Modulating Oxygen Evolution Reaction Pathways via (Oxy)Hydroxide-Driven Surface Reconstruction on TiC MXene Electrocatalysts.

The oxygen path mechanism (OPM) has gained increasing interest as an oxygen evolution reaction (OER) pathway with facile O-O coupling. Importantly, OPM differs from both adsorbate evolution (AEM) and lattice oxygen mechanism (LOM) routes, which involve multiple intermediates and lattice oxygen, respectively. Here, an electro-activated reduced TiC MXene (rTiC) system is introduced that modulates the OER pathway by governing the population of (oxy)hydroxide species on rTiC surfaces. Through operando Raman spectroscopy, the in situ formation of (oxy)hydroxide species on rTiC surfaces (rTiC-T) is evidenced during electro-activation, promoting OER active-site evolution through rational surface reconstruction. The increased (oxy)hydroxide concentration induces a 27% reduced OER overpotential at 10 mA cm and a 67% current density increment at high voltages against the TiC reference. Operando vibrational spectroscopy and direct probing measurements offer insight into the dynamic reconfiguration of rTiC-T surfaces, the nature of reaction intermediates, and, most importantly, into the transition from AEM to OPM routes during OER. First-principles calculations further validate a cooperative catalysis pathway with reduced energy barrier, corroborating the enhanced activity of (oxy)hydroxide-rich MXene catalysts. These findings underscore the potential of electrochemically-assisted surface engineering to promote the OPM pathway and substantially improve OER through selective surface modification.