A facile route of Ti decoration for modulating M–O–Ti (M = Ni, Co) and oxygen vacancies on NiCo-LDH electrocatalysts for efficient oxygen evolution reaction

Abstract

Bimetallic layered double hydroxides (LDHs) have attracted substantial attention as oxygen evolution reaction (OER) catalysts. In this work, we provide a facile route to prepare Ti-doped NiCo-LDH/NF electrocatalysts with M–O–Ti (M = Ni, Co) covalent bonds via a rapid immersion method for the OER process. The experiments and density functional theory (DFT) calculations elucidate that the doping of Ti (M–O–Ti) not only exfoliates the NiCo-LDH nanosheets into spheres but also causes lattice distortion to produce more oxygen vacancies, which promotes faster exchange of intermediates and improves the electron transfer efficiency. These superior physical characters endow Ti-NiCo-LDH with an excellent overpotential of 319 mV at a current density of 50 mA cm⁻², which is markedly lower than that of NiCo-LDH (391 mV at 50 mA cm⁻²). Even at a high current density of 100 mA cm⁻², NiCo-LDH displays an overpotential of 429 mV, whereas Ti-NiCo-LDH is capable of achieving an overpotential of 353 mV. Moreover, the water electrolyzer based on the Ti-NiCo-LDH bifunctional catalyst requires a low cell voltage of 1.60 V to achieve a current density of 10 mA cm⁻², and the Ti-NiCo-LDH catalyst has been successfully applied for solar cell-driven water electrolysis and the corresponding voltage is about 1.61 V. This work offers a novel strategy to fabricate high activity NiCo-LDH with rich oxygen vacancies toward the OER process.

Keywords: Ti-doping; NiCo-layered double hydroxide; Oxygen vacancy; Oxygen evolution reaction.