A high-performance and anti-sulfur poisoning oxygen reduction reaction catalysts derive from molybdenum-doping on PtCo alloy nanoparticles surface

During the operation of fuel cell vehicles, sulfur dioxide (SO2) as a primary air pollutant can be transported to the cathode of the fuel cell with the air, leading to poisoning of the cathodic Pt-based catalyst, and subsequently, causing performance degradation and even shutdown. Therefore, there is an urgent need for SO2-tolerant Pt-based catalysts to mitigate poisoning in the cathodic oxygen reduction reaction (ORR). Herein, we report a carbon-supported Mo doped PtCo alloy catalyst with high-performance and anti-sulfur poisoning, termed as Mo-PtCo/C. Detailed investigations demonstrate that the Co in PtCo alloy nanoparticles (NPs) greatly promote ORR activity but do little to improve the SO2-tolerance. However, the PtCo alloy NPs doped with Mo not only exhibit a higher ORR activity, but also a superior SO2 poisoning resistance and a superior recovery performance. The optimal Mo-PtCo/C catalyst demonstrates a high initial mass activity of 871.0 mA mgPt−1, which is higher than that of the PtCo/C catalyst (initial value=558.8 mA mgPt−1) and 6.6 times higher than that of the commercial Pt/C (20 wt.% Pt, initial value=174.6 mA mgPt−1), along with a low mass activity loss of 36.19% after SO2 poisoning, which is much lower than 82.4% of the PtCo/C catalyst and 81.3% of the commercial Pt/C. More importantly, it is revealed that MoO3 formed on the PtCo NPs surface after Mo doping helps to reduce the electrooxidation potentials of SO2 to the operating potential of the fuel cell, thereby markedly boosting SO2-tolerance. Furthermore, the fuel cells test also confirmed that MoO3 improved the SO2-tolerance of the Mo-PtCo/C catalysts.