Role of Oxide-Derived Cu on the Initial Elementary Reaction Intermediate During Catalytic CO₂ Reduction

The catalytic role of oxide-derived Cu (OD-Cu) in promoting CO₂ reduction (CO₂R) to C₂₊ products has been appreciated for decades. However, the dynamic evolution of the surface oxidation states, together with their real correlation to the binding of reaction intermediates, remains unclear due to technical challenges. Here, we show the time-resolved spectroscopic signatures of key OD-Cu-CO₂^•- intermediates during catalytic CO₂ reduction through one electron transfer from nanoseconds to seconds time scale. We generated the initial intermediate CO₂^•- radicals in the bulk solution and monitored the interfacial reaction kinetics with well-defined OD-Cu (Cu(0), Cu(I), and Cu(II)) nanoparticles. Combined with molecular simulations, transient absorption profiles analysis reveals that Cu(I) induced a faster CO₂^•- radical coupling reaction than Cu(0), whereas Cu(II) is only reduced to Cu(I) by the CO₂^•- radical. Furthermore, the newly developed multistep cumulative pulse methodology uncovered the transition in chemical states of mixed OD-Cu during radical coupling reactions. This pulse radiolysis study provides compelling evidence for the beneficial role of subsurface oxides in early time catalytic CO₂ transformation.