One-step Electrodeposition Method Research Articles

Ultra-fast electrochemical preparation of Ni-Cu-Fe nano-micro dendrite as a highly active and stable electrocatalyst for overall water splitting

The development of highly active, durable, and low-cost electrocatalysts for both the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER) to advance the commercial applications of overall water electrolysis is regarded as a crucial matter. We describe an ultra-fast synthesis of multi-metal Ni-Cu-Fe micro-nano dendritic electrocatalysts were synthesized on nickel foam using a simple one-step constant current electrodeposition method. According to DFT simulations, Fe incorporation causes a downshift movement in the d-band center and the formation of additional catalytic active sites. Ni-Cu-Fe nano-micro dendrites have potential applications as bifunctional catalysts for electrochemical water splitting. Also, the increased electrical conductivity of the Ni-Cu-Fe electrode is due to the placement of more electronic states near the Fermi level and creating an optimal and porous dendritic structure that causes better electrolyte penetration in the pores. Experiments show that in the 1.0 M KOH electrolyte, Ni-Cu-Fe catalysts need an ultra-low overpotentials of 42 mV and 300 mV to supply a current density of −10 mA cm−2 for the HER and 50 mA cm−2 for the OER. Also, when Ni-Cu-Fe electrocatalyst is used as a bifunctional electrode in the overall water splitting system, it displays a low cell voltage of 1.54 V in a current density of 10 mA cm−2 can maintain this activity for more than 100 h.

TiO2 nanotubes modified with cobalt oxyphosphide spheres for efficient electrocatalytic hydrogen evolution reaction in alkaline medium

Electronic and surface modulation through coupling between oxygen and phosphorous in cobalt oxyphosphide (CoOP) is identified as an effective approach to enhancing the electrocatalytic hydrogen evolution reaction (HER) in an alkaline medium. This work demonstrates a one-step and safe electrodeposition method to modify the surface of ordered titania nanotubes (TNTs) with CoOP spheres. The effect of electrodeposition charge density, pH of the electrodeposition bath, and presence of citric acid on the electrocatalytic HER performance of CoOP-modified TNTs was investigated. The Ti/TNTs/CoOP electrode requires only 130 mV overpotential to deliver 10 mA cm−2 in a 1.0 M KOH electrolyte. The Tafel slope is estimated to be 72.5 mV dec−1. Both the HER performance and Tafel value of Ti/TNTs/CoOP are superior to CoOP deposited on bare Ti foil (165 mV and 78.4 mV dec−1), FTO (185 mV; 88.1 mV dec−1), and glassy carbon (214 mV; 93 mV dec−1). The electrochemically active surface area (ECSA) and impedance spectroscopy findings revealed that the synergistic coupling between the CoOP and TNTs enhances the surface area and density of accessible active sites while reducing the charge transfer resistance at the electrode/electrolyte interface. Such a synergistic effect is ascribed to the effective electronic interaction between CoOP and TNTs, and the faster electron transfer kinetics because of the unidirectionality of the 1-D TNTs.

Phase Segregation in Cu0.5 Ni0.5 Alloy Boosting Urea-Assisted Hydrogen Production in Alkaline Media.

Coupling urea oxidation reaction (UOR) and hydrogen evolution reaction (HER) is promising for energy-efficient hydrogen production. However, developing cheap and highly active bifunctional electrocatalysts for overall urea electrolysis remains challenging. In this work, a metastable Cu0.5 Ni0.5 alloy is synthesized by a one-step electrodeposition method. It only requires the potentials of 1.33 and -28mV to obtain the current density of ±10mA cm-2 for UOR and HER, respectively. The metastable alloy is considered to be the main reason causing the above excellent performances. In the alkaline medium, the as-prepared Cu0.5 Ni0.5 alloy exhibits good stability for HER; and conversely, NiOOH species can be rapidly formed during the UOR due to the phase segregation of Cu0.5 Ni0.5 alloy. In particular, for the energy-saving hydrogen generation system coupled with HER and UOR, only 1.38V of voltage is needed at 10mA cm-2 ; and at 100mA cm-2 , the voltage decreases by ≈305mV compared with that of the routine water electrolysis system (HER || OER). Compared with some catalysts reported recently, the Cu0.5 Ni0.5 catalyst owns superior electrocatalytic activity and durability. Furthermore, this work provides a simple, mild, and rapid method for designing highly active bifunctional electrocatalysts toward urea-supporting overall water splitting.

