Electrocatalytic Reduction Of Nitrate Research Articles

Co-Carbonization of Straw and ZIF-67 to the Co/Biomass Carbon for Electrocatalytic Nitrate Reduction

Electrocatalytic nitrate reduction enables the recovery of nitrate from water under mild conditions and generates ammonia for nitrogen fertilizer feedstock in an economical and green means. In this paper, Co/biomass carbon (Co/BC) composite catalysts were prepared by co-carbonization of straw and metal–organic framework material ZIF-67 for electrocatalytic nitrate reduction using hydrothermal and annealing methods. The metal–organic framework structure disperses the catalyst components well and provides a wider specific surface area, which is conducive to the adsorption of nitrate and the provision of more reactive active sites. The introduction of biomass carbon additionally enhances the electrical conductivity of the catalyst and facilitates electron transport. After electrochemical testing, Co/BC-100 exhibited the best performance in electrocatalytic nitrate reduction to ammonia, with an ammonia yield of 3588.92 mmol gcat.−1 h−1 and faradaic efficiency of 97.01% at −0.5 V vs. RHE potential. This study provides a promising approach for the construction of other efficient cobalt-based electrocatalysts.

Amorphous Ni3B Promotes Electroreduction of Nitrate to Ammonia.

The electrocatalytic nitrate reduction to ammonia (NRA) can address nitrogen cycle imbalance and high carbon emissions; however, the intense competition of hydrogen evolution reaction (HER) restricts the rate of NH3 production. Herein, amorphous Ni3B (a-Ni3B) is designed to balance the NRA and HER. The NH3 yield of a-Ni3B surpasses those of pure Ni and NiO, which is attributed to the preferential adsorption of NO3- on the B and Ni sites of a-Ni3B for the NRA reaction, greatly inhibiting the HER. Furthermore, the a-Ni3B possesses advantages in NRA performance compared to crystalline Ni3B (c-Ni3B) due to more active hydrogen (*H) generated during the catalytic process. The *H in the NRA process on a-Ni3B is verified by the electron spin resonance technique. The NRA mechanism is comprehensively discussed based on the results of in situ characterization and density functional theory calculations. The a-Ni3B can enhance NH3 production by inhibiting HER, which provides ideas for sustainable NH3 synthesis.

Electrochemical Synthesis of Metasequoia-Like Reduced Graphene Oxide Coated Cobalt-Silver Catalyst for Stable and Efficient Electrocatalytic Nitrate Reduction to Ammonia.

Electrocatalytic nitrate (NO3 -) reduction to ammonia (NH3) is a green and efficient NH3synthesis technology. Metallic silver (Ag) is one of the well-known electrocatalysts for NO3 - reduction. However, under alkaline conditions, its poor water-splitting ability fails to provide sufficient protonic hydrogen required for NH3 synthesis, resulting in low NH3 selectivity. Additionally, metal catalysts are prone to leaching and oxidation during electrocatalysis, resulting in poor stability. Herein, cobalt (Co) into Ag (CoAg) catalyst is doped, which not only increases the NH3 selectivity by 34.4%, but also reduces the reduction potential by 0.1V. Meanwhile, reduced graphene oxide (rGO) as a protective "armor" is used to encapsulate the CoAg catalyst (rGO2.92@CoAg). The rGO2.92@CoAg catalyst shows excellent stability for over 300 hours (h) of continuous reaction. The Co and Ag contents in the rGO2.92@CoAg catalyst after continuous tests decreases by only 4.3% and 3.1%, respectively, which are much lower than those of the CoAg catalyst without the rGO (90.8%, 52.6%). Moreover, the rGO2.92@CoAg catalyst shows high Faradaic efficiency (99.3%) and NH3 yield rate (1.47mmol h-1 cm-2). Therefore, a high performance and strong stability rGO2.92@CoAg catalyst is obtained by Co doping and rGO coating, which provides theoretical basis for practical industrial application.

Nitrite-Mediated Pulsed Electrocatalytic Nitrate Reduction to Ammonia over Co@Cu NW with Dual Active Sites

Nitrite-Mediated Pulsed Electrocatalytic Nitrate Reduction to Ammonia over Co@Cu NW with Dual Active Sites

In situRaman investigation to electrochemical synthesis of ammonia on Pd nanocrystals.

