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

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 .