3D TiO2 modified with reduced graphene embed into polyvinyl alcohol: photoanode electrode for oxygen evolution reaction

Abstract

The photocatalytic hydrogen production from water splitting using solar energy is one of the promising trend research topics within the scope of green energy production. A photoelectrochemical set up consists of photoelectrode materials that directly uses photon energy convers water to hydrogen and oxygen. The photoelectrodes are photoanode and photocathode materials n-type and p-type semiconductor, respectively. In this study, the 3D TiO2 photoanode surface was modified by coating it with reduced graphene (rG) added polyvinyl alcohol (PVA) gel. PVA synthetic polymer with thermal stability, mechanical stability and low cost was preferred to provide distribution of rG material on 3D TiO2 active surfaces. In this context, different amounts of rG (2.5, 5, 10 and 20%, based on polymer weight) impregnated with PVA gel coated on the 3D TiO2 semiconductor surface were investigated. The solar light absorption behaviour and molecular interactions of the different amounts of rG in PVA on 3D TiO2 semiconductor were monitored by UV-vis and Raman spectrometer. A photocatalytic performance of photoelectrodes were conducted by Electrochemical Impedance spectroscopy (EIS), linear sweep voltammetry (LSV) and chronoamperometric measurement under 100 mW cm-2 solar light. Raman spectrum showed dispersion of RG in PVA. EIS measurement showed that the polarization resistance (Rp) increased in 3D TiO2 with only PVA coating, while the addition of rG to PVA caused a decrease in Rp at the semiconductor/electrolyte interface under sunlight. Furthermore, LSV and chronoamperometric measurement concluded that the increased amount of rG added to PVA increased the photoresponse of 3D TiO2 up to the limit rG value.