Nitrate and nitrite are widely present in industrial wastewater and domestic sewage, so electrocatalytic reduction of both nitrate and nitrite to ammonia synthesis is considered to be a sustainable development approach. Pd nanostructures have attracted much attention because of their high activity in catalyzing the nitrate electrochemical reduction reaction. Here we prepare Pd nanocube and octahedron for the electrochemical reduction of nitrate and nitrite. It is found that Pd octahedron shows slightly higher activity toward nitrate reduction than Pd nanocube, while for nitrite reduction, Pd octahedron shows much higher activity than Pd nanocube. The ammonia yield rate is more potential-dependent.In situRaman characterization further confirms the existence of adsorbed ammonia on the surface of nanocube and octahedron, indicating similar reduction pathways on (111)-facet octahedron and (100)-facet nanocube.

Vapor-Phase Hydrothermal Construction of Dispersed Au on Carbon Felt for Electrocatalytic Nitrate Reduction to Ammonia

Vapor-Phase Hydrothermal Construction of Dispersed Au on Carbon Felt for Electrocatalytic Nitrate Reduction to Ammonia

Transition metal atoms embedded graphyne as effective catalysts for nitrate electroreduction to ammonia: A theoretical study

Electrocatalytic nitrate reduction reaction (NO3RR) to ammonia has been proved to be a viable approach to dispose of nitrates pollution and simultaneously fabricate valuable ammonia at room temperature and pressure. It is essential to explore high-performance and selective electrocatalysts for NO3RR to overcome the sluggish kinetics. Herein, through adopting a four-step screening route based upon the calculation of density functional theory (DFT), we have performed a comprehensive investigation on the NO3RR catalytic activities for single-atom catalysts (SACs), taking transition metal atom embedded graphyne (TM-GY, TM = 3d ∼ 5d) as example. The computation results show that the electrochemical conversion of nitrate-to-ammonia can be realized on Cr-GY candidate with an extremely low limiting potential (-0.36 V) and high selectivity, which can be ascribed to the moderate adsorption strength between the intermediate species and Cr atom derived from its distinct electronic property. Our study not only reveals the NO3RR catalytic origin of TM-GY, but also provides a new route for the rational design of electrocatalysts for nitrate reduction to ammonia.

Electrocatalytic reduction of nitrate using Mg(OH)2 copper modified electrode

Electrocatalytic reduction of nitrate using Mg(OH)2 copper modified electrode

Coherent NiS2@SnS2nanosheet for accelerating electrocatalytic nitrate reduction to ammonia.

The development of an effective and selective catalyst is the key to improving the multi-electron transfer nitrate reduction reaction (NO3-RR) to ammonia. Here, we synthesized a coherent NiS2@SnS2nanosheet catalyst loaded on carbon cloth via one-step solvothermal method. Experimental data reveals that the integration of NiS2and SnS2can enhance the NO3-RR performance in terms of high NH3yield rate of 408.2μg h-1cm-2and Faradaic efficiency of 89.61%, as well as satisfying cycling and long-time stability.

A GO regulated bimetallic CoFe catalyst for efficient electrochemical nitrate reduction to ammonia under acidic conditions.

Electrocatalytic nitrate reduction to ammonia (ENRA) in acidic media is currently a challenge. Herein, we presented a CoFe2O4/GO catalyst that exhibited a high faradaic efficiency (95.51%) and ammonia yield rate (1268.04 μmol h-1 cm-2) for ENRA under acidic conditions. The ENRA reaction mechanism was investigated through in situ ATR-FTIR spectroscopy and isotope labeling experiments.

Enrichment of Active Hydrogen at Amorphous CoO/Cu2O Heterojunction Interfaces Enhances Electrocatalytic Nitrate Reduction to Ammonia.

