Methane-based nitridation was employed to produce wurtzite zinc-gallium oxynitride (ZnGaNO) photocatalyst particles using Zn/Ga/CO layered double hydroxides (LDHs) as precursor. Introduction of methane to nitridation would promote the formation of Zn-O bonding and suppress shallow acceptor complexes such as V-Ga and Ga-O in ZnGaNO particles. On the other hand, high flow rate of methane would induce breaking of Ga-N bonding and enhance surface deposition of metallic Ga atoms. After loading with Rh and RuO, ZnGaNO particles had free electron density in an order of S50 > S20 > S90 > S0, which correlated well with their photocatalytic performance upon visible-light irradiation. The best performance of the loaded S50 was ascribed to the relatively flat surface band bending of the particle. Methane-based nitridation of Zn/Ga/CO LDHs would provide a new route to tune the surface chemistry of ZnGaNO and enhance the photocatalytic performance to its full potential.