Structure Engineering Induces Precise Tensile Strain to Boost Hydrogen Evolution Catalysis.

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

In this work, a low cost and high yield method is proposed to synthesize 1T phase MoS 2 nanoflowers (NFs) by means of anion exchange using MoO 3 nanosheets as the exchange template. The synthesized MoS 2 NFs are composed of ultrathin MoS 2 nanoflakes with plenty of active edge sites, large specific surface area, and rich defects, as well as reduced intrinsic resistance. Therefore, they show enhanced hydrogen evolution reaction (HER) activity with an overpotential of 166 mV at 10 mA cm −2 and Tafel slope of 47 mV dec −1 , better than those of previously reported MoS 2 ‐based HER catalysts. A systematic study is carried out on the effects of mass loading and reaction temperature on its catalytic performance. It is shown that, with reaction temperature of 200 °C and mass loading of 0.43 mg cm −2 , the obtained MoS 2 NFs show the optimal HER activity. The present work provides a facile and cost‐effective way to synthesize 1T MoS 2 NFs with advanced HER performances, indicating significant potential for larger‐scale production in practical industrial applications.

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

The rational design of a step‐scheme (S‐scheme) heterojunctions in hybrid semiconductors by avoiding unwanted charge transport paths is considered as an attractive way to achieve high photocatalytic activity in hydrogen evolution reaction (HER). Here, a dual S‐scheme heterojunction formed in the lychee‐shaped W18O49/CdWO4/CdS nanostructures is proposed for improving the photocatalytic performance in HER under visible light irradiation. The remarkable activity in photocatalytic HER of W18O49/CdWO4/CdS is attributed to the unique structure and effective charge separation by the photoinduced defect‐transit dual S‐scheme mechanism and strong internal electric field. The measurements of X‐ray photoelectron spectroscopy (XPS), femtosecond transient absorption (fs‐TA) spectroscopy, and electron paramagnetic resonance (EPR) further confirm the photoinduced carrier transfer pathways following the dual S‐scheme mechanism. This research can provide a new strategy for designing the dual S‐scheme heterojunctions to improve photocatalytic performance through the defect band structure engineering.

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.

The hydrogen evolution reaction (HER) is crucially important for water splitting, for which platinum (Pt) has been considered the state-of-the-art electrocatalyst. Despite recent progress in non-Pt electrocatalysts, few Pt-free catalysts can compete against Pt in terms of HER activity particularly in alkaline solution. Here, we report a new efficient Pt-free HER catalyst – hybrid ruthenium cobalt phosphide (RuCoP) cluster where Ru exists in metallic chemical state in the hybrid. The unique hybridization allows electron transfer to take place from both Co and P to Ru, thereby significantly enhancing the hybrid’s HER activity. The as-synthesized RuCoP clusters demonstrate a considerably low overpotential (η) of 11 mV at -10 mA cm2 and a high turnover frequency (TOF) of 5.64 s-1 at η = 100 mV in 0.5 M H2SO4. Remarkably, even in alkaline solution (1.0 M KOH) the excellent HER performance of RuCoP remains, with a very low η 10 of 23 mV and exceptionally high TOF value of 3.85 s-1 at η = 100 mV. Moreover, the RuCoP catalysts show outstanding catalytic stability toward the HER in both acidic and alkaline solutions, superior to that of commercially available Pt/C catalysts. Figure 1

The development of efficient and cost-effective electrocatalyst for the hydrogen evolution reaction (HER) is essential for alkaline water electrolysis. Cobalt phosphide (Co2P) is a promising non-noble electrocatalyst material for HER due to its low cost and high stability in alkaline medium. Nevertheless, the HER activity of Co2P needs to be further improved as compared to noble metal based electrocatalysts. In this study, we have incorporated nickel (Ni) into Co2P using a co-sputtering system for enhanced HER performance, considering the junction of Ni/Co2P heterostructure. This junction serves as dual sites for water dissociation at Ni and hydrogen adsorption/desorption at Co2P, which synergistically enhances the HER activity. We also noticed that Ni concentration influences the heterojunction area as highly active site. Too low or high Ni concentration diminishes active sites by few Ni site formation or Ni agglomeration, respectively. Therefore, precise control over the Ni concentration is essential for maximizing the active site. Our optimized Ni incorporated Co2P sample showed outstanding HER performance with low overpotential of ~77 mV at 10 mA/cm2 and Tafel slope of ~47 mV/dec. The findings of this study will provide insight into the relationship between heterojunction formation and HER performance in transition metal-based heterostructure materials.

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.

