Electrochemical Research Articles

Electrodeposition of Ru on Nanoscale Trench Patterns

Abstract Ru deposition in advanced technology nodes can improve performance by providing low resistance in nanoscale features. In this study, we reported the electrochemical reactions of Ru3+ on an Ru surface using multi-cyclic voltammetry (CV) and behavior of additives during Ru electrodeposition using linear sweep voltammetry (LSV) and potentiostatic measurements. Disodium 3,3'-dithiobis(1-propanesulfonate) (SPS), polyvinylpyrrolidone (PVP), and a bromide ion (Br-) were added for bottom-up filling. We investigated the suppression behavior of PVP. The current density and the onset potential of suppressor breakdown were affected by the suppressor concentration. PVP interacted synergistically with Br- and showed additional suppression. PVP formed a suppressing layer with Br- after formation of a bromide layer. SPS could reduce roughness during electrodeposition of Ru. Based on these results, nano-trenches were filled with Ru using the optimized additive condition.

A liposome encapsulated methylene blue-mediated electrochemical and UV–visible dual mode split-type immunoassay for the detection of 17β-estradiol

Herein, we fabricated an electrochemical (EC) and UV–visible absorption (UV–vis) dual mode split-type immunoassay for the detection of 17β-estradiol (E2), which was mediated by liposome encapsulated methylene blue (MB@lip). MB molecule acted as the probe in the EC and UV–vis absorption dual mode detections, and its release was controlled by liposome. The competitive immune recognition was conducted between the E2 in the sample and E2 conjugated bovine serum protein (E2-BSA) adsorbed on the 96-wells plate in combining with E2 antibody labeled with MB@lip (E2-Ab/MB@lip). MB molecule could be released from the resulting immune composite of E2-BSA/E2-Ab/MB@lip in the presence of Triton X-100, and quantified by UV–vis and EC methods. The three-dimensional cross-linked reduced graphene oxide/Ti3C2 (3D-rGO/Ti3C2) aerogel was prepared through hydrothermal method, then complexed with the electroactive anthraquinone (AQ) and used as the electrode modified material. The AQ/3D-rGO/Ti3C2 composite had high surface area and provided abundant adsorption sites for MB, and the displacement/competitive behavior between AQ and MB could dexterously achieve the ratiometric EC detection of E2. In addition, the inherent blue color of MB allowed it to be analyzed by UV–vis absorption method. The proposed dual mode detection method exhibited broad linear ranges of 0.1 pg mL−1 to 50 ng mL−1 (by UV–vis) and 0.03 pg mL−1 to 50 ng mL−1 (by EC) for E2 detection, and the detection limits were 0.023 pg mL−1 (S/N = 3) and 8.0 fg mL−1 (S/N = 3), respectively. Moreover, the proposed immunoassay exhibited good practicability and was applied to monitor E2 in milk and serum successfully.

Spectroscopic investigations of a commercial graphite screen printed electrode modified by bismuth oxide drop deposition and electrochemical reduction, for cadmium and lead ions simultaneous determination

A single use graphite screen-printed electrode (GSPE) was easily modified, to take advantage of the proven affinity of the nontoxic post-transition metal bismuth (Bi), for metal ions to be detected by Square Wave Anodic Stripping Voltammetry (SWASV). A bismuth oxide (Bi2O3) or a chitosan coated (CS@Bi2O3) nanopowder suspension was drop-casted on the graphite working electrode (WE) surface, giving rise to the precursor of a Bi-modified GSPE. After that, an electrochemical reduction was performed to obtain the Bi– or the CS@Bi–GSPE.X-ray photoelectron spectroscopy and micro-X-ray fluorescence investigations were performed on the graphitic structure pre and post modification. The bismuth oxide deposition amount was considered as critical parameter to sensor performance, indicating a minimum and maximum threshold. Under improved measurement conditions, with a 300 s pre-concentration time, the attained sensors exhibited a linearity in the range (2.0–20.0) μg L−1 in the simultaneous analysis of Pb(II) and Cd(II). The Bi–GSPE showed LODs of 1.7 and 0.5 μg L−1 for Cd(II) and Pb(II) respectively, while 1.5 μg L−1 for Cd(II) and 0.2 μg L−1 for Pb(II) were recorded by the CS@Bi–GSPE. As an applicative proof in real sample, a spike test was carried out in a ground water sample, without any preliminary sample treatment.

