Accelerated Durability Assessment and a Proposed Degradation Mechanism of NiCoO _<i>x</i> OER Catalysts under Simulated Intermittent Renewable Power: Insights from XAS

The substantial cost reductions in renewable energy sources (RES), particularly solar and wind, could facilitate their large-scale integration into modern power systems, thereby accelerating the transition toward a carbon-neutral economy. However, the inherent intermittency of RES highlights the critical need for efficient energy storage technologies, with green hydrogen emerging as a promising and sustainable energy carrier. Alkaline water electrolysis offers a scalable and cost-effective solution; however, ensuring the long-term durability of electrodes under dynamic operation remains a critical challenge. In this study, the durability of NiCoO_<i>x</i> OER catalysts was evaluated using two accelerated degradation test (ADT) protocols: a conventional cyclic voltammetry (CV-ADT) protocol and a start-up/shut-down protocol. The latter was specifically designed to simulate the operational characteristics of (RES)-driven systems, including the effects of reverse current phenomenon typically observed in bipolar plate AWE stacks. This protocol imposed more severe stressors on the electrodes than the CV-ADT protocol, most likely providing a more realistic simulation of the intermittent conditions encountered in RES-based operation. Electrochemical measurements, along with <i>operando</i> and <i>ex situ</i> X-ray absorption spectroscopy, provided insights into the OER active sites and the degradation mechanisms of the catalyst under repeated start-up/shut-down ADT cycles. The results suggested that cobalt leaching at and beneath the electrode/electrolyte interface is a likely key factor contributing to catalyst detachment from the substrate.