Discovering Facet-Dependent Formation Kinetics of Key Intermediates in Electrochemical Ammonia Oxidation by a Electrochemiluminescence Active Probe.

Facile evaluation of formation kinetics of key intermediate is crucial for a comprehensive understanding of electrochemical ammonia oxidation reaction (AOR) mechanisms and the design of efficient electrocatalysts. Currently, elucidating the formation kinetics of key intermediate associated with rate-determining step is still challenging. Herein, 4-phtalamide-N-(4'-methylcoumarin) naphthalimide (CF) is developed as a molecular probe to detect N 2 H 4 intermediate during AOR via electrochemiluminescence (ECL) and further investigated the formation kinetics of N 2 H 4 on Pt catalysts with different crystal planes. CF probe can selectively react with N 2 H 4 to release ECL substance luminol. Thus, N 2 H 4 intermediate as a key intermediate can be sensitively and selectively detected by ECL during AOR. For the first time, Pt(100) facet is discovered to exhibit faster N 2 H 4 formation kinetics than Pt(111) facet, which is further confirmed by Density functional theory calculation and the finite element simulation. The AOR mechanism under the framework of Gerischer and Mauerer is further validated by examining N 2 H 4 formation kinetics during the dimerization process (NH 2 coupling). The developed ECL active probe and the discovered facet-dependent formation kinetics of key intermediates provide a promising new tool and strategy for the understanding of electrochemical AOR mechanisms and the design of efficient electrocatalysts.