Anuradha Verma

Gradient doping – a case study with Ti-Fe2O3 towards an improved photoelectrochemical response

The present study investigates the effect of gradient doping on modifying the photoelectrochemical response of Ti-doped Fe2O3 photoanodes for their use in sunlight based water splitting for hydrogen evolution. The deposition of a thin film over the ITO (tin doped indium oxide) substrate was carried out using a spray pyrolysis method. The concentration of dopant was varied from 0.5-8.0 at% and two sets of samples were also prepared with low to high (0.5-8%) and high to low (8-0.5%) dopant concentrations in the direction towards the substrate. The prepared thin films were characterized using X-ray Diffractometry (XRD), Scanning Electron Microscopy (SEM), Energy Dispersive X-ray (EDX) Spectroscopy, Secondary Ion Mass Spectroscopy (SIMS), X-ray Photoelectron Spectroscopy (XPS) and UV-visible Spectroscopy. The photoelectrochemical studies revealed that the deposition of dopant layers with a low to high concentration towards the substrate exhibited a highly improved photoresponse (200 times) in comparison to the pristine sample and a two fold enhancement in comparison to 2% Ti-doped Fe2O3. The improvement in the photoresponse has been attributed to the values of a high flat band potential, low resistance, high open circuit voltage, carrier separation efficiency, applied bias photon-to-current conversion efficiency (ABPE), and incident photon-to-current conversion efficiency (IPCE). A reduced charge transfer resistance has been demonstrated with Nyquist plots.

Synthesis and Characterization of CuO-TiO2 Core Shell Nanocomposites for Hydrogen Generation Via Photoelectrochemical Splitting of Water

Sol–gel derived CuO–TiO2 core shell nanocomposites were synthesized by modified Stober method [1] and characterized. XRD analysis revealed dominant evolution of CuO (tenorite phase) at the core on to which TiO2 (anatase) was coated. The average crystallite size, estimated from Scherrer’s computations was 30–33 nm. PEC studies indicated that core shell composites offer significant photocurrent. The effect of variation in concentration of titanium (IV) butoxide (precursor used for generating TiO2 coat over CuO) was also investigated. The increase in concentration of TBOT led to increase in photocurrent.