Energy harvesting for electrochemical OER and solar photocatalysis via dual functional GO/TiO2-NiO nanocomposite

Abstract

Highly efficient dual functional electrochemical and photocatalysts by incorporation of GO and TiO2 doped NiO composites have been developed. The prepared catalysts were subjected toward oxygen evolution reaction (OER) in electro catalytic water splitting and photocatalytic degradation of bromophenol blue (BPB). TiO2 doped NiO having monoclinic phase with GO is confirmed by XRD profile. The introduction of TiO2 into NiO matrix and addition of GO has reduced intensity of XRD peaks in composites. The morphological structures confirm fluffy NiO with small spherical dark patches of TiO2 nanoparticles which are dispersed randomly on broken sheets of GO in composite structure. UV–Vis spectra illustrated obvious band gap reduction (∼2.0–2.6 eV) in various GO/Ti-NiO composites with improvement in visible light absorption. The generation of Ti−Ni−C junction in composite samples is examined by FTIR and Raman analysis. In OER (1M KOH) 4.0 wt. % GO/Ti-NiO generated the small Tafel slope of ∼60 mVdec−1, low Rct∼4.1 Ω and high current density ∼70 mAcm−2 as compared to other samples. The composite materials govern OER process by Volmer-Heyrovsky mechanism. GO/Ti-NiO composite with 4.0 wt. % Ti shows the highest degradation (∼95 % )of BPB due to active surface sites generated by Ti−Ni−C linkages and interconnected conductive carbon materials of GO. Defective structure of GO provides favorable kinetics to the electro catalytic OER and supportive in enhancement of the electronic conduction. Ni2+ offers more active sites along with Ti4+ for OH−adsorption. Intermediate species of BPB have been identified by HPLC analysis. This work brings new insight for designing multifunctional materials for energy conversion and environmental remediation applications.