Flexible BiOI thin films photocatalysts toward renewable solar fuels production

Abstract

Bismuth oxyiodide (BiOI) is an emerging photocatalyst material with remarkable electrical and optical properties, bringing it to the forefront of materials research. Herein, thin films of BiOI photocatalysts have been successfully synthesized by a one-pot microwave-hydrothermal method. The BiOI films were deposited on earth-abundant mica substrates, which provide a flexible and effective surface for the controlled growth of well-dispersed flowers of high surface area and enhanced light absorption. The films were evaluated as photocatalyst to generate alternative and renewable solar fuels from CO2 reduction, H2O splitting, and N2 photofixation under visible light. The results demonstrated the ability of the flower-shaped BiOI films to generate various value-added compounds, such as HCOOH (4.8 mmoles g-1 h-1), CH3OH (9.5 mmoles g-1 h-1), H2 (0.6 mmoles g-1 h-1), and NH3 (0.11 mmoles g-1 h-1) under visible light irradiation. Mainly, the H2 evolution was promoted (x3) after adding 3% wt. of calcium gluconate as a sacrificial agent, reaching a continuous H2 production (1.8 mmoles g-1 h-1). This enhancement effect was related to the oxidation of the sacrificial agent, favoring a high number of electrons available to reduce H+ to H2. In addition, the recycling of the photocatalyst was evidenced after four cycles, which activity was reactivated after the fifth cycle with a thermal treatment at 160 °C under vacuum conditions.