Molybdenum-leaching induced rapid surface reconstruction of amorphous/crystalline heterostructured trimetal oxides pre-catalyst for efficient water splitting and Zn-air batteries

Abstract

Crystalline and amorphous structure can entitle a catalyst with high stability and activity, respectively. Oxygen evolution reaction (OER) catalysts, which widely used in water electrolysis and rechargeable Zn-air batteries, often undergo a surface phase reconstruction process and generate amorphous active phases under applied anodic potential. Although widely known, few studies and strategies have been reported to rationally tune OER pre-catalysts for enhanced reaction kinetics. Herein, we report a trimetallic oxides (a/c-NiFeMoOx) OER per-catalyst with rationally tunable amorphous/crystalline heterostructure degrees by a precise-tuning component strategy. The best a/c-NiFeMoOx electrode exhibits an OER overpotential merely of 256 mV and a small cell-voltage of 1.52 V to reach 10 mA cm–2 for water electrolysis, respectively. It is find that Mo leaching with tailored amorphous/crystalline heterostructure via the rational tuned degree of amorphousness promotes a rapid surface reconstruction of the a/c-NiFeMoOx pre-catalyst to form (oxy)hydroxide active species, whilst operando Raman, ex-situ X-ray photoelectron spectroscopy and density functional theory (DFT) analysis show the ample oxygen vacancies generated by phase transition significantly accelerates the deprotonation of OH* and lower the O* ➝ OOH* free energy for a fast oxygen evolution kinetics. Additionally, the practical application of a/c-NiFeMoOx cathode in rechargeable Zn-air battery delivers a robust long-term cycling (over 840 cycles).