Facile synthesis of solar active charcoal passivated Ag3PO4 and their two-channel mechanisms for H2O2 formation in aerated water

Abstract

This work presents the use of activated charcoal passivated-Ag3PO4 (CAgP) and bare Ag3PO4(AgP) nanoparticles (NPs) as effective photocatalysts for the generation of hydrogen peroxide (H2O2) in air-saturated water containing either formic acid (FA) or silver nitrate (AgNO3). The synthesized CAgP and pristine AgP were characterized using various state-of-the-art optical and electron microscopy techniques. The CAgP composites showed remarkable photocatalyzed H2O2 formation compared to bare AgP NPs. The CAgP photocatalyzed-assisted H2O2 formation from O2-saturated water under sunlight was achieved via two-channel mechanisms. First, in the presence of FA as a hole scavenger, enhanced H2O2 formation was facilitated by the decomposition of FA to produce proton (H+), followed by a spontaneous reduction of dissolved molecular oxygen by the valence band electrons. The second pathway involves the formation of H2O2 in the absence of electrons (using AgNO3 as an electron scavenger) which occurs via the oxidation of H2O by photo-induced holes to generate hydroxyl radicals (•HO) and the combination of •HO radicals to produce H2O2. The most notable feature of CAgP composite as a photocatalyst is the ease of H2O2 formation in O2/H2O and O2/H2O/FA system, as well as the ability to reuse the recovered CAgP catalyst for a few reaction cycles without losing substantial catalytic activity or mass.