Photoelectrochemical Water Splitting: A Visible-Light-Driven CoTiO₃@g-C₃N₄-Based Photoanode Interface Follows the Type II Heterojunction Scheme

Abstract

Harnessing solar energy can be efficiently used to generate hydrogen by photochemical water splitting, which is a sustainable and environmentally benign energy source. Here, a unique visible-light-driven CoTiO 3 @g-C 3 N 4 (CTOCN)-based photoanode interface has been optimized and developed with modification to follow the type II heterojunction for the enhancement of photoelectrochemical water splitting. Initially, a graphitic carbon nitride-loaded CoTiO 3 (with 10 wt % g-C 3 N 4 ) composite was obtained using a one-pot solvothermal method. Accordingly, the type II heterojunction interface between g-C 3 N 4 and CoTiO 3 has been successfully created and confirmed by the acquired phase, morphological, and optical examinations. Thereby, heterostructure generations with interfacial interaction were enabled to decrease photogenerated electron−hole pair recombination, leading to enhanced charge transfer for water oxidation kinetics. The minimal charge transfer resistance and hole relaxation lifetime (p) shown in Nyquist and Bode plots have further confirmed the rapid electron transport across the electrode/electrolyte interfaces, which is attributed to an enhanced absorption of holes for the water splitting process. Additionally, UV−vis spectroscopy, Mott−Schottky analysis, and UPS studies were used to determine the band edge locations of g-C 3 N 4 and CoTiO 3 . In comparison to previously developed nanohybrids and their equivalents, the CTOCN-d photoanode follows the type II charge transfer mechanism, resulting in a higher photocurrent density of 55.51 mA cm −2 .