Electronic structure and enhanced photocatalytic properties in $$\hbox {Ca(OH)}_{2}$$ Ca(OH) 2 /GeC van der Waals heterostructure

Two-dimensional (2D) van der Waals heterostructures (vdWHs) show great potential applications in the field of electronic and optoelectronic devices. In this work, first-principles calculations under hybrid HSE06 functional are performed to explore the electronic and optical properties of $$\hbox {Ca(OH)}_{2}/\hbox {GeC}$$ Ca(OH) 2 / GeC vdWH. Our results show that the $$\hbox {Ca(OH)}_{2}/\hbox {GeC}$$ Ca(OH) 2 / GeC vdWH owns a direct band gap of 2.73 eV, which is smaller than that of GeC monolayer. Meanwhile, this vdWH shows improved ability to absorb visible light and high-energy photons compared with the $$\hbox {Ca(OH)}_{2}$$ Ca(OH) 2 and the GeC monolayers. The valence band maximum (VBM) potential of $$\hbox {Ca(OH)}_{2}/\hbox {GeC}$$ Ca(OH) 2 / GeC is lower than that of GeC, which means that the $$\hbox {Ca(OH)}_{2}/\hbox {GeC}$$ Ca(OH) 2 / GeC vdWH has better oxidation than that of the GeC monolayer. On the other hand, the $$\hbox {Ca(OH)}_{2}/\hbox {GeC}$$ Ca(OH) 2 / GeC vdWH also satisfies the requirement for photocatalytic overall water splitting. These findings indicate that $$\hbox {Ca(OH)}_{2}/\hbox {GeC}$$ Ca(OH) 2 / GeC vdWH is a promising candidate for optoelectronic devices and photocatalysis. Graphic abstract The electronic structure and photocatalytic properties of Ca(OH)2/GeC van der Waals heterostructure (vdWH) have been investigated through first principles calculation based on density functional theory. The calculation results show that among GeC monolayer, Ca(OH) $$_{2}$$ 2 monolayer and Ca(OH) $$_2$$ 2 /GeC vdWH, the Ca(OH) $$_2$$ 2 /GeC vdWH has the smallest band gap. The charge is transferred from the Ca(OH) $$_2$$ 2 layer to the GeC layer when the vdWH is synthesized. The vdWH improves the absorption in the visible light range ( $$1.6~\mathrm{eV}