Neves-Garcia Tomaz, Hasan Mahmudul, Zhu Quansong, Li Jing, Jiang Zhan, Liang Yongye, Wang Hailiang, Rossi Liane M, Warburton Robert E, Baker L Robert
Department of Chemistry and Biochemistry, The Ohio State University, Columbus, Ohio 43210, United States.
Departamento de Química Fundamental, Instituto de Química, Universidade de São Paulo, São Paulo, São Paulo 05508-000, Brazil.
J Am Chem Soc. 2024 Nov 20;146(46):31633-31646. doi: 10.1021/jacs.4c09744. Epub 2024 Nov 6.
Direct electrochemical reduction of carbon dioxide (CO) capture species, i.e., carbamate and (bi)carbonate, can be promising for CO capture and conversion from point-source, where the energetically demanding stripping step is bypassed. Here, we describe a class of atomically dispersed nickel (Ni) catalysts electrodeposited on various electrode surfaces that are shown to directly convert captured CO to methane (CH). A detailed study employing X-ray photoelectron spectroscopy (XPS) and electron microscopy (EM) indicate that highly dispersed Ni atoms are uniquely active for converting capture species to CH, and the activity of single-atom Ni is confirmed using control experiments with a molecularly defined Ni phthalocyanine catalyst supported on carbon nanotubes. Comparing the kinetics of various capture solutions obtained from hydroxide, ammonia, primary, secondary, and tertiary amines provide evidence that carbamate, rather than (bi)carbonate and/or dissolved CO, is primarily responsible for CH production. This conclusion is supported by C nuclear magnetic resonance (NMR) spectroscopy of capture solutions as well as control experiments comparing reaction selectivity with and without CO purging. These findings are understood with the help of density functional theory (DFT) calculations showing that single-atom nickel (Ni) dispersed on gold (Au) is active for the direct reduction of carbamate, producing CH as the primary product. This is the first example of direct electrochemical conversion of carbamate to CH, and the mechanism of this process provides new insight on the potential for integrated capture and conversion of CO directly to hydrocarbons.
直接电化学还原二氧化碳（CO₂）捕获物种，即氨基甲酸盐和（双）碳酸盐，对于从点源捕获和转化CO₂可能是有前景的，因为在此过程中绕过了耗能巨大的解吸步骤。在此，我们描述了一类电沉积在各种电极表面上的原子分散镍（Ni）催化剂，这些催化剂被证明能将捕获的CO₂直接转化为甲烷（CH₄）。采用X射线光电子能谱（XPS）和电子显微镜（EM）进行的详细研究表明，高度分散的Ni原子对于将捕获物种转化为CH₄具有独特的活性，并且使用负载在碳纳米管上的分子定义的镍酞菁催化剂进行对照实验，证实了单原子Ni的活性。比较从氢氧化物、氨、伯胺、仲胺和叔胺获得的各种捕获溶液的动力学，提供了证据表明氨基甲酸盐而非（双）碳酸盐和/或溶解的CO₂是CH₄产生的主要原因。捕获溶液的¹³C核磁共振（NMR）光谱以及比较有无CO₂吹扫时反应选择性的对照实验支持了这一结论。借助密度泛函理论（DFT）计算可以理解这些发现，计算表明分散在金（Au）上的单原子镍（Ni）对于氨基甲酸盐的直接还原具有活性，以CH₄作为主要产物。这是氨基甲酸盐直接电化学转化为CH₄的首个实例，该过程的机制为CO₂直接集成捕获和转化为碳氢化合物的潜力提供了新的见解。