Corrosion protection of superhydrophobic/amphiphobic cobalt coating with anti-icing and self-cleaning properties fabricated by a one-step electrodeposition method

Fabrication of superhydrophobic cobalt-based coatings is a useful way to provide metals, including copper, with corrosion protection, anti-icing, and self-cleaning properties to enhance their industrial applications. A one-step electrodeposition process was applied to synthesize a cobalt coating on a copper substrate. Superhydrophobicity, amphiphobicity, anti-freezing, self-cleaning, corrosion protection, and long-term stability of the coating were investigated. The coating surface was studied using SEM and the water contact angles (CAs) were measured by an optical tensiometer. The coating showed a water CA of 155.6 ± 0.6° with a sliding angle of 4.8 ± 0.3°, denoting its superhydrophobicity. Also, it was amphiphobic with CAs over 120° for glycerol and ethylene glycol. The coating was highly corrosion resistant with a high charge transfer resistance of 756.3 kΩ.cm2. This was compatible with the stability of coating during 16 days of immersion in 3.5 wt% NaCl solutions (pH 1 and 14), when it remained hydrophobic with CA over 90°. The 23 min longer freezing time of water droplets on the coating at − 15° compared to the copper substrate was a proof of its excellent anti-icing. Only three rolling water drops were required to remove the alumina powder from 1.13 cm2 of the coating area, denoting excellent self-cleaning with a rare superiority over other similar research.

Facile electrodeposition synthesis and super performance of nano-porous Ni-Fe-Cu-Co-W high entropy alloy electrocatalyst

Establishing efficient nano-porous electrocatalysts for facilitating electron transfer is a one of the useful ways for enhance water splitting. Herein, Ni-Fe-Cu-Co-W high entropy alloy (NFCCW-HEA) electrocatalysts on the iron sheet substrate have been successfully prepared by a simple and efficient one-step electrodeposition method. High entropy alloys have a variety of active sites and unique atomic scale synergies, which makes the catalyst have good catalytic performance and stability. Meanwhile, the HEA coating like cauliflower by electrodeposition can provide more attachment sites, and significantly upgrade the OER catalytic activity. NFCCW-HEA catalysts exhibit an excellent overpotential of 247.3 mV under the current density of 10 mA·cm−2, and a low Tafel slope of 62.9 mV dec−1. The electrocatalyst shows long term stability of electrolysis for over 24 h in 1 mol·L−1 KOH alkaline solution, which shows good stability. We expect to provide a new idea for the preparation of nano porous high entropy alloy electrocatalysts by one-step electrodeposition technology.

One-step electrodeposition to fabricate superhydrophobic surfaces on flexible conductive films: Optimization of metallic compounds

Superhydrophobic surfaces were fabricated by a simple one-step electrodeposition technique to deposit three distinct micro/nano hierarchical structures of Ce, Mg, or Cu-based compounds on Ag films on a flexible polymer substrate. Scanning electron microscopy was used to examine the surface morphologies of obtained structures with different deposition. Compared with the bare Ag films, one-step electrodeposition process resulted in superhydrophobicity, including a water contact angle of 159.7° for Ce-modified surfaces, 157.0° for Mg-modified surfaces, and 153.8° for Cu-modified surfaces. Besides, these surfaces showed high thermal stability below 120 ℃, and good flexibility but low electrical conductivity. EDS and XPS results suggest the production of low surface energy materials that formed the superhydrophobic features on the Ag films. Besides, because of the formation of CeO2, Ce-SHS had better superhydrophobicity than Mg-SHS and Cu-SHS. In addition, the potentiodynamic polarization experiments showed that the electrodeposited superhydrophobic surfaces had lower Icorr, higher Ecorr and impedance values in NaCl solution, Na2SO4 solution and Simulated body fluid, and artificial sweat solution compared with the bare silver film, indicating that the electrodeposited protective film has good anti-corrosion properties. These results suggest that the one-step electrodeposition method is a promising strategy to fabricate conducting films with superhydrophobic surfaces for surface protection under various corrosive environments.

Electrodeposited copper–nickel nanoparticles as highly efficient electrocatalysts for nitrate reduction to ammonia

CuNi NPs on Ti mesh (CuNi/TM) prepared by a one-step electrodeposition method were verified as efficient electrocatalysts for nitrate electroreduction, which can produce large quantities of ammonia in a wide range of concentrations of nitrate-containing electrolytes.

