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.