Anodic Current Research Articles

Ammonia electrosynthesis from nitrate using a stable amorphous/crystalline dual-phase Cu catalyst

Renewable energy-driven electrocatalytic nitrate reduction reaction presents a low-carbon and sustainable route for ammonia synthesis under mild conditions. Yet, the practical application of this process is currently hindered by unsatisfactory electrocatalytic activity and long-term stability. Herein we achieve high-rate ammonia electrosynthesis using a stable amorphous/crystalline dual-phase Cu catalyst. The ammonia partial current density and formation rate reach 3.33 ± 0.005 A cm−2 and 15.5 ± 0.02 mmol h−1 cm−2 at a low cell voltage of 2.6 ± 0.01 V, respectively. Remarkably, the dual-phase Cu catalyst can maintain stable ammonia production with a Faradaic efficiency of around 90% at a high current density of 1.5 A cm−2 for up to 300 h. A scale-up demonstration with an electrode size of 100 cm2 achieves an ammonia formation rate as high as 11.9 ± 0.5 g h−1 at a total current of 160 A. The impressive electrocatalytic performance is ascribed to the presence of stable amorphous Cu domains which promote the adsorption and hydrogenation of nitrogen-containing intermediates, thus improving reaction kinetics for ammonia formation. This work underscores the importance of stabilizing metastable amorphous structures for improving electrocatalytic reactivity and long-term stability.

Fluorine Doping-Assisted Reconstruction of Isolated Cu Sites for CO2 Electroreduction Toward Multicarbon Products.

The electrocatalytic synthesis of multicarbon compounds from CO2 is a promising method for storing renewable electricity and addressing global CO2 issues. Single-atom catalysts are promising candidates for CO2 reduction, but producing high-value multicarbon (C2+) products using a single-atom structure remains a significant challenge. In this study, a fluorine doping strategy is proposed to facilitate the reconstruction of isolated Cu atoms, promoting multicarbon generation. The in situ formed Cu nanocrystals contain a substantial amount of stable Cu+ species, demonstrating remarkable activity for CO2-to-multicarbon conversion. Notably, they achieve the highest Cu utilization, with a C2+ partial current density of -2.01 A mgper Cu -1and a C2+ formation rate of 7.03mmol h-1 mgper Cu -1at ≈-1V versus RHE. In situ Raman spectroscopy and density functional theory calculations confirm the crucial role of fluorine atoms in structural evolution and electrolysis.

Regulating Asymmetric C–C Coupling with Interfacial Alkalinity for Efficient CO2 to C2+ Electroconversion

AbstractThe electrocatalytic reduction of CO2 in neutral electrolytes is a promising avenue to minimize energy losses linked to carbonate formation. However, selectivity for multi‐carbon (C2+) products is hampered by kinetic barriers in C–C coupling. Here, the regulation of asymmetric C–C coupling is achieved with interfacial alkalinity, facilitating efficient CO2 to C2+ electroconversion. This is realized by co‐engineering copper electrodes with ZrO2 sites and CeOx sites to enable a favorable microenvironment that greatly boosts intrinsic catalytic activity. In situ spectroscopic results and theoretical analyses demonstrates that CeOx facilitates the dissociation of H2O into *H and *OH, effectively regulating *H coverage at the catalytic interface and promoting the protonation of *CO to *COH. Meanwhile, ZrO2 sites significantly enhance the adsorption of in situ‐produced *OH, optimize the local pH on the Cu surface, and enable the formation of C2+ products via a low‐energy *OC–COH coupling pathway. A notable CO2 to C2+ electroconversion in 1.0 M KCl electrolyte, with Faraday efficiency of 67.2 ± 2.1% and a partial current density of 413.0 ± 9.9 mA cm−2 is achieved. This synergistic enhancement of hydroxyl adsorption and stabilization at the catalytic interface, driven by the activation of H2O, is crucial for boosting the overall catalytic performance of the system.

Atomically Dispersed Ni-N-C Catalysts for Electrochemical CO2 Reduction.

