Optimizing the O-intermediates' chemisorption behavior of Pd metallene via cation doping enables a highly efficient oxygen reduction in PEMFCs

Modulating the electronic structure and O-intermediates' chemisorption behavior of Pd metallene with boosted oxygen reduction reaction (ORR) performance is critical to advance proton exchange membrane fuel cells (PEMFCs). Herein, Hf doping Pd metallene (Hf-Pd metallene) is developed for efficient ORR electrocatalysis. Multiple characterizations and theoretical simulations disclose that the Hf dopant located in the inner atomic layers of Hf-Pd metallene could modulate the electronic configuration of Pd, lower the binding energies of the Pd d-band centers toward O-related intermediates, deliver a much reduced overpotential during O* hydrogenation into OH*, and thus enhance the catalytic activity. Consequently, the Hf-Pd metallene delivers superior ORR electrocatalytic activity together with excellent stability, surpassing commercial Pt/C and various advanced Pd-based catalysts. Encouragingly, when utilized as the cathode in a PEMFC, the Hf-Pd metallene achieved the higher maximum power density (722.75 mW cm−2) as compared to Pt/C-based batteries, elucidating the practical application of Hf-Pd metallene in PEMFCs.