Unlocking the potential of the formate pathway in the photo-assisted Sabatier reaction

Although solar irradiation has demonstrated beneficial synergy for catalytic CO₂ hydrogenation, it has long been debated as to whether the observed photo-assisted catalytic enhancement has a photo-activation component or is driven solely by the heating effect. Here, we confirm that surface adsorbates play a critical role in photo-assisted CO₂ activation. We isolate the rate-determining intermediate species in the photo-assisted Sabatier reaction by in situ isotopic spectroscopy. Specifically, we reveal that photo-activation of the formate adsorbate (HCO₂*) offers an eightfold photo-enhancement on NiO_x/La₂O₃@TiO₂. Concurrently, the active La₂O₃@TiO₂ support facilitates the adsorption of CO₂, which may contribute to the sustained HCO₂* formation and conversion. The findings are crucial as they provide surface intermediary insights in the design of catalysts for photo-assisted CO₂ conversion. Ultimately, the understanding may unlock the solar-driven hydrogenation catalytic pathway for other reactions involving HCO₂* such as the synthesis of methanol. [Figure not available: see fulltext.].