Concentration-gradient driven atom diffusion to synthesize high-loaded and sub-5 nm PtCo intermetallic compound for fuel cells

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. • Advanced microscopic and molecule-dynamics simulations reveal the promotion mechanism of concentration-gradient driven PtCo alloying and ordering • Ex situ XRD, XAS and TEM characterizations shed light on the structural evolution mechanism from Pt seeds to PtCo-IMC • High-loaded (44.3 wt.%) and small-sized (4.5 nm) PtCo-IMC/C is synthesized under relatively low temperature • PtCo-IMC/C catalyst achieves 1.15 W cm −2 under H 2 -air fuel cell condition at a Pt loading of 0.1 mg cm −2