Electrochemical Reduction Of Nitrate Research Articles

Outside Back Cover: In‐tandem Electrochemical Reduction of Nitrate to Ammonia on Ultrathin‐Sheet‐Assembled Iron–Nickel Alloy Nanoflowers

Outside Back Cover: In‐tandem Electrochemical Reduction of Nitrate to Ammonia on Ultrathin‐Sheet‐Assembled Iron–Nickel Alloy Nanoflowers

Outside Back Cover: In‐tandem Electrochemical Reduction of Nitrate to Ammonia on Ultrathin‐Sheet‐Assembled Iron–Nickel Alloy Nanoflowers

Outside Back Cover: In‐tandem Electrochemical Reduction of Nitrate to Ammonia on Ultrathin‐Sheet‐Assembled Iron–Nickel Alloy Nanoflowers

Revealing the Tandem Behavior of Iron‐Group/Copper Binary Catalysts in the Electroreduction of Nitrate to Ammonia

AbstractAs a green strategy for both ammonia (NH3) production and wastewater purification, electrochemical reduction of nitrate (NO3RR) faces challenges due to the nitrite (NO2−) accumulation and competitive hydrogen evolution reaction (HER). Tandem catalysis (NO3− to NO2− to NH3) offers great potential for enhancing NH3 production and selectivity. Herein, iron‐group (Fe, Co, or Ni) nanosheets are introduced onto Cu nanowires to construct Cu‐Fe, Cu‐Co, and Cu‐Ni tandem systems respectively. Specifically, Cu sites facilitate the conversion of NO3− to NO2−. Fe sites, similar to Cu, reduce NO3− to NO2−, exacerbating NO2− accumulation rather than converting it to NH3, due to their inability to precisely capture NO2−. Co sites, exhibiting excellent NO2− conversion and moderate HER activity, can seamlessly operate with Cu and realize a well‐ordered relay catalysis, which achieves a superior NH3 yield rate of 48.44 mg h−1 cm−2. Ni sites demonstrate superior NO2− removal capability at low overpotentials, leading to NH3 Faraday efficiency of 99.47%. However, its remarkable HER‐active property demonstrated via in situ polarization imaging makes it a challenge at ampere‐level current densities. This work identifies the relay behavior of iron‐group sites coupled with Cu, providing a reference for the design and further optimization of the tandem system.

Copper‐Based Nitrides Outperform Phosphides in Nitrate Electroreduction to Ammonia: The Cooperative Role of the Cu3N/CuO Interface

AbstractBinary compounds consisting of Cu(I) and moderately electronegative elements (N, P) are attractive semiconductors for optoelectronic and electrocatalytic applications. This study investigates the electrochemical reduction of nitrate to ammonia (NO3RR) using copper‐based catalysts, specifically Cu3N and Cu3P. Inhibiting the competitive hydrogen evolution reaction and ensuring active hydrogen (H*) for NH3 production during NO3RR pose significant challenges. Our research demonstrates that while Cu₃P is effective in the initial reduction of nitrate to nitrite, it fails to produce NH₃ at more negative potentials due to competition with the hydrogen evolution reaction (HER). In contrast, Cu₃N exhibits remarkable performance, achieving an ammonia yield rate of 48.8 mmol h−1 mmol−1cat at −0.9 VRHE, accompanied by considerable Faradaic efficiency and durability. The formation of a Cu3N/CuO interface during the catalysis is crucial for its activity, facilitating efficient NO3RR through a stepwise reduction mechanism. The study provides insights into the surface modifications and mechanistic aspects of these catalysts during NO3RR, offering guidance for strategically developing more efficient catalysts for nitrate reduction to ammonia.

