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 NiOx/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. Although the light-promoted Sabatier reaction has great potential for CO2 remediation strategies, its mechanism is not fully understood. Now, a steady-state isotopic kinetic analysis coupled with infrared spectroscopy reveals important aspects of this hydrogenation process over a NiOx/La2O3@TiO2 composite catalyst.