Flame synthesized MoO3 nanobelts and nanoparticles coated with BiVO4 for photoelectrochemical hydrogen production

•MoO3 nanoparticles and MoO3 nanobelts were prepared by flame synthesis.•BiVO4/MoO3 heterojunction was designed for solar hydrogen production.•Growth mechanism for MoO3 nanostructure was proposed.•The effect of morphology on photoelectric performance was investigated. MoO3 nanoparticles and nanobelts are synthesized by flame synthesis. Flame synthesis is used in combination with spin coating as the main method to prepare the BiVO4/MoO3 heterojunction photoelectrode. Compared with the use of MoO3 and BiVO4 as a single material, the BiVO4/MoO3 heterojunction broadens the range of light absorption and improves charge transport and separation performance, overcoming the constraints of low visible light utilization and slow water oxidation kinetics of single material. The experiment shows that the increase of BiVO4/MoO3 nanobelts composite structure in photocurrent production is three times more than that of BiVO4/MoO3 nanoparticles under the same condition. When the applied external bias is 1.23 V vs. RHE, BiVO4/MoO3 nanoparticles will produce a photocurrent density of 0.18 mA/cm2, while the optimal BiVO4/MoO3 nanobelts heterojunction produces a photocurrent density of 0.54 mA/cm2. In the process of testing, the BiVO4/MoO3 nanobelts have more stability within the same deteriorating time. The photocurrent decay rate of BiVO4/MoO3 nanoparticles heterojunction is 27.8% while that of the BiVO4/MoO3 nanobelts is only 18.4%. In addition, abundant oxygen vacancies or defects are found in the BiVO4/MoO3 nanobelts composite structure, which accelerate the transfer and separation of charge carriers, resulting in higher photocatalytic activity. Thus, the results show that the composite photoelectrode of BiVO4 and one-dimensional MoO3 is a promising material for solar hydrogen production.