The Universal Role of Gallium in Promoting Methanol Formation across CO <sub>2</sub> Hydrogenation Catalysts
Colin Hansen, Wei Zhou, Christophe Copéret
Abstract
High Resolution Image Download MS PowerPoint Slide Conspectus The production of value-added chemicals from CO 2 has been a thriving topic of research for the past few decades because of its contribution to a circular carbon economy. Combined with CO 2 capture and storage, thermocatalytic hydrogenation of CO 2 to CH 3 OH with green or blue hydrogen, offers an attractive route to mitigate CO 2 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 x 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 operando techniques along with computational modeling, including ab initio molecular dynamic calculations. Dynamic alloying–dealloying behaviors under reaction conditions and the formation of M/MGa–GaO x interfaces are identified as key drivers for efficient methanol formation.