Single Platinum Atoms Immobilized on Monolayer Tungsten Trioxide Nanosheets as an Efficient Electrocatalyst for Hydrogen Evolution Reaction

Monolayer WO₃·H₂O (ML-WO₃·H₂O) nanosheets are synthesized via a space-confined strategy, and then a single-atom catalyst (SAC) is constructed by individually immobilizing Pt single atoms (Pt-SA) on monolayer WO₃ (ML-WO₃). The Pt-SA/ML-WO₃ retains the monolayer structure of ML-WO₃·H₂O, with a quite high monolayer ratio up to ≈ 93%, and possesses rich defects (O and W vacancies). It exhibits excellent electrocatalytic performance, with a small overpotential (η) of − 22 mV to drive − 10 mA cm⁻² current, a low Tafel slope of ≈ 27 mV dec⁻¹, an ultrahigh turnover frequency of ≈ 87 H₂ s⁻¹ site⁻¹ at η  =   − 50 mV, and long-term stability. Of particular note, it exhibits an ultrahigh mass activity of ≈ 87 A mg_Pt⁻¹ at η  =   − 50 mV, which is ≈ 160 times greater than that of the state-of-the-art commercial catalyst, 20 wt% Pt/C ( ≈ 0.54 A mg_Pt⁻¹). Experimental and DFT analyses reveal that its excellent performance arises from the strong synergetic effect between the single Pt atoms and the support. This work provides an effective route for large-scale fabrication of ML-WO₃ nanosheets, demonstrates ML-WO₃ is an excellent support for SACs, and also reveals the great potential of SACs in reducing the amount of noble metals used in catalysts.     

Revisiting the Role of Active Sites for Hydrogen Evolution Reaction through Precise Defect Adjusting

2D transition metal dichalcogenides (TMDs) have presented outstanding potential for efficient hydrogen evolution reaction (HER) to replace traditional noble metal catalysts. Here, to achieve enhanced HER performance, specific areas of the few‐layer 1T'‐MoTe₂ film are precisely controlled with a focused ion beam to create particular active sites. Electrochemical measurements indicate that the HER performance, although inconspicuous in pristine 1T'‐MoTe₂ ultrathin films prepared through the chemical vapor deposition method, can be greatly enhanced after patterning and precisely controlled by the morphologies as well as the amounts of the defects, reaching a small onset potential and a record‐low Tafel slope of 44 mV per decade for few‐layer TMDs. Conductivity tests, visualized copper electrodeposition, and density functional theory calculations also confirm that the enhancement of HER performance comes from the exposed edges by patterning. In this pioneering work, not only is the catalysis mechanism of the edge active sites of 1T'‐MoTe₂ unveiled, but also a universal route to study the properties of 2D materials is demonstrated.     

Synergistically Tuning Electronic Structure of Porous β‐Mo2C Spheres by Co Doping and Mo‐Vacancies Defect Engineering for Optimizing Hydrogen Evolution Reaction Activity

The development of novel non‐noble electrocatalysts with controlled structure and surface composition is critical for efficient electrochemical hydrogen evolution reaction (HER). Herein, the rational design of porous molybdenum carbide (β‐Mo₂C) spheres with different surface engineered structures (Co doping, Mo vacancies generation, and coexistence of Co doping and Mo vacancies) is performed to enhance the HER performance over the β‐Mo₂C‐based catalyst surface. Density functional theory calculations and experimental results reveal that the synergistic effect of Co doping with Mo vacancies increases the electron density around the Fermi‐level and modulates the d band center of β‐Mo₂C so that the strength of the Mo? H bond is reasonably optimized, thus leading to an enhanced HER kinetics. As expected, the optimized Co₅₀‐Mo₂C‐12 with porous structure displays a low overpotential (η₁₀ = 125 mV), low‐onset overpotential (η_onset = 27 mV), and high exchange current density (j₀ = 0.178 mA cm^?2). Furthermore, this strategy is also successfully extended to develop other effective metal (e.g., Fe and Ni) doped β‐Mo₂C electrocatalyst, indicating that it is a universal strategy for the rational design of highly efficient metal carbide‐based HER catalysts and beyond.