Sonocatalytic carbon dioxide reduction for syngas production over surface‐roughened Cu x O catalyst

Abstract The transition to a carbon‐circular economy requires efficient technologies for converting CO 2 into value‐added chemical feedstocks. Sonocatalytic CO 2 conversion has recently emerged as a compelling approach to drive this conversion. Here, we report a surface‐roughened Cu x O catalyst for sonocatalytic CO 2 reduction in aqueous media, achieving a marked CO 2 ‐to‐CO conversion alongside H 2 production, yielding tunable syngas (CO/H 2 ) ratios relevant to Fischer–Tropsch and methanol synthesis processes. We demonstrate that the CO/H 2 ratio is systematically controlled by varying the solution composition (KHCO 3 , CH 3 COOK, and KCl), revealing solution‐mediated selectivity as an unexplored lever in CO 2 sonocatalytic systems. Prolonged testing in CO 2 ‐saturated KHCO 3 solutions induced morphological deformations of the Cu x O catalyst which were shown to benefit sonolysis, as evidenced by higher CO production rates during long‐term operation. Our findings highlight surface‐roughened Cu x O catalyst for sonocatalytic conversion of CO 2 ‐saturated solutions to syngas and introduce solution engineering as a new approach to tune product selectivity.