Activation of Ni Particles into Single Ni-N Atoms for Efficient Electrochemical Reduction of CO2
Activation of Ni Particles into Single Ni-N Atoms for Efficient Electrochemical Reduction of CO2
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DOI：
10.1002/aenm.201903068
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发表时间：
2019-12-05
影响因子：
27.8
通讯作者：
Sun, Zhenyu
中科院分区：
文献类型：
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作者：
Fan, Qun;Hou, Pengfei;Sun, Zhenyu
电化学还原二氧化碳（CO2）为燃料和增值工业化学品是保持能源供应和净碳排放之间健康平衡的一种有前途的策略。本文报道了碳纳米管中残留的Ni颗粒催化剂通过一步纳米限制热解策略，被多孔的n掺杂碳鞘包裹成具有可能的NiN3片段的热稳定的单个Ni原子。这些结构变化通过x射线吸收精细结构分析和密度泛函理论（DFT）计算得到证实。分散的Ni单原子有助于在低过电位下高效地电催化CO2还原生成CO，提供超过90%的CO法拉第效率，周转率接近12 000 h(-1)，金属质量活性达到约10 600 mA mg(-1)，优于目前最先进的CO2还原成CO的单原子催化剂。DFT计算表明Ni@N-3（吡啶）位点有利于形成自由能低于Ni@N-4的COOH。此外，放热CO解吸，从而提高电催化CO2转化。这一发现为制备低成本、丰富和高活性的单原子催化剂提供了一条简单、可扩展和有前途的途径，有利于未来的实际二氧化碳电解。
Electrochemical reduction of carbon dioxide (CO2) to fuels and value-added industrial chemicals is a promising strategy for keeping a healthy balance between energy supply and net carbon emissions. Here, the facile transformation of residual Ni particle catalysts in carbon nanotubes into thermally stable single Ni atoms with a possible NiN3 moiety is reported, surrounded with a porous N-doped carbon sheath through a one-step nanoconfined pyrolysis strategy. These structural changes are confirmed by X-ray absorption fine structure analysis and density functional theory (DFT) calculations. The dispersed Ni single atoms facilitate highly efficient electrocatalytic CO2 reduction at low overpotentials to yield CO, providing a CO faradaic efficiency exceeding 90%, turnover frequency approaching 12 000 h(-1), and metal mass activity reaching about 10 600 mA mg(-1), outperforming current state-of-the-art single atom catalysts for CO2 reduction to CO. DFT calculations suggest that the Ni@N-3 (pyrrolic) site favors *COOH formation with lower free energy than Ni@N-4, in addition to exothermic CO desorption, hence enhancing electrocatalytic CO2 conversion. This finding provides a simple, scalable, and promising route for the preparation of low-cost, abundant, and highly active single atom catalysts, benefiting future practical CO2 electrolysis.