Modulating Oxygen Evolution Reaction Pathways via (Oxy)Hydroxide-Driven Surface Reconstruction on Ti₃C₂ MXene...

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 Ti₃C₂ MXene (rTi₃C₂) system is introduced that modulates the OER pathway by governing the population of (oxy)hydroxide species on rTi₃C₂ surfaces. Through operando Raman spectroscopy, the in situ formation of (oxy)hydroxide species on rTi₃C₂ surfaces (rTi₃C₂-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^-2 and a 67% current density increment at high voltages against the Ti₃C₂ reference. Operando vibrational spectroscopy and direct probing measurements offer insight into the dynamic reconfiguration of rTi₃C₂-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.