The photoelectrochemical responses of a TiO2 nanotube anode in ethylene glycol (EG), glycerol, ammonia, ethanol, urea, and Na2S electrolytes with different concentrations were investigated. The TiO2 nanotube anode was highly efficient in photoelectrocatalysis in these solutions under UV light illumination. The photocurrent density is obviously affected by the concentration change. Na2S generated the highest photocurrent density at 0, 1, and 2？V bias voltages, but its concentration does not significantly affect the photocurrent density. Urea shows high open circuit voltage at proper concentration and low photocurrent at different concentrations. Externally applied bias voltage is also an important factor that changes the photoelectrochemical reaction process. In view of the open circuit voltage, EG, ammonia, and ethanol fuel cells show the trend that the open circuit voltage (OCV) increases with the increase of the concentration of the solutions. Glycerol has the highest OCV compared with others, and it deceases with the increase in the concentration because of the high viscosity. The OCV of the urea and Na2S solutions did not show obvious concentration effect. 1. Introduction Titanium dioxide (TiO2) has been widely studied because it has good photovoltaic property. Photoelectrochemical cell (PEC) is a device that could degrade pollutants, splitting water by utilizing photon energy while electric energy is generated. Clean energy generation by environmentally friend method is a very important issue. Hydrogen is used in fuel cells, but nature gas is still a main source for hydrogen production. It contains contaminative byproducts. Only a few part of hydrogen is produced by water splitting in the world [1]. Pollutant degradation is another very important application of PEC. TiO2 nanostructured anode has the high potential for clean energy production and hazard material degradation. Many hazardous organic materials can be converted into clean substances by TiO2 anode PEC, which include methylene blue [2, 3], glucose [4], organic compounds [5, 6], waste water [7], dye pollutant [8], and even CO2 [9] of the greenhouse gas. By using various electrolytes, different levels of open circuit voltage, current density, filling factor can be reached [10–12]. The bias potential and concentration of electrolytes can also influence the performance of a PEC cell. Normally, the additionally applied external bias voltage can further enhance the PEC reaction process because the conduction band edge of anode material cannot lie above the energy level. Quan et al. [13]
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