The M (M = Ag, Cu) nanoparticles were deposited by a fast in-situ photoreduction method onto the AgTaO3 photocatalyst surface using 1, 2, and 5 wt % ratios, in order to investigate their photocatalytic properties for hydrogen production. The obtained results indicated a nanoparticles growth <20 nm in diameter during 10 min of photoreduction process for both nanoparticles. The M (M = Ag, Cu) NPs/AgTaO 3 exhibited superior photocatalytic activity than bare AgTaO3, with an efficiency increment of around 11 and 30 times at 2 wt % ratio of Ag and Cu nanoparticles, respectively. The excellent photocatalytic activity could be related to the surface plasmon resonance effect of nanoparticles, preventing the electronhole recombination. Additionally, the opticad photoelectrochemical characterization revealed the presence and the effect of oxidized species of the nanoparticles, with a direct impact on the transport of photogenerated charge carriers for the improvement of the photocatalytic activity. (C) 2020 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.