Tungsten carbide (WC) is an established model electrocatalyst for the hydrogen evolution reaction (HER) in aqueous solutions. In spite of extensive interest in and work on this material, a systematic atomistic understanding of the combined role of faceting and heteroatom doping for hydrogen evolution on WC electrocatalysts in aqueous solution is not available. To fill this knowledge gap, here we explore the interplay of these parameters for the electrocatalytic performance of WC by means of density functional theory (DFT) simulations. In our simulations, we explicitly account for solvent (water) effects and related electrochemical potential-dependent oxygen or hydroxyl (co)adsorption on the WC surfaces as determined by the analysis of surface Pourbaix diagrams. Among the several low-index WC surfaces screened, the DFT simulations indicate that the W-terminated (−100) and (111) surfaces of WC show comparable exchange currents of 3.908 and 0.133 mA/cm2, respectively. The simulations also suggest that V or N doping can substantially increase the HER activity of some WC surfaces to levels comparable to commercial Pt/C electrocatalysts, with current densities as large as 10.555, 1.730, and 0.636 mA/cm2 for the V-doped W-terminated (001), V-doped (101), and N-doped (101) WC surfaces, respectively. The improved HER activities are rationalized in terms of the d-band or p-band center, which are both shown to be related to the capability of tuning the hydrogen adsorption, and thence the HER performance. The calculated strong dependence of the HER activity on the presence of the electrochemical adsorption of oxygen and hydroxyls reiterates the importance of modeling realistic electrochemical conditions for WC pristine or doped surfaces. We expect the DFT results presented to provide timely and original guidelines for further theoretical and experimental studies of HER activity on WC-related electrocatalysts.

Surface strain engineered Ni-NiO for boosting hydrogen evolution reaction in alkaline media

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

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.

Fe0.95 S1.05 with high reactivity and stability was incorporated into WS2 nanosheets via a one-step solvothermal method for the first time. The resulted hybrid catalyst has much higher catalytic activity than WS2 and Fe0.95 S1.05 alone, and the optimal WS2 /Fe0.95 S1.05 hybrid catalyst was found by adjusting the feed ratio. The addition of Fe0.95 S1.05 was proven to be able to enhance the hydrogen evolution reaction (HER) activity of WS2 , and vice versa. At the same time, it was found that the catalytic effect of the hybrid catalyst was the best when the feed ratio was W : Fe=2 : 1. In other words, we confirmed that there is a synergistic effect between W- and Fe-based sulfide hybrid catalysts, and validated that the reason for the improved HER performance is the strong interaction between the two in the middle sulfur. WS2 /Fe0.95 S1.05 -2 hybrid catalyst leads to enhanced HER activity, which shows a low overpotential of ∼0.172 V at 10 mA cm-2 , low Tafel slope of ∼53.47 mV/decade. This study supplies innovative synthesis of a highly active WS2 /Fe0.95 S1.05 hybrid catalyst for HER.

HighlightsWhat are the main findings?The HCl treatment of porous carbon can generate abundant hydroxyl and carboxyl groups, while the further heat treatment can transform into thermally stable carbonyl and ether groups.Carbonyl and ether groups within porous carbon supports is beneficial to the improvement of HER performance of catalysts.What is the implication of the main finding?The surface properties of porous carbon supports can be well tuned via a HCl treatment followed by an appropriate heat treatment.The feasible improvement of HER performance by regulating surface oxygen functional groups of porous carbon supports.The oxygen functionalization of carbon materials has widely been employed to improve the catalytic performance of carbon-supported Pt (Pt/C) catalysts. Hydrochloric acid (HCl) has often been employed to clean carbons during the preparation of carbon materials. However, the effect of oxygen functionalization through a HCl treatment of porous carbon (PC) supports on the performance of the alkaline hydrogen evolution reaction (HER) has rarely been investigated. Herein, the impact of HCl combined with the heat treatment of PC supports on the HER performance of Pt/C catalysts has been comprehensively investigated. The structural characterizations revealed similar structures of pristine and modified PC. Nevertheless, the HCl treatment resulted in abundant hydroxyl and carboxyl groups and the further heat treatment formed thermally stable carbonyl and ether groups. Among the catalysts, Pt loading on the HCl-treated PC followed by a heat treatment at 700 °C (Pt/PC-H-700) exhibited elevated HER activity with a lower overpotential of 50 mV at 10 mA cm−2 when compared to the unmodified Pt/PC (89 mV). Pt/PC-H-700 also exhibited better durability than the Pt/PC. Overall, novel insights into the impact of the surface chemistry properties of porous carbon supports on the HER performance of Pt/C catalysts were provided, which were useful for highlighting the feasible improvement of HER performances by regulating the surface oxygen species of porous carbon supports.

Transition‐metal borides (TMBs) have recently attracted attention as excellent hydrogen evolution (HER) electrocatalysts in bulk crystalline materials. Herein, we show for the first time that VB and V3B4 have high electrocatalytic HER activity. Furthermore, we show that the HER activity (in 0.5 m H2SO4) increases with increasing boron chain condensation in vanadium borides: Using a −23 mV overpotential decrement derived from −0.296 mV (for VB at −10 mA cm−2 current density) and −0.273 mV (for V3B4) we accurately predict the overpotential of VB2 (−0.204 mV) as well as that of unstudied V2B3 (−0.250 mV) and hypothetical “V5B8” (−0.227 mV). We then derived an exponential equation that predicts the overpotentials of known and hypothetical VxBy phases containing at least a boron chain. These results provide a direct correlation between crystal structure and HER activity, thus paving the way for the design of even better electrocatalytic materials through structure–activity relationships.