Y(1-x)Sc(x)BaZn3GaO7 (0 ≤ x ≤ 1): Structure Evolution by Sc-Doping and the First Example of Photocatalytic Water Reduction in "114" Oxides.

"114" oxides have shown intriguing physical properties while their performance in photocatalysis has not yet been reported probably due to the instability in aqueous solution. YBaZn3GaO7 is an exception, which is stable and indeed shows observable photocatalytic H2 evolution (∼2 μmol/h/g) in methanol aqueous solution under UV light. This activity was enhanced to 23.6 μmol/h/g by a full replacement of Y(3+) by Sc(3+). Optical absorption spectra and theoretical calculations show no significant difference upon Sc(3+)-doping. Instead, a systematic analysis of the structure evolution by Rietveld refinements for Y(1-x)Sc(x)BaZn3GaO7 (0 ≤ x ≤ 1) suggests that the increase of the catalytic activity is likely due to the decrease of the structural defects and thus the lower level of recombination rate of e(-) and h(+). In detail, Sc(3+) substitution leads to a shrinkage of YO6 octahedra, and successively the adjustment of the Zn(2+)/Ga(3+) occupancy behaviors in tetrahedra sites. The photocatalytic H2 evolution rate was further optimized to 118.2 μmol/h/g in methanol solution and 42.9 μmol/h/g in pure water for 1 wt % Pt-loaded ScBaZn3GaO7. Here, the relatively less investigated nonmagnetic "114" oxides were, for the first time, proved to be good candidates for photocatalytic water reduction.