Photocurrent improvisation of BiVO$_{\mathrm{4}}$ photocatalyst by electronic structure engineering via Nb doping

Monoclinic BiVO$_{\mathrm{4}}$ has been said to achieve one of the highest hydrogen production efficiency. Although BiVO$_{\mathrm{4\thinspace }}$is a good sunlight absorber, the transport of photo generated charge carriers is complex. The electron-hole recombination is a major barrier to achieve higher photo-current in BiVO$_{\mathrm{4}}$. The conduction band minima of BiVO$_{\mathrm{4}}$ is composed of V 3d localized band which contributes to higher resistivity of the photo generated charge carriers. In this present study, density functional theory (DFT) has been used to study Nb incorporation in BiVO$_{\mathrm{4}}$ to see the electronic structure changes. It was found that Nb incorporation in BiVO$_{\mathrm{4}}$ changes the conduction band minima and V 3d band is replaced by less localized Nb 4d bands. It was also found that it may create shallow donor level. Less localized Nb 4d band in conduction band minima and donor level in the band structure will facilitate the charge carrier transport and hence improve the photocurrent of BiVO$_{\mathrm{4}}$. The solubility of Nb within BiVO$_{\mathrm{4}}$ has been studied. In addition, via chemical potential landscape analysis, the single-phase stability zone of BiVO$_{\mathrm{4}}$ with Nb will be presented.