Engineering the Oxygen Vacancies in Perovskite Oxides for Electricity Generation from Water Evaporation

The development of new suitable material systems is paramount for water evaporation-induced electricity generation associated with the energy harvesting technology. Herein, to the best of the knowledge, the first demonstration of perovskite oxides for efficient electricity generation from water evaporation is presented and discover the key role of oxygen vacancies in promoting the performance. As a proof-of-concept example, the A-site-deficient La_0.95FeO_3-δ perovskite with abundant oxygen vacancies in a single generator can achieve an absolute value of output voltage up to ≈1.5 V for 200 h under ambient conditions and even up to ≈2.5 V at specific conditions, about one order of magnitude higher than the stoichiometric LaFeO₃ counterpart. Noticeably, a voltage reversal phenomenon during the evaporation process is observed due to the zeta potential inversion mediated by the surface functional hydroxyl groups on the perovskite films. Theoretical calculations and systematic experiments demonstrate that oxygen vacancies in La_0.95FeO_3-δ enable to enhance surface charges and facilitate water dissociation, leading to stronger water-solid interfacial interaction and more ion transport in capillary networks, ultimately boosting the voltage output. More importantly, it is found that the promoting effect of oxygen vacancy in water evaporation-induced electricity is universal and applicable for metal oxides with varied structures and compositions.