Gamma Radiolysis-Synthesized Carbon Nanotube–Supported Palladium as Electrocatalyst for Oxygen Reduction Reaction

Electrocatalysts are used to promote efficient energy conversion in fuel cell, especially for the sluggish oxygen reduction reaction (ORR) at the cathode that inhibits the performance of the device. In this work, we demonstrate the use of a facile gamma radiolysis technique to synthesize carbon nanotube-supported palladium (Pd) metal particles as electrocatalysts for the ORR application. The Pd precursor concentration used in the preparation process was found to contribute greater effects on the Pd content and Pd crystallite size of the synthesized product compared to the gamma irradiation dose. The results showed that gamma radiolysis could successfully reduce Pd ions from its precursor solution as evidenced from field emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectroscopy (EDS), and X-ray diffraction (XRD) characterization. The optimal ORR electrocatalyst was prepared using 0.01-M Pd precursor and a gamma radiation dose of 50 kGy. It displays a high half-wave potential (E_1/2) of 0.84 V (vs. RHE) and superior electron transfer number (n) of 3.96, as well as a low peroxide yield of 1.8%. This impressive ORR electrocatalytic performance was also attributed to the synergistic effect of Pd metal particles with CNT. The findings showed that Pd/CNT is a promising electrocatalyst for ORR application and that gamma radiolysis provides a facile and eco-friendly approach in synthesizing electrocatalysts.