The atomic dispersion of nickel in Ni-N-C catalysts is key for the selective generation of carbon monoxide through the electrochemical carbon dioxide reduction reaction (CO2RR). Herein, the study reports a highly selective, atomically dispersed Ni1.0%-N-C catalyst with reduced Ni loading compared to previous reports. Extensive materials characterization fails to detect Ni crystalline phases, reveals the highest concentration of atomically dispersed Ni metal, and confirms the presence of the proposed Ni-Nx active site at this reduced loading. The catalyst shows excellent activity and selectivity toward CO generation, with a faradaic efficiency for CO generation (FECO) of 97% and partial current density for CO (jco) of -9.0 mA cm-2 at -0.9 V in an electrochemical H-type cell. CO2RR activity and selectivity are also studied by rotating disk electrode (RDE) measurements where transport limitations can be suppressed. It is expected that the utility of these Ni-N-C catalysts will lie with tandem CO2RR reaction schemes to multi-carbon (C2+) products.

Engineering Atom-Scale Cascade Catalysis via Multi-Active Site Collaboration for Ampere-Level CO2 Electroreduction to C2+ Products.

Electrochemical reduction of CO2 to value-added multicarbon (C2+) productions offers an attractive route for renewable energy storage and CO2 utilization, but it remains challenging to achieve high C2+ selectivity at industrial-level current density. Herein, a Mo1Cu single-atom alloy (SAA) catalyst is reported that displays a remarkable C2+ Faradaic efficiency of 86.4% under 0.80 A cm-2. Furthermore, the C2+ partial current density over Mo1Cu reaches 1.33 A cm-2 with a Faradaic efficiency surpasses 74.3%. The combination of operando spectroscopy and density functional theory (DFT) indicates the as-prepared Mo1Cu SAA catalyst enables atom-scale cascade catalysis via multi-active site collaboration. The introduced Mo sites promote the H2O dissociation to fabricate active *H, meanwhile, the Cu sites (Cu0) far from Mo atom are active sites for the CO2 activation toward CO. Further, CO and *H are captured by the adjacent Cu sites (Cu&+) near Mo atom, accelerating CO conversion and C─C coupling process. Our findings benefit the design of tandem electrocatalysts at atomic scale for transforming CO2 to multicarbon products under a high conversion rate.

Dynamically Stable Cu0Cuδ+ Pair Sites Based on In Situ‐Exsolved Cu Nanoclusters on CaCO3 for Efficient CO2 Electroreduction

AbstractCopper‐based catalysts are the choice for producing multi‐carbon products (C2+) during CO2 electroreduction (CO2RR), where the Cu0Cuδ+ pair sites are proposed to be synergistic hotspots for C−C coupling. Maintaining their dynamic stability requires precise control over electron affinity and anion vacancy formation energy, posing significant challenges. Here, we present an in situ reconstruction strategy to create dynamically stable Cu0Cu0.18+OCa motifs at the interface of exsolved Cu nanoclusters and CaCO3 nanospheres (Cu/CaCO3). In situ XAFS analysis confirmed the low‐valency state of Cuδ+ during CO2RR. DFT calculations demonstrated that the nanocluster size arises from the balance between metal‐support interactions and Cu−Cu cohesive energy, while the dynamic stability of rich interfacial Cuδ+ sites is attributed to their low electron affinity and high CO32− vacancy formation energy, which collectively contribute to reduced reducibility. The transformed Cu/CaCO3 exhibits an impressive C2+ Faradaic efficiency of 83.7 % at a partial current density of 393 mA cm−2, facilitated by adsorption of *CO with varying electronegativity at heterogeneous copper sites that lowers the C−C coupling energy barrier. Our findings establish insoluble carbonate as an effective anion pairing for Cu0Cuδ+ sites, highlighting the effectiveness of the in situ reconstitution strategy in producing a high density of dynamically stable Cu0Cuδ+ pair sites.

Copper-Catalysed Electrochemical CO2 Methanation via the Alloying of Single Cobalt Atoms.

