Engineered Superhydrophilic/Superaerophobic Catalyst: Two-Dimensional Co(OH) 2 -CeO 2 Nanosheets Supported on Three-Dimensional Co Dendrites for Overall Water Splitting.

Efficient electrocatalysts require not only a tunable electronic structure but also great active site accessibility and favorable mass transfer. Here, a two-dimensional/three-dimensional (2D/3D) hierarchical electrocatalyst consisting of Co(OH) 2 -CeO 2 nanosheet-decorated Co dendrites is proposed, named as Co(OH) 2 -CeO 2 /Co. Based on the strong electronic interaction of the Co(OH) 2 -CeO 2 heterojunction, the electronic structure of the Co site is optimized, which facilitates the adsorption of intermediates and the dissociation of H 2 O. Moreover, the open 2D/3D structure formed by introducing the Co substrate further reduces the accumulation of heterogeneous nanosheets and promotes the radial diffusion of the electrolyte, significantly improving the utilization of active sites and shortening the electron transfer pathway. In addition, the superhydrophilic/superaerophobic interface achieved by constructing the hierarchical micro-nanostructure is beneficial to electrolyte infiltration and bubble desorption, thus ensuring favorable mass transfer. Therefore, Co(OH) 2 -CeO 2 /Co exhibits an excellent overall water-splitting activity in alkaline solution.