Cold Plasma for Preparation of Pd/graphene Catalysts toward 4-nitrophenol Reduction: Insight into Plasma Treatment

Objective: Controllable synthesis of high-performance palladium catalysts toward 4-nitrophenol (4-NP) reduction still remains a significant challenge. This work aims to exploit a facile dielectric barrier discharge (DBD) plasma treatment method to synthesize the graphene-supported palladium catalysts (Pd/G-P), and to as certain the effect of plasma discharge voltage and discharge time on the structure-performance relationship of Pd/G-P, then provides insight into the synthesis of high-performance Pd/G-P by DBD plasma. Methods: A graphene-supported palladium precursor was prepared by excess impregnation method firstly, and then treated using hydrogen DBD plasma to synthesize Pd/G-P catalysts. The effect of discharge voltage and discharge time on the structure-performance relationship of Pd/G-P were systematically investigated based on the reaction model of 4-NP reduction. Results: The Pd/G-P prepared by DBD plasma at discharge voltage of 13.0kV and discharge time of 4min exhibited the highest performance for 4-NP reduction with a rate constant (k) of as high as 0.88min-1. The discharge diagnosis and sample characterization results showed that Pd/G-P with much higher than Pd/C and O/C atomic ratios, and surface defects density can be obtained at the optimal discharge parameters. These features enabled the formation of small-sized and highly-dispersed palladium nanoparticles, thereby enhancing the catalytic activity. The experimental study of reaction kinetics showed that plasma synthesized Pd/G-P at optimal parameters can adsorb intermediate reactants more effectively and enhance the catalytic performance. Conclusion: In this work, controllable synthesis of high-performance Pd/G-P were synthesized, which provides important reference significance for preparing other catalysts by plasma regulation.