Ion sieving membrane for direct seawater anti-precipitation hydrogen evolution reaction electrode

In seawater, severe hydroxide-based precipitation on the hydrogen evolution reaction (HER) electrode surface is still a major stumbling block for direct seawater electrolysis. Here, we design a direct seawater HER electrode with excellent anti-precipitation performance based on an Ni(OH)₂ nanofiltration membrane in situ grown on nickel foam (NF) at room temperature. The positively charged Ni(OH)₂ membrane with nanometer-scale cracks realises an ion sieving function, which apparently hinders the transfer of Mg²⁺/Ca²⁺ ions to suppress precipitation, while rapidly transporting OH^- and H₂O to ensure HER mass transfer. Therefore, the Ni(OH)₂-membrane-decorated seawater HER electrode reduces precipitation by about 98.3% and exhibits high activity and stability. Moreover, in the application of a direct seawater electrolyser and magnesium seawater battery, the Ni(OH)₂ membrane-decorated electrode also shows low precipitation and high stability. This work highlights a potential strategy to solve HER electrode precipitation in seawater via an ingenious electrode structure design.