The electrochemical reduction of carbon dioxide (CO2) to methane (CH4) presents a promising solution for mitigating CO2 emissions while producing valuable chemical feedstocks. Although single-atom catalysts have shown potential in selectively converting CO2 to CH4, their limited active sites often hinder the realization of high current densities, posing a selectivity-activity dilemma. In this study, we developed a single-atom cobalt (Co) doped copper catalyst (Co1Cu) that achieved a CH4 Faradaic efficiency exceeding 60% with a partial current density of -482.7 mA cm-2. Mechanistic investigations revealed that the incorporation of single Co atoms enhances the activation and dissociation of H2O molecules, thereby lowering the energy barrier for the hydrogenation of *CO intermediates. In situ spectroscopic experiments and density functional theory simulations further demonstrated that the modulation of the *CO adsorption configuration, with stronger bridge-binding, favours deep reduction to CH4 over the C-C coupling or CO desorption pathways. Our findings underscore the potential of Co1Cu catalysts in overcoming the selectivity-activity trade-off, paving the way for efficient and scalable CO2-to-CH4 conversion technologies.

Additives-Modified Electrodeposition for Synthesis of Hydrophobic Cu/Cu2O with Ag Single Atoms to Drive CO2 Electroreduction.

Copper-based electrocatalysts are recognized as crucial catalysts for CO2 electroreduction into multi-carbon products. However, achieving copper-based electrocatalysts with adjustable valences via one-step facile synthesis remains a challenge. In this study, Cu/Cu2O heterostructure is constructed by adjusting the anion species of the Cu ions-containing electrolyte during electrodeposition synthesis. Then, Cu/Cu2O with tuned nanoarchitectures ranging from dendrites to polyhedrons is achieved by introducing transition metal ions as additives, leading to an adjustable interfacial microenvironment for CO2/H2O adsorption on the Cu/Cu2O electrodes. Additionally, the polyhedral Cu/Cu2O catalysts are used as templates for depositing Ag single atoms (AgSA), which are known as synergistic active sites for promoting *CO to *COH toward C2+ products. The prepared AgSA-Cu/Cu2O catalyst is evaluated in a flow cell and exhibited a FEC2+ of 90.2% and a partial current density (jc2+) of 426.6mAcm-2 for CO2 electroreduction. As revealed by in situ Raman spectra and density functional theory calculations, the introduction of Ag single atoms slows down the reduction of Cu+ during CO2 electroreduction, especially at a high current density. This work provides a promising paradigm for diverse control of the compositions and hydrophobicity of Cu-based catalysts for selective CO2 electroreduction to C2+ products.

Interfacial Oxygen Vacancy-Copper Pair Sites on Inverse CeO2/Cu Catalyst Enable Efficient CO2 Electroreduction to Ethanol in Acid.

Renewable electricity-driven electrochemical reduction of CO2 offers a promising route for production of high-value ethanol. However, the current state of this technology is hindered by low selectivity and productivity, primarily due to limited understanding of the atomic-level active sites involved in ethanol formation. Herein, we identify that the interfacial oxygen vacancy-neighboring Cu (Ov-Cu) pair sites are the active sites for CO2 electroreduction to ethanol. A linear correlation between the density of Ov-Cu pair sites and ethanol productivity is experimentally evidenced. Moreover, a high Faradaic efficiency of 48.5% and a partial current density of 344.0 mA cm-2 for ethanol production are achieved over the inverse CeO2/Cu catalyst with a high density of Ov-Cu pair sites in acid. Mechanistic studies that combine density functional theory calculations and spectroscopic techniques propose an Ov-involved mechanism where interfacial Ov sites directly activate and dissociate CO2 into *CO in a thermodynamically spontaneous manner, thus favoring the subsequent *CHO formation and asymmetric CHO-CO coupling. Besides, the asymmetric Ov-Cu pair sites could preferentially stabilize the *CH2CHOH intermediate, resulting in the favorable formation of ethanol over ethylene. Our findings provide new atomic-level insights into CO2 electroreduction to ethanol, paving the way for the rational design of future catalysts.

Coupled Stacking Faults in Silver Nanorods for CO2 Electroreduction.

The interaction of defects has been proven effective in regulating the mechanical properties of structural materials, while its influence on the physicochemical performance of functional materials has been rarely reported. Herein, we synthesized Ag nanorods with dense stacking faults and investigated how the defect interaction affects the catalytic properties. We found that the stacking faults can couple with each other to form a unique structure of opposite atoms with extortionately high tensile strain. Experimental and theoretical analyses reveal that the opposite-atom structure facilitates the adsorption and activation of CO2 molecules, thus improving the catalytic performance of the carbon dioxide electroreduction reaction (CO2RR). As a result, Ag nanorods achieve high CO partial current density (-11.87 mA cm-2 at -0.8 V vs RHE) and high Faraday efficiency (>95%), superior to most Ag-based catalysts. Our work indicates that the defect interaction is an effective means to boost the performance of functional materials.

