Engineering stable Ti3+ defects in a titanium dioxide matrix by wet bead-milling: Visible-light assisted efficient photocatalytic hydrogen production from water

Abstract

Solar-driven hydrogen production technologies are of increasing interest. In this work, Ti³⁺ was incorporated into titanium dioxide via wet bead-milling, resulting in enhanced photocatalytic activity under both UV and visible light irradiation. The broad optical absorption obtained from the presence of Ti³⁺ ranged from the visible to near-infrared regions of the spectrum (specifically from 400 to over 900 nm) and this absorption could be enhanced by increasing the diameter of the beads used for wet milling. The hydrogen production rate from water in response to ultraviolet (UV)-visible light with ethanol as a sacrificial reagent was also found to vary depending on the bead diameter. Producing the optimal level of Ti³⁺ incorporation in the titanium oxide matrix while maintaining a high specific surface area increased the extent of hydrogen production during water decomposition. A sample prepared using 0.3 mm diameter beads exhibited the highest hydrogen production rate of 145 μmol h⁻¹ g⁻¹, which was 15 times that obtained from commercially available anatase-type titanium dioxide having higher specific surface area. The hydrogen production rate under only UV light (<400 nm) was decreased to one-ninth of that obtained using both UV and visible light simultaneously. No hydrogen gas was generated in trials using only visible light (>410 nm). These results indicate that visible light significantly promoted the photocatalytic reaction when both UV and visible light were irradiated simultaneously.