Topological Luttinger-semimetal CoAs3 dye-sensitized photocatalyst for efficient solar hydrogen evolution.

Solar-driven photocatalytic water splitting is a process for hydrogen production from a renewable source. The practical implementation of this technology is limited by the low conversion efficiency of the hydrogen evolution reaction under visible light and the insufficient long-term stability of photocatalysts. Here we demonstrate a dye (Eosin Y)-sensitized photocatalyst for efficient hydrogen production. The topological semimetal CoAs3 achieves a hydrogen production rate of 2688 μmol h-1 g-1 (λ ≥ 420 nm) and an apparent quantum efficiency of 15.2% at λ = 500 nm. Efficient photocatalytic activity is attributed to the electronic properties of CoAs3, which facilitate electron transfer at the Eosin Y/CoAs3 interface, determined by transient absorption spectroscopy. Density functional theory calculations predict that CoAs3 is a Luttinger semimetal, exhibiting a quadratic band touching point near the Fermi level and an associated topological insulator gap. The carrier mobility of the material facilitates the transfer of injected electrons from the dye to active sites. Herein, we report a topological photocatalyst that exhibits enhanced stability and efficiency for solar hydrogen production.