The reduction of nitrate into valuable ammonia via electrocatalysis offers a green and sustainable synthetic pathway for ammonia. The electrocatalytic nitrate reduction reaction (NO3RR) encompasses two crucial reaction steps: nitrate deoxygenation and nitrite hydrogenation. Notably, the nitrite hydrogenation reaction is regarded as the rate-determining step of the process. Herein, the amorphous CoO support introduced for the construction of the a-CoO/Cu2O tandem catalyst provides sufficient active hydrogen and synergistically catalyzes the NO3RR. The a-CoO/Cu2O catalyst showed excellent performance with a maximum NH3 Faradaic efficiency of 95.72% and a maximum yield rate of 0.96mmol h-1 mgcat -1 at -0.4V. In the flow cell, the maximum NH3 yield rate of 12.14mmol h-1 mgcat -1 is achieved at -800mA. The high NO3RR activity of a-CoO/Cu2O is attributed to the synergistic cascade effect of amorphous CoO and Cu2O at the heterojunction interface, where Cu2O serves as the adsorption site for NO3 -, while the accelerated active hydrogen generation of amorphous CoO promotes the nitrite hydrogenation reaction. This work provides a strategy for designing multi-site cascade catalysts centered on amorphous structures to achieve efficient NO3RR.

Electrochemical production of ammonia: Nitrate reduction over novel Cu-Ni-Al metallic glass nanoparticles used as highly active and durable catalyst

It is a great challenge to design and synthesize catalysts that can regulate both adsorption and desorption processes for electrocatalytic nitrate reduction to ammonia (NRA). Herein, amorphous Cu-Ni-Al nanometallic glasses (NG) were synthesized using a facile thermal evaporation coupled Joule heating method. The Cu50Ni25Al25-NG exhibits remarkable Faradaic efficiency (98.81 %) and NH3 yield-rate (211.14 μmol h−1cm−2) at an outstanding positive potential of −0.15 V vs. RHE. Aluminum atoms of low work-function when intercalated at different positions in Cu50Ni25Al25-NG enhance both adsorption and desorption processes during NRA. The oscillatory properties of surface potential detected by Kelvin-probe force microscopy demonstrate the diversity of active sites on Cu50Ni25Al25-NG. Two potential-regulated reaction mechanisms in NRA on the surface of Cu50Ni25Al25-NG were proposed using in-situ electrochemical Raman spectra. This work provides a new method for the preparation of multi-element NG enriched with low work-function metals and a new idea for the synthesis of synergistic catalytic-sites for NRAs.

Role of electrons and H* in electrocatalytic nitrate reduction to ammonium for CuNi alloy

Electrocatalytic reduction of nitrate (NO3-) to ammonium (NH4+) is an environment friendly approach for treating nitrogen-containing wastewater. Consequently, electrocatalysts capable of effectively and selectively reducing NO3- to NH4+ receives growing attention. However, Cu-based catalysts demonstrate limited efficiency and the drawback of generating toxic NO2- though it is prevalent in the field of electrocatalytic reduction of NO3- (NO3RR). In this work, a CuNi alloy was synthesized on a Co foil through electrodeposition (marked as CuNi@Co) and its electrocatalytic performance for NO3RR was evaluated. XRD, EDS mapping and XPS characterization indicate CuNi exists with alloy state. Electrocatalytic experiments demonstrate that CuNi@Co exhibits an exceptional FENH3 of 99.12% at -0.64 V (vs. RHE). Importantly, no detrimental NO2- generated during NO3RR process because the reduction rate from NO2- to NH4+ is faster than that from NO3- to NO2-. Mechanistic analysis suggests that Cu serves as a ‘reservoir’ to provide electrons to facilitate the reduction of NO3- to NO2- during NO3RR process and the synergistic effect of Ni and Cu promotes more active hydrogen (H*) to participate the reduction process of NO2- to NH4+ not H2 generation, ultimately improving FENH3. This work elucidates the role of electrons and H* in electrocatalytic nitrate reduction to ammonium for CuNi alloy, providing new insights into the reduction process of NO3RR for Cu-based materials.

Reversible Hydrogen Acceptor-Donor Enables Relay Mechanism for Nitrate-to-Ammonia Electrocatalysis.

