2D Ti3C2 MXene interfaced ZnO/WO3 thin film nanostructures towards improved photoelectrochemical water splitting

Abstract

We explored the morphology evolution approach for sustained photoelectrochemical (PEC) water splitting by developing dual heterojunction. Herein, novel ZnO/WO3/Ti3C2 photoelectrode has been developed for the first time by the integration of flake-like ZnO, nanocrystal featured WO3, and layer-structured two-dimensional (2D) Ti3C2 MXene morphologies towards PEC activity under simulated solar light. By adjusting the radio frequency (RF) magnetron sputtering and post-annealing, flake-like/nanocrystals featured ZnO/WO3 heterostructure observed with uniform growth of WO3 nanocrystals over the flake-like ZnO. Further, efficient integration of layer-structured 2D Ti3C2 MXene on ZnO/WO3 was provided through spin-coating. Utilizing robust surface interface between ZnO, WO3, and Ti3C2, optical transmittance and band gap have been modified. Accordingly, ZnO/WO3/Ti3C2 improved the photocurrent generation about 1.4 x 10-3 A/cm2 compared to pure ZnO (7.8 x 10-4 A/cm2) and ZnO/WO3 (1.1 x 10-3 A/cm2) at +0.4 V. These findings further provided a photoconversion efficiency of 1.16 % by the ZnO/WO3/Ti3C2 at +0.4 V. The PEC studies proved that electrically conductive Ti3C2 MXene can significantly separate the charge carriers from ZnO/WO3. On the other hand, this morphology-induced architecture proved sustainable surface interaction with KOH electrolyte than Na2SO3 and Na2SO4 media. Overall, the above developments suggest a robust interface in ZnO/WO3/Ti3C2 under controlled surface morphology and PEC water splitting activity.