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A visible-light active catechol–metal oxide carbonaceous polymeric material for enhanced photocatalytic activity

Karthik, P., Vinoth, R., Selvam, P., Balaraman, E., Navaneethan, M., Hayakawa, Y., Neppolian, B.
Journal of materials chemistry A 2016 v.5 no.1 pp. 384-396
catechol, chromium, energy, hydrogen production, irradiation, photocatalysis, photosynthesis, polymerization, polymers, remediation, renewable energy sources, titanium dioxide, toxicity
Designing new materials for sustainable energy and environmental applications is one of the prime focuses in chemical science. Here, an unprecedented visible-light active catechol–TiO₂ carbonaceous polymer based organic–inorganic hybrid material was synthesized by a photosynthetic route. The visible light induced (>400 nm) photosynthetic polymerization of catechol led to the formation of carbonaceous polymeric deposits on the surface of TiO₂. The band gap energy of hybrids was shifted to the visible region by orbital hybridization between 3d(Ti) of TiO₂ and 2p(O), π(C) of catechol. The Tauc plot clearly revealed that 1.0 wt% catechol–TiO₂ carbonaceous polymer remarkably tailored the optical band gap of TiO₂ from 3.1 eV to 1.9 eV. The synthesized hybrid materials were thoroughly characterized and their photocatalytic activity was evaluated towards toxic Cr(vi) to relatively less toxic Cr(iii) reduction under visible light irradiation (>400 nm), and solar light-driven H₂ production through water splitting. Very interestingly, the hybrid material showed 5- and 10-fold enhanced activity for photocatalytic Cr(vi) reduction and solar light-driven H₂ production respectively compared with pure TiO₂. Moreover, the hybrid materials showed enhanced stability during photocatalysis. Thus, the simple photosynthetic strategy for developing light harvesting organic–inorganic hybrid materials can open up potential applications in energy and environmental remediation.