Molecular Nitrogen–Carbon Catalysts, Solid Metal Organic Framework Catalysts, and Solid Metal/Nitrogen‐Doped Carbon (MNC) Catalysts for the Electrochemical CO₂ Reduction

Abstract

The CO2 electrochemical reduction reaction (CO2RR) is a promising technology for converting CO2 into chemicals and fuels, using surplus electricity from renewable sources. The technological viability of this process, however, is contingent on finding affordable and efficient catalysts. A range of materials containing abundant elements, such as N, C, and non‐noble metals, ranging from well‐defined immobilized complexes to doped carbon materials have emerged as a promising alternative. One of the main products of the CO2RR is CO, which is produced on these catalysts with selectivities comparable to those of noble metal catalysts. Furthermore, other valuable products, such as formic acid, hydrocarbons, and alcohols, have also been reported. The factors that control the catalytic performance of these materials, however, are not yet fully understood. A review of recent work is presented on heterogeneous nitrogen‐containing carbon catalysts for the CO2RR. The synthesis and characterization of these materials as well as their electrocatalytic performance are discussed. Combined experimental and theoretical studies are included to bring insight on the active sites and the reaction mechanism. This knowledge is key for developing optimal catalyst materials that meet the requirement in terms of activity, selectivity, and stability needed for commercial applications.

Catalytic Mechanisms and Design Principles for Single‐Atom Catalysts in Highly Efficient CO2 Conversion

“…We have calculated the overpotentials for the Co-N x -C SACs with different coordination environments (x = 0-4) ( Figure S20, Supporting Information) and found that the Co-N 4 -C structures have the lowest overpotentials, which favors CO 2 RR over HER. [44,[46][47][48][49][50][51] Though relying on this certain case only, the discovered descriptors can be considered as effectively universal design principles of various M-N-C SACs for highly efficient CO 2 conversion. Therefore, the M-N 4 -C structures are dominant active centers among the various M-N-C structures.…”

A Disquisition on the Active Sites of Heterogeneous Catalysts for Electrochemical Reduction of CO2 to Value‐Added Chemicals and Fuel

“…For instance, Ni, Co, and Fe SACs are demonstrated to be highly selective towards CO 2 RR whereas the bulk metals are very active towards the competing HER. [212,221,222] This is because in the bulk form, the catalyst surface is covered with *H that hinders CO 2 RR and promotes HER reaction kinetics. It must be noted that most report of active SAC catalysts are based on metal single atoms coordinated with nitrogen-doped carbon.…”

Metal-organic frameworks for electrochemical reduction of carbon dioxide: The role of metal centers

“…In the past decades, various CO 2 reduction approaches have been developed, including electrocatalytic reduction [24][25][26][27][28][29][30] , photocatalytic reduction [31][32][33][34][35][36][37][38][39][40][41] , chemical and biochemical reduction [42] . Among these methods, electrocatalytic reduction CO 2 as a promising method has attracted the wide attention of researchers, since it can not only be conducted in ambient conditions, but also can be driven by renewable energy (e.g., solar, wind, and tide) [2,43] . However, extremely stable chemical structure of CO 2 molecule requires large kinetic and thermodynamic energy barrier to be overcome to finish the reduction of CO 2 .…”