Band-gap tailoring and visible-light-driven photocatalytic performance of porous (GaN)_1-x(ZnO)_x solid solution

(GaN)_1-x(ZnO)_x solid solution has attracted extensive attention due to its feasible band-gap tunability and excellent photocatalytic performance in overall water splitting. However, its potential application in the photodegradation of organic pollutants and environmental processing has rarely been reported. In this study, we developed a rapid synthesis process to fabricate porous (GaN)_1-x(ZnO)_x solid solution with a tunable band gap in the range of 2.38-2.76 eV for phenol photodegradation. Under visible-light irradiation, (GaN)_0.75(ZnO)_0.25 solid solution achieved the highest photocatalytic performance compared to other (GaN)_1-x(ZnO)_x solid solutions with x = 0.45, 0.65 and 0.85 due to its higher redox capability and lower lattice deformation. Slight Ag decoration with a content of 1 wt% on the surface of the (GaN)_0.75(ZnO)_0.25 solid solution leads to a significant enhancement in phenol degradation, with a reaction rate eight times faster than that of pristine (GaN)_0.75(ZnO)_0.25. Interestingly, phenol in aqueous solution (10 mg L^-1) can also be completely degraded within 60 min, even under the direct exposure of sunlight irradiation. The photocurrent response indicates that the enhanced photocatalytic activity of (GaN)_0.75(ZnO)_0.25/Ag is directly induced by the improved transfer efficiency of the photogenerated electrons at the interface. The excellent phenol degradation performance of (GaN)_1-x(ZnO)_x/Ag further broadens their promising photocatalytic utilization in environmental processing, besides in overall water splitting for hydrogen production.