Plasma synthesis of graphite oxide supported PdNi catalysts with enhanced catalytic activity and stability for 4-nitrophenol reduction

Catalytic removal of 4-nitrophenol (4-NP) in wastewater remains a significant challenge due to the poor activity and stability of the catalysts. Herein, low-cost graphite oxide (GO) supported Pd and Ni NPs (PdNi/GO) with enhanced catalytic activity and stability for 4-NP reduction were synthesized by a plasma method in the aqueous solution of Pd(NO3)2, Ni(NO3)2, and GO. The normalized rate constant knor over the PdNi/GO with Pd/Ni= 1.8:0.2 for 4-NP reduction was as high as 5480 min−1·g−1·L, which was comparable with that of Pd/GO, and it was about 50.7 times higher than that of Pd/rGO-H prepared by traditional thermal reduction method. Importantly, after six reaction cycles, it only decreased to 74.8% of the initial value, which was much higher than that of the Pd/GO catalyst (59.8%). The characterization results indicated that plasma synthesized Pd/GO catalyst can keep the oxygen-containing groups (OCGs) on the GO surface, generate abundant defects, and facilitate the adsorption of the 4-NP. Interestingly, the addition of Ni could keep these merits, and the formed PdNi alloyed structure may facilitate the electron transfer between PdNi NPs and GO, contribute to the strong adsorption of 4-NP and the rapid generation of active hydrogen. Consequently, the PdNi/GO catalyst exhibited outstanding catalytic activity and stability for 4-NP reduction. This work provided a fast, facile, environmentally friendly, and easy to scale up plasma method for synthesizing high performance Pd-based catalysts.