Optimizing Materials to Boost the Valorization of CO₂: Tuning Cobalt–Cobalt Interactions on In₂O₃-Based Photothermal Catalysts

The valorization of CO₂ is an important challenge within the current panorama, since this molecule is probably the main contributor to climate change. In this study, the synthesis of materials based on a nanostructured batonnet-type indium oxide is carried out. In them, different amounts of Co are introduced, varying between 2 and 8% mol. It is verified that the most active sample in the transformation of carbon dioxide to carbon monoxide contains 6 mol %. of Co. This sample's activity under dual excitation exceeds the thermal counterpart by more than 30%. After carrying out a complete physical and chemical characterization with the help of X-ray absorption spectroscopy and other techniques, it is shown that catalysts with amounts of cobalt equal to or below 4 mol % contain isolated single-atom species, while those with higher amounts of metal display a Co-Co interaction which triggers the evolution of the samples under reaction conditions. The optimum control of this Co-Co interaction and the nature of the final cobalt-containing species determine dual photothermal catalytic properties. This work establishes a structure-activity relationship to interpret the catalytic behavior of highly dispersed subnanometric cobalt species, and thus an avenue to optimize the photothermal valorization of carbon dioxide.