A two-dimensional heterogeneous structured Ni3Se2@MoO3 catalyst for seawater electrolysis

Ni3Se2@MoO3/CF catalysts were prepared by a one-step electrodeposition method, and the catalyst showed excellent stability at high current densities as a bifunctional catalyst for seawater electrolysis.

Synergistic combination of a Co-doped σ-MnO2 cathode with an electrolyte additive for a high-performance aqueous zinc-ion battery

The key challenges in aqueous zinc-manganese dioxide batteries (MnO2//Zn) are their poor electrochemical kinetics and stability, which are mainly due to low conductivity and the inevitable dissolution of MnO2. A synergistic combination of a Co-doped σ-MnO2 electrode (Co-MnO2) and a Co(CH3COO)2•4H2O (CoAc) electrolyte additive is here developed to design a high-performance aqueous MnO2//Zn battery (denoted as a Co-MnO2//Zn battery with CoAc). The introduction of Co ions (Co3+/Co2+) into the σ-MnO2 electrode is achieved via a facile one-step electrodeposition method. Benefitting from the synergistic coupling effect of the Co-MnO2 electrode and the CoAc electrolyte additive, the fabricated Co-MnO2//Zn battery with CoAc shows a commendable discharge capacity of 313.8 mAh g−1 at 0.5 A g−1, excellent rate performance, excellent durability over 1000 cycles (∼ 92% capacity retention at 1.0 A g−1) and admirable energy density (439.3 Wh kg−1), which is a significant improvement compared with an un-doped σ-MnO2//Zn battery.

Design of AgNPs doped chitosan/sodium lignin sulfonate/polypyrrole films with antibacterial and endotoxin adsorption functions

There is an urgent need to develop materials to prevent bacterial infection and the deleterious effects of endotoxins. In this study, we introduce a one-step electrodeposition method to prepare films composed of chitosan/Ag/polypyrrole and layer-by-layer self-assembly to introduce lignin sulphonate (LS) to obtain chitosan/Ag/polypyrrole/LS films. Antibacterial effects against both E. coli and S. aureus are shown by bacterial growth profiles and observation of bacteriostatic zones. Meanwhile, the addition of self-assembled LS improved the antibacterial effect of the film. For E. coli, the inhibition zone diameter was 0.93 cm, while for S. aureus, the inhibition zone diameter was 0.72 cm. Rapid and efficient endotoxin adsorption effects were shown whereby the electrostatic interactions between chitosan and endotoxin molecules played a major role. After adsorption for 1 h, in initial concentration of 1 EU/mL endotoxin solution, the adsorption efficiency could reach up to 85 %, while in initial concentration of 5 EU/mL endotoxin solution, the adsorption efficiency could reach up to 87.6 %. The results suggest chitosan/Ag/polypyrrole/LS films for their capability as a new type of antibacterial film with intrinsic endotoxin adsorption activity.

Gold Nanospikes Formation on Screen-Printed Carbon Electrode through Electrodeposition Method for Non-Enzymatic Electrochemical Sensor

In this study, we reported the construction of Gold Nanospike (AuNS) structures on the surface of screen-printed carbon electrode (SPCE) used for non-enzymatic electrochemical detection. This modification was prepared with a one-step electrodeposition method by controlling the electrodeposition parameters, such as applied potential and deposition time, via Constant Potential Amperometry (CPA). Those parameters and precursor solution concentration were varied to investigate the optimum electrodeposition configuration. The results confirmed that AuNS were homogenously deposited and well-dispersed on the working electrode surface of SPCE. The AuNS-modified SPCE was implemented as a non-enzymatic sensor toward dopamine and could enhance the electrocatalytic ability compared with the bare SPCE. Further examination shows that the sensing performance of the AuNS-modified SPCE produced an increase in electrochemical surface area (ECSA) at 17.25 times higher than the bare electrode, a sensitivity of 0.056 µA mM−1 cm−2 with a wide linear range of 0.2–50 µM and a detection limit of 0.33 µM. In addition, AuNS-modified SPCE can selectively detect dopamine among other interfering analytes such as ascorbic acid, urea, and uric acid, which commonly coexist in the body fluid. This work demonstrated that AuNS-modified SPCE is a prospective sensing platform for non-enzymatic dopamine detection.