A Linear Correlation of p-Band Center with the Performance of Electrochemical CO2 Reduction Revealed by Sn Single-Atom Catalysts

The correlation between p-orbital energy level and catalytic activity of electrochemical CO2 reduction reaction (ECRR) is rarely reported, but significantly desired for further design of highly effective main group single-atom catalysts (SACs). Herein, a series of Sn-SACs (Sn-N3S1, Sn-N3P1, Sn-N3B1, and Sn-N4) were developed as a model system to explore structure-activity relationships of main group SACs for ECRR. Coordination environment regulation could upshift the p-band center of Sn, facilitating the adsorption of intermediates and improving the catalytic activity. Sn-N3S1 with the most positive p-band center shows a 100% Faradaic efficiency of CO (FECO), superior over that of Sn-N4 and other reported SACs. Notably, the catalytic performance of Sn-SACs shows a linear relationship with p-band center of Sn, indicating a high applicability of p-band center as a descriptor for catalytic performance. This work provides a new way to boost ECRR by lowering the p-orbital energy level of main group metal.

Anchored silver-palladium aerogel on carbon cloth via diazonium chemistry for electrochemical reduction of CO2

Electrochemical CO2 reduction reaction (eCO2RR) is a promising route for removal of CO2 from the atmosphere and transforming it into value-added products. The development of new and efficient catalysts plays a vital role in this regard. Here a combination of carbon grafting and bimetallic metal aerogel is presented as a catalyst for eCO2RR. The grafted surface plays an essential function in assembling the catalyst on the carbon cloth (CC) surface as a supported catalyst. Herein, we describe the use of para-aminothiophenol (p-TP) as a grafting agent combined with diazonium chemistry to fix a metallic aerogel catalyst on CC as support. The silver, palladium and bi-metallic silver-palladium aerogels (Ag-p-TP, Pd-p-TP, and AgPd-p-TP) anchored onto the surface of CC yielding the corresponding surface-bound materials were used for testing the electrochemical reduction of CO2. The mono-metallic Ag carbon cloth (Ag-p-TP/CC) exhibited the ability in reducing CO2 to CO with moderate Faradaic efficiency (FE) of 74 % in 0.1 M, NaHCO3 electrolyte at pH = 7.5. The bimetallic AgPd-p-TP-CC further enhanced the Faradaic efficiency for CO formation to 88.7 %, with an unexpectedly low onset potential of −0.09 V vs. RHE. Surprisingly, formate was identified to be the liquid product when Pd-p-TP-CC and AgPd-p-TP-CC were used, with maximal FEformate of 19.0 % and 25.7 % at −1.0 V vs. RHE, respectively. In contrast, CC lacking the chemical grafting that allows immobilization of the metal aerogel (Ag-Pd/CC) exhibits lower FEco% for eCO2RR, highlighting the importance of this chemical modification of the carbon cloth surface. Diazonium chemistry coupled with metal aerogels is a new approach to generating surface-bound catalysts for the effective reduction of CO2.

Enhanced electrochemical nitrate reduction on copper nitride with moderate intermediates adsorption

