Ir NCs Embedded Co-MOF Nanosheets for Boosting Electrochemical Nitrate Reduction to Ammonia Performance

Abstract

In this study, Ir nanoclusters adorned with abundant p-mercaptobenzoic acid (p-MBA) ligands were employed to fabricate an electrocatalytic material consisting of Ir nanoclusters embedded within two-dimensional Co-MOF nanosheets (Ir NCs@Co-MOF) for the electrocatalytic NO₃^– reduction reaction (NO₃^–RR). TEM analysis confirmed that Ir nanoclusters are uniformly distributed in 2D Co-MOF nanosheets, with an average diameter of about 1.8 nm. At a potential of −0.8 V vs RHE, the Ir NCs@Co-MOF catalyst achieved a nitrate conversion rate, ammonia selectivity, and yield of 92.5, 81.4%, and 230.1 μg·h^–1·cm^–2, respectively, over a reaction duration of 120 min. The strong interaction between Ir nanoclusters and Co-MOF serves to enhance electrocatalytic activity and accelerate the rate of nitrate reduction. Stability tests indicated that after 20 cycles, both the nitrate conversion and ammonia selectivity of the Ir NCs@Co-MOF catalyst demonstrated relative stability, thereby indicating a robust performance for this catalytic system. The results of EPR and TBA quenching experiments indicate that *H plays a key role in the NO₃^–RR process. In situ DEMS investigations revealed that during the NO₃^–RR process, the reaction pathway was as follows: *NO₃ → *NO₂ → *NO → *NOH → *NH₂OH → *NH₂ → *NH₃ → NH₃.