Reconstruction‐Determined Alkaline Water Electrolysis at Industrial Temperatures

• Published in: Advanced materials (Weinheim) 2020-10, Vol.32 (40), p.e2001136-n/a
• Main Authors: Liu, Xiong, Guo, Ruiting, Ni, Kun, Xia, Fanjie, Niu, Chaojiang, Wen, Bo, Meng, Jiashen, Wu, Peijie, Wu, Jinsong, Wu, Xiaojun, Mai, Liqiang
• Format: Article
• Language: English
• Subjects: alkaline water electrolysis; Boundaries; Catalysis; Catalysts; complete reconstruction; Electrolysis; grain/phase boundaries; in situ low‐/high‐temperature Raman; industrial temperatures, nanowire arrays; Materials science; Molybdenum oxides; Nanoparticles; Oxygen evolution reactions; Reaction kinetics; Reconstruction
• ISSN: 0935-9648; 1521-4095
• DOI: 10.1002/adma.202001136

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. Complete reconstruction of molybdate oxygen‐evolving pre‐catalysts and its fundamental understanding at industrial temperatures of 50–80 °C are uncovered. In situ low‐/high‐temperature Raman and electron tomography identify the reconstruction mechanism, real active species, and stereoscopic structural characteristics. The boundary–vacancy co‐effect enables fast catalytic kinetics. The coupled cat.‐51.9 and MoO2‐Ni hydrogen‐evolving arrays provide stable electrolysis operation (220 h) at 51.9 °C.