High photoelectrochemical response of SrTiO3/TiO2/TiN films synthesized via hydrothermal-galvanic couple method with reductive annealing

Abstract Heterostructures have been extensively employed to enhance charge separation and improve performance in photoelectrochemical (PEC) systems. In this study, SrTiO 3 /TiO 2 /TiN heterostructured films were synthesized via a straightforward hydrothermal-galvanic couple (HT-GC) method, followed by annealing under controlled atmospheres with varying nitrogen and oxygen partial pressures. Conductive TiN seed layers were deposited using a facile, air-based sputtering technique, and granular SrTiO 3 films were subsequently grown through the HT-GC process. Post-annealing produced well-defined SrTiO 3 /TiO 2 /TiN heterostructures. Films annealed in reductive N 2 /H 2 at 900 °C exhibited the highest photocurrent density of 7.2 ± 0.4 mA/cm 2 , surpassing previously reported SrTiO 3 /TiO 2 systems. This enhancement is attributed to the formation of large-grained TiO 2 both between SrTiO 3 grains and at the SrTiO 3 /TiN interface, generating abundant SrTiO 3 /TiO 2 heterointerfaces, along with the introduction of oxygen vacancies. These features promote efficient charge separation and suppress recombination. The TiN underlayer also contributes to the improved PEC response via plasmonic effects and high-quality interfaces. This work demonstrates a facile strategy for engineering oxygen-vacancy-rich heterostructures, advancing their potential for PEC applications.