Atomically dispersed nickel–nitrogen–carbon (Ni-N-C) moieties are promising for efficient electrochemical CO₂-to-CO conversion. To improve the intrinsic electrocatalytic activity, it is essential but challenging to steer the coordination environment of Ni centers for promoting the CO formation kinetics. Here, we introduce alien sulfur atoms to tune the local electronic density of unsaturated NiN₂ species. A coordinated structure evolution is detected and S vacancies are generated at high overpotentials, as confirmed by X-ray absorption spectroscopy. The sulfur dopants enhance CO selectivity and activity over normal unsaturated NiN₂ structure, reaching a high CO Faradaic efficiency of 97 % and a large CO current density of 40.3 mA cm⁻² in a H-cell at −0.8 V and −0.9 V (vs. RHE), respectively. DFT calculations reveal both doped S atoms and evolved S vacancies in the NiN₂ coordination environment contribute to the reduced energy barriers for CO₂ electroreduction to CO.

中文翻译：

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硫掺杂促进 CO2 在配位不饱和 Ni-N2 部分上的电还原

原子分散的镍-氮-碳 (Ni-NC) 部分有望用于有效的电化学 CO ₂到 CO 转化。为了提高固有的电催化活性，控制 Ni 中心的配位环境以促进 CO 形成动力学是必不可少但具有挑战性的。在这里，我们引入外来硫原子来调整不饱和 NiN ₂物种的局部电子密度。X 射线吸收光谱证实，在高过电位下检测到协调结构演变并产生 S 空位。硫掺杂剂比普通不饱和 NiN ₂结构增强了 CO 选择性和活性，达到了 97 % 的高 CO 法拉第效率和 40.3 mA cm ^-2的大 CO 电流密度分别在 -0.8 V 和 -0.9 V（相对于 RHE）的 H 电池中。DFT 计算表明，NiN ₂配位环境中掺杂的 S 原子和演化的 S 空位都有助于降低 CO ₂电还原为 CO 的能垒。