Insights into the Surface Electronic Structure and\nCatalytic Activity of InO<sub><i>x</i></sub>/Au(111) Inverse\nCatalysts for CO<sub>2</sub> Hydrogenation to Methanol

The\ndirect conversion of carbon dioxide (CO<sub>2</sub>) into methanol\n(CH<sub>3</sub>OH) via low-temperature hydrogenation is crucial for\nrecycling anthropogenic CO<sub>2</sub> emissions and producing fuels\nor high value chemicals. Nevertheless, it continues to be a great\nchallenge due to the trade-off between selectivity and catalytic activity.\nFor CO<sub>2</sub> hydrogenation, In<sub>2</sub>O<sub>3</sub> catalysts\nare known for their high CH<sub>3</sub>OH selectivity. Subsequent\nstudies explored depositing metals on In<sub>2</sub>O<sub>3</sub> to\nenhance CO<sub>2</sub> conversion. Despite extensive research on metal\n(M) supported In<sub>2</sub>O<sub>3</sub> catalysts, the role of In–M\nalloys and M/In<sub>2</sub>O<sub>3</sub> interfaces in CO<sub>2</sub> activation and CH<sub>3</sub>OH selectivity remains unclear. In\nthis work, we have examined the behavior of In/Au(111) alloys and\nInO<sub><i>x</i></sub>/Au(111) inverse systems during CO<sub>2</sub> hydrogenation using synchrotron-based ambient-pressure X-ray\nphotoelectron spectroscopy (AP-XPS) and catalytic tests in a batch\nreactor. Indium forms alloys with Au(111) after deposition. The In–Au(111)\nalloys display high reactivity toward CO<sub>2</sub> and can dissociate\nthe molecule at room temperature to generate InO<sub><i>x</i></sub> nanostructures. At very low coverages of In (≤0.05\nML), the InO<sub><i>x</i></sub> nanostructures are not stable\nunder CO<sub>2</sub> hydrogenation conditions and the active In–Au(111)\nalloys produces mainly CO and little methanol. An increase in indium\ncoverage to 0.3 ML led to stable InO<sub><i>x</i></sub> nanostructures\nunder CO<sub>2</sub> hydrogenation conditions. These InO<sub><i>x</i></sub>/Au(111) catalysts displayed a high selectivity (∼80%)\ntoward CH<sub>3</sub>OH production and an activity for CO<sub>2</sub> conversion that was at least 10 times larger than that of plain\nIn<sub>2</sub>O<sub>3</sub> or Cu(111) and Cu/ZnO(0001̅) benchmark\ncatalysts. The results of AP-XPS show that InO<sub><i>x</i></sub>/Au(111) produces methanol via methoxy intermediates. Inverse\noxide/metal catalysts containing InO<sub><i>x</i></sub> open\nup a possibility for improving CO<sub>2</sub> → CH<sub>3</sub>OH conversion in processes associated with the control of environmental\npollution and the production of high value chemicals.