Karst landform-featured monolithic electrode for water electrolysis in neutral media

The development of cheap and efficient electrodes for water splitting is an ongoing challenge. Herein, a nickel foam-based monolithic electrode is reported with high performance for both hydrogen and oxygen evolution reactions in neutral media. The karst landform-featured electrode consists of metallic Ni in the valley areas and Ni/α-Ni(OH)₂ heterostructures as towers on the surface. Remarkably, the electrode can switch between HER and OER reversibly and flexibly with long-term viability. Scanning electrochemical microscopy (SECM) analysis and computational studies proved the vital roles of the karst landform structure and the interface of the heterostructure in its efficient bifunctionality. Combined with a common photovoltaic cell, a water electrolysis cell with the bifunctional electrode can implement splitting of natural seawater (pH ∼ 8.0) with a high solar-to-hydrogen (STH) conversion efficiency of 16.5%. This cheap, flexible, robust, easily obtained and bifunctional electrode has potential applications for water splitting in the hydrogen economy.