Synthesis of photoactive heterostructures for green hydrogen production

Abstract

Photoelectrochemical (PEC) production of hydrogen directly uses sunlight to drive the watersplitting reaction. The development of heterostructured photoactive electrodes have been a topic of study in recent years due to their properties for producing the well-known "green" hydrogen. In this work, three strategies have been studied to improve the performance of a photoanode composed of bismuth vanadate, a semiconductor with a bandgap in the visible region: the introduction of a hole-extracting layer the effect of using catalytic metals and the replacement of the oxygen evolution reaction (OER) by the glycerol oxidation reaction (GOR). All these combinations of photodepositions and electrodepositions have been carried out on a conductive glass, thus allowing the connection of the photoanode, where the oxidation reaction of glycerol will take place, with the cathode, where protons will be reduced to hydrogen, completing a global reaction that is free of harmful emissions to the environment. In summary, the work shows how the introduction of polyaniline (PANI) as hole-extracting layer on the chosen semiconductor has a positive effect on the presented photocurrent density. Moreover, the addition of metals such as gold or platinum acting as catalysts for the oxidation of glycerol also has an impact on the increase of this desired magnitude. In parallel, the decision of using glycerol instead of water due to its lower oxidation potentials has been proved. Also, a study of the different resulting products from oxidation has been done, demonstrating that this value-added compounds turn glycerol into a really important precursor, and aim at converting this reaction into the future of biodiesel industrial surpluses