Lewis Acid Fe‐V Pairs Promote Nitrate Electroreduction to Ammonia

Abstract

Electrochemical reduction of nitrate to ammonia (NO 3 RR) has been recognized as an appealing approach to realize both sustainable NH 3 production and waste nitrate removal. Herein, from the perspective of Lewis acid-base interaction, a single-atom Fe-doped V 2 O 5 (Fe-V 2 O 5 ) catalyst enriched is designed with Lewis acid sites, which present the maximum NH 3 -Faradaic efficiency of 97.1% with the corresponding NH 3 yield of 12.5 mg h −1 cm −2 at -0.7 V versus RHE. Mechanistic studies based on theoretical calculations and operando spectroscopic characterizations identify the creation of Lewis acid Fe-V pairs on Fe-V 2 O 5 , which can synergetically activate the NO 3 − , promote the hydrogenation energetics, and restrain the hydrogen evolution, leading to the enhanced NO 3 RR activity and selectivity.

Sub-nm RuOx Clusters on Pd Metallene for Synergistically Enhanced Nitrate Electroreduction to Ammonia

“…Linear sweep voltammetry (LSV; Figure S12) curves initially confirm the active RuO x /Pd toward the NO 3 RR, as indicated by the largely enhanced current density in an NO 3 – -containing electrolyte relative to an NO 3 – -free electrolyte . In light of the LSV results, the initial electrolysis potential of 0.0 V is chosen to quantitatively evaluate the NO 3 RR performance of RuO x /Pd through combined chronoamperometric (1 h electrolysis) and colorimetric measurements. − Figure a shows that RuO x /Pd delivers a maximum NH 3 -Faradaic efficiency of 98.6% with a corresponding NH 3 yield rate of 23.5 mg h –1 cm –2 and a partial current density of 296.3 mA cm –2 (Figure S13) at −0.5 V vs RHE, surpassing those of almost all state-of-the-art NO 3 RR catalysts ever reported (Table S1). The controlled UV–vis tests (Figure S14) and qualitative/quantitative 14 NO 3 – / 15 NO 3 – isotope labeling nuclear magnetic resonance (NMR) experiments (Figure b and Figure S15) forcefully affirm that the generated NH 3 stems from the NO 3 RR on RuO x /Pd. − …”

Single‐Atom Bi Alloyed Pd Metallene for Nitrate Electroreduction to Ammonia

“…The enhanced protonation energetics of Bi 1 Pd can be further substantiated by the operando EPR measurements using 5,5‐dimethyl‐1‐pyrroline‐N‐oxide (DMPO) as the *H trapping reagent. [ 66–67 ] As displayed in Figure 5f, upon electrolysis in NO 3 − ‐free electrolyte, Pd metallene and Bi 1 Pd exhibit the similar and strong DMPO‐H signals, suggesting that they both have the great ability to dissociate H 2 O and generate abundant *H radicals required for protonation. This can be attributed to the critical contribution of Pd which is known to be highly active for H 2 O dissociation.…”

Electrocatalytic NO Reduction to NH3 on Mo2C Nanosheets

“…The electrochemical stability of Mo 2 C for the NORR was finally evaluated. There are no obvious changes in the NORR performances for ten cycles of electrolysis (Figure g), suggesting the good cycling durability of Mo 2 C. − Mo 2 C also exhibits favorable long-term durability, as confirmed by little decay in FE NH 3 and current density for continuous 20 h electrolysis (Figure h). − These electrochemical test results prove that Mo 2 C is a promising catalyst toward effective and durable NORR.…”