Tandem Nitrate Electroreduction to Ammonia with Industrial-Level Current Density on Hierarchical Cu Nanowires Shelled with NiCo-Layered Double Hydroxide

Abstract

Electrochemical conversion of industrial nitrate wastewater to valuable ammonia (NH 3 ) is an attractive method for nitrate removal and NH 3 production. However, the energy efficiency is limited by the high reaction overpotential and poor selectivity. Herein, we demonstrate a tandem electrode composed of hierarchical Cu nanowires shelled with NiCo-layered double hydroxide (NiCo LDH/Cu NW) that exhibits an industrial-relevant NH 3 partial current density of 570 mA cm −2 while maintaining a Faradaic efficiency of 94.25% through the nitrate reduction reaction (NO 3 RR). The practical application of the NO 3 RR route in simulated wastewater with different NO 3 − concentrations and in membrane electrode assembly is developed, which demonstrates great potential for industrial application. Furthermore, online differential electrochemical mass spectrometry, in situ Fourier transform infrared spectroscopy, and density functional theory calculations confirm the tandem catalysis mechanism of NiCo LDH/Cu NW, suggesting that the activity of catalysts for NO 3 RR could be attributed to the synergy effects, in which Cu nanowires would preferentially catalyze the reduction of NO 3 − to NO 2 − and then NiCo LDH catalyzes the reduction of NO 2 − to NH 3 .

Unraveling Rigidified Superexchange Couplings in Organic Donor–Acceptor Polymers for Boosting the Photocatalytic Reduction of Nitrate

“…AFM images reveal that the uniform thickness of D-PDI is about 3–7 nm (Figure c). On the other hand, a clear lattice fringe of about 0.32 nm can be observed in Figure d, confirming the intermolecular H-type π–π stacking interaction, demonstrating that the face-to-face overlap of the geometrical configuration provides a delocalized electron cloud for promoting the carrier migration between layers. − In addition, the elemental distribution in D-PDI exhibits a homogeneous dispersion of C, N, and O elements (Figure e,h). Moreover, the Brunauer–Emmett–Teller (BET)-specific surface area of D-PDI is 65.8 m 2 g –1 , which is much larger than those of other PDI polymers (Figure S4), indicating that the special structure of D-PDI makes more active sites exposed …”

Tandem catalysis in electrocatalytic nitrate reduction: Unlocking efficiency and mechanism

“…Other tandem catalytic systems have also demonstrated boosted electrochemical NO 3 RR performance with rational design of catalytic sites, such as copper-cobalt oxides, [104] copper-cobalt-based bimetallic hollow nanobox, [105] CoO-CuO x heterostructure, [106] hollow mesoporous carbon supported Co-modified Cu/ Cu 2 O, [107] Cu/Co bimetallic conductive metal-organic frameworks (MOFs), [108] Cu─Ni metal-organic frameworks, [109] CuNi alloy, [110] bifunctional copper-cobalt spinel, [111] hetero-structured Co-doped-Cu 2 O/Cu, [112] Fe and Cu double-doped Co 3 O 4 , [113] modulated hydrogen adsorption on Fe─N interface, [114] Fe-and Mo-based atomically dispersed electrocatalyst, [115] Fe atoms doped TiO 2 , [116] multilayer core-shell oxide/nitride/C catalyst (MoO 2 /Fe 4 N/C), [117] and hierarchical Cu NWs with NiCo layered double hydroxide shell. [118] The variable oxidation states, diverse electronic structures and coordination geometries, high thermal stability and resistance to poisoning by reaction intermediates, the ability of forming ally or bimetallic structures enable transition metal-related tandem catalysts with high potential in electrochemical NO 3 RR.…”

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

“…Meanwhile, the introduction of P 8 W 48 Lewis acid sites further promotes the adsorption of NO 2 − . The CoNi-LDH phase possesses an extremely low energy barrier in the protonation reaction (the rate-determining step), 42 while the P 8 W 48 species can serve as an electron-transfer carrier to further accelerate the reaction kinetics, 37,71…”

“…− + H + → NO 2 H (ads) ). 42 Predictably, the hybrid of P 8 W 48 /CoNi-LDH can simultaneously maintain the excellent electron reservoir ability of P 8 W 48 and good intrinsic electrocatalytic activity of CoNi-LDH. This combination can not only improve the stability of P 8 W 48 , but it is also expected to achieve a synergistic effect between the two components.…”

“…Among these, LDH represents a type of cationic layered material pillared by interlayer anions, where the interlayer anions can be replaced by POM anions and the stable nanocomposites of POM/LDH with high specific surface area can be easily obtained . It is also worth mentioning that CoNi-LDH possesses an extremely low energy barrier of 0.08 eV for the rate-determining step in the NO 2 RR process (NO 2(ads) – + H + → NO 2 H (ads) ) . Predictably, the hybrid of P 8 W 48 /CoNi-LDH can simultaneously maintain the excellent electron reservoir ability of P 8 W 48 and good intrinsic electrocatalytic activity of CoNi-LDH.…”