Electrocatalytic nitrate reduction is a crucial process for sustainable ammonia production. However, to maximize ammonia yield efficiency, this technology inevitably operates at the potentials more negative than 0 V vs. RHE, leading to high energy consumption and competitive hydrogen evolution.To eradicate this issue, hydrogen tungsten bronze (HxWO3) as reversible hydrogen donor-acceptor is partnered with copper (Cu) to enable a relay mechanism at potentials positive than 0 V vs. RHE, which involves rapid intercalation of H into HxWO3 lattice, prompt de-intercalation of the lattice H and transfer onto Cu, and spontaneous H-mediated nitrate-to-ammonia conversion on Cu.The resulting catalysts demonstrated a high ammonia yield rate of 3332.9±34.1 mmol gcat-1 h-1 and a Faraday efficiency of ~100 % at 0.10 V vs. RHE, displaying a record-low estimated energy consumption of 17.6 kWh kgammonia-1. Using these catalysts, we achieve continuous ammonia production in an enlarged flow cell at a real energy consumption of 17.0 kWh kgammonia-1.

Reversible Hydrogen Acceptor–Donor Enables Relay Mechanism for Nitrate‐to‐Ammonia Electrocatalysis

Electrocatalytic nitrate reduction is a crucial process for sustainable ammonia production. However, to maximize ammonia yield efficiency, this technology inevitably operates at the potentials more negative than 0 V vs. RHE, leading to high energy consumption and competitive hydrogen evolution. To eradicate this issue, hydrogen tungsten bronze (HxWO3) as reversible hydrogen donor‐acceptor is partnered with copper (Cu) to enable a relay mechanism at potentials positive than 0 V vs. RHE, which involves rapid intercalation of H into HxWO3 lattice, prompt de‐intercalation of the lattice H and transfer onto Cu, and spontaneous H‐mediated nitrate‐to‐ammonia conversion on Cu. The resulting catalysts demonstrated a high ammonia yield rate of 3332.9±34.1 mmol gcat−1 h−1 and a Faraday efficiency of ~100 % at 0.10 V vs. RHE, displaying a record‐low estimated energy consumption of 17.6 kWh kgammonia−1. Using these catalysts, we achieve continuous ammonia production in an enlarged flow cell at a real energy consumption of 17.0 kWh kgammonia−1.

Enhanced ammonia electrosynthesis over phosphorus-doped nickel across broad nitrate concentrations via regulating trade-offs in pathways

Electrocatalytic nitrate reduction reaction (NO3RR) holds promise for carbon-neutral ammonia production but requires efficient electrodes to minimize the formation of nitrite and hydrogen by-products, from either concentrated or dilute feedstocks. Here, we report a trade-off effect upon phosphorus incorporation into Ni, wherein Ni- and P-rich surfaces tend to inhibit nitrite and hydrogen formation, respectively, while promoting the generation of the respective opposite by- products. Under 0.1 M nitrate concentration, the selectivity switch between the by-products presented a correlation with the intrinsic HER activity of surfaces, highlighting the critical role of *H supply. Through ex-situ and in-situ spectroscopies, the reconstructed P-doped Ni (R-NiP) was found to exhibit an oxidation state and local atomic environment intermediate between those of Ni and P-doped Ni (NiP), effectively integrating the suppressing traits of both Ni and P. Consequently, an ammonia Faradaic efficiency of 89 % was achieved at a reduced potential on R-NiP, along with a 2- and 8-fold enhancement in intrinsic activity compared to NiP and Ni, respectively. By leveraging this trade-off, we also showcase the adaptability of NiP platform for effective operation across both lower and higher nitrate concentrations, emphasizing that nitrate bulk concentration should be factored in when regulating *H supply for efficient ammonia electrosynthesis.

Integrating few-atom layer metal on high-entropy alloys to catalyze nitrate reduction in tandem

While high-entropy alloy (HEA) catalysts seem to have the potential to break linear scaling relationships (LSRs) due to their structural complexity, the weighted averaging of properties among multiple principal components actually makes it challenging to diverge from the symmetry dependencies imposed by the LSRs. Herein, we develop a ‘surface entropy reduction’ method to induce the exsolution of a component with weak affinity for others, resulting in the formation of few-atom-layer metal (FL-M) on the surface of HEAs. These exsolved FL-M surpass the confines of the original configurational space of conventional HEAs, and collaborate with the HEA substrate, serving as geometrically separated active sites for multiple intermediates in a complex reaction. This FL-M-covered HEA shows an outstanding performance for electrocatalytic reduction of nitrate to ammonia (NH3) with a Faradaic efficiency of 92.7%, an NH3 yield rate of 2.45 mmol h–1 mgcat.–1, and high long-term stability (>200 h). Our work achieves the precise manipulation of atomic arrangement, thereby expanding both the chemical space occupied by known HEA catalysts and their potential application scenarios.

