New insight into the effect of interface supercapacitance on the perforamce of titanium dioxide/carbon nanowire array for photoelectrochemical water oxidation

Abstract The electrode/electrlyte interface is of great signifance to photoelectrochemical (PEC) water oxidation as the reaction mainly occur here. Herein, we focus on the effect of supercapactance of the electrode/electrlyte interface on the performance of PEC. It is discovered that the supercapacitor on the interface is crucial because it links the charge transport and solution ion adsorption on its two sides. In this study, we demonstrate an approach to promote the performance of TiO2 nanowire array (TiO2 NWs) photoanode in photoelectrochemical cells (PECs) by increasing its supercapacitance. A 2-5 nm carbon layer was coated and the interface supercapacitance increases by about 150 times. This enhances the separation rate of electron-hole pairs by collecting more holes. Meanwhile, it also promotes the water oxidation rate by adsorbing more OH― on its surface. As a result, the photocurrent density of C-TiO2 NWs was about 8 times higher than that of its carbon-free counterpart. This approach of increasing the supercapacitance of photoanodes would be attractive for enhancement of the efficiency of PECs and this work demonstrate the importance of supercapacitance of the interface for PECs.