N-doped Ti3+ rich SrTiO3 for efficient photoelectrochemical water splitting

In this work, hydrothermally synthesized SrTiO₃ (STO) is subjected to ammonia reduction for 15 h and 45 h at 1000 ℃ under controlled conditions. The ammonia treatment reduced the band gap of SrTiO₃ from 3.2 eV to 2.8 eV in ammonia-treated SrTiO₃ samples (STON). XRD and Raman analysis confirm the presence of cubic phase in the STO and ammonia-treated STON-15 and STON-45 samples. Additionally, the presence of N due to ammonia reduction in STON-15 and STON-45 samples is verified by XPS analysis. In addition, XPS data shows an increase in the Ti³⁺ concentration in the STON-15 sample relative to the STON-45 sample when N is incorporated. STON-15 showed higher photocurrent density throughout the potential range of water splitting. An increase from 98 μA/cm² to 250 μA/cm² in the cathodic photocurrent density at 0 V_RHE is obtained for STON-15 sample compared to STO sample. In contrast to STO, which only displayed a photocurrent density of 4.97 μA/cm², STON-15 showed an anodic photocurrent density of 140 μA/cm² at 1.23 V_RHE. All the photoelectrochemical studies were carried out without using co-catalysts and sacrificial agents.