Ravi Tejasvi (Prof. Suddhasatwa Basu )
08th February 2017, Wednesday, 04:30‐05:00 pm (25+5 mins), ChE Seminar hall
Solar Photo Electrochemical CO2 Utilization Assisted Through Water Splitting
Since the pioneering works on photoelectrochemical water splitting by Fujishima and Honda and on application of semiconductor heterojunctions in water splitting by Grätzel, the pair of anatase titania (TiO2) and the exfoliated form of graphitic carbon nitride (eC3N4) have been envisioned as the most promising catalyst pair to form an efficient heterojunction towards solar hotoelectrochemical water splitting. It has been envisaged that the heterojunction can also be scaled-up as a heterojunction based photoelectrochemical device that can generate hydrogen using water as primary electrolyte.
However, the catalytic heterojunction still suffers from low efficiency jeopardizing the commercial viability of the device. The efficacy of the heterojunction relies mainly on the amount of contact area, particle size, and particle boundary lengths, of substrate scaffold asmuch as on the ease of migration of photo-generated charge carriers through the sensitizer layer. Though, nanotubular and nanoparticle structures of titania have been used widely, the compatibility of such morphologies of TiO2 to form a good heterojunction with e-C3N4 is disputed, primarily due to the structural limitations of the substrate. Also e-C3N4 cannot be electrodeposited which renders spin coating as the only viable option for thin film based sensitization of the titania substrate. We report the preparation of a hierarchical, stemmed nanoflower structure of titania. It grants more physical access to the sensitizer vis-à-vis that available in nanotubular arrays of TiO2. The interconnected features of different characteristic lengths enables better charge mobilization in the new nanostructure. Here, we also present a novel and eco-friendly method to assemble a thin film of 2d nanosheets of the sensitizer without the risks of the fugitive emissions of the solvents. Linear sweep voltammetry and electrochemical impedance spectroscopy ascertain that the photoelectrochemical activity of the new eC3N4/TiO2 heterojunction has improved. It marks the progress towards the realization of the aforesaid photoelectrochemical device.