Dynamically Stable Cu0Cuδ+ Pair Sites Based on In Situ-Exsolved Cu Nanoclusters on CaCO3 for Efficient CO2 Electroreduction.

Copper-based catalysts are the choice for producing multi-carbon products (C2+) during CO2 electroreduction (CO2RR), where the Cu0Cuδ+ pair sites are proposed to be synergistic hotspots for C-C coupling. Maintaining their dynamic stability requires precise control over electron affinity and anion vacancy formation energy, posing significant challenges. Here, we present an in situ reconstruction strategy to create dynamically stable Cu0Cu0.18+OCa motifs at the interface of exsolved Cu nanoclusters and CaCO3 nanospheres (Cu/CaCO3). In situ XAFS analysis confirmed the low-valency state of Cuδ+ during CO2RR. DFT calculations demonstrated that the nanocluster size arises from the balance between metal-support interactions and Cu-Cu cohesive energy, while the dynamic stability of rich interfacial Cuδ+ sites is attributed to their low electron affinity and high CO3 2- vacancy formation energy, which collectively contribute to reduced reducibility. The transformed Cu/CaCO3 exhibits an impressive C2+ Faradaic efficiency of 83.7 % at a partial current density of 393 mA cm-2, facilitated by adsorption of *CO with varying electronegativity at heterogeneous copper sites that lowers the C-C coupling energy barrier. Our findings establish insoluble carbonate as an effective anion pairing for Cu0Cuδ+ sites, highlighting the effectiveness of the in situ reconstitution strategy in producing a high density of dynamically stable Cu0Cuδ+ pair sites.

Interplanar synergy of a copper-based electrocatalyst favors the reduction of CO2 into C2+ products

A Cu-based catalyst with interplanar synergy between the Cu(100) and Cu(111) facets significantly enhances C2+ selectivity in CO2 electroreduction, achieving a 78% faradaic efficiency and 663 mA cm−2 partial current density.

The effect of carbon supports on the electrocatalytic performance of Ni-N-C catalysts for CO2 reduction to CO

Carbon-supported nickel and nitrogen co-doped (Ni-N-C) catalysts have been extensively studied as selective and active catalysts for CO2 electroreduction to CO. Most studies have focused on adjusting the coordination structure of Ni-Nx active sites, while the impact of the carbon supports has often been overlooked. In this study, a series of Ni-N-C catalysts on different carbon supports, including carbon black (CB), multi-walled carbon nanotubes (CNT), and activated nitrogen-doped biochar (ANBC), were synthesized using a ligand-mediated method. The effect of the carbon support on the electrocatalytic performance for CO2 reduction was investigated at both low current densities, in a H-cell, and high current densities, in a MEA electrolyzer. All of the prepared Ni-N-C catalysts show good faradaic efficiencies (FE) toward CO production (up to ~90%), however, the onset potentials and partial current densities for CO production vary greatly. The textural properties of the carbon support and the distribution of Ni-Nx active sites on the carbon support are demonstrated as the main factors behind the performance differences. In particular, hierarchical porous structures with large specific surface area are helpful to facilitate mass transport and improve the dispersion of active sites, which allows for a better CO2 reduction performance of Ni-N-ANBC compared to Ni-N-CB and Ni-N-CNT. This study demonstrates the importance of the carbon support for Ni-N-C catalysts and provides new insights into the design of efficient Ni-N-C catalysts for the CO2RR.

A low-cost disposal pencil electrode for cyclic voltammetry analysis

This study explores the use of disposable pencil electrodes in cyclic voltammetry (CV) and compares their performance to traditional glassy carbon electrodes. We conducted CV tests to evaluate different pencil grades, HB, 2B, 4B, 6B, 8B, and 10B along with glassy carbon to assess response time, peak current, and electrode stability during the analysis of potassium ferrocyanide. The results showed that the 4B pencil outperformed other grades and the glassy carbon electrode, with faster response times, higher peak currents, and greater stability. Notably, the 4B pencil's anodic and cathodic currents were higher at 25 mV/s scan rate. This work demonstrates that 4B pencils can serve as cost-effective and reliable alternatives to glassy carbon electrodes in electrochemical applications, offering an accessible option for potassium ferrocyanide analysis and broader electrochemical studies.

