Improvement in Photoelectrochemical Water Splitting Performance of GaN-nanowire Photoanode Using MXene.

The photoelectrochemical water splitting (PEC-WS) performance of a photoanode consisting of GaN nanowires (NWs) is significantly improved using a Ti 3 C 2 -MXene coating as an intermediate layer to promote carrier transfer toward the electrolyte. The maximum current density and applied-bias photon-to-current efficiency of the photoanode comprising GaN NWs coated with Ti 3 C 2 -MXene (MGNWs) are measured to be 34.24 mA/cm 2 and 14.47% at 1.2 and 0.4 V versus a reversible hydrogen electrode (RHE), respectively. These values are much higher than those of the GaN-NW photoanode without Ti 3 C 2 -MXene (4.04 mA/cm 2 and 1.95%) and also markedly exceed those of previously reported photoanodes. After 8 days of PEC-WS, the current density was measured to be 31.07 mA/cm 2 , which corresponds to 97.58% of that measured immediately after the reaction started. Based on the time dependence of the current density, the hydrogen evolution rate over the reaction time is calculated to be 0.58 mmol/cm 2 ·h. The results confirm that the PEC-WS performance of the optimized MGNW photoanode is superior to and more stable than those of previously reported photoanodes.