Janus-Structured Co-Ti3C2 MXene Quantum Dots as a Schottky Catalyst for High-Performance Photoelectrochemical Water Oxidation

MXene materials have attracted increasing attention in electrochemical energy-storage applications while MXene also becomes photo-active at the quantum dot scale, making it an alternative for solar-energy-conversion devices. A Janus-structured cobalt-nanoparticle-coupled Ti3C2 MXene quantum dot (Co-MQD) Schottky catalyst with tunable cobalt-loading content serving as a photoelectrochemical water oxidation photoanode is demonstrated. The introduction of cobalt triggers concomitant surface-plasmon effects and acts as a water oxidation center, enabling visible-light harvesting capability and improving surface reaction kinetics. Most importantly, due to the rectifying effects of Co-MQD Schottky junctions, photogenerated carrier separation/injection efficiency can be fundamentally facilitated. Specifically, Co-MQD-48 exhibits both superior photoelectrocatalysis (2.99 mA cm(-2) at 1.23 V vs RHE) and charge migration performance (87.56%), which corresponds to 194% and 236% improvement compared with MQD. Furthermore, excellent photostability can be achieved with less than 6.6% loss for 10 h cycling reaction. This fills in gaps in MXene material research in photoelectrocatalysis and allows for the extension of MXene into optical-related fields.