The feature endowing atomic Ni–N–C electrocatalysts with exceptional intrinsic alkaline hydrogen evolution activity is hitherto not well-documented and remains elusive. To this end, we rationally exploited the hierarchical porous carbon microstructures as scaffolds to construct unique Ni–N₂₊₂–S active sites to boost the sluggish Volmer reaction kinetics. Density functional theory reveals an obvious d-band center (ϵ_d) upshift of the edge-hosted Ni–N₂₊₂–S sites compared with pristine Ni–N₄, which translates to a more stabilized OH adsorption. Moreover, the synergetic dual-site (Ni and S atom) interplay gives rise to a decoupled regulation of the adsorption strength of intermediate species (OH_ad, H_ad) and thereby energetic water dissociation kinetics. Bearing these in mind, sodium thiosulfate was deliberately adopted as an additive in the molten salt system for controllable synthesis, considering the simultaneous catalyst morphology and active-site modulation. The target Ni–N₂₊₂–S catalyst delivers a low working overpotential (83 mV@10 mA cm^–2) and Tafel slope (100.5 mV dec^–1) comparable to those of representative transition metal-based electrodes in alkaline media. The present study provides insights into the metal active-site geometry and promising synergistic effects over single-atom catalysis.

中文翻译：

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协同增强单原子镍催化碱性析氢反应

迄今为止，赋予原子 Ni-N-C 电催化剂具有出色的固有碱性析氢活性的特征尚未得到充分证明，并且仍然难以捉摸。为此，我们合理地利用分级多孔碳微结构作为支架来构建独特的 Ni-N ₂₊₂ -S 活性位点，以提高缓慢的 Volmer 反应动力学。密度泛函理论揭示了与原始 Ni-N ₄相比，边缘承载的 Ni-N ₂₊₂ -S 位点的明显 d 带中心 (ε _d ) 上移，这转化为更稳定的 OH 吸附。此外，协同双位点（Ni 和 S 原子）相互作用导致对中间物质（OH _ad , H_ad ) 和因此高能水离解动力学。考虑到这些，考虑到同时催化剂形态和活性位点调节，特意采用硫代硫酸钠作为熔盐体系中的添加剂以进行可控合成。目标 Ni-N ₂₊₂ -S 催化剂在碱性介质中具有与代表性过渡金属基电极相当的低工作过电势 (83 mV@10 mA cm ^–2 ) 和 Tafel 斜率 (100.5 mV dec ^{–1 )。}本研究提供了对金属活性位点几何形状和对单原子催化的有希望的协同效应的见解。