One-step electrodeposition of ZnO/graphene composites with enhanced capability for photocatalytic degradation of organic dyes.

Zinc oxide is a popular semiconductor used in catalysts due to its wide bandgap and high exciton binding energy. However, the photocatalytic performance of ZnO was compromised by its insufficient electron-hole separation efficiency and electron transfer rate. Herein, ZnO-reduced graphene oxide (rGO) composite solid catalyst was synthesized by one-step electrodeposition method on FTO substrate using lithium perchlorate (LiClO4) as the supporting electrolyte. Scanning electron microscopy, Raman, Fourier Transform Infrared, and XRD characterizations confirmed the deposition of ZnO and the reduction of graphene oxide Owing to the cooperative effect between rGO and ZnO, the as-prepared ZnO-rGO composites show much enhanced photocatalytic degradation ability compared with pure ZnO nanorods. By optimizing the conditions of electrodeposition of ZnO-rGO composites, the degradation rate of methylene blue can reach 99.1% within 120min. Thus, the simple preparation and the excellent performance could endow the ZnO-rGO composites with promising application in practical dye-polluted water treatment.

Absorption-based electromagnetic interference shielding composites with sandwich structure by one-step electrodeposition method

The absorption-dominant electromagnetic interference (EMI) shielding materials with light weight, great flexibility, fast heat dissipation and excellent mechanical strength are highly demanded in civil and military applications. In this regard, the absorption-based CNT/Co composite film with sandwich structure (Co/Co-CNT/Co layer) was designed for highly EMI shielding performance and heat dissipation. The existence of Co layers on CNT/Co composite film has suitable impedance matching between film and free space, which can increase EM waves absorption and decrease EM waves reflection. Appropriately incorporating Co nanoparticles into the CNT film can facilitate the interfacial polarization, dipole polarization and dielectric loss derived from conduction loss, thus CNT/Co composite film shows high EMI shielding effectiveness (EMI SE: 49 dB), tensile strength (120 MPa), excellent electrical and thermal conductivity of 61.1 S/cm and 66.8 W/mK respectively. Furthermore, the ratio of absorption (SEA) and total EMI SE (SET) for pristine CNT film is 86.64% and for CNT/Co composite film is 93.31%, and the ratios of A/R for pristine CNT film (0.58) and CNT/Co composite film (1.20) manifest that the EMI shielding mechanism transforms from reflection to absorption. This work offers a novel method to develop the sandwich-structure composites with absorption-dominant EMI shielding performance in the application of advanced multifunctional electromagnetic shielding field.

Nickel-cobalt layered double hydroxide fabricated on TiO2/C nanofiber arrays as free standing electrode for high performance supercapacitors

Nickel-cobalt layered double hydroxides (LDHs) as electrode materials have recently received intense interests. However, the low conductivity, sluggish charge transfer kinetics and poor electrolyte penetration restrict the capacitive performance and hinder their practical applications. Herein, the Ni-Co-LDH nanosheets were introduced to the core/shell structured TiO2/C nanofiber arrays (TiO2/C NFAs) to construct a free-standing composite electrode for supercapacitor through a one-step electrodeposition method. The best-performing Ni1Co1-LDH/TiO2/C NFAs electrode exhibits high specific capacitance (1717.8 F g−1 at 1 mA cm−2), remarkable rate capability with 75.1 % retention when the current density increased from 1 mA cm−2 to 75 mA cm−2, and excellent cycling stability (84.1 % of the original capacitance after 5000 cycles at 78.1 A g−1), surpassing most of the Ni-Co-LDH electrodes reported before. This excellent performance owes to the high conductivity of TiO2/C NFAs which can endow the low ohmic resistance and high diffusion coefficient of Ni-Co-LDH which may alleviate the structure degradation. Meanwhile, the Ni-Co-LDH with the optimized Ni/Co ratio of 1:1 can provide proper particle size of LDH nanosheets, small charge transfer resistance (Rct), and high stability of Ni-Co-LDH to resist the structure degradation in the long-term cycling process.

