In this study, we propose a top-down approach for the controlled preparation of undercoordinated Ni–N_x (Ni-hG) and Fe–N_x (Fe-hG) catalysts within a holey graphene framework, for the electrochemical CO₂ reduction reaction (CO₂RR) to synthesis gas (syngas). Through the heat treatment of commercial-grade nitrogen-doped graphene, we prepared a defective holey graphene, which was then used as a platform to incorporate undercoordinated single atoms via carbon defect restoration, confirmed by a range of characterization techniques. We reveal that these Ni-hG and Fe-hG catalysts can be combined in any proportion to produce a desired syngas ratio (1–10) across a wide potential range (−0.6 to −1.1 V vs RHE), required commercially for the Fischer–Tropsch (F–T) synthesis of liquid fuels and chemicals. These findings are in agreement with our density functional theory calculations, which reveal that CO selectivity increases with a reduction in N coordination with Ni, while unsaturated Fe–N_x sites favor the hydrogen evolution reaction (HER). The potential of these catalysts for scale up is further demonstrated by the unchanged selectivity at elevated temperature and stability in a high-throughput gas diffusion electrolyzer, displaying a high-mass-normalized activity of 275 mA mg^–1 at a cell voltage of 2.5 V. Our results provide valuable insights into the implementation of a simple top-down approach for fabricating active undercoordinated single atom catalysts for decarbonized syngas generation.

中文翻译：

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在多孔石墨烯上设计欠配位的 Ni-Nx 和 Fe-Nx 以将 CO2 电化学转化为合成气

在这项研究中，我们提出了一种自上而下的方法，用于在多孔石墨烯框架内受控制备欠配位的 Ni-N _x (Ni-hG) 和 Fe-N _x (Fe-hG) 催化剂，用于电化学 CO ₂还原反应(CO ₂ RR) 到合成气 (syngas)。通过对商业级掺氮石墨烯进行热处理，我们制备了一种有缺陷的多孔石墨烯，然后将其用作平台，通过碳缺陷修复，由一系列表征技术证实。我们发现，这些 Ni-hG 和 Fe-hG 催化剂可以以任何比例组合，以在广泛的电位范围内（-0.6 至 -1.1 V 对 RHE）产生所需的合成气比（1-10），这是 Fischer -Tropsch (F-T) 合成液体燃料和化学品。这些发现与我们的密度泛函理论计算一致，这表明 CO 选择性随着 N 与 Ni 配位的减少而增加，而不饱和 Fe-N _x位点有利于析氢反应 (HER)。这些催化剂在高温下的选择性不变和高通量气体扩散电解槽的稳定性进一步证明了这些催化剂的放大潜力，在 2.5 V 的电池电压下显示出 275 mA mg ^–1的高质量归一化活性我们的结果为实施一种简单的自上而下的方法来制造用于脱碳合成气生成的活性欠配位单原子催化剂提供了宝贵的见解。