Alternating current and electrolyte engineering-promoted surface reconstruction of NiFeOxHy catalysts for amper-level oxygen evolution reaction

Abstract

Oxygen evolution reaction (OER) holds vital significance for energy conversion and sustainable synthesis, but the scope of achievable reactions using active and durable electrocatalysts remains limited. Nearly all employed electrocatalyst surfaces undergo uncontrolled reconstruction processes during OER, resulting in inevitable uncertainties and randomness in the formation and evolution of the reconstituted layer. Most current efforts are confined to a single process or region, leaving the energy supply and microenvironment uncontrollable. Here, we propose a novel approach using alternating current (AC) for energy supply and nitrate ions for electrolyte engineering to optimize the reconstruction process of NiFeOxHy. The AC profile induces an opposite electrochemical process, significantly enhancing the stability of the newly formed reconstruction layer against reverse currents originating from the intermittent operation of the electrolyzer. Additionally, nitrate ions act as inducers, optimizing the microenvironment and facilitating the rational formation of the reconstruction layer. The combined energy and electrolyte engineering result in a well-defined reaction surface, promoting fast charge transfer, mass transfer, and abundant active sites for reducing OER kinetics. As a result, an anode based on the optimized catalysts achieves a 17.8 % increase in current density at 2.4 V (vs. reversible hydrogen electrode). For potential practical applications, the current density can be improved by 92 %, with long-term stability lasting up to 200 h under the condition of 1 A cm−2. Moreover, the optimized catalysts remain stable even after intermittent operation at a current density of 1 A cm−2 for 1400 cycles. This work provides a unique strategy for surface reconstruction of energy-related catalysts, effectively manipulating their catalytic properties and functionalities.