KBr Solutions Research Articles

Impact of Hofmeister anion type on the structural and mechanical properties of composite whey protein hydrogels

Biopolymer hydrogels are widely employed in food products to provide desirable functional attributes, especially texture and mouthfeel. Hydrogels can be created from whey proteins, but they are too soft and brittle for certain applications. Previously, it was shown that the mechanical properties of whey protein hydrogels could be enhanced by embedding whey protein nanofibers in them. In the current study, the impact of soaking these nanofiber-filled composite hydrogels in salt solutions containing anions in different positions within the Hofmeister series was studied. In addition, the impact of hydrogel pH (1, 3, 7, or 9) on the properties of the hydrogels was investigated. The hardness and shear modulus of the hydrogels increased appreciably after they were soaked in the salt solutions. For example, at pH 7 and pH 9, the hardness of the composite hydrogels soaked in K2SO4, KCl, and KBr solutions were around 5.8-, 4.8-, and 2.3-fold higher and 7.3-, 6.0-, and 3.3-fold higher than that of the original hydrogels, respectively. The magnitude of increase in gel strength was consistent with the position of the anions in the Hofmeister series: SO42− > Cl− > Br−. Fourier transform infrared showed that the presence of Hofmeister ions increased the number density and strength of protein-protein bonds in the gel network by strengthening hydrogen bonding and hydrophobic interactions. Therefore, composite whey protein hydrogels with different structural and textural characteristics could be produced by controlling their pH values and/or by soaking them in salt solutions containing anions in different positions within the Hofmeister series.

Simultaneous selective separation and enrichment of bromine and cesium ions by electrochemically switched amphoteric ion membrane

A BiOBr film electrode was prepared by electrodeposition method for verifying an electrochemically switched amphoteric ion exchange (ESAIX) mechanism. Physical and electrochemical characterization results reveal that the BiOBr can switch the valence of Bi between Bi3+ and Bi(3-x)+ to selectively insert Cs+ with simultaneously release Br− at a reduction potential, while it can selectively insert Br− with simultaneously release Cs+ at an oxidation potential. The separation factors of BiOBr film electrode for Cs+/K+, Cs+/Na+, Cs+/Li+, and Cs+/Rb+ cations were 3.71, 3.23, 4.94, and 7.46, respectively, and for Br−/F−, Br−/Cl− and Br−/NO3− anions were 2.11, 1.55 and 3.83, respectively, which showed relatively excellent selectivity for Br− and Cs+. Density functional theory (DFT) calculations reveal that the selectivity of BiOBr towards Br− and Cs+ comes from the lower ion migration energy barrier in the BiOBr lattice. Based on the ESAIX mechanism, a novel electrochemically switched amphoteric ion membrane coupling permselective (ESAIM-CP) system was further developed for the simultaneous separation and enrichment of Br− and Cs+, which successfully achieved the enriched CsBr with 2 folds of the original concentration from a mixed solution of Cs2SO4 and KBr.

Facile synthesis of BiOCl/BiOBr heterojunctions via anion exchange reactions

BiOCl/BiOBr heterojunctions were prepared through the reaction of pre-synthesized BiOCl nanosheets and KBr solution. The anion exchange reaction kinetics can be easily controlled by synergistically adjusting the temperature, reaction time and reactant (KBr solution) concentration. As a result, the phase transition from parent BiOCl to Br-doped BiOCl or BiOCl/BiOBr heterojunctions or Cl-doped BiOBr was readily achieved. The BiOCl/BiOBr heterojunction prepared with the lowest energy consumption exhibited superior photocatalytic performance compared to the parent BiOCl due to its improved light absorption and charge separation efficiency. This work is expected to boost the development of various bismuth oxide halide-based heterojunctions.

