Locally Controllable Catalytic Environment Constructed by Lewis Acids Enables Highly Efficient and Stable Water Splitting

Green hydrogen production from seawater electrolysis offers a promising route to harness intermittent renewable energy, particularly in resource-rich coastal regions. However, Cl– in seawater triggers parasitic side reactions and corrosion, which degrade both the activity and durability of electrocatalysts and thus hinder the practical deployment of this technology. Here, a hard Lewis acid overlayer was constructed on the catalyst surface to promote water dissociation and accumulate in-situ generated OH– in the vicinity of the active sites. Such locally generated alkalinity suppresses chlorine chemistry at the catalyst surface. Moreover, the strong affinity between the Lewis acid layer and OH– limits the capture of hydroxide by Mg2+ and Ca2+ in bulk seawater, thereby alleviating precipitate formation. The Cr2O3(30)-NiMoO4(10) catalyst exhibits exceptional hydrogen evolution reaction and oxygen evolution reaction activity, with overpotentials of 56 mV and 220 mV at 10 mA cm–2. The overall water splitting based on the catalysts for both electrodes reaches a low voltage of 1.72 V@0.5 A cm–2.