Concentration-gradient driven atom diffusion to synthesize high-loaded and sub-5 nm PtCo intermetallic compound for fuel cells
Qingqing Cheng, Tao Wang, Yihe Chen, Yongyu Pan, Yubin Chen, Bo Yang, Hui Yang
Abstract
The synthesis of Pt intermetallic compounds (IMCs) typically necessitates high-temperature annealing to overcome the atom-diffusion kinetic barrier, which inevitably results in considerable nanoparticle sintering, especially for the high-loaded catalyst, thus leading to diminished performance in proton exchange membrane fuel cells. We propose a concentration-gradient-driven atom diffusion strategy to synthesize Pt intermetallic compounds (IMCs), overcoming the atom-diffusion kinetic barrier under relatively low temperature. This method efficiently transforms high-loaded Pt seeds/C into sub-5 nm L 10 -PtCo-IMC/C (44.3 wt.%) catalyst. Advanced characterizations and molecular dynamic simulations reveal that locally concentrated Co precursors accelerate atom diffusion and enhance nanoparticle anti-sintering ability. Temperature-dependent analyses further elucidate the structural transformation mechanism by tracking crystal structure and nanoparticle size evolution. Membrane electrode assembly (MEA) integrated with the optimized PtCo-IMC/C at a low Pt usage (0.1 mg cm −2 ) delivers a maximum power density of approximately 1.15 W cm −2 and excellent stability (a 26-mV loss at 0.8 A cm −2 ) after 30000 cycles of accelerated stress testing under H 2 -air conditions. This scalable synthesis pathway (20 g per batch) holds great promise for advancing high-loaded fuel cell electrocatalysts.