2D Titanate Nanosheet–Supported NiMoO_<i>x</i> Core@shell Nanospikes for Overall Electrocatalytic Water-Splitting Reactions

Carbon-based materials that act as supports to design electrocatalysts have been actively pursued for fuel cells and overall water-splitting (OWS) applications. However, carbon-based supports face serious carbon corrosion at high positive potentials, affecting catalyst activity and stability and hindering practical applicability. Herein, carbon-free transition metal-oxide–based 2D titanate nanosheet support has been proposed, demonstrating the applicability of titanate nanosheets as an alternative support for designing electrocatalysts. A new chemical route to produce large 2D nanosheets of titanate via exfoliation has been discovered. Colloidal 2D titanate nanosheet support allows the growth of active nickel molybdenum oxide (NiMoOx) forming Titanate@NiMoOx core–shell materials. Fine heat treatment at different temperatures facilitates in situ formation of MoOx in NiMoOx layers on 2D titanate boosting catalytic activity. An increase in heat treatment facilitates an increase in the semiconductivity of the titanate phase and a simultaneous decay of the active MoOx component, resulting in poor activity. The optimal catalyst Titanate@NiMoOx_200 required an overpotential of 0.54 and 1.19 VRHE for the HER and the OER and an overall cell voltage of 1.75 V to deliver a current density of 10 mA cm–2 with spectacular stability for up to 24 h in KOH media. Spectroscopic and microscopy analyses prove the efficient electronic interaction between MoOx and NiMoOx in the hybrid components. Density functional theory and experimental work suggest that the MoOx/NiMoOx hybrid shows higher water adsorption energy and excellent water-splitting performance. This work sheds light on the feasibility and practical application of titanate support for the rational design of diverse electrocatalysts from noble to non-noble metal-based electrocatalysts for a range of electrochemical applications.