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.