Preferentially Stabilizing the Watershed Intermediates by Adsorbate‐adsorbate Interaction to Accelerate CO2 Electroreduction to Ethanol

AbstractReturning CO2 to liquid ethanol powered by clean energy offers considerable economic benefits and contributes to reaching the goal of carbon neutrality, but it remains a formidable challenge to achieve high ethanol selectivity due to the inevitable strong competition among various pathways. Herein, an investigation is presented to accelerate CO2 electroreduction to ethanol via preferentially stabilizing the precarious watershed intermediates (*CHCOH) by creating strong adsorbate‐adsorbate interaction. The highly ordered CuOx nanoplates (HO‐CuOx NPLs) featuring abundant amorphous‐crystalline interface exhibit an exceptional ethanol Faradaic efficiency (FEEtOH) of 63.8% and an ethanol‐to‐ethylene ratio of 6.1 at a large ethanol partial current density (jethanol) of 232.8 mA cm−2. The findings decipher that abundant in‐between nanogaps in the amorphous‐crystalline interface enhance the adsorption of *OH, which can preferentially strengthen C─O bonds while weakening the Cu─C interaction of *CHCOH through adsorbate‐adsorbate interaction, thereby enabling a predilection for CO2 to ethanol conversion. Beyond an efficient ethanol‐oriented CO2RR electrocatalyst, the investigations provide an in‐depth understanding of adsorbate‐adsorbate interaction on key CO2RR steps and precise intermediates regulation, which can be extended to a range of energy conversion technologies.

Selective Electroreduction of CO2 to CO over Ultrawide Potential Window via Implanting Active Site with Long-Range P Regulation on Periodic Pores.

Electroreduction of CO2 to CO represents a highly promising way for artificial carbon cycling, but obtaining high selectivity over a wide potential window remains a challenge due to the sluggish CO generation and diffusion kinetics. Here we report an integration of long-range P modified asymmetrical bismuth atomic site on an ordered macroporous carbon skeleton with mesoporous "wall" (MW-BiN3-POMC) for efficient electroreduction of CO2. In-depth in-situ investigations with theoretical computations reveal that the incorporation of long-range P atom is able to strengthen the orbital interaction between the C 2p of CO2 and Bi 6p, thereby establishing an electronic transport bridge for the activation of CO2 molecule. Additionally, the ordered macropore with mesoporous wall effectively facilitates the diffusion of CO. As a result, MW-BiN3-POMC exhibits an ultrawide potential window of 1000 mV for high CO selectivity (>90%) and a maximal CO partial current density of 414 mA cm-2. Moreover, MW-BiN3-POMC can also be employed as the cathode to integrate the solar-driven electrolytic cell (anode of Co3O4-OMC) toward CO2 reduction coupled with 5-hydroxymethylfurfural oxidation to simultaneously yield CO and 2,5-furandicarboxylic acid.

Photoinduced Lattice Compression of Cu for Enhanced Production of Ethylene from CO2

AbstractWhile engineering lattice strain has been proven effective in enhancing the electrochemical CO2 reduction performance of a catalyst, the correlation between strain effect and the intrinsic catalytic mechanism has remained elusive. Herein, a photolithography‐inspired method is proposed to regulate Cu(111) lattice strain. By irradiating the photosensitive Cu(Acac) sol–gel, Acac chelate bond undergoes π→π* electronic transition, and the ring‐closed Cu(Acac) decompose into the stabilized Cu(Acac) mesh which presents as nanospots embedded onto the surface of the Cu cluster. The photoinduced nanospots serve to exert compressive strain to the Cu(111) lattice in which the lattice distance is reduced by 5.7–11.4%. Herein, the catalyst with 11.4% lattice compression exhibits enhanced C2H4 production capabilities, reaching a maximal Faradaic efficiency of 57.00%, and a high partial current density of 456.01 mA cm−2. Theoretical calculations reveal that the compressed Cu(111) lattice exhibits reduced surface energies, leading to a significant drop in the C─C coupling reaction free energy from 1.16 eV over the pristine lattice, to 0.57 eV over the 10% compressed lattice. Additionally, the 10% compressed lattice facilitates spontaneous *O splitting immediately after OC─CHO coupling which leads to the generation of C2H4‐favoring *CCH intermediate.

