Large-Scale Synthesis of Spinel NixMn3-xO4 Solid Solution Immobilized with Iridium Single Atoms for Efficient Alkaline Seawater Electrolysis

Abstract

Seawater electrolysis not only affords a promising approach to produce clean hydrogen fuel but also alleviates the bottleneck of freshwater feeds. Here, a novel strategy for large-scale preparing spinel NixMn3-xO4 solid solution immobilized with iridium single-atoms (Ir-SAs) is developed by the sol–gel method. Benefitting from the surface-exposed Ir-SAs, Ir1/Ni1.6Mn1.4O4 reveals boosted oxygen evolution reaction (OER) performance, achieving overpotentials of 330 and 350 mV at current densities of 100 and 200 mA cm–2 in alkaline seawater. Moreover, only a cell voltage of 1.50 V is required to reach 500 mA cm–2 with assembled Ir1/Ni1.6Mn1.4O4‖Pt/C electrode pair under the industrial operating condition. The experimental characterizations and theoretical calculations highlight the effect of Ir-SAs on improving the intrinsic OER activity and facilitating surface charge transfer kinetics, and evidence the energetically stabilized *OOH and the destabilized chloride ion adsorption in Ir1/Ni1.6Mn1.4O4. This work demonstrates an effective method to produce efficient alkaline seawater electrocatalyst massively.