Developing SrTiO3/TiO2 heterostructure nanotube array for photocatalytic fuel cells with improved efficiency and elucidating the effects of organic substrates

Photocatalytic fuel cell (PFC) system is the next generation of energy converters which can consume organic waste to generate electricity. The magnitude of generated photocurrent in PFC is determined by charge separation efficiency of photoanode and the ability of photohole consumption by adsorbed organic molecules. In this study, the SrTiO3 (16.6 wt%) is deposited on the TiO2 photoanode surface to enhance the charge separation, as reflected by the increase in photocurrent. Further photocurrent responses of SrTiO3/TiO2 photoanode were studied in presence of different organic classes, including carboxylic acids, alcohols, amines and amides, which exhibits the dependence on the adsorption of the organics and on the associated oxidation mechanisms. The rate (zeta) of photocurrent generation per amount of adsorbed organic molecule was determined for the first time. Simple and short-chained molecules, such as methanol and formic acid, has a higher zeta value in the corresponding carboxylic acid and alcohol group. Furthermore, the direct hole scavengers show higher zeta values than the hydroxyl radical scavengers in PFC. The triethanolamine (TEOA) has the highest zeta value (131 mu A mu mol-1), which further results in the optimal PFC performance with a highest short-circuit current density 0.32 mA cm-2, opencircuit voltage 1.3 V and maximum power density output 0.098 mW cm-2.