Stabilizing amorphous NiFe-based catalysts via borate bridging for water oxidation under industrial conditions

Abstract

The practical deployment of an anion exchange membrane water electrolyzer (AEMWE) relies on the exploration of active and durable electrocatalysts towards the sluggish oxygen evolution reaction (OER). Although amorphous NiFe-based catalysts (a-NiFeO_xH_y) emerge as the competitive candidate due to impressive intrinsic OER activity, their unique defective structure renders the metal sites more susceptible to over-oxidation and dissolution, leading to poor stability. To address this challenge, we incorporate borate groups (BO₃³⁻) into the a-NiFeO_xH_y lattice by occupying the oxygen vacancy sites. The bridged borates not only maintain the structural stability via filling the oxygen vacancies, but also assist electron transfer from Ni to Fe to suppress Fe ion dissolution, thereby enhancing the catalytic stability of a-NiFeO_xH_y. Moreover, the tailored electronic structure of Ni favors electrochemical reconstruction to high-valence Ni active species and optimizes adsorption of oxygen intermediates towards superior OER activity. Therefore, a-B-NiFeO_xH_y integrated into the AEMWE can deliver a noteworthy current density of 4.75 A cm⁻² at a voltage of 2.0 V and maintain stable operation at 0.5 A cm⁻² for 3000 hours. This study not only affords a promising electrocatalyst for the AEMWE, but also paves a new avenue to break the activity-stability trade-off of amorphous materials for the OER.