Synergistic enhancement of solar H2O2 and HCOOH production over TiO2 by dual co-catalyst loading in a tri-phase system

Cocatalysts, especially precious metallic cocatalysts, are predominant in promoting photocatalytic H2O2 production. However, chemisorbed H2O2 is exceedingly apt to decompose on newly formed Pt(O). Herein, the dual cocatalysts (Pt and Co polyoxometalate (POM)) modified TiO2 was synthesized by electrostatic self-assembly and photodeposition methods. It shows a drastically elevated H2O2 yield of 0.93 mM h−1 and concurrent HCOOH production rate at 0.46 mM h−1. The X–ray photoelectron spectroscopy and theoretical calculations reveal that oxo-bridged POM leads to the electron redistribution of adjacent Pt and thus facilitates H2O2 desorption as well as retarding further decomposition. Simultaneously, deposited Co POM serves as the reservoir of photoelectrons and the bridge for electron transfer to metallic Pt through its ligand fragments. Lightweight polystyrene (PS) spheres enable the photocatalysts to float on a liquid surface with enhanced light utilization and intimate contact with gas reactants. This research not only furnishes insight into designing the highly-efficient photocatalytic system for hydrogen peroxide production but also explores the interaction between cocatalysts.