Ag/Pd bimetallic nanoparticle-loaded Zr-MOF: an efficacious visible-light-responsive photocatalyst for H2O2 and H2 production

Abstract

Photocatalytic production of H₂O₂ and H₂ holds promise for conquering the impending energy crisis. In order to accomplish this goal, the photocatalysts must be robust and effective enough to harvest photons from a wide solar spectrum as well as having a high rate of exciton antirecombination. Low visible light absorption and fast recombination of exciton pairs are two major setbacks encountered in pristine MOF-based photocatalysts. Herein, the MOF UiO-66-NH₂ modified with noble bimetallic nanoparticles (Ag/Pd) was synthesized via a facile adsorption–reduction technique and utilized for effective photocatalytic H₂O₂ and H₂ production. The composite (1 : 2) Ag/Pd@UiO-66-NH₂ displayed a H₂O₂ production rate of 39.4 μmol h⁻¹ in an O₂-saturated environment in the presence of IPA and water under visible light illumination, which is almost four-fold more than that of the pristine UiO-66-NH₂ MOF and twofold greater than those of the monometallic counterparts (Ag@MOF or Pd@MOF). Moreover, the photocatalytic H₂ evolution of the prepared materials was studied and a similar trend was observed in which the composite (1 : 2) Ag/Pd@UiO-66-NH₂ showed the highest H₂ evolution capacity of 448.2 μmol h⁻¹. The enhanced photocatalytic performance of the Ag/Pd@MOF composite can be attributed to its ability to suppress exciton recombination, superior photon reception, and fast charge transfer. Mechanistically the transfer of photogenerated electrons from the UiO-66-NH₂ surface to the bimetallic component was promoted through the LSPR effect of Ag and this is further enhanced by the Pd support. The electron-trapping capacity of the bimetallic nanoparticle (NP)-based co-catalyst enhances the overall reaction mechanism by giving highly surface active sites on the surface for the photocatalytic production of H₂O₂ and H₂ as a sustainable means of green energy production.