Built-in electric fields and strain modulated photocatalytic performance in monolayer Janus piezoelectric AlBX2(X = O/S/Se/Te)

The distribution of photogenerated carriers and their redox capacity are key factors that influence photocatalysis for water splitting. Here, we investigated the electronic and photocatalytic properties of monolayer Janus piezoelectric AlBX₂ (X = O/S/Se/Te). The results show that the built-in electric fields within AlBX₂ can separate photogenerated electrons and holes to participate in the redox reaction. The potential difference Δφ at two surfaces significantly enhance the overpotential (χ₁) for hydrogen evolution reaction (HER). Besides, the HER/oxygen evolution reaction (OER) barriers are extremely low (0 ∼ 0.02 eV/0 ∼ 0.17 eV) with light on. Furthermore, the biaxial strain can significantly modulate the potential difference Δφ (−0.58 eV ∼ 2.16 eV) of AlBO₂. The HER barrier of AlBO₂ at pH = 7 decreases from 1.27 eV to 0.05 eV with −6 % compressive strain. These results reveal that AlBX₂ members are efficient and controllable high performance photocatalysts for water splitting.