Visible light switchable bR/TiO2 nanostructured photoanodes for bio-inspired solar energy conversion
Today, regarding the limitation and environmental side effects of fossil fuel resources, solar hydrogen production is one of the main interests in the energy research area. The development of visible light sensitized semiconductors based on non-toxic components, low cost and available bio-species is an ongoing approach for H2 generation based on water splitting reactions. Here, two different morphologies of TiO2 photoanodes, nanoparticulated and nanotubular, have been modified with simply extracted bacteriorhodopsin (bR) without any linker. Achieving a significant enhancement in photoconversion efficiency of TiO2 photoanodes, η% was increased from 2.9 to 16.5 by bR addition to the TiO2 nanoparticulate electrode, whereas it increased from 0.5 to 1.9 for the nanotubular system. This result indicated that because of the large size of the extracted purple membranes, nanoparticles showed a greater number of explosion sites for bR attachment, and they were more efficient than the nanotubes. Moreover, comparing these values with the ones reported for bR/TiO2 photoanodes before, the simple proposed decoration method displayed a remarkable improvement in the visible response of the TiO2 based photoanodes. This approach can be beneficial to the area of solar water splitting, photoelectrochemical sensing, and any other photoresponsive systems.