Preparation And Photocatalytic Performance Of Semiconductor Materials By Cocatalyst Modification

Nowadays, environmental pollution and energy shortage are the two major challenges. Photocatalysis not only can mineralize organic pollutants in the water and air, but also can produce H2 energy through water splitting. Traditional semiconductor materials are not suitable for large-scale practical applications because of their low visible-light response and quantum efficiency. In recent years, how to improve the photocatalytic activity of semiconductor materials to meet the needs of practical application is becoming a hot topic in the field of photocatalysis. In this paper, the preparation and photocatalytic performance of cocatalyst modified photocatalysts are explored, and the main points can be summarized as follows:1. Enhanced light absorption and effective separation of photogenerated charges are the main strategies to improve the photocatalytic performance of photocatalytic materials. In this study, the enhanced light absorption and effective separation of photogenerated charges in Ag3PO4 photocatalyst can be easily realized via the simultaneous loading of Ag nanoparticles and Fe(III) cocatalyst. In this case, the noble metallic Ag nanoparticles not only function as a visible-light active component to strongly absorb visible light owing to its localized surface plasmon resonance, but also can improve the bandgap visible-light absorption of Ag3PO4, resulting in the generation of more photogenerated charges. Photocatalytic experimental results suggested that the simultaneously modified Fe(III)/Ag-Ag3PO4 photocatalyst(k = 0.038 min-1) showed an obviously higher photocatalytic activity than the pure Ag3PO4(0.024 min-1), and single-component modified Fe(III)/Ag3PO4(0.03 min-1) and Ag-Ag3PO4(0.032 min-1) photocatalysts. On the basis of the experimental results, a possible synergistic effect mechanism of Ag nanoparticles and Fe(III) cocatalyst was proposed to account for the improved photocatalytic performance of Fe(III)/Ag-Ag3PO4 photocatalyst, namely, the metallic Ag nanoparticles cause an obviously enhanced visible-light absorption to produce more photogenerated charges, while the Fe(III) works as an effective active site for the following oxygen reduction to reduce the recombination rate of photogenerated electrons and holes.2. Effective separation of photogenerated charges is one the main strategies to improve the photocatalytic performance and photostability of photocatalytic materials. In this study, Pt-MnOx/CdS photocatalyst was firstly prepared by a simple impregnation method for MnOx loading and then by a photoreduction method for Pt nanoparticles. Photocatalytic performance was tested under visible-light with Na2S/Na2SO3 solution as a sacrificial agent. It was found that the simultaneously modified Pt-MnOx/CdS photocatalyst showed the highest photocatalytic activity with a H2 evolution rate is 535.6 ?mol.g-1.h-1, which is about 6.0, 2.9 and 1.2 times than that of the pure CdS, single-component modified MnOx/CdS and Pt/CdS photocatalysts, respectively. On the basis of the experimental results, a possible synergistic effect mechanism of Pt nanoparticles and MnOx cocatalyst was proposed to account for the improved photo-catalytic performance of Pt-MnOx/CdS photocatalyst, namely, the metallic Pt nanoparticles cause effective transfer of photogenerated electrons, while the MnOx works as an effective hole cocatalyst to rapid transfer the photogenerated holes, remarkably improving the photoinduced stability of CdS.