A New Accelerated Durability Test Protocol for Water Oxidation Electrocatalysts of Renewable Energy Powered Alkaline Water Electrolyzers

For electrocatalysts of oxygen evolution reaction (OER), a new accelerated durability test (ADT) protocol is presented. The protocol is designed to closely mimic the fluctuations of renewable energies. The unit cycle of the current ADT protocol represents the "ON/OFF" operation mode. In the "ON" step, the electrolyzer operates under a DC current of 0.6A cm(-2). In the "OFF" step, the electrocatalyst is subjected to a constant potential that is clearly more cathodic than its OER onset potential (namely, 0.3, 0.5, and 0.7 V vs. RHE) for 10 or 60s. The transition from the "ON" state to the "OFF" state occurs through a cathodic linear sweep voltammetry of a fast sweep rate to mimic the sudden changes in the renewable power. A NiCoOx/Ni-mesh electrode was used as a case study. The electrode showed remarkable durability under continuous operation (i = 0.6 A cm(-2)) for about 900 hours. However, it did suffer severe degradation after a certain number of ADT cycles, and the rate of degradation mainly depends on the potential value and the duration of the "OFF" step. Interestingly, the inclusion of the 10-sec open-circuit potential step after the "ON" step clearly mitigates the impact of energy fluctuations on the durability of OER electrocatalysts. (C) The Author(s) 2020. Published by ECSJ.