Fabrication of mixed phase TiO₂ heterojunction nanorods and their enhanced photoactivities

Abstract

Substantial efforts have been made in recent times in solving the major limiting factors affecting the efficiency of a photocatalyst. The fabrication of efficient junction architectures is one of the viable approaches to resolve this setback. We have developed a facile and systematic approach for the synthesis of anatase TiO₂ (AT) nanoparticles and 1-D anatase and rutile TiO₂ (ART) heterojunction nanorods to enhance the interfacial contact area by adjusting the titanium(IV) butoxide (TBOT) to titanium chloride (TiCl₄) volume ratio. Their narrower band gap, increasing surface area and anatase phase composition engineered by adjusting the relative concentrations of titanium butoxide (TBOT) and titanium chloride (TiCl₄) (TBOT/TiCl₄, 1 : 0, 1 : 0.25, 1 : 1 and 1 : 4 v/v for ART-I, ART-II, ART-III and AT respectively) are also addressed. The materials showed impressive photocatalytic activity for H₂ evolution from water/methanol and the photodegradation of organic pollutants like rhodamine B (RhB) and methylene blue (MB) dyes. ART-II showed superior activity (16.4 mmol g⁻¹ h⁻¹) with an apparent quantum efficiency (AQE) of 7.7% together with its long-term stability. This is attributed to the synergistic effect observed in the mixed phase ART nanorod heterojunction photocatalyst. Methyl viologen (MV²⁺) has been used as a probe to elucidate the photocatalytic activities and highlight the heterojunction driven separation of photo-excited charge carriers for enhanced hydrogen production.