In-situ assembly of Ni-Cu-N bimetallic nitride catalyst for highly stable direct ammonia solid oxide fuel cells

Direct ammonia solid oxide fuel cells (DA-SOFCs) are promising next-generation energy-conversion devices that directly utilize ammonia (NH 3 ), offering cost-effectiveness and high efficiency. However, the severe degradation of DA-SOFCs owing to nickel reoxidation and nickel nitridation still hinders their commercialization. In this study, we propose a new design strategy that, instead of suppressing the nitridation of nickel, exploits it through the in-situ formation of a Ni–M–N bimetallic nitride catalyst, thereby achieving higher performance. We demonstrate the in-situ assembly of Ni–Cu–N (NCN), a bimetallic nitride catalyst that exhibits both high performance and stability. Compared with the bare cell, which continuously degraded during operation, the performance of the Cu-infiltrated cell continuously improved during operation owing to the in-situ formation of NCN and increased electrochemical reactions and ammonia decomposition rates. This resulted in a ~ 10-fold reduction in the degradation rate (0.0124%/h) after 300 h, surpassing the performance of previously reported DA-SOFCs. Furthermore, density functional theory calculations reveal that NCN can facilitate ammonia decomposition and suppress nickel reoxidation, enabling high stability and performance. This study highlights that multicomponent catalysts can be chemically modified by operating in a fuel environment to enhance their performance and stability.