A superhydrophilic NiFe electrode for industrial alkaline water electrolysis

Abstract

NiFe-based materials are among the most promising alkaline oxygen evolution reaction (OER) catalysts because of their high intrinsic activities and abundance. Although many advanced NiFe-based catalysts have been developed, few exhibit simultaneous high activity, stability, good mass transfer, and cost-effective large-scale preparation. Furthermore, NiFe-based catalysts have rarely been studied in alkaline water electrolyzers (AWE) where the catalysts work under a large current density in an alkaline electrolyte at high temperatures and high concentrations with tight assembly pressure. This study successfully developes robust and highly active NiFe nanocone array (NA) catalysts that exhibit both fast and cost-effective mass production capabilities. Benefiting from the in situ-formed OER-active NiFe layered double hydroxide (LDH) and the superhydrophilic structure-induced fast mass transfer, the optimized NiFe NA sample presentes a low OER overpotential of 269 mV at 500 mA cm−2 in a 30 wt% KOH solution. The NiFe core-NiFe LDH shell structure and metallic bond between NiFe nanocones and the substrate are crucial for enabling the NiFe electrode to maintain a minimal potential increase of only 4% even after 250 h of testing at 500 mA cm−2 in a 30 wt% KOH solution. Moreover, the AWE using NiFe NA anodes and NiMo cathodes (NiFe//NiMo) works stably at 500 mA cm−2 under 80 °C in 30 wt% KOH solution and presents a power energy consumption of 4.0 kWh Nm−3 H2, much lower than that of the Ni mesh//Ni mesh counterpart and most commercial AWEs. This study, for the first time, evaluates the performance of NiFe electrodes in AWE and demonstrates their industrial application prospects in alkaline water electrolysis.