Self-assembled deposition of polyaniline/cobalt porphyrin based on flexible PET to improve sensing of room-temperature NH3 sensor

The development of efficient and flexible ammonia (NH3) detection equipment for monitoring air quality remains a great challenge. Herein, a room-temperature polyaniline/cobalt porphyrin (PANI/CoTPP, PCT) NH3 sensor based on an ITO-PET substrate was prepared by a one-step self-assembled electrodeposition method. Although the aggregated CoTPP particles reduced the conductivity of PANI molecular chains, they could help to capture NH3 molecules. Thus, the fabricated PCT flexible sensor showed superior sensitivity with a theoretical detection limit of ∼ 0.83 ppm NH3, high selectivity, and excellent sensing stability. The NH3 sensing mechanism of the PCT sensor was further investigated with the aid of density functional theory (DFT) calculations. Hence, the combination of conductive polymer with porphyrin-based sensitive material in the form of a flexible sensor is expected to be used as a simple device for tracing NH3 in the environment.

Electrochemical fabrication of interleaved vanadium oxide nanosheets coated nickel foam 3D electrode with improved oxygen evolution reaction performance

An interleaved vanadium oxide nanosheets coated on nickel foam (V/NF) is proposed as an excellent 3D electrode for oxygen evolution, which exhibits high activities with overpotential of 232 mV at 10 mA cm−2 and the Tafel slope is 50.1 mV dec−1, showing catalytic activity comparable to that of noble metals. The V/NF material are designed by a one-step facile electrodeposition method at low temperature in ethaline deep eutectic solvent and XRD analysis indicates that these nanosheets are mainly made up of VO(OH)2, V2O5 and NiVO3. The formation of these V-containing compounds on the surface of NF is regarded to be responsible for the electrocatalytic activity.

Electrodeposited amorphous nickel–iron phosphide and sulfide derived films for electrocatalytic oxygen evolution

The preparation of inexpensive and efficient electrocatalysts for oxygen evolution reaction (OER) is crucial in the widespread application of water electrolyzers. A simple one-step aqueous electrodeposition method is utilized to prepare amorphous nickel-iron sulfide (Ni–Fe–S) and phosphide (Ni–Fe–P) films on Ni foam. The deposited films are highly porous, and can convert to active electrocatalysts for OER. In 1 M KOH, the Ni–Fe–S shows the highest OER activity, and requires only 230 mV overpotential to reach 0.05 A cm−2 OER current densities. The Fe–Ni–S also sustains the 30 h 0.05 A cm−2 galvanostatic OER test. Ex-situ characterizations show that sulfur in the Fe–Ni–S is oxidized and leached into the solution during OER, and that (oxy)hydroxide layer is formed at the surface. The adsorption energy of the hydroxyl group, an OER intermediate, is tuned by the electron interaction between the Ni and Fe, and the Ni–Fe–S exhibits the optimum hydroxyl group adsorption energy and the most facile OER kinetics. Also, higher intrinsic OER activity is observed for the electrodeposited amorphous nickel phosphide-derived film than the amorphous nickel sulfide-derived film.

Electrochemically Dealloyed 3D Porous Copper Nanostructure As High-Performance Anode Current Collector of Li-Metal Batteries

Li metal anode is the ultimate choice for Li batteries owning to its highest theoretical capacity (3806 mAh/g) and lowest redox potential (-3.04 V vs. standard hydrogen electrode) among possible candidates.[1] However, despite the advantages of Li metal anodes, a number of remaining challenges must be addressed before its commercialization: undesired dendrite growth of Li, and irreversible parasitic reactions between Li and electrolyte, etc.Stabilization of Li metal is essential for commercial application of Li metal anodes. In the past few years, several strategies have been developed to suppress Li dendrite growth and stabilize SEI formation during Li plating/stripping processes. Among these strategies, 3D current collectors showed its high potential in Li anode stabilization due to its much larger surface area, which can provide much more Li nucleation sites, alleviate volumetric changes of Li anode, and decrease practical current density. Thus, compared to flat Cu foil used in commercial Li-ion batteries, 3D Cu current collectors can facilitate uniform Li deposition, mitigate Li dendrite growth, and enhance Li cycling stability.[2]Our previous work reported a 3D porous Cu current collector fabricated via a facile one-step electrodeposition method directly on commercial Cu foil. [3] The fabricated 3D porous Cu current collector showed stable long-term cycling with a high areal capacity of 6 mAh/cm2 and no Li dendrite growth was observed during cycling process. However, for the one-step electrodeposition method, the thickness of the porous Cu deposition layer is limited. Thus, preparation of 3D porous Cu layers with both high thickness and high porosity is necessary to further improve the areal capacity of this current collector. Recently, we developed a new two-step electrochemical process to fabricate thick and porous Cu layer: a thick Cu-Zn alloy was first electrodeposited on commercial Cu foil, and Zn was then removed electrochemically, leaving a thick and highly porous 3D Cu layer. Compared to our previous method, this 3D Cu layer has a high thickness of ~14 um and porosity of ~72%. This new 3D Cu current collector can achieve stable Li cycling up to 230 h at high areal capacity of ~10 mAh/cm2 at a high current density of 10 mA/cm2, demonstrated its high commercial application potential in Li-metal batteries. Tarascon, J.M. and M. Armand, Issues and challenges facing rechargeable lithium batteries. Nature, 2001. 414(6861): p. 359-367.Yang, C.P., et al., Accommodating lithium into 3D current collectors with a submicron skeleton towards long-life lithium metal anodes. Nature Communications, 2015. 6.Ma, X., Z. Liu, and H. Chen, Facile and scalable electrodeposition of copper current collectors for high-performance Li-metal batteries. Nano Energy, 2019. 59: p. 500-507.

