Structurally Disordered RuO₂ Nanosheets with Rich Oxygen Vacancies for Enhanced Nitrate Electroreduction to Ammonia

Abstract

Electrochemical reduction of nitrate pollutants to ammonia has emerged as an attractive alternative for ammonia synthesis. Currently, many strategies have been developed for enhancing nitrate reduction to ammonia (NRA) efficiency, but the influence of the degree of structural disorder is still unexplored. Here, carbon‐supported RuO2 nanosheets with adjustable crystallinity are synthesized by a facile molten salt method. The as‐synthesized amorphous RuO2 displays high ammonia Faradaic efficiency (97.46 %) and selectivity (96.42 %), greatly outperforming the crystalline counterparts. The disordered structure with abundant oxygen vacancies is revealed to modulate the d‐band center and hydrogen affinity, thus lowering the energy of the potential‐determining step (NH2*→NH3*).

Electrochemical ammonia synthesisvianitrate reduction on perovskite LaxFeO3−δwith enhanced efficiency by oxygen vacancy engineering

“…This could be attributed to the promotion of nitrate reduction by the presence of oxygen vacancies, which was consistent with previous reports. 3,25–29 It was worth noting that the current density of L 0.9 F in the electrolyte without nitrate was remarkably lower than that of LF. This proved that the oxygen vacancies could even suppress the competitive HER.…”

“…27 Subsequently, NO* is gradually converted to HNO*, NH*, NH 2 *, and finally NH 3 * after a series of hydrogenation reactions. 29 Therefore, La x FeO 3− δ ( x = 0.95, 0.9) can afford outstanding NH 3 yield, faradaic efficiency and selectivity due to the promoted adsorption and conversion of NO 3 − in stage I and the enhanced NO 2 *-NH 3 process in stage II. Besides, previous studies have illustrated that oxygen vacancies can serve as the active sites of the catalysts to facilitate reactions at low overpotentials; deficiencies on the surface of catalysts can optimize the charge distribution and the conductivity of catalysts, and the charge transfer efficiency between the catalysts and electrolytes is effectively enhanced.…”

“…The oxygen atoms in NO 3 À tend to ll the oxygen vacancies to form NO 3 *, resulting in the lower adsorption energy of NO 3 À on La x FeO 3Àd (x ¼ 0.95, 0.9) than on the original LaFeO 3 catalyst. [27][28][29] And the N-O bonds in NO 3 * are broken to form NO 2 * by adsorbing protons coupled with electrons. 25 Similarly, the oxygen atoms in NO 2 * are easy to capture by oxygen vacancies, and the N-O bonds are broken to form NO*.…”

“…25 Similarly, the oxygen atoms in NO 2 * are easy to capture by oxygen vacancies, and the N-O bonds are broken to form NO*. 28,29 Another explanation is that NO 2 * experiences a more favorable hydrogenation (hydrogenation on oxygen) to form NO* on oxygen vacancy-rich catalysts instead of hydrogenation on nitrogen occurring on catalysts without oxygen vacancies, which effectively inhibits the formation of byproducts (NO 2 and HNO 2 ). 27 Subsequently, NO* is gradually converted to HNO*, NH*, NH 2 *, and nally NH 3 * aer a series of hydrogenation reactions.…”

Highly Efficient Decarboxylation of L-Lysine to Cadaverine Catalyzed by RuO2 Encapsulated in FAU Zeolite

“…Diffraction patterns of RuO 2 were not observed, indicating that no crystal phase was formed when it came to the zeolite-confined RuO 2 compound. The Raman spectrum of RuO 2 @FAU was given as an inserted graph in Figure 1A and characteristic peaks centered at 518 cm −1 , 634 cm −1 and 706 cm −1 were all assigned to RuO 2 for both amorphous and crystalline samples [21,22]. Raman characteristic lines indicated the existence of RuO 2 in the catalyst.…”