Nitrate in surface and underground water caused systematic risk to the ecological environment. The electrochemically reduction of nitrate into ammonia (NO3RR), offering a sustainable route for nitrate containing wastewater treatment and ammonia fertilizer conversion. Exploration of improved catalysts activity with lower energy barriers is still challenging. Herein, we present a copper nitride (Cu3N) catalyst with moderate *NOx and·H2O intermediates adsorptions showed enhanced NO3RR performance. Density functional theory calculations reveals that the unique electronic structure of Cu3N provides efficient active sites for NO3RR, and enables balanced adsorption of *NO3 and·H2O (ΔE descriptor) and moderate intermediate (*NO3 → HNO3, *NH2→*NH3) adsorption energy. Interestingly, in-situ analysis proved the potential-driven reconstruction and rehabilitation of Cu3N, thus implied for better mechanism understanding. The NO3RR activity of Cu3N surpasses that of most recent catalysts and demonstrates superior stability and implies the application for NH4+ fertilizer recovery, which maintaining an NH3 Faradaic efficiency of 93.1 % and high yield rate of 2.9 mg cm2h−1 at −0.6 V versus RHE.

Mixed crystal FeFx submicron spheres loaded on fluorinated graphene as cathode materials for Lithium-Ion batteries

Iron fluoride (FeF3 and FeF2) is a potential candidate for the next generation of lithium-ion battery (LIBs) cathode materials due to their high theoretical specific capacity and low cost. However, previous studies have reported that the poor conductivity of FeF3 and FeF2 prevents their theoretical specific capacity from being effectively realized. Herein, fluorinated graphene loaded FeFx (FeFx@FG) submicron sphere was synthesized using graphene oxide and utilized as cathode materials for LIBs. Characterization by X-ray diffraction and transmission electron microscopy confirmed that the synthesized FeFx (x = 2 and 3) contains mixed FeF3 and FeF2crystals. The mixed crystal structure enables the FeFx@FG submicron sphere composite to display two steps in the electrochemical reaction when FeF3 and FeF2 discharge cooperatively, leading to excellent discharge performance. In addition, since the FG prepared by acid thermal method has good conductivity, it can significantly improve the FeFx conductivity and specific capacity when being connected to FG via C-F bond. The electrochemical tests show that the initial discharge capacity of FeFx@FG is as high as 394.24 mAh/g at the rate of 0.2C in the range of 1.5–4.0 V at 25 °C and display an excellent discharge capacity retention rate after the first discharge process, showing great potential of the mixed crystalline iron fluoride cathode in the field of lithium-ion batteries.

Electrochemistry of 2D-materials for the remediation of environmental pollutants and alternative energy storage/conversion materials and devices, a comprehensive review

This review article explores into the complicated relationship between electrochemistry and 2D materials, exploring their mutual influences and the consequential advancements in energy conversion, storage, and environmental applications. Electrochemical reactions, manifested through oxidations and reductions at submerged electrodes, form the linchpin connecting the electrochemistry of 2D materials with their practical utility. Various electrochemical cell topologies are investigated for their role in enhancing material flexibility, operational states, energy conversion efficiency, and device design adaptability. The comprehensive discussion extends to diverse applications, emphasizing the pivotal roles of 2D materials in environmental remediation, alternate energy storage and conversion, and chemical reactivity. Noteworthy applications include pollutant detection, adsorption and absorption of pollutants, elimination of both organic and inorganic pollutants, and photocatalytic degradation. The review also addresses materials synthesis via electrochemical processes, detailing functionalization, handling, and deposition techniques. Particular focus is directed towards local electrochemical techniques enabling the analysis and local alteration of 2D materials. Moreover, this paper concludes the article published in the recent years with this topic and most significant trends observed in 2022 and 2023 with electrochemistry of materials for the remediation of environmental pollutants. While the trends of article publishing increased from 2020 to 2023 with topic alternative energy storage/conversion materials. Finally, offering a comprehensive overview of the synergistic relationship between electrochemistry and 2D materials and their transformative potential in sustainable technologies. Broader contextThe decreasing availability of energy resources and the contamination of the environment are two significant worldwide concerns that need immediate attention. The focus on 2D materials and associated technologies is important for the efficient conversion of solar energy into chemical energy. These materials have diverse applications in fields such as energy (e.g., water splitting), synthesis (e.g., production of valuable chemicals and N2 reduction), and the environment (e.g., CO2 reduction and environmental remediation). Furthermore, Electrochemical energy storage and conversion (EESC) technologies are widely acknowledged as the most viable solutions to address the escalating energy crisis and environmental degradation because to their exceptional energy efficiency and little environmental footprint. Currently, there have been several reports discussing the use of 2D-materials in energy applications and wastewater treatment. However, there is a lack of comprehensive reviews that summarize the electrochemistry of 2D-materials, their preparation strategies, modification techniques, and related properties. Furthermore, there is a need for detailed analysis of the progress in applying 2D-materials for environmental pollution remediation, electrocatalytic performance, energy storage, and conversion technologies and devices. In this paper, we systematically and comprehensively review the electrochemistry of 2D-materials and innovatively analyze the design principles and difficulties of 2D-materials. We discussed comprehensively the remediation of environmental pollutants through 2D-materials in water treatment fields such as photocatylsts, adsorption/absorption and dyes removal as an entry point and provide an in-depth knowledge and outlook on the current status and development potential of specific applications of energy storage and conversion materials and devices.

