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

Sonochemical carbon dioxide (CO₂) 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 CO₂ reduction via ultrasound-induced cavitation. Specifically, we investigate Cu₂O cubes, Cu₇S₄/Cu₂O cubes, Cu₇S₄ cages and Cu₇S₄ sheets morphologies. Each nanostructure is found to produce CO and H₂ in various ratios ranging from 1.0 – 2.3. Through a systematic study, we investigate the role of different acoustic conditions on affecting CO₂ sonolysis, involving the measurements in CO₂-saturated H₂O, 5 %CO₂/Ar-saturated H₂O, N₂-saturated H₂O, 5 %CO₂/N₂-saturated H₂O and CO₂-saturated KHCO₃. We show that Cu₂O cubes have the highest CO₂-to-CO conversion (up to 4286.4 μmol·L⁻¹·g⁻¹·h⁻¹) in 5 %CO₂/Ar-saturated H₂O. In addition, the as-synthesized Cu₂O cubes exhibited promising sonochemical stability, with CO and H₂ 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 Cu₂O cubes maintain relatively high CO₂-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 CO₂ reduction.