Unravelling rate-determining step and consequence of O₂- or H₂O-assisted, wet CO transformation on catalytic CuO-CeO₂ domains via interfacial engineering

CO generates CO₂, a feedstock of chemicals including alcohols, alkenes, etc., through exothermic oxidation/water–gas shift (WGS) on CuO-CeO₂ interfaces. However, CO oxidation/WGS with wet, low-temperature gases have been partially explored with regard to surface dynamics, rate laws, rate-determining steps, and catalytic consequences. This study clarifies the aforementioned conundrums via control runs and kinetic assessments. Two CuO-CeO₂ interfaces were engineered to possess comparable quantities of CO/H₂O-accessible Cu^+/2+ species or O₂/H₂O-accessible mobile (O_M), labile (O_L), and vacant oxygens, yet, provide distinct binding strengths with CO (E_CO), O_M (E_OM), and H₂O (E_H2O) alongside with dissimilar H₂O-accessible surface areas (S_H2O). ¹⁸O₂-labelling control runs and energy barriers (E_BARRIER) of the CuO-CeO₂ interfaces corroborated that O_M migration outweighed O_L migration as the rate-determining step for CO oxidation. The E_BARRIER/S_H2O values of the CuO-CeO₂ interfaces demonstrated that H₂O scission overrode CO₂ evolution as the rate-determining step for the WGS. CO oxidation competed with yet outperformed WGS in converting CO using wet, low-temperature gases, highlighting the importance of lowering the E_CO/E_OM values in boost O_M migration on CuO-CeO₂ interfaces and reducing their E_H2O values for hindering WGS. These findings can promote the low-temperature CO transformation performance maximum-obtainable on CuO-CeO₂ interfaces.