Most photocatalysts for solar hydrogen absorb only ultraviolet light, a sliver of the solar spectrum, while infrared light, which carries more than half of the Sun's power, goes largely unused. Organic semiconductors can capture it, but until now efficient versions have required blends of two materials, an electron donor and acceptor, that are difficult to mix uniformly and prone to instability.
KAUST chemists led by Huabin Zhang, working with Omar Mohammed's spectroscopy group, designed a way around the blend problem: a double-cable polymer whose backbone carries the electron-donating units while electron-accepting groups hang from it as side chains. Packaging donor and acceptor in one molecule separates the light-generated electron and hole quickly, suppressing the recombination that normally squanders captured energy.
Nanoparticles of the polymer produced hydrogen at a rate 57 times higher than donor-only controls, and nanosecond transient absorption spectroscopy confirmed that the excited states were unusually long-lived, explaining the gain. The work appears in Science Advances. The team is now testing performance in a customised panel reactor and exploring hydrogen production from industrial wastewater, with an eye on Saudi Arabia's abundant sunlight as the engine of an exportable clean fuel.