The photocatalytic action of metalic nanoparticles its associated with localized plasmons of surface, the colective oscilation of electrons in the surface of nanosized metals. Beyond this the electrochemical reduction potential its a role to achieve a good performance. A good initial point to understand this phenomenum its compare the reduction potentials of metals and the relative position to HOMO and LUMO states of dyes. Generally, you observe in absorption UV-vis spectrum the decrease of absorption band associated with the dye. To close the electrochemical cycle, generally the reduction of oxygen its commom.

See these papers:

Silver nanoparticles stabilized in polymer hydrogels for catalytic degradation of azo dyes

https://www.sciencedirect.com/science/article/abs/pii/S0147651320307636

https://doi.org/10.1016/j.ecoenv.2020.110924

Ferrites, modified with silver nanoparticles, for photocatalytic degradation of malachite green in aqueous solutions

https://www.sciencedirect.com/science/article/abs/pii/S0920586119304080

https://doi.org/10.1016/j.cattod.2019.07.052

Thank you Felipe