Au-Pd@g-C₃N₄ as an Efficient Photocatalyst for Visible-Light Oxidation of Benzene to Phenol: Experimental and Mechanistic Study

Abstract

In the present study, a mesoporous photocatalyst based on Au–Pd nanoparticles incorporated into g-C3N4 was prepared by a coassembly method using melamine as the carbon and nitrogen source, polyvinyl pyrrolidone as the dispersing agent, and pulse laser ablation in liquid technique for preparing gold nanoparticles and subsequent decoration with Pd nanoparticles. At the final stage, Au–Pd/g-C3N4 nano-photocatalyst was obtained via low-ramping pyrolysis in an argon atmosphere. The activity of the catalyst was related to its structure, which was characterized by high-resolution transmission electron microscopy, field-emission scanning electron microscopy, X-ray photoelectron spectroscopy, energy-dispersive X-ray spectroscopy, and Brunauer–Emmett–Teller analysis. The results demonstrated that the Au–Pd-containing catalyst exhibited superior performance compared to its counterparts containing monometallic nanoparticles. The influence of variables such as reaction temperature, time of irradiation, amount of hydrogen peroxide, and amount of metal nanoparticles was investigated. Under optimized conditions, the Au–Pd/g-C3N4 photocatalyst showed benzene conversion of 26% at a phenol selectivity of 100%, giving no dihydroxylated byproducts. The catalyst was highly stable and recyclable, thus showing promise for the direct conversion of benzene to phenol. Time-dependent density functional theory (TD-DFT) calculations describe the activation of the oxidant by charge transferring from the metal clusters to the graphitized carbon nitride support and explain why the Au–Pd/g-C3N4 composite (rather than Au/g-C3N4) has superior efficiency in promoting the benzene-to-phenol conversion. The same DFT calculations showed that the Pd/g-C3N4 composite cannot catalyze the same processes.

Point‐Defect Engineering: Leveraging Imperfections in Graphitic Carbon Nitride (g‐C3N4) Photocatalysts toward Artificial Photosynthesis

“…Typically, noble metals like Pt, Pd, and Ag are the common cocatalysts employed in reaction. [208][209][210] Nevertheless, the cost and low abundance of these noble metals restrict the real and commercial applications. Therefore, recent research attention has been directed toward the development of nonnoble metal based cocatalysts for enhanced photocatalytic performances.…”

Self‐Assembly of Hollow, Pompon‐Like and Nanosheet‐Structured Carbon Nitride for Photodegradation of Tetracycline Hydrochloride

“…[1][2][3][4] However, the fast electron-hole (e − /h + ) recombination rate, low crystallinity, and small surface area limit largely its use in photocatalysis. [5,6] Many strategies including heteroatom doping, [7,8] metal deposition, [9,10] semiconductor coupling, [11][12][13] and morphology control [14] have been attempted to improve the photocatalytic performances of g-CN and got great success. Among them, the control of microstructure and morphology is an attractive route, which can yield changes in the crystallinity, the surface area, effects of reaction conditions on the activity of hp-CN-6, the best catalyst for the reaction, were investigated.…”

Single Atomic Cu-N2 Catalytic Sites for Highly Active and Selective Hydroxylation of Benzene to Phenol

“…Nitrogen-doped carbon materials have been found to be active for hydroxylation of benzene with H 2 O 2 under mild condition yet shows low catalytic activity (Yang et al., 2013). Metal-doped carbon nitride shows an improved activity for hydroxylation of benzene with H 2 O 2 to phenol but still remains unsatisfactory (Chen et al., 2009, Di et al., 2010, Xu et al., 2018, Zhang et al., 2018a, Zhang et al., 2018b; Hosseini et al., 2018). Therefore, developing efficient catalysts for benzene hydroxylation with H 2 O 2 to phenol is of great urgency.…”