Paradigmatic demonstration of sonochemical carbon dioxide reduction proceeded over Cu-based catalysts

Sonochemical carbon dioxide (CO 2 ) reduction represents a promising decarbonization technology. However, relevant studies regarding the usage of solid catalysts in sonochemical reactor are rare. Herein, we investigate four distinct highly nanostructured cuprous oxides and sulfides for sonochemical CO 2 reduction via ultrasound-induced cavitation. Specifically, we investigate Cu 2 O cubes, Cu 7 S 4 /Cu 2 O cubes, Cu 7 S 4 cages and Cu 7 S 4 sheets morphologies. Each nanostructure is found to produce CO and H 2 in various ratios ranging from 1.0 – 2.3. Through a systematic study, we investigate the role of different acoustic conditions on affecting CO 2 sonolysis, involving the measurements in CO 2 -saturated H 2 O, 5 %CO 2 /Ar-saturated H 2 O, N 2 -saturated H 2 O, 5 %CO 2 /N 2 -saturated H 2 O and CO 2 -saturated KHCO 3 . We show that Cu 2 O cubes have the highest CO 2 -to-CO conversion (up to 4286.4 μmol·L −1 ·g −1 ·h −1 ) in 5 %CO 2 /Ar-saturated H 2 O. In addition, the as-synthesized Cu 2 O cubes exhibited promising sonochemical stability, with CO and H 2 production rates stabilizing at around 890.3 μmol·L −1 ·g −1 ·h −1 and 966.9 μmol·L −1 ·g −1 ·h −1 , respectively. Post sonochemical analysis indicated that the Cu 2 O cubes maintain relatively high CO 2 -to-CO conversion, as well as their morphology. This work provides the first proof-of-concept demonstration of using inexpensive Cu-based catalysts to enable low-carbon sonochemical CO 2 reduction. • Adoption of Cu catalysts with distinct morphologies for CO 2 sonolysis, achieved efficient CO 2 -to-CO conversion. • H 2 produced as a byproduct across all the resultant catalysts, with CO/H 2 ratios of 1.0 – 2.3 belonging to syngas. • Cu 2 O cube achieved the highest CO 2 -to-CO conversion of 1428.8 μmol·L −1 ·g −1 in 5 %CO/Ar-saturated H 2 O owing to Ar-induced strong cavitation effects. • Cu 2 O cube exhibited a largely reduced CO 2 reduction activity in CO 2 -saturated KHCO 3 solution owing to its considerably deformed catalyst structure. • Advanced ex situ techniques verified the morphology stability of Cu 2 O cube giving rise to its performant CO 2 sonolysis performance.