Evaluating high temperature photoelectrocatalysis of TiO₂ model photoanode

Sunlight concentration has been demonstrated as one promising strategy for practically photoelectrochemical (PEC) water splitting with exceeding 10% solar-to-hydrogen efficiency. However, the operating temperature of PEC devices, including the electrolyte and photoelectrodes, can be elevated to 65 ℃ naturally due to the concentrated sunlight and the thermal effect of near-infrared light. In this work, high temperature photoelectrocatalysis is evaluated using titanium dioxide (TiO₂) photoanode as a model system, which is believed to be one of the most stable semiconductors. During the studied temperature range of 25-65 ℃, a linear increment of photocurrent density with a positive coefficient of 5.02 μA cm^-2 K^-1 can be observed. The onset potential for water electrolysis shows a significant negative shift by 200 mV. An amorphous titanium hydroxide layer and a number of oxygen vacancies generate on the surface of TiO₂ nanorods, promoting the water oxidation kinetics. During long-term stability testing, the NaOH electrolyte degradation and TiO₂ photocorrosion at high temperatures could cause the decaying photocurrent. This work evaluates the high temperature photoelectrocatalysis of TiO₂ photoanode and reveals the mechanism of temperature effects on TiO₂ model photoanode.