2D Catalysts for Electrocatalytic Nitrate Reduction and C–N Coupling Reactions

AbstractPowering the electrochemical nitrate reduction reaction (NO3⁻RR) by renewable energy is a sustainable way to restore the environment and produce nitrogen–hydrogen compounds. However, the process requires multiple electron transfers and complex reaction paths, making it essential to understand the reaction mechanisms at the molecular level. In this regard, 2D materials attract significant interest due to their large surface area, tunable electronic structures, and suitability as model catalysts for studying structure–activity relationships. Advances in the use of 2D materials in the electrocatalytic NO3⁻RR and C–N coupling reactions are analyzed and elucidated the influence of various 2D catalyst design strategies on reaction mechanisms. Using advanced in situ/operando measurement techniques, conducting rigorous theoretical analyses, and scaling up industrial electrolyzers are pivotal to unlocking the practical potential of the NO3⁻RR and beyond. A map for developing next‐generation electrocatalysts and devices is provided to enable a sustainable and efficient nitrogen cycle using electrocatalysis.

Integrated Three-in-one to Boost Nitrate Electroreduction to Ammonia Utilizing a 1D Mesoporous Carbon Cascade Nanoreactor.

The electrochemical reduction of nitrate (NO3-) offers a promising waste-to-value strategy for synthesizing ammonia (NH3), yet it involves a complex multi-interface system with several stages such as mass transport, species enrichment, and interfacial transformation. This complexity necessitates catalysts with diverse structural characteristics across multiple temporal and spatial scales. Herein, a three-in-one nanoreactor system is designed with 1D geometry, open mesochannels, and synergistic active sites for optimized NH3 synthesis. Guided by finite element simulations, a 1D mesoporous carbon carrier is engineered to create a distinctive microenvironment that enhances NO3- transfer and adsorption while confining reaction intermediates. Meanwhile, iron single atomic sites (Fe-N4 SAs) and iron nanoclusters (Fe4 NCs) are embedded in situ into the carbon carrier, yielding an efficient cascade nanoreactor. This design demonstrates large Faraday efficiencies, rapid NO3- removal rates, and impressive NH3 yield rates under both neutral and alkaline conditions. Detailed in situ experimental results and theoretical analysis reveal that Fe-N4 SAs and Fe4 NCs can adapt their electronic structures in tandem, allowing the Fe-N4 SAs to effectively reduce NO3- and Fe4 NCs to oxidize H2O. As a demonstration, the assembled Zn-NO3- battery achieves a power density of 20.12 mW cm-2 coupled with excellent rechargeability.

Porphyrin-Based Conductive Polymer Derived from Tetrakis[biphenyl-bis(bithiophene)] Porphyrinato Cobalt(II) for Efficient Electrochemical Nitrate Reduction to Ammonia.

Electrochemical nitrate reduction reaction is a sustainable pollutant remedy tool and offers wider application for green ammonia production. The overall electrochemical reaction mostly depends on the electrode material, which thus requires a highly active and efficient electrocatalyst that is both green and cost-effective. Here, we show electropolymerized cobalt porphyrin-containing tetrakis-biphenyl-bis(bithiophene) entities as efficient electrocatalysts for ammonia production via electrochemical nitrate reduction. The newly developed electrocatalyst was able to achieve a high Faradaic efficiency of 92.7% at -0.4 V vs. Ag/AgCl for ammonia production with very low production of other side products and exhibited long-term durability without any significant physical and chemical deterioration. Experimental findings were well-supported by DFT calculations.

Electrodeposited P-Doped CuNi Alloy from Deep Eutectic Solvent for Efficient and Selective Nitrate-to-Ammonia Electroreduction.

