Semiconducting and photoelectrochemical properties of the ilmenite CoTiO3 prepared by wet method and its application for O2 evolution under visible light

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

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 CoTiO3@g-C3N4 (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 CoTiO3 (with 10 wt % g-C3N4) composite was obtained using a one-pot solvothermal method. Accordingly, the type II heterojunction interface between g-C3N4 and CoTiO3 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-C3N4 and CoTiO3. 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.

g-C3N4/Ca2Fe2O5 heterostructures for enhanced photocatalytic degradation of organic effluents under sunlight

g-C₃N₄/Ca₂Fe₂O₅ heterostructures were successfully prepared by incorporating g-C₃N₄ into Ca₂Fe₂O₅ (CFO). As prepared g-C₃N₄/CFO heterostructures were initially utilized to photodegrade organic effluent Methylene blue (MB) for optimization of photodegradation performance. 50% g-C₃N₄ content in CFO composition showed an enhanced photodegradation efficiency (~ 96%) over g-C₃N₄ (48.15%) and CFO (81.9%) due to mitigation of recombination of photogenerated charge carriers by Type-II heterojunction. The optimized composition of heterostructure was further tested for degradation of Bisphenol-A (BPA) under direct sunlight, exhibiting enhanced photodegradation efficiency of about 63.1% over g-C₃N₄ (17%) and CFO (45.1%). The photoelectrochemical studies at various potentials with and without light illumination showed significant improvement in photocurrent response for g-C₃N₄/Ca₂Fe₂O₅ heterostructures (~ 1.9 mA) over CFO (~ 67.4 μA). These studies revealed efficient solar energy harvesting ability of g-C₃N₄/Ca₂Fe₂O₅ heterostructures to be utilized for organic effluent treatment.