Enhanced nitrite electroreduction to ammonia via interfacial dual-site adsorption

The nitrite (NO 2 − ) to ammonia (NH 3 ) electroreduction reaction (NO 2 − RR) would be impeded by sluggish proton-coupled electron transfer kinetics and competitive hydrogen evolution reaction (HER). A key to improving the NH 3 selectivity is to facilitate adsorption and activation of NO 2 − , which is generally undesirable in unitary species. In this work, an efficient NO 2 − RR catalyst is constructed by cooperating Pd with In 2 O 3 , in which NO 2 − could adsorb on interfacial dual-site through “Pd–N–O–In” linkage, leading to strengthened NO 2 − adsorption and easier N=O bond cleavage than that on unitary Pd or In 2 O 3 . Moreover, the Pd/In 2 O 3 composite exhibits moderate H* adsorption, which may facilitate protonation kinetics while inhibiting competitive HER. As a result, it exhibits a fairly high NH 3 yield rate of 622.76 mmol h −1 g −1 cat with a Faradaic efficiency (FE) of 95.72%, good selectivity of 91.96%, and cycling stability towards the NO 2 − RR, surpassing unitary In 2 O 3 and Pd/C electrocatalysts. Besides, computed results indicate that NH 3 production on Pd/In 2 O 3 follows the deoxidation to hydrogenation pathway. This work highlights the significance of H* and NO 2 − adsorption modulation and N=O activation in NO 2 − RR electrochemistry by creating synergy between a mediocre catalyst with an appropriate cooperator.