In situ hybridization of an MXene/TiO₂/NiFeCo-layered double hydroxide composite for electrochemical and photoelectrochemical oxygen evolution

Electrochemical and photoelectrochemical (PEC) oxygen evolution reactions (OER) are receiving considerable attention owing to their important roles in the overall water splitting reaction. In this contribution, ternary NiFeCo-layered double hydroxide (LDH) nanoplates were in situ hybridized with Ti₃C₂T_x (the MXene phase) via a simple solvothermal process during which Ti₃C₂T_x was partially oxidized to form anatase TiO₂ nanoparticles. The obtained Ti₃C₂T_x/TiO₂/NiFeCo-LDH composite (denoted as TTL) showed a superb OER performance as compared with pristine NiFeCo-LDH and comercial IrO₂ catalyst, achieving a current density of 10 mA cm^-2 at a potential of 1.55 V versus a reversible hydrogen electrode (vs. RHE) in 0.1 M KOH. Importantly, the composite was further deposited on a standard BiVO₄ film to construct a TTL/BiVO₄ photoanode which showed a significantly enhanced photocurrent density of 2.25 mA cm^-2 at 1.23 V vs. RHE under 100 mW cm^-2 illumination. The excellent PEC-OER performance can be attributed to the presence of TiO₂ nanoparticles which broadened the light adsorption to improve the generation of electron/hole pairs, while the ternary LDH nanoplates were efficient hole scavengers and the metallic Ti₃C₂T_x nanosheets were effective shuttles for transporting electrons/ions. Our in situ synthetic method provides a facile way to prepare multi-component catalysts for effective water oxidation and solar energy conversion.