Unexpected visible light driven photocatalytic activity without cocatalysts and sacrificial reagents from a (GaN) (ZnO) solid solution synthesized at high pressure over the entire composition range.

Optical and photocatalytic properties were determined for the solid solution series (GaN) (ZnO) synthesized at high pressure over the entire compositional range ( = 0.07 to 0.9). We report for the first time photocatalytic H evolution activity from water for (GaN) (ZnO) without cocatalysts, pH modifiers and sacrificial reagents. Syntheses were carried out by reacting GaN and ZnO in appropriate amounts at temperatures ranging from 1150 to 1200 °C, and at a pressure of 1 GPa. ZnGaO was observed as a second phase, with the amount decreasing from 12.8 wt% at = 0.07 to ∼0.5 wt% at = 0.9. The smallest band gap of 2.65 eV and the largest average photocatalytic H evolution rate of 2.31 μmol h were observed at = 0.51. Samples with = 0.07, 0.24 and 0.76 have band gaps of 2.89 eV, 2.78 eV and 2.83 eV, and average hydrogen evolution rates of 1.8 μmol h, 0.55 μmol h and 0.48 μmol h, respectively. The sample with = 0.9 has a band gap of 2.82 eV, but did not evolve hydrogen. An extended photocatalytic test showed considerable reduction of activity over 20 hours.