High-Throughput screening of metal nitrides for electrochemical nitrogen reduction

Metal nitrides have garnered considerable attention in the context of nitrogen reduction reactions (NRR) due to their rich lattice nitrogen and abundant nitrogen vacancies to activate N2. However, the identification of suitable metal nitrides with superior stability, activity, and selectivity (vs. hydrogen evolution reaction, HER) for electrochemical NRR under rigorous isotope labeling experiments remains a perplexing challenge in experiments. In this study, we implemented a systematic screening protocol to assess the electrochemical stability and efficiency of various metal nitrides for NRR by high-throughput density functional theory calculations, aiming to search out promising metal nitride catalysts. Through a set of predetermined criteria, a subset of 6 candidates emerges as the most promising metal nitrides for NRR from a pool of 668 metal nitrides sourced from the Materials Project Database, all of which catalyze NRR following the Mars-van Krevelen pathway. Importantly, based on the analysis of these candidates, the unique structural property (i.e., four(or three)-coordinate lattice nitrogen) and energy descriptor (i.e., the formation energy of the lattice nitrogen vacancy is around 2.1 eV) of potential metal nitrides for electrochemical NRR were extracted, which could be used as the direction to rationally design metal nitride catalyst. This research not only serves as a valuable guide for experimental investigations into potential metal nitrides for NRR, but also provides an efficient method for high-throughput screening of potential catalysts for other electrochemical reactions.

A conductive flexible carbon nanoyarns embedded with VN quantum dots for highly Kinetics-Compatible Li-Ion capacitors

Lithium-ion capacitors (LICs) with high energy and power density has gained widespread attention. However, the kinetics mismatch between the anode and cathode of LICs limits its further development. Vanadium nitride (VN) with high electrical conductivity is a suitable anode to reduce the kinetic gap between the two electrodes of LICs, but the VN usually undergoes severe volume changes (～240 %) during the electrochemical reaction. Herein, the VN@N-PCYS-0.4 films that ultrafine VN quantum dots uniformly embedded in polyacrylonitrile-derived carbon (PAN-DC) nanoyarns were synthesized by a simple sacrificial silica template-assisted electrostatic spinning technique. Ultra-small particle size of VN (∼1 nm) mitigates the volume expansion and enriches the active sites. The super loose porous structure of PAN-DC nanoyarns shortens ions/electrons diffusion pathways and enhances electrolyte penetration. Correspondingly, on the basis of such free-standing VN@N-PCYS-0.4 anode, a LICs was assembled by matching activated carbon (AC) cathode, which exhibits a high energy density of 99.7 Wh kg−1 and a high power density of 24.0 kW kg−1. Such rational design for carbon-based material can surmount kinetics incompatibility between anode and cathode of LIC and provides a perspective to enhance the electrochemical properties of LIC anode in terms of volume expansion suppression and charge transfer resistance reduction.

