Controllable La Deficiency Engineering within Perovskite Oxides for Enhanced Overall Water Splitting

Recently, perovskite (ABO₃) nanomaterials have been widely explored as a class of versatile electrocatalysts for oxygen evolution reactions (OER) due to their remarkable compositional flexibility and structural tunability, but their poor electrical conductivity hinders hydrogen evolution reaction (HER) activity and further limits the large-scale application of perovskite oxide in overall water splitting (OWS). In this study, hollow-nanotube-structure La_xCo_0.4Fe_0.6O_3-δ (x = 1.0, 0.9, and 0.8) perovskites with superior HER/OER activity were synthesized on nickel-iron alloy foam (denoted La_xCoFe/NFF) using hydrothermal with a subsequent calcination strategy. Among them, La_0.9CoFe/NFF not only exhibited extraordinary HER electrocatalytic performance (160.5 mV@10 mA cm^-2 and 241.0 mV@100 mA cm^-2) and stability (20 h@10 mA cm^-2), but also displayed significant OER electrocatalytic activity (234.7 mV@10 mA cm^-2 and 296.1 mV@100 mA cm^-2) and durability (20 h@10 mA cm^-2), outperforming many recently reported HER/OER perovskite catalysts. The increase in oxygen vacancies caused by the introduction of La deficiency leads to the expansion of the lattice, which greatly accelerates the HER/OER process of La_0.9CoFe/NFF. Additionally, the naturally porous skeleton can prevent catalysts from aggregating as well as delay the corrosion and dissolution of catalysts in the electrolyte under high applied potentials. Furthermore, the assembled two-electrode configuration, utilizing La_0.9CoFe/NFF (cathode and anode) electrodes, only requires a low cell voltage of 1.573 V at 10 mA cm^-2 for robust alkaline OWS, accompanied by remarkable durability over 20 h. This work provides inspiration for the design and preparation of high-performance and stable bifunctional perovskite electrocatalysts for OWS.