Abstract
Fuel cells is severely restricted by the sluggish oxygen reduction reaction (ORR) kinetics at the cathode side, which demands highly active and enduring catalysts for producing adequate rates. Herein, we report a systematic study to investigate the effect of structure configuration on the oxygen reduction reaction (ORR) activity of tri-metallic nanocatalysts (NC)s comprising atomic Ir-clusters (0.5 wt.% of Ir) anchored Pd nanoparticles on the tetrahedral symmetric Ni-oxide support (denoted as NPI). The electrochemical activities of NPI NCs are programmable via a temperature-controlled wet chemical reduction method. For the optimum condition when the Ni-crystal impregnation temperature is 40oC, the Ir-clusters decorated Ni@Pd nanoislands are formed (hereafter denoted as NPI-40), outperforming the commercial J.M.-Pt/C (20 wt.% Pt) catalyst by ~180-folds with an unprecedented high mass activity of ~12,000 mAmgIr -1 at 0.85 V vs RHE in 0.1 M KOH. More importantly, NPI-40 NC retained 100 % ORR performance with no degradation up to 20k accelerated degradation test cycles, while only a 5 mV loss in half-wave potential (E1/2 ) is observed after 30k ADT cycles. The results of physical structure inspections and electrochemical analysis suggest that such an exceptional ORR performance of NPI-40 NC originates from the potential synergetic effect between the high density of occupied Ir-d-orbital and adjacent compressively strained Ni-Pd interface. With this structure configuration, Ir-sites offer optimal adsorption energy for O2 splitting and Ni-Pd interface facilitates the subsequent desorption of hydroxide ions (OH-). We believe that the obtained results will open new approach for the design of Pt-free NCs for fuel cell cathode. Keywords: Oxygen reduction reaction, Fuel cells, Mass activity, Ir clusters
Published Version
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