Enhancing electrocatalytic performance for rechargeable Zn-air battery through interface engineering and dual-doping strategy

In this study, we report on the preparation of uniform hollow-structured nanosphere which has abundant N, S co-doped CNT encapsulating heterostructured Co/CoS2 nanoparticles (Co/CoS2/NSCNT). The bifunctional electrocatalytic performance of these materials for ORR and OER is significantly enhanced by the synergistic effect of strongly coupled heterojunctions in the Co/CoS2 nanoparticles and abundant heteroatom dopants in the CNT shells. The Co/CoS2/NSCNT exhibits half-wave potential of 0.890 V vs. RHE and overpotential of 359 mV at 10 mA cm−2 for ORR and OER, respectively. Moreover, rechargeable ZAB assembled with the Co/CoS2/NSCNT catalyst delivers a specific capacity of 746 mAh gZn−1 and a peak power density of 156.8 mW cm−2, which exceed those values of precious metal-based ZAB (673 mAh gZn−1 and 136.9 mW cm−2, respectively). Additionally, the heteroatom-doped CNT shell prevents the dissolution and aggregation of transition metal-based active species during the electrochemical reaction in alkaline condition, thereby contributing excellent long-term cyclability of rechargeable ZAB. These findings demonstrate the potential of Co/CoS2/NSCNTs as high-performance electrocatalysts for rechargeable ZABs, and provide insights into the design of efficient and cost-effective electrocatalysts for energy storage applications.

An FPGA-Accelerated Quartz Crystal Measurement System Based on a Negative Feedback Loop With Quadrature Demodulation

Rapid measurement of the resonant frequency of quartz crystal (QC) devices plays a key role in applying QC-based dynamic monitoring, such as respiration monitoring and kinetic process in electrochemical reactions. This work develops an FPGA-accelerated QC measurement system without software-based curve fitting. A negative feedback loop based on the susceptance response collected by the quadrature demodulation circuit is constructed. Moreover, a proportional-integral-differential control and tracking strategy is applied to improve the measurement speed significantly. The test results show that the implemented system can track a frequency shift of 5 kHz bandwidth within 50 ms. The standard deviation of the measured frequency of a QC device under test is only 0.17 Hz, which indicates that the proposed system is high stability and high precision. The frequency measurement results have a relative error of 0.8 ppm compared with the Agilent 4294A impedance analyzer. It is demonstrated that the proposed QC measurement system has great potential for QC-based dynamic detection.

Efficient and durable oxygen reduction in alkaline media by doping heteroatomic boron into FeSA-NC catalyst

Despite extensive research has been conducted on atomic dispersion catalysts for various reactions, altering the electronic structure of the central metal to enhance electrochemical reactivity remains a challenging task. Herein, the electrochemical reactivity was considerably enhanced by introducing heteroatomic B to adjust the d-band of single Fe center. In specific, the obtained FeSA-BNC catalyst demonstrated an outstanding ORR performance (E1/2 = 0.87 V) and exhibited greater long-term durability in alkaline media compared to Pt/C. The performance of FeSA-BNC in Zn–air battery was also higher than that of Pt/C. According to theoretical calculations, a downward shift in the d-band center of Fe was induced by introducing B, thereby improving the desorption of intermediates and facilitating the oxygen reduction reaction (ORR).

Phase transfer-assisted indium recovery from spent liquid crystal display panels and its extension in preparing indium-based electrocatalysts for CO2 reduction

Transforming discarded electronic devices into low-cost and high-efficiency catalysts presents a win–win approach to address the scarcity of rare resources and sustainable energy challenges. Herein, we report an effective strategy that combines an ethanol-mediated dodecylamine (DDA) phase transfer with hydrothermal methods for facilitating the facile synthesis of indium (In)-based nanomaterials from the leachates of liquid crystal display panels (LCDPs) toward high-efficiency electrochemical CO2 reduction reaction (eCO2RR). In this strategy, the rapid formation of coordinating compounds between the –NH2 group of DDA and metal ions facilitates the separation of In3+ cations from the acidic LCDPs leach solution by transferring them into an organic phase, which are then converted into InOOH nanoparticles with abundant oxygen vacancies (denoted as In-LCDPs and hereafter) through a low-temperature hydrothermal process. The eCO2RR evaluations confirm the superior electrocatalytic performance of the In-based nanoparticles produced from the LCDPs. In specific, within a broad potential range (−0.77 to −1.17 V vs RHE), the In-LCDPs show a Faradaic efficiency for formate (FEformate) of 85 %, with the highest FEformate of 90.23 % at −0.97 V vs RHE, which is comparable to the FEformate (93.8 % at −0.97 V vs RHE) of In-based catalyst prepared from pure In precursors using the same method. Further investigations reveal that the Sn and Al impurities have minimal impact on the catalytic performance of In-LCDPs, while the presence of Fe3+ impurities significantly enhance the production of hydrogen during the eCO2RR. This work might have provided a scalable pathway to transform LCDPs into value-added electrocatalysts for eCO2RR.

