Demonstration of enhanced carrier transport, charge separation, and long-term stability for photocatalytic water splitting by a rapid hot pressing process

Abstract

In this study, a rapid hot pressing process (HPP) has been adopted to enhance the photocatalytic water splitting efficiency of the TiO₂–Fe₂O₃ metal oxide cocatalyst. Without complicated nanostructure fabrication, the hot pressed sample demonstrated more than 6-fold photocurrent enhancement compared to the untreated sample at an applied voltage of 1.2 V. This enhancement is attributed to the improvement of carrier transport properties in the TiO₂–Fe₂O₃ matrix due to a significant reduction of the film thickness after the hot pressing process. In addition to the enhanced photocurrent, we observed a significant improvement of the stability and resistance to corrosion in a 1 M NaOH electrolyte due to the increase in the stiffness of the thin film from 80 GPa to 125 GPa after the hot pressing process. The improvements of carrier transport and charge separation are measured using photoluminescence (PL) spectroscopy and electrochemical impedance spectroscopy (EIS). The crystallinity and grain size of TiO₂–Fe₂O₃ have been characterized by high-resolution transmission electron microscopy (HRTEM) before and after the hot pressing process. We also examined the plasmonic resonance effect by integration of plasmonic gold nanoparticles (NPs) into this hot pressed TiO₂–Fe₂O₃ cocatalyst to achieve a further enhancement of hydrogen production.