Electrochemical nitrate reduction reaction (NO3RR) offers a promising alternative for ammonia production using electricity generated from renewable energy sources. Active electrocatalysts with high selectivity and high yield are required to selectively catalyze NO3RR to ammonia. Here, P-doped Cu0.51Ni0.49 alloy thin films are electrodeposited from a deep eutectic solvent of choline chloride-ethylene glycol (ChCl/EG). The P-Cu0.51Ni0.49 produces 1616.94µg h-1 cm-2 of ammonia at -0.55 VRHE (V versus reversible hydrogen electrode), with a Faradaic efficiency of 98.38% and ammonia selectivity of 97.84% at -0.25 VRHE, much better than the P-Ni and P-Cu prepared under similar condition. The high ammonia production rate, Faradaic efficiency and selectivity are originated from high number of electrochemically active sites and more facile kinetics. Mechanistic study and density functional theory calculation proves that P-Cu0.51Ni0.49 exhibits higher conductivity and more facile NO3 - adsorption compared to P-Ni and P-Cu, induced by the electron interaction. Characterizations after NO3RR cycling show that the crystallinity of P-Cu0.51Ni0.49 decreases, with the content of divalent metal ions increases at the surface. The P-Cu0.51Ni0.49 is an active and stable material to electrocatalyze NO3RR to ammonia in neutral aqueous solutions.

Promoting *NO2 Hydrogeneration on Cobalt-Doped Copper Oxides for Selective Ammonia Electrosynthesis from Nitrate.

Electrochemical nitrate reduction reaction (NO3RR) driven by renewable energy has attracted extensive attention, which can realize nitrate degradation and ammonia production simultaneously under ambient conditions. Copper-based catalysts are the most widely used due to their high activity but are subject to low selectivity owing to intermediate nitrite accumulation. This work has reported cobalt-doped copper oxide (Co/CuO) composites, while introduced Co sites accelerate the hydrogenation of nitrogen species. The prepared Co/CuO composites realize a 93.9 % Faradaic efficiency at the applied potential of -0.4 V (vs. RHE), yielding ammonia at 0.5441 mmol⋅h-1 cm-2. The exceptional stability of Co/CuO composites has also been affirmed by following continuous recycling tests. In situ characterization confirms that the existence of Co sites is prone to conversion of *NO2 to *NH2, thus exhibiting high performance for NO3RR.

Tailoring asymmetric RuCu dual-atom electrocatalyst toward ammonia synthesis from nitrate

Atomically dispersed Ru-Cu dual-atom catalysts (DACs) with asymmetric coordination are critical for sustainable ammonia production via electrochemical nitrate reduction (NO3RR), but their rational synthesis remains challenging. Here, we report a pulsed discharge strategy that injects a microsecond pulse current into ruthenium (Ru) and copper (Cu) precursors supported by nitrogen-doped graphene aerogels (NGA). The atomically dispersed Ru and Cu dual atoms anchor onto nanopore defects of NGA (RuCu DAs/NGA) through explosive decomposition of the metal salt nanocrystals. The catalyst achieves 95.7% Faraday efficiency and 3.1 mg h−1 cm−2 NH3 yield at −0.4 V vs. RHE. In situ studies reveal an asymmetric RuN2-CuN3 active-site dynamic evolution during NO3RR. Density functional theory calculations demonstrate that asymmetric RuN2CuN3/C structure synergistically optimizes intermediate adsorption and reduces energy barriers of key steps. The pulsed discharge enables ultrafast synthesis of various DACs (e.g., PtCu, AgCu, PdCu, FeCu, CoCu, NiCu) with tailored coordination environments, offering a general-purpose strategy for the precise preparation of atomically dispersed dual-atom catalysts, which are traditionally challenging to synthesize.

Highly defective Cu5FeS4/MnO2 catalyst: An innovation on sustainable ammonia production via electrochemical nitrate reduction

Highly defective Cu5FeS4/MnO2 catalyst: An innovation on sustainable ammonia production via electrochemical nitrate reduction

Electroreduces nitrate to ammonia and converts to nitrogen through chloride ions by Co3O4/GF cathode: Performance, regulation and mechanism.

Electroreduces nitrate to ammonia and converts to nitrogen through chloride ions by Co3O4/GF cathode: Performance, regulation and mechanism.

The breaking of charge symmetry at the M-site in octahedral units of KMF3 perovskite induces enhanced electrochemical nitrate reduction in ammonia.

