Insight into the Light-Driven Hydrogen Production over Pure and Rh-Doped Rutile in the Presence of Ascorbic Acid: Impact of Interfacial Chemistry on Photocatalysts

Abstract

The surface states of a semiconductor photocatalyst are essential for interfacial charge transfer in heterogeneous photocatalytic reactions. Here, we report that the light-driven hydrogen evolution reaction (HER) activity of 0.5 mol % Rh-doped rutile increases by more than 30 times compared with that of rutile when ascorbic acid is used as a sacrificial agent. Intensity-modulated photocurrent spectroscopy and surface photovoltage spectroscopy are employed to reveal the impact of surface states on the photo-oxidation reactions. It is found that the adsorption of ascorbic acid molecules dramatically reduces the activity of rutile due to coverage of the HER-active Ti sites. Nevertheless, for Rh-doped rutile, ascorbic acid neutralizes the Rh­(IV) sites that would otherwise cause severe recombination of electron–hole pairs and resurrects its photocatalytic performance. This work demonstrates the key role of interfacial chemistry in photocatalytic reactions and provides a strategy for excavating the potential of various photocatalysts.

Orienting Charge Migration in TiO2 Photocathode through Directionally Distributed Rh Dopant

“…Subsequently, the products underwent calcination at 973 K for 8 h in a muffle furnace and were exposed to air with a ramping rate of 600 K/h, followed by natural cooling. The collected powders were ground using a pestle and mortar for approximately 0.5 h. 52 Preparation of Rh−TiO 2 Monolayer Electrode. Preparation of Rh−TiO 2 Single Layer.…”

“…All of the distinguishable Rh 3d peaks are located near 309.4 eV, which correspond to Rh 4+ (Figure S3). UV–vis diffuse reflection spectroscopy (DRS) plots of electrodes display an absorption edge at 500 nm, which is associated with a Rh 3+ to conduction band (Ti 3d) transition (Figure b). After sputtering for 10 and 30 min, the sloped background above 600 nm associated with Rh 4+ is suppressed, which is as a result of removal of Rh 4+ positioned on the top of the monolayer particles. , Such minor changes in absorption have a negligible impact on the amount of electron–hole pairs generated during PEC tests.…”

“…Rh-doped rutile particles are prepared by chemical impregnation adopted from our previous work, which have heavy Rh accumulation near the surface. 41 To create the desired asymmetric gradient doping of Rh in rutile thin films, where Rh content is higher toward the back contact and lower near the front surface, a single layer of Rh-doped rutile particles deposited onto a conductive substrate is designed for such configuration, which is fabricated herein by a particle engineering technique named rubbing. 42 Next, magnetron Ar + sputtering is conducted for different durations (0 to 30 min) to remove top layers where the Rh elements are heavily doped.…”

Rhodium-Doped Barium Titanate Perovskite as a Stable p-Type Photocathode in Solar Water Splitting

“…Current–potential curves were measured from negative to positive potentials at a scanning speed of 10 mV/s. SPS was performed at the open circuit using a home-built system reported elsewhere . The light intensity was set at 0.5 mW cm –2 for all wavelengths by a graded attenuation wheel to exclude the spectral dependence on the Xe lamp and was chopped at 20 Hz.…”

“…SPS was performed at the open circuit using a home-built system reported elsewhere. 35 The light intensity was set at 0.5 mW cm −2 for all wavelengths by a graded attenuation wheel to exclude the spectral dependence on the Xe lamp and was chopped at 20 Hz. The SPS of the Rh/BaTiO 3 electrode was measured in 0.1 M Na 2 B 4 O 7 solution, which was kept purged with Ar gas to exclude O 2 before the SPS measurements.…”