Technical Note: A Homemade Light Shutter to Shed Light on Electron-Hole Recombination of TiO and BiVO during Water Photoelectrooxidation.

Photoelectrochemical (PEC) water oxidation is a promising strategy for renewable energy conversion, but the intricate dynamics of electron-hole recombination in photoanodes require advanced methodologies for precise investigation. While essential for controlled illumination in photocatalysis, existing light shutters are often expensive, inflexible, or challenging to customize for specific experiments. To address this gap, we developed a low-cost, Arduino-controlled mechanical light shutter designed for versatile and precise control of light exposure during photoelectrochemical studies. The system was tested using TiO and BiVO photoanodes for PEC water oxidation. The light shutter was assembled using off-the-shelf components and programmed for variable cutoff times ranging from 0.1 to 50 s. The results revealed distinct transient photocurrent spikes in BiVO at low scan rates (<10 mV/s), also observed under potentiostatic (low and high bias) conditions, attributed to significant electron-hole recombination, while TiO exhibited lower recombination effects due to its faster water oxidation kinetics, as expected. Compared with existing designs, our light shutter stands out for its simplicity, cost-effectiveness, and ease of integration, providing precise and reliable light modulation without requiring complex fabrication, specialized components, or advanced programming skills. The findings highlight the ability of the developed light shutter to elucidate recombination dynamics by accurately modulating light exposure. This tool provides an accessible and effective alternative for exploring photocatalytic materials, offering insights into their charge carrier behavior and advancing the development of efficient photoanodes for solar-driven water splitting.