Highly Durable and Efficient Seawater Electrolysis Enabled by Defective Graphene-Confined Nanoreactor.

Direct seawater electrolysis is a promising technology for massive green hydrogen production but is limited by the lack of durable and efficient electrocatalysts toward the oxygen evolution reaction (OER). Herein, we develop a core-shell nanoreactor as a high-performance OER catalyst consisting of NiFe alloys encapsulated within defective graphene layers (NiFe@DG) by a facile microwave shocking strategy. This catalyst needs overpotentials of merely 218 and 276 mV in alkalized seawater to deliver current densities of 10 and 100 mA cm, respectively, and operates continuously for 2000 h with negligible activity decay (1.0%), making it one of the best OER catalysts reported to date. Detailed experimental and theoretical analyses reveal that the excellent durability of NiFe@DG originates from the formation of the built-in electric field triggered by the defective graphene coating against chloride ions at the electrode/electrolyte interface, thus protecting the active NiFe alloys at the core from dissolution and aggregation under harsh operation conditions. Further, a highly stable and efficient seawater electrolyzer is assembled with the NiFe@DG anode and the Pt/C cathode to demonstrate the practicability of the catalysts.