LAUSR

Evaluating the alkaline water electrolysis (AWE) at 50-80 °C required in industry can veritably promote practical applications. Here, the thermally induced complete reconstruction (TICR) of molybdate oxygen evolution reaction (OER) pre-catalysts at 51.9 °C and its fundamental mechanism are uncovered. The dynamic reconstruction processes, the real active species, and stereoscopic structural characteristics are identified by in situ low-/high-temperature Raman, ex situ microscopy, and electron tomography. The completely reconstructed (CR) catalyst (denoted as cat.-51.9) is interconnected by thermodynamically stable (oxy)hydroxide nanoparticles, with abundant boundaries and low crystallinity. For alkaline OER, cat.-51.9 exhibits a low overpotential (282.3 mV at 20 mA cm-2 , 25.0 °C) and ultrastable catalysis at 51.9 °C (250 h, with a negligible activity decay of 19.6 µV h-1 ). The experimental observations combined with theoretical analyses confirm the fast catalytic kinetics enabled by the co-effect of boundaries and vacancies. The coupled cat.-51.9 and MoO2 -Ni hydrogen-evolving arrays provide stable electrolysis operation at 51.9 °C for 220 h. This work uncovers new reconstruction phenomenon of pre-catalysts under realistic conditions and exceptional durability of CR catalysts toward practical high-temperature AWE.