Rhombohedral platinum-copper intermetallic compound: A high phosphate tolerance electrocatalyst for HT-PEMFC

• The ultrafine L 1 1 -PtCu intermetallic compound nanoparticles were synthesized. • They showed high resistance to phosphate poisoning. • It exhibits a superior peak power density of 800.5 mW cm −2 in 160℃ H 2 -O 2 HT-PEMFC. In high-temperature proton exchange membrane fuel cells (HT-PEMFC), phosphate anions act as a poisonous 'spectator species', binding strongly to the Pt surface through Pt O bonds similarly to O 2 . This blocks the Pt active sites, resulting in slow ORR kinetics. Herein, we synthesized ultrafine L 1 1 -PtCu intermetallic compound nanoparticles (O-PtCu/S-C) loaded on an S-doped carbon support with an average size of about 3 nm through wet impregnation followed by hydrogen annealing, which showed high resistance to phosphate poisoning. The introduction of S notably improved the metal-support interaction and prevented particle growth during annealing, which is beneficial for the uniform distribution of nanoparticles and prevents detachment and agglomeration during ADT. The pronounced Cu-Pt electronic interaction in O-PtCu/S-C induced electron transfer from Cu to Pt, which effectively modified the electronic structure of Pt and weakened the adsorption energy of phosphate anions on the catalyst surface. In addition, the phosphate poisoning test results from both room temperature RDE and high-temperature RDE demonstrate that O-PtCu/S-C possesses excellent phosphate tolerance, superior ORR activity, and remarkable stability. It exhibits a superior peak power density of 800.5 mW cm −2 in 160°C H 2 -O 2 HT-PEMFC with Pt loading of 0.5 mg cm −2 . This research offers a novel approach to designing phosphate-resistant electrocatalysts for HT-PEMFC.