Transition Metal Chalcogenides as a Versatile and Tunable Platform for Catalytic CO2 and N2 Electroreduction

Group VI transitionmetal chalcogenides are the subject of increasingresearch interest for various electrochemical applications such aslow-temperature water electrolysis, batteries, and supercapacitorsdue to their high activity, chemical stability, and the strong correlationbetween structure and electrochemical properties. Particularly appealingis their utilization as electrocatalysts for the synthesis of energyvectors and value-added chemicals such as C-based chemicals from theCO(2) reduction reaction (CO2R) or ammonia fromthe nitrogen fixation reaction (NRR). This review discusses the roleof structural and electronic properties of transition metal chalcogenidesin enhancing selectivity and activity toward these two key reductionreactions. First, we discuss the morphological and electronic structureof these compounds, outlining design strategies to control and fine-tunethem. Then, we discuss the role of the active sites and the strategiesdeveloped to enhance the activity of transition metal chalcogenide-basedcatalysts in the framework of CO2R and NRR against theparasitic hydrogen evolution reaction (HER); leveraging on the designrules applied for HER applications, we discuss their future perspectivefor the applications in CO2R and NRR. For these two reactions,we comprehensively review recent progress in unveiling reaction mechanismsat different sites and the most effective strategies for fabricatingcatalysts that, by exploiting the structural and electronic peculiaritiesof transition metal chalcogenides, can outperform many metallic compounds.Transition metal chalcogenides outperform state-of-the-art catalystsfor CO2 to CO reduction in ionic liquids due to the favorableCO(2) adsorption on the metal edge sites, whereas the basalsites, due to their conformation, represent an appealing design spacefor reduction of CO2 to complex carbon products. For theNRR instead, the resemblance of transition metal chalcogenides tothe active centers of nitrogenase enzymes represents a powerful nature-mimickingapproach for the design of catalysts with enhanced performance, althoughstrategies to hinder the HER must be integrated in the catalytic architecture.