Efficient electrochemical hydrogen evolution reaction and solar activity via bi-functional GO/Co3O4–TiO2 nano hybrid structure

Abstract

Highly proficient electro and solar catalyst of mixed metal oxides Co3O4–TiO2 modified with graphene oxide (GO) have been synthesized by simple and cost-effective way using sol-gel methodology. This catalyst demonstrated versatile bi-functional features towards the hydrogen evolution reaction (HER) in catalytic water splitting along with solar photo catalytic activity in the degradation of Methyl Orange (MO). XRD profile confirmed that composite presented an anatase and cubic phase for TiO2 and Co3O4, respectively, with the GO network. The morphological structures confirm flaky texture of Co3O4 with small irregular spheres of TiO2 nanoparticles randomly dispersed on the broken sheets of GO. GO and clusters of Co2+/Co3+ in different regions of host TiO2 are accountable for decreasing band gap in the composite samples. Co–O–Ti and Co–Ti–C linkages in the composite materials are confirmed by Raman and FTIR studies. In electro catalytic HER in alkaline medium GO/Co3O4–TiO2 catalyst illustrated low onset potential ~343 mV vs. RHE, high current density ~43 mA cm−2 corresponding small Tafel slope ~97 mV/dec and small Rct as compared to other catalysts. For HER in GO/Co3O4–TiO2, Co2+ sites are more catalytically active than Co3+ sites along with Ti4+ and GO provides the more active surface area by reducing the agglomeration between the mixed metal oxides. GO/Co3O4–TiO2 shows the highest photo catalytic performance over MO as compared to binary and ternary composites. Pining of metal oxides with reactive oxygen functional moieties of GO considerably improve the photo catalytic degradation activity and helpful in the separation of charge carriers for HER.