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

Abstract

Electrochemical reduction of nitrate to ammonia (NO 3 RR) holds a great promise for attaining both NH 3 electrosynthesis and wastewater purification. Herein, single-atom Bi alloyed Pd metallene (Bi 1 Pd) is reported as a highly effective NO 3 RR catalyst, showing a near 100% NH 3 -Faradaic efficiency with the corresponding NH 3 yield of 33.8 mg h −1 cm −2 at −0.6 V versus RHE, surpassing those of almost all ever reported NO 3 RR catalysts. In-depth theoretical and operando spectroscopic investigations unveil that single-atom Bi electronically couples with its neighboring Pd atoms to synergistically activate NO 3 − and destabilize *NO on Bi 1 Pd, leading to the reduced energy barrier of the potential-determining step (*NO→*NOH) and enhanced protonation energetics of NO 3 − -to-NH 3 pathway.

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. − …”

p-Block Antimony Single-Atom Catalysts for Nitric Oxide Electroreduction to Ammonia

“…In situ Fourier transform infrared spectroscopy (FTIR, Figure a–d) is carried out to identify the reaction intermediates during the NORR electrolysis. For Sb 1 /a-MoO 3 (Figure a,b), with increasing potentials from 0 V to −0.6 V, besides the strong H–O–H bending mode of water at ∼1650 cm –1 , many NORR-related infrared bands, including NO molecules (1710–1760 cm –1 ), hydrogenation intermediates (H–N–H at ∼1510 cm –1 , −NH 2 at ∼1290 cm –1 , and *NH 2 OH at ∼1200 cm –1 ) − and produced NH 3 (NH 4 + at 1450 cm –1 ), appear and gradually enhance in peak intensity, suggesting the efficient electroreduction of NO to generate plentiful hydrogenation intermediates for successive NH 3 synthesis. In sharp comparison, pristine a-MoO 3 (Figure c,d) shows a strong NO band but rather weak bands of hydrogenation intermediates and NH 3 , which means that a-MoO 3 is active for NO adsorption but catalytically less effective for NO hydrogenation to produce NH 3 , eventually leading to the sluggish NORR reaction energetics and poor NORR performance of a-MoO 3 .…”

Self-Tandem Electrocatalytic NO Reduction to NH3 on a W Single-Atom Catalyst

“…Operando FTIR is conducted to further monitor the reaction intermediates during the NORR process. − As shown in Figure f,g, a pair of peaks at 1720–1780 cm –1 are assigned to linear and bent coordination modes of absorbed NO molecules, , a strong peak at ∼1650 cm –1 represents the H–O–H bending mode of water molecules, and other peaks correspond to protonation intermediates (H–N–H at ∼1480 cm –1 , −NH 2 at ∼1320 cm –1 , and *NH 2 OH at ∼1200 cm –1 ) and generated NH 3 (NH 4 + at ∼1440 cm –1 ). − For W 1 /MoO 3– x (Figure f), with increasing potentials, all of the peaks of absorbed NO, protonation intermediates, and NH 4 + can be observed, and their peak intensity is gradually enhanced, indicating the effective activation and protonation of NO on W 1 /MoO 3– x to continuously produce plentiful intermediates which are finally converted to NH 3 . In sharp comparison, for bare MoO 3– x (Figure g), only the pronounced peaks of absorbed NO are observed, whereas other peaks of protonation intermediates and NH 4 + are greatly weakened.…”