Catalytic CO2 reduction reactions featuring high selectivity toward formate are relatively rare. In some homogeneous molecular CO2-reducing electrocatalysis, using triethylamine (TEA) and isopropanol ...

The oxidation of metal-aquo and -hydroxo complexes to generate the high-valent metal-oxo species used in oxidative catalysis is often kinetically slow due to sluggish proton transfer between ligated −H2O/–OH in the proton-coupled electron transfer (PCET) chemistry. In this research, a ruthenium water oxidation catalyst anchored to a conductive tin-doped indium oxide (ITO) thin film, abbreviated ITO|RuII–OH2, was characterized by spectroscopic and electrochemical methods in acetate or phosphate buffers. The deprotonated intermediate, RuII–OH, was observed spectroscopically in the PCET half-reaction ITO(e–)|RuIII–OH + H+ → ITO|RuII–OH2 indicating an underlying stepwise ET-PT mechanism. In contrast, at elevated buffer concentrations, this intermediate was absent, and a 2–4 order of magnitude increase in the proton transfer rate constant was observed. Kinetic data for this PCET reaction measured as a function of the driving force provided the reorganization energy λ = 1.05 eV and was assigned to a concerted electron–proton transfer (EPT) mechanism. In addition, the standard heterogeneous rate constants for two PCET equilibria, RuIII–OH + H+ + e– ⇌ RuII–OH2 and RuIV = O + H+ + e– ⇌ RuIII–OH were enhanced by these same buffers. Collectively, the data show that the added buffers can enhance the kinetics and thermodynamics for PCET reactions relevant to oxidative catalysis.

We present the first examples of installing a redox reporter and CO2 reduction (CO2R) catalyst onto freshly HF-etched Si (photo)electrodes using a solution-phase nitrocyclocondensation (NCC) reaction....