Modulating Hydroxyl Adsorption on Pd-Rh Heterostructures through Interfacial Electron Redistribution: A Pathway to High-Efficiency Alkaline HOR Catalysis

Abstract

The practical implementation of anion exchange membrane fuel cells (AEMFCs) using cost-effective reformate hydrogen is severely hindered by the trade-off between catalytic activity and CO tolerance of electrocatalysts in alkaline hydrogen oxidation reaction (HOR). Here, we report a rational design of Pd-Rh bimetallic interfaces with tailored electronic gradients to tackle with this dilemma. By constructing Pd-Rh heterostructures, the optimal PdRh0.05/C catalyst displays an exceptional balance between HOR activity and CO resistance. At overpotential of 50 mV, the PdRh0.05/C gives 30.7 times enhancement on SA and 35 times enhancement on MA, in comparison to Pd/C. The PdRh0.05/C also displays exceptional endurance with only 13% current decay after 10,000 s operation, compared to >40% degradation recorded for Pd/C. Furthermore, the PdRh0.05/C delivers improved CO tolerance and can preserve 83% performance under 1000 ppm CO/H₂ after 1500s, while Pd/C lost 78% performance. DFT studies demonstrate that the Pd-Rh interface promotes valence electron redistribution, greatly improving Rh-O orbital hybridization, reducing the OH* adsorption barrier by 326%, and so accelerating the rate-determining Volmer phase and raising overall HOR performance. This study presents an exceptional Pd-Rh bimetallic electrocatalyst exhibiting both elevated hydrogen oxidation reaction activity and carbon monoxide tolerance, while also introducing a comprehensive technique for regulating electronic structures in high-efficiency electrocatalysts.