The breaking of charge symmetry at the M-site in octahedral units of KMF3 perovskite induces enhanced electrochemical nitrate reduction in ammonia.

A Cu/Fe3O4@CN tandem catalyst for efficient ammonia electrosynthesis from nitrate reduction

A Cu/Fe3O4@CN tandem catalyst for efficient ammonia electrosynthesis from nitrate reduction

Synergistic Cu/Cu2O/Co3O4 catalyst with crystalline-amorphous interfaces for efficient electrochemical nitrate reduction to ammonia

Synergistic Cu/Cu2O/Co3O4 catalyst with crystalline-amorphous interfaces for efficient electrochemical nitrate reduction to ammonia

Self-Triggering a Locally Alkaline Microenvironment of Co4Fe6 for Highly Efficient Neutral Ammonia Electrosynthesis.

Electrochemical nitrate reduction reaction (eNO3-RR) to ammonia (NH3) holds great promise for the green treatment of NO3- and ambient NH3 synthesis. Although Fe-based electrocatalysts have emerged as promising alternatives, their excellent eNO3-RR-to-NH3 activity is usually limited to harsh alkaline electrolytes or alloying noble metals with Fe in sustainable neutral electrolytes. Herein, we demonstrate an unusual self-triggering localized alkalinity of the Co4Fe6 electrocatalyst for efficient eNO3-RR-to-NH3 activity in neutral media, which breaks down the conventional pH-dependent kinetics restrictions and shows a 98.6% NH3 Faradaic efficiency (FE) and 99.9% NH3 selectivity at -0.69 V vs RHE. The synergetic Co-Fe dual sites were demonstrated to enable the optimal free energies of eNO3-RR-to-NH3 species and balance water dissociation and protonation of adsorbed NO2-. Notably, the Co4Fe6 electrocatalysts can attain a high current density of 100 mA cm-2 with a high NH3 FE surpassing 96% and long-term stability for over 500 h eNO3-RR-to-NH3 in a membrane electrode assembly (MEA) electrolyzer. This work provides insight into tailoring the self-reinforced local-alkalinity on the Fe-based alloy electrocatalysts for eNO3-RR-to-NH3 and thus avoids alkaline electrolytes and noble metals for practical sustainable nitrate upcycling technology.

Maximizing Available Active Hydrogen on FeNi Substitutional Solid-Solution Alloy to Boost Electrosynthesis of Ammonia from Nitrate.

Electrochemical nitrate reduction reaction (NO3RR) stands out as a promising route for sustainable ammonia synthesis, in which active hydrogen (*H) plays a crucial role in both the deoxygenation and hydrogenation steps. However, the regulation of surface *H is still overlooked, and without intervention, the competing hydrogen evolution reaction is kinetically more favored over the NO3RR, leaving the current system as far from satisfactory. Herein, based on reverse utilization of the Sabatier principle, a series of FexNiy substitutional solid-solution alloys (SSAs) are synthesized to manipulate *H behavior for enhanced NO3RR. Upon precise optimization of the alloy composition, the d-band center of HER-active Ni shifts toward the Fermi level, endowing the catalyst with strong interaction to *H and greatly prolonging its lifetime, which enables abundant supply to facilitate the NO3RR. As expected, a maximum NH3 yield rate of 31.46 mmol h-1 mg-1 is delivered over the optimized Fe3Ni1-SSA, which is considerably higher than most of the extensively reported works. Several in situ characterizations are combined to gain in-depth insight. Especially, in situ Fourier transform infrared spectroscopy in internal reflection mode directly observes *H enrichment on the catalyst surface, while the accompanied facilitation of the NO3RR process is verified by external reflection mode.

Periodic Table Exploration of MXenes for Efficient Electrochemical Nitrate Reduction to Ammonia.

