Mechanism-Guided Catalyst Design for CO2 Hydrogenation to Formate and Methanol

ConspectusCO2 to formate/formic acid and methanol has emerged as a promising method for utilizing CO2 in chemical and fuel synthesis, as well as reducing CO2 emissions when H2 is produced through renewable energy sources. This reaction requires the activation of two chemically distinct molecules, CO2 and H2, along with the selective formation of the desired product. Creating efficient catalysts that surpass the limitations of existing catalysts remains a significant challenge. Historically, the development of catalysts has largely depended on trial and error until successful outcomes are achieved. However, recent advances in material synthesis for well-defined structures, reaction kinetics analysis, in situ characterization techniques, and computational studies have facilitated a systematic understanding of catalytic reactions and enabled mechanism-guided catalyst development. This innovative approach has empowered researchers to strategically design effective catalysts that optimize the target reaction, particularly the rate-determining step, while tackling other limitations, such as selectivity and stability.This Account provides an overview of our recent efforts in catalyst development for CO2 hydrogenation through mechanism-guided engineering, which are primarily divided into two sections: (i) formic acid/formate and (ii) methanol production. For the CO2 hydrogenation to formate/formic acid, we first discuss the structure–activity correlation studies of various metal/support catalyst systems, including different metal particle sizes, types of support, and crystalline morphologies of the support. These studies highlight the crucial role of electron-rich metal sites for H2 splitting and an adequate number of weak basic sites for CO2 activation, which inform the design of improved catalysts with unique architectures. Notably, encapsulated metal cluster catalysts enhance the utilization of metal species and optimize the synergistic interaction between metal active sites and the support material. The encapsulation strategy can also be applied to inexpensive metal elements such as Ni, facilitating the development of highly efficient catalysts.Our primary focus for CO2-to-methanol catalysts is the design of active and durable oxide-based catalysts. We first identify that the critical limitation of metal oxide catalysts is their poor H2 activation capability, based on a comprehensive review of classical and state-of-the-art understanding of the CO2-to-methanol catalysts. Consequently, the principal catalyst design concept involves coupling metal promoters, which provide high H2 activation functionality, with metal oxide catalysts that enable the adsorption of CO2 and selective methanol synthesis. An essential synthetic approach is the doping of metal promoters on the surface of oxide catalysts. Specifically, atomically dispersed metal promoters significantly improve methanol yield by maximizing interfacial synergy with the oxide catalyst. A remarkable strategy is the incorporation of a hydrogen dispenser, such as conductive carbon, between the metal promoter and the oxide catalyst. This multicomponent composite dramatically enhances hydrogen delivery from metal sites to active sites via long-range hydrogen spillover, resulting in accelerated methanol synthesis. The approach overcomes the limitation of conventional metal/oxide systems, which constrain hydrogen movement across the surface of the oxide catalyst. We conclude by discussing the underlying implications of these observations and offering perspectives on future research and development opportunities.