Photoelectrocatalytic Hydrogen Production Supported by Ascorbic Acid

Abstract

Photoelectrochemical hydrogen production combines electrochemistry and photocatalysis, resulting in sustainable hydrogen production. The process can be improved by the addition of hole scavengers, which reduce the recombination of electrons and holes, increasing the utilisation of solar radiation. Because of its low oxidation potential, ascorbic acid (AA) is an environmentally friendly and readily available hole scavenger. The commonly studied photocatalyst TiO2 makes little utilisation of solar radiation energy due to its high energy gap of 3.2 eV. The metal sulphide SnS2 attracts attention due to its low energy band gap of 2.2 eV, which allows the use of the visible region of the spectrum. In this work, the electrochemical characterisation of SnS2 and TiO2 photoanodes in NaCl solution in the presence and absence of AA was performed. The effect of AA on the photoresponse was investigated using the linear polarisation method and monitoring the open circuit potential. The results confirmed that SnS2 and TiO2 electrodes are photoactive, and that AA has good hole scavenging properties. Hydrogen production was performed at constant potentials of 0.6 and 1.35 V, respectively. TiO2 exhibited higher photoactivity, thus producing more hydrogen at 0.6 V. On the other hand, at a potential of 1.35 V, most of the hydrogen produced was the result of an electrochemical reaction rather than a photoelectrochemical reaction, thus, a larger amount of hydrogen was produced with the SnS2 electrode. The highest amount of hydrogen produced in this work was at 1.35 V for the SnS2 electrode in an argon atmosphere and it was 0.799 ml h−1 cm−2.

Keywords

• ascorbic acid
• hydrogen
• hole scavenger
• photoelectrochemical hydrogen production
• tin(iv) sulphide
• titanium(iv) oxide