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<p>Rational design of metal–nitrogen–carbon (M–N–C) single-atom catalysts (SACs) for selective CO<sub>2</sub> electro-reduction is still largely guided by first-shell coordination engineering, while the catalytic impact of the surrounding non-coordinated “second-shell” microenvironment remains underexplored. Here, we show that tailoring the peripheral nitrogen microenvironment can decisively switch product selectivity in Cu-based SACs, even with an identical Cu–N<sub>4</sub> first-shell motif. Using a polymer coordination strategy, pyrrolic-N–regulated Cu–N<sub>pr</sub>–C and pyridinic-N–regulated Cu–N<sub>py</sub>–C exhibit strikingly divergent behaviors: Cu–N<sub>pr</sub>–C selectively produces formate with 72.6% Faradaic efficiency (FE) at −0.7 V vs. RHE and sustains &gt;67% FE over 10 h, whereas Cu–N<sub>py</sub>–C predominantly drives H<sub>2</sub> evolution (up to 69% FE). <i>In situ</i> attenuated total reflection surface enhanced infrared spectroscopy captures an earlier emergence of the key HCOO* intermediate on Cu–N<sub>pr</sub>–C, evidencing accelerated formate-pathway kinetics enabled by the pyrrolic microenvironment. Density functional theory calculations further support that pyrrolic second-shell regulation promotes the O-bound formate route while disfavoring hydrogen adsorption, whereas the pyridinic microenvironment renders H adsorption more competitive and biases the reaction toward hydrogen evolution reaction. Extending this second-shell strategy to Ni SACs confirms its generality: Ni–N<sub>py</sub>–C achieves 96.8% CO selectivity, while Ni–N<sub>pr</sub>–C shows mixed CO/H<sub>2</sub> production. This work establishes second-shell microenvironment regulation as a general and actionable design principle for steering selectivity in M–N–C SACs toward targeted CO<sub>2</sub> reduction products.</p>

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Peripheral nitrogen microenvironment engineering of Cu–N4 single-atom catalysts enables selective electrochemical CO2 reduction to formate

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2026年4月16日

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  • Wengang Liu,
  • Jie Chen,
  • Pengyu Du,
  • Longyue Hu,
  • Ji Yang,
  • Haifeng Qi

摘要

Rational design of metal–nitrogen–carbon (M–N–C) single-atom catalysts (SACs) for selective CO2 electro-reduction is still largely guided by first-shell coordination engineering, while the catalytic impact of the surrounding non-coordinated “second-shell” microenvironment remains underexplored. Here, we show that tailoring the peripheral nitrogen microenvironment can decisively switch product selectivity in Cu-based SACs, even with an identical Cu–N4 first-shell motif. Using a polymer coordination strategy, pyrrolic-N–regulated Cu–Npr–C and pyridinic-N–regulated Cu–Npy–C exhibit strikingly divergent behaviors: Cu–Npr–C selectively produces formate with 72.6% Faradaic efficiency (FE) at −0.7 V vs. RHE and sustains >67% FE over 10 h, whereas Cu–Npy–C predominantly drives H2 evolution (up to 69% FE). In situ attenuated total reflection surface enhanced infrared spectroscopy captures an earlier emergence of the key HCOO* intermediate on Cu–Npr–C, evidencing accelerated formate-pathway kinetics enabled by the pyrrolic microenvironment. Density functional theory calculations further support that pyrrolic second-shell regulation promotes the O-bound formate route while disfavoring hydrogen adsorption, whereas the pyridinic microenvironment renders H adsorption more competitive and biases the reaction toward hydrogen evolution reaction. Extending this second-shell strategy to Ni SACs confirms its generality: Ni–Npy–C achieves 96.8% CO selectivity, while Ni–Npr–C shows mixed CO/H2 production. This work establishes second-shell microenvironment regulation as a general and actionable design principle for steering selectivity in M–N–C SACs toward targeted CO2 reduction products.