Effect of the In by Bi substitution in the Sm$_{\mathrm{2}}$InTaO$_{\mathrm{7}}$ system for the photocatalytic splitting of water

Tantalum oxide-based photocatalysts with octahedrally coordinated d$^{\mathrm{10}}$ configuration, represent promising semiconductor systems to develop photocatalysts with visible-light response in the photochemical splitting of water. Several Indium oxide-based compounds have shown acceptable activity in water photolysis. Recently, the pyrochlore Sm$_{\mathrm{2}}$InTaO$_{\mathrm{7}}$ (a 4f-d$^{\mathrm{10}}$-d$^{\mathrm{0}}$ system) was reported as a visible-light photocatalyst for water splitting. In the present work, by solid state reaction, we have obtained and structurally characterized compounds of the Sm$_{\mathrm{2}}$In$_{\mathrm{1-x}}$Bi$_{\mathrm{x}}$TaO$_{\mathrm{7\thinspace }}$system. In these systems we have found that the optical band gap value depends on the Bi content; this value is 2.7, 2.52 and 2,1eV for x$=$0, 0.15 and 0.30 respectively. The specific surface area values we have found are typical of solid state reaction products, 0.5-1.2 m$^{\mathrm{2}}$/g. To understand the effect of the In substitution by Bi, the compounds were studied with first principles calculations using the WIEN2k package and the gap was evaluated using the mBJ potential