Fabrication of mixed phase TiO2 heterojunction nanorods and their enhanced photoactivities†
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.