Reconstruction‐Determined Alkaline Water Electrolysis at Industrial Temperatures

TLDR

Alkaline water electrolysis at 50–80 °C is essential for industrial applications and its evaluation can promote practical use. The study uncovers thermally induced complete reconstruction of molybdate OER pre‑catalysts at 51.9 °C and investigates its fundamental mechanism. Dynamic reconstruction, active species, and stereoscopic structural features were identified using in‑situ Raman, ex‑situ microscopy, and electron tomography. The reconstructed cat‑51.9 catalyst delivers a low overpotential of 282 mV at 20 mA cm⁻² (25 °C), remains ultrastable for 250 h at 51.9 °C, and, due to boundaries and vacancies, enables 220 h stable electrolysis when paired with MoO₂–Ni hydrogen arrays.

Abstract

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.