Graphene Related Materials and Composites: Strategies and Their Photocatalytic Applications in Environmental Remediation

Photochemical reactions hold great promise in solving energy and environment related problems and likely contribute towards development of sustainable society. Despite of recent advancements, the inherent catalytic efficiency of conventional photocatalyst has been severely limited by myriad complexity associated with (i) ineffective light absorption in visible region, (ii) unproductive recombination’s of e−/h+ pair in excited state, and (iii) low chemical stability. Contemporary researches on photocatalysts that can be viable for commercial applications has yet to be realized. Graphene has attracted an immense research interests to enhancing the photocatalysts efficiency endowing from their unique optical and electronic properties and salient features such as surface area, mechanical strength and photochemical stability. In this book chapter, we discussed graphene related material (GRMs) to produce hybrid architectures or nanocomposites that can be used as efficient photocatalysts for the degradation of organic pollutants (dyes, pharmaceutical wastes, pesticides etc.) in wastewater. Lastly, we summarize the key insights in photocatalytic electron transfer mechanism, challenges and future perspective which help understand the rationale of GRMs in this field

CuO Quantum Dots Decorated TiO₂ Nanocomposite Photocatalyst for Stable Hydrogen Generation

An efficient and stable CuO-TiO₂ nanocomposite photocatalyst was synthesized by using the simple molten-salt method. Characterization by HR-TEM confirmed the existence of both TiO₂ and CuO in the nanocomposite, revealing hexagonal TiO₂ nanoparticles (NPs) with average particles size of 23.8 nm. CuO QDs decorated on the TiO₂ surface were in the range of 2.2 to 4.6 nm. Photocatalytic experiments for hydrogen (H₂) production were carried out under an LED (λ = 365 nm) lamp and natural solar light. The effect of Cu-loading in CuO-TiO₂ NCs and synthesis time were studied. The optimized CuO-TiO₂ NCs abbreviated as CuT-4 and CuT-3 showed 27.7- and 9.0-fold superior rate of H₂ production compared to pristine TiO₂ NPs under LED and solar irradiation, respectively. At optimal conditions, CuO-TiO₂ NCs demonstrated good photostability for H₂ evolution during 75 h illumination under LED light. The experimental results confirmed the cocatalytic role of CuO for improved H₂ generation by a minimized recombination of excitons