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

Abstract

Electrocatalytic NO reduction to NH3 (NORR) offers a prospective approach to attain both harmful NO removal and efficient NH3 electrosynthesis. Main-group p-block metals are promising NORR candidates but still lack adequate exploration. Herein, p-block Sb single atoms confined in amorphous MoO3 (Sb1/a-MoO3) are designed as an efficient NORR catalyst, exhibiting the highest NH3 yield rate of 273.5 μmol h–1 cm–2 and a NO-to-NH3 Faradaic efficiency of 91.7% at −0.6 V vs RHE. In situ spectroscopic characterizations and theoretical computations reason that the outstanding NORR performance of Sb1/a-MoO3 arises from the isolated Sb1 sites, which can optimize the adsorption of *NO/*NHO to lower the reaction energy barriers and simultaneously exhibit a higher affinity to NO than to H2O/H species. Moreover, our strategy can be extended to prepare Bi1/a-MoO3, showing a high NORR property, demonstrating the immense potential of p-block metal single-atom catalysts toward the high-performing NORR electrocatalysis.

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.…”

“…W 1 /MoO 3– x was prepared by a facile supercritical CO 2 approach which enabled the generation of amorphous MoO 3– x containing abundant O-vacancies (O V ), − while O V can readily trap and immobilize W single atoms. The TEM image (Figure a) displays the typical nanosheet morphology of W 1 /MoO 3– x .…”

Amorphous NiB2for electroreduction of NO to NH3

“…A series of experiments are performed to verify the NH 3 source. [54][55][56] + is detected in the 1 H nuclear magnetic resonance (NMR, Fig. S12 †) spectra when using 15 NO as the feed gas.…”

“…A series of experiments are performed to verify the NH 3 source. 54–56 Fig. S10† shows that negligible NH 3 is generated in Ar-electrolyte or at open circuit potential (OCP).…”

Boron phosphide as an efficient metal-free catalyst for nitrate electroreduction to ammonia

“…Ammonia (NH 3 ) is a critical industrial chemical and also an appealing carbon-free energy carrier. [1][2][3][4][5][6] The well-established Haber-Bosch process for commercial NH 3 synthesis is highly energy-intensive and results in large amount of greenhouse gas emissions. [7][8][9][10] Electrochemical N 2 fixation in aqueous electrolytes has received extensive attention as an attractive route for green NH 3 synthesis, [11][12][13][14][15][16][17] but its NH 3 yield rates and NH 3faradaic efficiency (FE NH 3 ) are rather low due to the ultrahigh NuN dissociation energy.…”