Abstract
Single-atom catalysts (SACs) with metal–nitrogen (M–N) sites are one of the most promising electrocatalysts for electrochemical carbon dioxide reduction (ECO2R). However, challenges in simultaneously enhancing the activity and selectivity greatly limit the efficiency of ECO2R due to the improper interaction of reactants/intermediates on these catalytic sites. Herein, we report a carbon-based nickel (Ni) cluster catalyst containing both single-atom and cluster sites (NiNx-T, T = 500–800) through a ligand-mediated method and realize a highly active and selective electrocatalytic CO2R process. The catalytic performance can be regulated by the dispersion of Ni–N species via controlling the pyrolysis condition. Benefitting from the synergistic effect of pyrrolic-nitrogen coordinated Ni single-atom and cluster sites, NiNx-600 exhibits a satisfying catalytic performance, including a high partial current density of 61.85 mA cm−2 and a high turnover frequency (TOF) of 7,291 h−1 at −1.2 V vs. RHE, and almost 100% selectivity toward carbon monoxide (CO) production, as well as good stability under 10 h of continuous electrolysis. This work discloses the significant role of regulating the coordination environment of the transition metal sites and the synergistic effect between the isolated single-site and cluster site in enhancing the ECO2R performance.
Highlights
Electrochemical carbon dioxide reduction (ECO2R) of valuable fuel/chemicals, driven by renewable energy sources, offers a promising route to solve global warming and realize carbon neutrality (Shaikh et al, 2018; Sharifian et al, 2021)
These results all together confirm the amorphous state of Ni species on the carrier and verify the absence of Ni nanoparticles (Ni NPs) for NiNx-T samples (Yan et al, 2018)
The TEM and highresolution TEM (HRTEM) images show the presence of Ni nanoparticles with a diameter of approximately 50 nm, accompanied with the exposed (111) plane (Fan et al, 2020), which is consistent with its XRD pattern (Supplementary Figures S8A–D)
Summary
Electrochemical carbon dioxide reduction (ECO2R) of valuable fuel/chemicals, driven by renewable energy sources, offers a promising route to solve global warming and realize carbon neutrality (Shaikh et al, 2018; Sharifian et al, 2021). The produced high value-added chemicals/ fuels can contribute to an industrial production-oriented carbon cycle and greatly alleviate the energy crisis (Kondratenko et al, 2013; Qiao et al, 2014). Noble metal catalysts, such as Au and Ag, have demonstrated a promising catalytic performance concerning the generated current density (>10 mA cm−2) and Faradaic efficiency (>90%) for CO products, offering feasibility for CO2 valorization (Ma et al, 2016; Wuttig et al, 2016). Their high cost seriously limits further application of these noble metal catalysts in ECO2R.
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