Facile electrochemical synthesis of Ni-Sb nanostructure supported on graphite as an affordable bifunctional electrocatalyst for hydrogen and oxygen evolution reactions

• A novel Ni-Sb nanostructure as a bifunctional electrocatalyst was fabricated by a facile electrodeposition method. • The Ni-Sb nanostructure exhibited outstanding activity and long-term stability toward HER and OER performances. • The unique morphology and the synergistic effect between Ni and Sb elements are responsible for the best electrocatalytic characteristics. • Sb with a 2D layered structure improves the conductivity and charge transfer ability of electrodes. The design of bifunctional electrocatalysts with high activity and long-term stability is essential for water splitting systems. Herein, a binder-free and cost-effective Ni-Sb nanostructured catalyst was prepared using the one-step electrodeposition method from an organic solution, and its electrochemical characteristics for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in an alkaline medium were studied. The optimized Ni-Sb electrode demonstrated the best electrocatalytic activity for hydrogen and oxygen evolution reactions. Benefiting from the unique morphology, super-hydrophilic properties, and the synergistic effect between Ni and Sb elements, low overpotentials of 158 mV and 367 mV are needed to produce a current density of 10 mA.cm −2 for HER and OER, respectively. Noteworthy, the Ni-Sb bifunctional catalyst displayed enhanced electrocatalytic stability at a current density of 100 mA.cm −2 and works for 60,000 s. Our experimental data based on the electrochemical impedance spectroscopy (EIS) measurements before and after the stability test confirmed that the optimized electrode retains its catalytic performances for HER and OER owing to high conductivity and fast charge transfer. This study thus provides helpful avenues to design new antimonide-based catalysts for various applications.

Concentration Optimization of Localized Cu0 and Cu+ on Cu-Based Electrodes for Improving Electrochemical Generation of Ethanol from Carbon Dioxide.

Copper-based electrodes can catalyze electroreduction of CO2 to two-carbon products. However, obtaining a specific product with high efficiency depends on the oxidation state of Cu for the Cu-based materials. In this study, Cu-based electrodes were prepared on fluorinated tin oxide (FTO) using the one-step electrodeposition method. These electrodes were used as efficient electrocatalysts for CO2 reduction to ethanol. The concentration ratio of Cu0 and Cu+ on the electrodes was precisely modulated by adding monoethanolamine (MEA). The results of spectroscopic characterization showed that the concentration ratio of localized Cu+ and Cu0 (Cu+/Cu0) on the Cu-based electrodes was controlled from 1.24/1 to 1.54/1 by regulating the amount of MEA. It was found that the electrode exhibited the best electrochemical efficiency and ethanol production in the CO2 reduction reaction at the optimal concentration ratio Cu+/Cu0 of 1.42/1. The maximum faradaic efficiencies of ethanol and C2 were 48% and 77%, respectively, at the potential of −0.6 V vs. a reversible hydrogen electrode (RHE). Furthermore, the optimal concentration ratio of Cu+/Cu0 achieved the balance between Cu+ and Cu0 with the most favorable free energy for the formation of *CO intermediate. The stable existence of the *CO intermediate significantly contributed to the formation of the C–C bond for ethanol production.