Size-Dependent Photocatalysis by Wurtzite InP Quantum Dots Utilizing the Red Spectral Region

Photocatalytic hydrogen generation offers a sustainable method for generating solar fuels. Indium phosphide (InP) nanocrystal quantum dots (QDs), with their adjustable band gaps and versatile surface properties, present an eco-friendly alternative to heavy-metal-based semiconductor NCs as photocatalysts. We report the synthesis of wurtzite InP (w-InP) QDs and their performance as photocatalysts for hydrogen generation from water by using the red part of the solar spectrum. Size-controlled w-InP QDs with absorption edges extending to 750 nm were synthesized via a cation exchange route. Stabilized in water with sulfides, these QDs demonstrated higher hydrogen generation efficiencies compared with other narrow-band-gap QDs. The overall hydrogen generation efficiency sharply decreases with the size. A mixed-size approach combining the high efficiency of small QDs with the broad absorption range of large QDs enhances the solar-to-hydrogen conversion by a more effective utilization of the solar spectrum. Such an approach shows promise for effective solar fuel generation.