Highly Efficient Electrocatalytic Nitrate Reduction to Ammonia: Group VIII-Based Catalysts.

The accumulation of nitrates in the environment causes serious health and environmental problems. The electrochemical nitrate reduction reaction (e-NO3RR) has received attention for its ability to convert nitrate to value-added ammonia with renewable energy. The key to effective catalytic efficiency is the choice of materials. Group VIII-based catalysts demonstrate great potential for application in e-NO3RR because of their high activity, low cost, and good electron transfer capability. This review summarizes the Group VIII catalysts, including monatomic, bimetallic, oxides, phosphides, and other composites. On this basis, strategies to enhance the intrinsic activity of the catalysts through coordination environment modulation, synergistic effects, defect engineering and hybridization are discussed. Meanwhile, the ammonia recovery process is summarized. Finally, the current research status in this field is prospected and summarized. This review aims to realize the large-scale application of nitrate electrocatalytic reduction in industrial wastewater.

Tuned targeted catalytic engineering enables high-selective electrochemical low-concentration nitrate-to-ammonia

Electrocatalytic nitrate reduction reaction (NO3RR) is anticipated to enable utilization of NO3- from wastewater, providing a prospective solution to address global nitrogen-cycle imbalance. Nevertheless, high-selective conversion of low-concentration NO3--to-NH3 in non-alkaline environment remains challenging, stemming from kinetic retardation and hydrogen evolution reaction (HER). Herein, a targeted synergistic-cascade strategy is proven for breaking through the bottleneck. Significantly, the rationally-designed asymmetric oxygen vacancies (VO)-mediated Cu-Co dual-site catalyst achieve a NH3 selectivity of 95.79 % and a NH3-N yield of 1.528 mg h−1 cm−2 under 140 ppm NO3--N environment. The mitigation of kinetic bottlenecks is attributed to the NO3- activation capability of Cu sites and intermediate hydrogenation of Co sites on the optimized cascade catalytic system. Density functional theory (DFT) reveals that the asymmetric VO fine-tuned the electronic structure and d-band center of Cu-Co dual-sites, which synergistically reduce the energy barrier of NO3RR and alleviate the competing HER. An integrated system is constructed for the in situ conversion of NO3- to ammonium sulfate under low NO3--N concentration water body, showcasing the potential for practical application.

Rapid Fabrication of N-, Cu-, and Co-Doped Electrodes with Strong Electronic Coupling by Cold Plasma for Electrocatalytic Reduction of Nitrate to Ammonia.

Electrochemical NOx- reduction (NOxRR) is a sustainable technology for ammonia synthesis. The development of a simple, fast, and economical catalytic electrode preparation technique is crucial for large-scale ammonia synthesis. Herein, we propose a plate-to-plate DBD plasma strategy to synthesize the catalytic electrodes M-N/CP (M = Cu, Co, Ni, CuCo, and CuNi), achieving in suit codoping of N and bimetals on carbon paper (CP) at room temperature within 3 h. N-doping improves the metal loading and the NOxRR performance by forming N-M bonds. The electronic coupling and synergistic effect of Cu and Co sites facilitate the relay conversion of NO3- to NO2- to NH3. Notably, the NO3- removal efficiency of CuCo-N/CP reaches 82%, with NH3 yield rate of 346 μg h-1 cm-2, and the faradaic efficiency is as high as 86% at -0.58 V vs RHE, which remains competitive in terms of NOxRR performance. Importantly, wet flue gas denitrification and desulfurization coupled with electrocatalytic reduction can convert NOx and SO2 to (NH4)2SO4, Additionally, the maneuverability of plasma technology offers the potential for batch preparation of CuCo-N/CP electrodes for electrochemically driven wet denitrification wastewater valorization.