Effects of PEG templating of spray-pyrolyzed TiO2 films on their nanoscale roughness and eventual photoelectrochemical properties

This paper reports the effects of polyethylene glycol (PEG) as a morphological template for spray-pyrolyzed TiO2 films. The virtues of PEG-modified TiO2 films as photoanodes in a photoelectrochemical (PEC) water splitting system are determined by the formation of nano-sized roughness, which is proposed to be originated from the role of PEG in controlling polycondensation of TiO2 precursor and segregating seed growth. Results in this paper, combined with those we reported earlier, show that the concentration of PEG in precursor solutions is more important than its molecular weight in enhancing the morphology of the resultant films and their eventual PEC properties. Based on PEC assessments, critical concentrations of PEG were found in the range of 25-50 mM, where nano-sized features are optimally developed and uniformly distributed across the surface. The best rough-surface TiO2 in this study managed to achieve PEC efficiency of as high as 1.23% and charge-transfer resistance of as low as 2.4 k Omega at - 0.7 V vs HgO vertical bar Hg, remarkably superior to the smooth-surface unmodified film with 0.40% efficiency and nearly 19 k Omega charge-transfer resistance at the same applied potential. [GRAPHICS] Controlled PEG templating leads to distinct characteristics of nanoscale roughness of spray-pyrolized-TiO2 films, which drive their eventual photoelectrochemical output.