N-doped LaPO₄: An effective Pt-free catalyst for electrocatalytic oxygen reduction

This work provides a novel rare-earth-based catalyst of N-regulated lanthanum phosphate (N-LaPO₄/C) and the corresponding rational measurement of catalytic activity for the oxygen reduction reaction (ORR). Developed N-LaPO₄/C displays more positive half-wave potential (0.88 V) and onset potential (1.02 V) for the ORR, surpassing commercial Pt/C (0.96 and 0.85 V) and most reported research works. The robust stability of N-LaPO₄/C for the ORR is also demonstrated. Comprehensive analyses through X-ray absorption spectroscopy, surface Pourbaix diagram, microkinetic modeling, and data mining based on an advanced explainable machine learning demonstrate a self-oxidation process on LaPO₄ during the alkaline ORR and identify the key role of N in LaPO₄ in promoting ORR. N-doped LaPO₄ in N-LaPO₄/C is found to be an active center. Further findings show that N-LaPO₄/C + RuO₂ can be applied in rechargeable Zn-air batteries as an air cathode, showing a good power density and a long cycle life.