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In the electrocatalytic CO2 reduction reaction (CO2RR), metal catalysts with an oxidation state generally demonstrate more favorable catalytic activity and selectivity than their corresponding metallic counterparts. However, the persistence of oxidative metal sites under reductive potentials is challenging since the transition to metallic states inevitably leads to catalytic degradation. Herein, a thorough review of research on oxidation-state stabilization in the CO2RR is presented, starting from fundamental concepts and highlighting the importance of oxidation state stabilization while revealing the relevance of dynamic oxidation states in product distribution. Subsequently, the functional mechanisms of various oxidation-state protection strategies are explained in detail, and in situ detection techniques are discussed. Finally, the prevailing and prospective challenges associated with oxidation-state protection research are discussed, identifying innovative opportunities for mechanistic insights, technology upgrades, and industrial platforms to enable the commercialization of the CO2RR. [ABSTRACT FROM AUTHOR]

Developing robust electrocatalysts and advanced devices is important for electrochemical carbon dioxide (CO2) reduction toward the generation of valuable chemicals. We present herein a carbon‐confined indium oxide electrocatalyst for stable and efficient CO2 reduction. The reductive corrosion of oxidative indium to the metallic state during electrolysis could be prevented by carbon protection, and the applied carbon layer also optimizes the reaction intermediate adsorption, which enables both high selectivity and activity for CO2 reduction. In a liquid‐phase flow cell, the formate selectivity exceeds 90 % in a wide potential window from −0.8 V to −1.3 V vs. RHE. The continuous production of ca. 0.12 M pure formic acid solution is further demonstrated at a current density of 30 mA cm−2 in a solid‐state electrolyte mediated reactor. This work provides significant concepts in the parallel development of electrocatalysts and devices for carbon‐neutral technologies. [ABSTRACT FROM AUTHOR]

We report an amino‐functionalized indium‐organic framework for efficient CO2 reduction to formate. The immobilized amino groups strengthen the absorption and activation of CO2 and stabilize the active intermediates, which endow an enhanced catalytic conversion to formate despite the inevitable reduction and reconstruction of the functionalized indium‐based catalyst during electrocatalysis. The reconstructed amino‐functionalized indium‐based catalyst demonstrates a high Faradaic efficiency of 94.4 % and a partial current density of 108 mA cm−2 at −1.1 V vs. RHE in a liquid‐phase flow cell, and also delivers an enhanced current density of ca. 800 mA cm−2 at 3.4 V for the formate production in a gas‐phase flow cell configuration. This work not only provides a molecular functionalization and assembling concept of hybrid electrocatalysts but also offers valuable understandings in electrocatalyst evolution and reactor optimization for CO2 electrocatalysis and beyond. [ABSTRACT FROM AUTHOR]