Photocatalytic water splitting solar-to-hydrogen energy conversion: Perovskite-type hydride XBeH3 (X = Li or Na) as active photocatalysts

Abstract

A highly enhanced photocatalytic hydrogen production system has been achieved, by substitution of Na by Li and moving from cubic to orthorhombic phase in XBeH3 system. Ab-initio calculations from first- to second-principles methods were performed to investigate the suitability of the perovskite-type hydride namely; NaBeH3 and LiBeH3 in cubic phase and LiBeH3 in orthorhombic phase to be used as active photocatalysts. We found significant increases in the fundamental energy band gap when we move from NaBeH3-cubic (0.94eV)→LiBeH3-cubic (1.34eV)→LiBeH3-orthorhombic (2.44eV). The obtained energy band gap's values show good agreement with the previous reported results. Enlarging the fundamental energy band gap from 0.94→1.34→2.44eV shows the investigated materials to be promising candidates for light-driven photocatalysts and highly enhanced photocatalytic H2 production systems. The absorption level of NaBeH3-cubic, LiBeH3-cubic and LiBeH3-orthorhombic exhibited an obvious enhancement in the UV-light region (absorption edge λ=343.4nm)→visible light region (λ=431.9nm)→UV-light region (λ=349.2nm), respectively.