Bio-inspired bimetallic models for electrochemical CO2 reduction.

Inspired by the carbon monoxide dehydrogenase (CODH) active site where two metal ions synergistically catalyze the interconversion between CO2 and CO, we have developed a family of rhenium dipyridine derivatives (1-3), in which potassium 1-aza-18-crown-6-ether (KN18C6) moiety functions as a Lewis acid to assist the CO2 reduction reaction (CO2RR). We found that such design leads to dramatically strong deposition on the electrode under CO2 in the presence of potassium cation, and a clear trend for the deposition rate was observed following the flexibility of linkage between the framework and the KN18C6 moiety; the more flexible, the faster. The origin of deposition was further characterized by a series of control experiments and infrared spectroelectrochemistry (IR-SEC). Unfortunately, the deposition suppresses the subsequent C-O bond cleavage reaction.

Ambient N[tbnd]N bond weakening hydrogenation by utilizing the highly defective Cu3BiS3/MnO2 electrocatalyst for ammonia yield above 3 mg/h.cm2: The N2-nano dipole interaction micromechanism

This study introduces a novel Cu3BiS3/MnO2 composite catalyst for the electrochemical nitrogen reduction reaction (eNRR) to address challenges in sustainable ammonia production, aiming to replace the energy-intensive Haber-Bosch process. The ternary Cu3BiS3/MnO2 catalyst exhibited impressive results, achieving a high ammonia yield rate of 3604µgh-1cm-2 and a significant Faradaic efficiency of 31.4% at -0.75V vs. RHE in a 0.5M Na2SO4 solution, while only 446µgh-1cm-2 from binary metal CuMn(2:3). This success was attributed to abundant cation and anion defects with multiple valence charges in the Cu3-xBiS3/MnO2-y catalyst, created by introducing the third metal, Bi, into the binary CuMn system. These defects served as trapping centers for dynamic nitrogen molecule activation and facilitated charge transport, enhancing the eNRR process. This study underscores the potential of highly defective Cu3-xBiS3/MnO2-y as an efficient and sustainable catalyst for electrochemical nitrogen fixation, offering a greener approach to ammonia production.

Interfacial interactions of Cu/MnOOH enhance ammonia synthesis from electrochemical nitrate reduction

Interfacial interactions of Cu/MnOOH enhance ammonia synthesis from electrochemical nitrate reduction

Tailoring the catalytic microenvironment of CuO with hydrophobic CuSA2 for selective CO2 electroreduction to C2+ products

Advancing the Faraday efficiency (FE) and current density of Cu catalyzed electrochemical CO2 reduction (ECR) reaction to produce C2+ products is important for its practical applications. Constructing a hydrophobic interface to regulate the local reaction environment is an effective method to improve the selectivity of C2+ products, but it is limited by the low reaction current density. In this work, we fabricated a novel hydrophobic and ECR active copper stearate (CuSA2) decorated CuO nanoparticle catalyst (CuO/CuSA2) for ECR reaction toward C2+ products. As a result, the CuO/CuSA2 catalyst achieved an FE of 61.33 % and a partial current density of 429.33 mA cm−2 for C2+ products. The CuSA2 and CuO nanoparticle cooperate very well for the formation of C2+ products. The in-situ attenuated total reflectance surface-enhanced infrared absorption spectroscopy (ATR-SEIRAS) and electrochemical adsorption experiments indicated that the hydrophobic CuSA2 regulated the local ECR reaction environment. The local ∗CO2.- and *CO adsorption were strengthened by hydrophobic CuSA2 modification while the H2O adsorption was inhibited. CuO nanoparticle promotes *CO coupling reaction and enhances C2 intermediates (*OCCOH and *OC2H5) adsorption. Hydrophobic CuSA2 and CuO nanoparticle synergistically promote the generation of C2+ products. This work provides new insights into the design of hydrophobic CO2 reduction electrocatalysts for the preparation of C2+ products.

