The Universal Role of Gallium in Promoting Methanol Formation across CO ₂ Hydrogenation Catalysts

ConspectusThe production of value-added chemicals from CO₂ has been a thriving topic of research for the past few decades because of its contribution to a circular carbon economy. Combined with CO₂ capture and storage, thermocatalytic hydrogenation of CO₂ to CH₃OH with green or blue hydrogen, offers an attractive route to mitigate CO₂ emissions and to decarbonize the chemical industry. Numerous studies have been focused on catalysts based on supported metallic nanoparticles; these catalysts consist of at least one transition or coinage metal and a promoter element combined with an oxide support to disperse the active phase. Besides Zn-promoters used in Cu-based hydrogenation catalysts, numerous reports point to Ga as a promoter for methanol synthesis. In recent years, Ga has been shown to convert almost all transition metals toward selective methanol synthesis, but its specific role remains a topic of discussions.In this Account, we summarize how surface organometallic chemistry (SOMC) has enabled the discovery of novel catalysts and the development of detailed structure-activity relationships. Particularly, we show that Ga uniquely generates alloys with transition and coinage (Cu) metal elements across groups 8-11 and converts them into selective methanol synthesis catalysts. Specifically, we highlight the role of M-Ga alloy formation, alloy stability, and the formation of M(Ga)-GaO_<i>x</i> interfaces under reaction conditions. This has been possible thanks to the combination of SOMC, which enables the formation of supported nanoparticles with tailored compositions and interfaces, and state-of-the-art characterization including <i>operando</i> techniques along with computational modeling, including <i>ab initio</i> molecular dynamic calculations. Dynamic alloying-dealloying behaviors under reaction conditions and the formation of M/MGa-GaO_<i>x</i> interfaces are identified as key drivers for efficient methanol formation.