Boosting Formate Production in Electrocatalytic CO2 Reduction on Bimetallic Catalysts Enriched with In-Zn Interfaces.

We present an effective strategy for developing the dispersing strong-binding metal In on the surface of weak-binding metal Zn, which modulates the binding energy of the reaction intermediates and further facilitates the efficient conversion of CO2 to formate. The In-Zn interface (In-Zn2) benefits from the formation of active sites through favorable orbital interactions, leading to a Faradaic efficiency of 82.7% and a formate partial current density of 12.39 mA cm-2, along with stable performance for over 15 h at -1.0 V versus the reversible hydrogen electrode. Both in situ Fourier transform infrared spectroscopy and density functional theory calculations show that the In-Zn bimetallic catalyst can deliver superior binding energy to the *OCHO intermediate, thereby fundamentally accelerating the conversion of CO2 to formate. In addition, the exposed bimetallic interface promotes efficient capture and activation of CO2 molecules and the dynamics within the In-Zn catalyst significantly reduce the energy barrier associated with the generation of HCOO-, thus augmenting the selectivity and catalytic activity for formate generation.

Determination of Methotrexate Using an Electrochemical Sensor Based on Carbon Paste Electrode Modified with NiO Nanosheets and Ionic Liquid

In this paper, the application of NiO nanosheets (NiO NSs) for the detection of methotrexate (MTX) is described. The NiO NSs were synthesized using a hydrothermal method. The electrocatalytic activity of two modifiers, ionic liquid (IL) and NiO NSs, was examined on a carbon paste electrode (CPE) in relation to MTX, utilizing voltammetry methods such as cyclic voltammetry (CV), linear sweep voltammetry (LSV), differential pulse voltammetry (DPV), and chronoamperometry at 0.1 M phosphate buffer solution (PBS) pH = 7.0. The anodic peak currents for MTX on the NiO NSs/IL/CPE were approximately 3.5 times greater than those on unmodified CPE. Based on DPV measurements, the electrochemical sensor demonstrated a linear response in the concentration range (LDR: 0.01 µM to 160.0 µM), with a limit of detection (LOD: 0.003 µM). Moreover, the NiO NSs/IL/CPE sensor demonstrated good stability, repeatability, reproducibility, and selectivity, which were of importance in the electroanalysis of compounds. Lastly, the practicality of the NiO NSs/IL/CPE sensor was assessed by analyzing MTX levels in urine samples and pharmaceutical formulation, yielding satisfactory recovery rates of 97.1% to 103.3%.

CO2 Electroreduction to Multicarbon Products Over Cu2O@Mesoporous SiO2 Confined Catalyst: Relevance of the Shell Thickness

AbstractDespite the advantage of high carbon utilization, CO2 electroreduction (CO2ER) in acid is challenged by the competitive hydrogen evolution reaction (HER). Designing confined catalysts is a promising strategy to suppress HER and boost CO2ER, yet the relationship between the confined structure and catalytic performance remains unclear, limiting rational design. Herein, using Cu2O@mesoporous SiO2 core‐shell catalysts as a well‐defined platform, a volcano‐shaped relationship is found between the thickness of mesoporous SiO2 layer and productivity of multicarbon (C2+) products in CO2 electroreduction. The optimal shell thickness of 15 nm is identified, with in situ spectroscopies and theoretical simulations attributing this to the trade‐off between the local alkalinity and CO2 concentration, arising from the nanoconfinement effect. At this optimal thickness, the Cu2O@ mesoporous SiO2 catalyst achieves a C2+ Faradaic efficiency of 83.1% ± 2.5% and partial current density of 687.8 mA cm−2 in acidic electrolytes, exceeding most reported catalysts. This work provides valuable insights for the rational design of confined catalysts for electrocatalysis.