Polyoxometalate-Intercalated Tremella-Like CoNi-LDH Nanocomposites for Electrocatalytic Nitrite–Ammonia Conversion

Abstract

The electrocatalytic reduction of NO 2 − (NO 2 RR) holds promise as a sustainable pathway to both promoting the development of emerging NH 3 economies and allowing the closing of the NO x loop. Highly efficient electrocatalysts that could facilitate this complex six-electron transfer process are urgently desired. Herein, tremella-like CoNi-LDH intercalated by cyclic polyoxometalate (POM) anion P 8 W 48 (P 8 W 48 /CoNi-LDH) prepared by a simple two-step hydrothermal−exfoliation assembly method is proposed as an effective electrocatalyst for NO 2 − to NH 3 conversion. The introduction of POM with excellent redox ability tremendously increased the electrocatalytic performance of CoNi-LDH in the NO 2 RR process, causing P 8 W 48 /CoNi-LDH to exhibit large NH 3 yield of 0.369 mmol h −1 mg cat −1 and exceptionally high Faradic efficiency of 97.0% at −1.3 V vs the Ag/AgCl reference electrode in 0.1 M phosphate buffer saline (PBS, pH = 7) containing 0.1 M NO 2 − . Furthermore, P 8 W 48 /CoNi-LDH demonstrated excellent durability during cyclic electrolysis. This work provides a new reference for the application of POM-based nanocomposites in the electrochemical reduction of NO 2 − to obtain value-added NH 3 .