Tailoring the d-band center of ordered Pd-Zn pair in ultra-small PdZn intermetallic for efficient methanol oxidation

Direct methanol fuel cells (DMFCs) face commercialization challenges due to sluggish methanol oxidation reaction (MOR) and catalyst poisoning. Pd-based alloy catalysts show promise in alkaline media, but their high cost, poor stability, and CO intermediate toxicity hinder practical applications. Herein, we present a melamine-assisted confinement strategy to construct ultra-small PdZn ordered intermetallic nanoparticles (O-PdZn@MEL/C) with optimized electronic configurations. The carbon shell derived from pyrolyzed melamine imposes spatial constraints that suppress nanoparticle coalescence while enhancing structural stability. Zn incorporation induces d-orbital hybridization, which downshifts the Pd d-band center to weaken CO* adsorption while strengthening OH* binding at Zn sites. The catalyst demonstrates exceptional mass activity (2505.35 mA·mg_Pd⁻¹), 3.65 times higher than that of commercial Pd/C, with a lower onset potential (0.47 V vs. reversible hydrogen electrode (RHE)). Stability tests reveal 94.3% activity retention after 500 cyclic voltammetry (CV) cycles and only 52.5% current density decay during 4000 s operation. This work establishes d-band engineering through ordered intermetallic design as an effective pathway to develop CO-tolerant, high-performance anode catalysts for advanced fuel cells.