Breaking the scaling relationship for oxygen reduction via amino-molecule-interface-mediated metallene electrocatalysts

Abstract

Developing highly stable and active Pd-based catalysts for the oxygen reduction reaction (ORR) is crucial for enabling the large-scale application of anion exchange membrane fuel cells (AEMFCs) in hydrogen utilization. However, the conventional oxygen associative pathway limits ORR efficiency due to the persistent scaling relationship. Unlike commonly reported alloying strategies, here we report a polyethyleneimine (PEI)-mediated interface engineering strategy to modify the PdRh metallene (PdRh@PEI) for efficient ORR catalysis and fuel cells. The PdRh@PEI catalyst exhibits a high half-wave potential (E_1/2) of 0.96 V (vs. RHE) and mass activity of 1.23 A mg_Pd⁻¹ at 0.9 V, which is higher than that of the benchmark Pt/C and most reported Pd-based catalysts, certifying its top-level performance. In situ vibrational spectroscopy and computational investigations unveiled that the PEI modification donates electron density from PEI to the PdRh atoms, resulting in a pronounced downshift of the d-band center, a reduced activation barrier in the rate-limiting step, and enhanced oxygen dissociation from *OOH to *O via a dissociative mechanism. When utilized as a cathode in AEMFCs, PdRh@PEI demonstrates a high power density (164.3 mW cm⁻²) and outstanding operational durability (over 24 h without voltage decay), highlighting the effectiveness of molecular interface modification in the design of efficient Pd-based metallenes for energy conversion applications.