Applying electrochemical nitrate reduction reaction (NO3RR) to produce ammonia offers a sustainable alternative to the energy-intensive Haber-Bosch process, which is crucial for clean energy and agricultural applications. While 2D MXenes hold great promise as electrocatalysts for NO3RR, their application for ammonia production remains underexplored. This study combines experimental and theoretical approaches to evaluate the catalytic performance of a series of MXenes with different central metal atoms for NO3RR. Among the materials studied (Ti3C2Tx, Ti3CNTx, Ti2CTx, V2CTx, Cr2CTx, Nb2CTx, and Ta2CTx), Ti3-based MXenes exhibit superior faradaic efficiency, ammonia yield rate, and stability. Density functional theory calculations offer further insights explaining the structure-activity-based observations. This research establishes a foundation for future studies aimed at leveraging MXenes for electrochemical nitrate reduction for green synthesis of ammonia.

In‐tandem Electrochemical Reduction of Nitrate to Ammonia on Ultrathin‐Sheet‐Assembled Iron‐Nickel Alloy Nanoflowers

AbstractThe development of alternative routes for ammonia (NH3) synthesis with high Faradaic efficiency (FE) is crucial for energy conservation and to achieve zero carbon emissions. Electrocatalytic nitrate (NO3−) reduction to NH3 (e‐NO3RRA) is a promising alternative to the energy‐intensive, fossil‐fuel‐driven Haber–Bosch process. The implementation of this innovative NH3 synthesis technique requires an efficient electrocatalyst and in‐depth mechanistic understanding of e‐NO3RRA. In this study, we developed an ultrathin sheet (μm) iron–nickel nanoflower alloy through electrodeposition and used it for e‐NO3RRA under alkaline conditions. The prepared Fe−Ni alloy exhibited an FE of 97.28±1.36 % at −238 mVRHE and an NH3 yield rate up to 3999.1±242.59 μg h−1 cm−2. Experimental electrolysis, in situ Raman spectroscopy, and density functional theory calculations showed that the adsorption and reduction of NO3− to NO2− occurred on the Fe surface, whereas subsequent hydrogenation of NO2− to NH3 occurred preferentially on the Ni surface. The catalysts exhibited comparable FE for at least 10 cycles, with a long‐term stability of 216 h. Electron paramagnetic resonance results confirmed that adsorbed hydrogen was consumed during e‐NO3RRA. This work introduces a sustainable, robust, and efficient Fe−Ni alloy electrocatalyst, offering an environmentally friendly approach for synthesizing NH3 from NO3−‐contaminated water.

In-tandem Electrochemical Reduction of Nitrate to Ammonia on Ultrathin-Sheet-Assembled Iron-Nickel Alloy Nanoflowers.

The development of alternative routes for ammonia (NH3) synthesis with high Faradaic efficiency (FE) is crucial for energy conservation and to achieve zero carbon emissions. Electrocatalytic nitrate (NO3-) reduction to NH3 (e-NO3RRA) is a promising alternative to the energy-intensive, fossil-fuel-driven Haber-Bosch process. The implementation of this innovative NH3 synthesis technique requires an efficient electrocatalyst and in-depth mechanistic understanding of e-NO3RRA. In this study, we developed an ultrathin sheet (µm) iron-nickel nanoflower alloy through electrodeposition and used it for e-NO3RRA under alkaline conditions. The prepared Fe-Ni alloy exhibited an FE of 97.28 ± 1.36% at -238 mVRHE with an NH3 yield rate of 3999.1 ± 242.59 mg h-1 cm-2. Experimental electrolysis, in-situ Raman spectroscopy, and density functional theory calculations showed that the adsorption and reduction of NO3- to NO2- occurred on the Fe surface, whereas subsequent hydrogenation of NO2- to NH3 occurred preferentially on the Ni surface. The catalysts exhibited comparable FE for at least 10 cycles, with a long-term stability of 216 h. Electron paramagnetic resonance results confirmed that adsorbed hydrogen was consumed during e-NO3RRA. This work introduces a sustainable, robust, and efficient Fe-Ni alloy electrocatalyst, offering an environmentally friendly approach for synthesizing NH3 from NO3--contaminated water.