Modulating hydroxyl adsorption on Pd–Rh heterostructures through interfacial electron redistribution: a pathway to high-efficiency alkaline HOR catalysis†

The practical implementation of anion exchange membrane fuel cells (AEMFCs) using cost-effective reformate hydrogen is severely hindered by the trade-off between the 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 this dilemma. The construction of Pd–Rh heterostructures enables the optimal PdRh_0.05/C catalyst to exhibit an exceptional balance between HOR activity and CO resistance. At an overpotential of 50 mV, PdRh_0.05/C shows a 30.7 times enhancement in specific activity and a 35 times enhancement in mass activity, compared to Pd/C. PdRh_0.05/C also exhibits exceptional endurance with only 13% current decay after 10 000 s of operation, compared to >40% degradation recorded for Pd/C. Furthermore, PdRh_0.05/C delivers improved CO tolerance and can preserve 83% of its performance under 1000 ppm CO/H₂ after 1500 s, while Pd/C loses 78% of its 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 thus accelerating the rate-determining Volmer step and increasing 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.