Promoting interfacial free water supply through the hydration of single-atom lanthanide doping for acidic water oxidation

Interfacial free water plays a vital role in accelerating electrocatalytic water splitting. However, the low proportion of free water at the interface significantly limits the reaction rate. Herein, we demonstrate a new strategy to increase the interfacial free water supply by doping single lanthanide atoms into Co 3 O 4 for acidic oxygen evolution (OER). Taking La as an example, the doped La at the surface of Co 3 O 4 spontaneously captures water molecules from the electrolyte through hydration, providing a sufficient free water supply for the OER. In addition, La doping strengthens Co−O bonding, affording strong structural stability. As a result, La-doped Co 3 O 4 has a small overpotential of 288 mV at a current density of 10 mA cm −2 and can remain stable for 230 h. Except for La, other lanthanide elements, such as Sm and Pr, also have similar effects on the OER. Our work not only develops efficient electrocatalysts for the acidic OER but also provides a universal strategy to increase the interfacial free water supply.