Parameterization and quantification of two key operando physio-chemical descriptors for water-assisted electro-catalytic organic oxidation

Abstract

Electro-selective-oxidation using water as a green oxygen source demonstrates promising potential towards efficient and sustainable chemical upgrading. However, surface micro-kinetics regarding co-adsorption and reaction between organic and oxygen intermediates remain unclear. Here we systematically study the electro-oxidation of aldehydes, alcohols, and amines on Co/Ni-oxyhydroxides with multiple characterizations. Utilizing Fourier transformed alternating current voltammetry (FTacV) measurements, we show the identification and quantification of two key operando parameters (ΔI_harmonics/I_OER and ΔV_harmonics) that can be fundamentally linked to the altered surface coverage ( $\Delta {\theta }_{{\mathrm{OH}}^{*}}/{\theta }_{{\mathrm{OH}}^{*}}^{\mathrm{OER}}$ ) and the changes in adsorption energy of vital oxygenated intermediates ( ${\Delta G}_{\mathrm{OH}*}^{\mathrm{EOOR}}-{\Delta G}_{\mathrm{OH}*}^{\mathrm{OER}}$ ), under the influence of organic adsorption/oxidation. Mechanistic analysis based on these descriptors reveals distinct optimal oxyhydroxide surface states for each organics, and elucidates the critical catalyst design principles: balancing organic and M^3+δ-OH* coverages and fine-tuning ΔG for key elementary steps, e.g., via precise modulation of chemical compositions, crystallinity, defects, electronic structures, and/or surface bimolecular interactions.