Sol-gel-based synthesis of nanostructured Bi2WO3 covered with Li2MnO3 nanoparticles as enhanced nanocomposite photocatalyst for visible-light production of hydrogen

Abstract

Photocatalytic hydrogen (H2) production over semiconducting nanocomposite photocatalysts signifies a facile way for renewable fuels future. This emerging technique required enhanced light absorption besides stability in the solution. In this work, the synthesis of bismuth tungstate (Bi2WO4) nanocrystals with a high surface area of 160.0 m2g‒1 and bandgap (Eg) of 2.80 eV is achieved by surfactant-aided sol-gel route. Additionally, narrow Eg Lithium manganese oxide (Li2MnO3) is coupled with Bi2WO4 at 5.0–20.0 wt % by impregnation to enhance carrier separation and improve visible-light harvesting. The constructed heterojunctions were used as photocatalysts for generating H2 from a glycerol/water solution in the occurrence of platinum cocatalyst traces. The combination of 15.0 wt% Li2MnO3 has fascinatingly improved the H2 generation by ∼3.5 times (1.970 mmol g−1h−1) compared to pristine Bi2WO4 (0.567 mmol g−1h−1). The enhanced photocatalytic activity is attributed to the effective separation of photoinduced charges and reduction of overall Eg to 2.38 eV. Moreover, the evolved H2 is further boosted to 2.757 mmol g−1h−1 through dose optimization at 2.5 gL−1. The constructed heterojunction also presents interesting stability for five cycles with 95.5% of the initially produced H2.