Piezoelectric activation of dual lattice-oxygen mechanism through OH^- Grotthuss transport in water electrolysis‏.

Abstract

The realization of multi-energy water oxidation systems is impeded by the challenge of integrating multiple energy inputs. Here, we overcome this limitation via ultrasonic pre-treatment of the electrolyte, which triggers a mechano-electrochemical coupling effect through piezoelectric polarization. This process promotes a Grotthuss-type OH^- state that weakens O-H bonds and increases the interfacial OH^- concentration, thereby influencing the electrochemical reconstruction of Ni(OH)₂ to NiOOH and modifying water electrolysis pathways. These changes enhance Ni-O covalency and synergistically activate two low-energy water oxidation pathways on NiOOH involving lattice oxygen: one couples lattice oxygen with adsorbed oxygen, while the other facilitates direct lattice oxygen-oxygen coupling. Both routes bypass the high-energy ^*OOH intermediate typical of the conventional adsorbate evolution mechanism (^*OH → ^*O → ^*OOH → O₂), with the latter also avoiding ^*O adsorption entirely. Notably, just one minute of ultrasonic stimulation reduces the overpotential by 222 mV at 100 mA cm^-2. This pulsed-energy strategy thus offers an efficient and scalable approach to realizing multi-energy-enhanced water splitting.