PtP 2 nanoparticles on N,P doped carbon through a self-conversion process to core–shell Pt/PtP 2 as an efficient and robust ORR catalyst

• Published in: Journal of materials chemistry. A, Materials for energy and sustainability Materials for energy and sustainability, 2020-10, Vol.8 (39), p.20463-20473
• Main Authors: Tian, Wu, Wang, Yanwei, Fu, Weiwei, Su, Jinfeng, Zhang, Han, Wang, Yu
• Format: Article
• Language: English
• ISSN: 2050-7488; 2050-7496
• DOI: 10.1039/D0TA06566H

Proton-exchange membrane fuel cells have been reported as one of the most promising substitutes for fossil fuels. However, limited oxygen reduction reaction (ORR) kinetics on the cathode still remains the main bottleneck for commercialization. We report the synthesis of size-controllable monodisperse PtP 2 nanoparticles (NPs) on nitrogen- and phosphorus-doped carbon (NPC) with initial ORR mass and specific activities of 0.466 A mg Pt −1 and 0.438 mA cm −2 at 0.9 V in 0.1 M HClO 4 solution, via a combined template and pyrolysis method. The activities increase to 0.724 A mg Pt −1 and 0.508 mA cm −2 after 3000 potential cycles and remain stable for a further 20 000 cycles, exhibiting an obvious improvement over the commercial Pt benchmark (0.142 mA cm −2 and 0.098 A mg Pt −1 at 0.9 V). The facilitated ORR activity of PtP 2 @NPC after incipient cycles of the stability test is due to the self-conversion process from PtP 2 to core–shell Pt/PtP 2 with a thin (≈1 nm) Pt shell and the consequential geometric and strain effects of the Pt skin which contribute to both the robustness and catalytic efficiency of the catalysts. Meanwhile, a four-electron pathway towards the ORR also indicates the high selectivity of our catalyst. Combined computational analysis indicates that the core–shell structure intensifies ORR activity by a more feasible rate-determining step and lower d-band center value.