Catalytic Photothermal Hydrogenation of Carbon Dioxide to Liquid Fuels using Pt/GaN Prepared via Surface Organometallic Chemistry

Renewable liquid fuels are expected to play a crucial role in transitioning to a more sustainable future. Their synthesis via the hydrogenation of CO₂ using solar energy emerges as a promising technology, combining both the utilisation of a renewable primary energy source and the (re)utilisation of a major greenhouse gas. In this context, GaN has attracted a lot of attention in harnessing solar energy to drive chemical transformations. In this work, we study GaN by ¹H solid-state NMR spectroscopy, revealing the presence of terminal Ga-OH, bridging Ga-NH-Ga, as well as Ga-OH-Ga surface functional groups and combinations thereof. With this knowledge in hand, we make use of surface organometallic chemistry (SOMC) to prepare a Pt/GaN catalyst with highly dispersed Pt nanoparticles on GaN. Under photothermal conditions using visible light (>320 nm), the synthesised Pt/GaN promotes the hydrogenation of CO₂ to C₂₊ products such as acetone, EtOH, ⁱPrOH, and acetic acid in a batch reactor at 60 °C and 1 bar of pressure, while the pristine GaN counterpart only produces minor amounts of MeOH and acetone. Furthermore, a recycling test was performed to showcase the stability of the catalyst over multiple batch reaction cycles.