Understanding the First Activation Step of Electrochemical CO2 Reduction over Ag and Ni-N-C Active Sites

Understanding the first elementary step of CO2 activation over electrode surfaces is a prerequisite for its following precise valorization process. Even for CO2-to-CO conversion, the simplest 2e reduction reaction, the identity of its rate-limiting step (RLS) and the dependence of its reaction kinetics remain controversial. Herein, we comparatively evaluate the electrocatalytic kinetics of CO2 reduction over Ni-N-C single atom catalyst, polycrystalline and oxide-derived Ag nanocatalysts at well-defined reactant mass transport conditions using a membrane electrode assembly electrolyzer. We find the reaction kinetics for CO evolution is independent of CO2 partial pressure on Ni-N-C but be dependent on polycrystalline Ag, whereas this dependency is weakened on oxide-derived Ag with more under-coordinated surface sites exposed. The first principles calculations reveal the initial electron transfer to CO2 is the RLS for both oxide-derived and polycrystalline-Ag, while the subsequent proton transfer to CO2 is the RLS for Ni-N-C. Our findings indicate that the distinct electrostatic interactions between active sites and the adsorbed CO2 primarily contribute to these differences.

Lattice-dislocated bismuth nanowires formed by in-situ chemical etching on copper foam for enhanced electrocatalytic CO2 reduction

Electrochemical CO2 reduction reaction (CO2RR) to HCOOH is one of the most feasible and economical methods to achieve carbon neutrality. Bismuth (Bi), as a metal catalyst for CO2RR, is considered to have great potential for application and has been widely studied due to its high formate selectivity, low toxicity, cheapness, and abundance. Unfortunately, low current density and short electrode lifetime have hindered its progress towards practical applications. In this work, we present a method that enables the chemical etching of Bi on Cu, which is capable of spontaneously accomplishing the loading of Bi on Cu foam in the liquid phase at room temperature. Additionally, to provide more abundant catalytically active sites, twisted Bi nanowires (BiNWs) with lattice dislocations were successfully prepared on the surface of Cu foam using a three-step chemical method involving oxidation, reduction, and in-situ etching. The Cu Foam@BiNWs was found to be a highly active electrocatalyst for CO2 reduction to formate at a low applied potential, achieving a faradaic efficiency for formate (FEFormate) of 95 % and a formate partial current density of ∼ 12 mA cm−2 at −0.78 V vs. RHE (reversible hydrogen electrode). Even within such a wide potential window of −0.68 ∼ -1.08 V vs. RHE, the FEFormate is consistently above 90 %. Such exceptional CO2 reduction activity can be attributed to the distortions and lattice dislocations present in the surface BiNWs. Furthermore, the Cu Foam@BiNWs electrode demonstrated a total current density close to 100 mA cm−2 at −0.98 V in an alkaline flow cell, while maintaining excellent catalytic stability over a prolonged 30-hour period of high current density electrochemical activity, thus showing potential for advancing the industrialisation of formate production. This work emphasizes the crucial role of size-dependent catalysis and crystal defect engineering strategies in the field of electrocatalysis, elucidates the mechanism of the rate-determining step (RDS) in the electrocatalytic CO2 reduction process on the developed catalysts, which can provide valuable insights into the design and development of high performance electrocatalysts not only in CO2RR but also in other fields.