Hydration Processes in HCl and Aqueous Salt Solutions

In this work, the number of hydration of ions (K+ and Cl-, K+ and Br-, K+ and I-, H+ and Cl-, Li+ and Cl-, Cs+ and Cl-, Na+ and Cl-) in dilute aqueous solutions of some electrolytes of KCl, KBr, KI, HCl, LiCl, CsCl, and NaCl was studied by the proposed refractometric method. Further, the effect of polyethylene glycol (PEG-6000) on the hydration processes for ions in aqueous solutions of KCl and KBr was studied. It turned out that when the polymer is introduced into the solution, the hydration numbers of ions decrease, which is apparently due to the role of the PEG oxygen atom competing with ions in interaction with water molecules.

Enhancing Surface Integrity of Micro-Holes Machined on Inconel 718 using Shaped Tube Electrochemical Machining via Hydroxide Mixing

This research explores enhancing surface integrity of high aspect ratio (AR>5) micro-holes machined on Inconel 718 using Shaped Tube Electrochemical Machining (STEM) by mixing limited amount of metal hydroxides in the different electrolyte solutions. Typically, STEM employs hazardous acid solutions. These solutions cause machine corrosion, environmental risks, and harm to operators. This research aims to explore eco-friendly and safe alternatives. The efficacy of adding NaOH or KOH to eco-friendly neutral aqueous solutions of NaCl, KBr, and NaNO3 on machined surfaces is expounded. We assess electrolyte mixing parameters, including concentration and composition, and explore the effects of varying electrolyte temperature, voltage, and tool feed rate. Surface assessment uses SEM, EDX, XRD, and profilometry. Results reveal that adding hydroxides to neutral salt solutions improves surface roughness and reduces pitting. Hydroxide ions aid in dissolving oxide films during STEM of Inconel 718. Under specific conditions (9 g l−1, 18°C, 8 V, 0.8 mm min−1), NO3│OH yielded the lowest Ra (1.64 μm), while Br│OH resulted in the highest Ra (2.14 μm) with pitting, cracks, and deposits. NO3│OH exhibited a 25% decrease in Ra when a hydroxide concentration rise from 3 g l−1 to 15 g l−1. This research supports eco-friendly STEM for improved surface quality without process performance compromise.

Controlling the optical and morphological stability of 4-mercaptobenzoic acid-modified triangular silver nanoplates in saline environments

The structural instability of triangular silver nanoplates (AgNTs) due to the etching effect that occurs in biological environments significantly modifies their shape and plasmonic properties and releases Ag ions making them extremely toxic. Herein, we control the morphological and optical stability of citrate-coated AgNTs by modifying their surface with various amounts of 4-mercaptobenzoic acid (MBA). We find that the shape evolution is completely inhibited for AgNTs modified with 10−3 M MBA concentration both in the presence of NaCl, KCl, KBr, KI, and H2O2 solutions, as well as cellular medium or simulated body fluid enriched with human serum albumin. In contrast, the etching process cannot be stopped for AgNTs modified with lower MBA concentrations, but it can be reduced. Photothermal experiments under near-infrared (NIR) laser irradiation at 785 nm further support the remarkable stability of AgNTS-MBA 10−3 M and their high light-to-heat conversion efficacy of 72 %. Finally, AgNTs-MBA exhibit intrinsic photoluminescence emission (PL) as well as surface-enhanced Raman scattering (SERS) signal under NIR excitation. We show that nanoparticle stability is crucial in controlling the PL-SERS signal. Owing to their high optical and morphological stability and localized surface plasmon resonances in the NIR region, AgNTs-MBA are excellent candidates for photothermal applications.

Thermodynamic Modeling of Methane Hydrate Phase Equilibria in Chloride and Bromide Solutions

The formation of hydrates is a major issue in the oil and gas industry. Injection of electrolytes is considered one of the best ways to prevent its formation. A thermodynamic model is developed from the Klauda and Sandler model, PRSV EoS, and Pitzer’s correlation to study the phase equilibria of methane hydrate in chloride and bromide electrolyte solutions. The model employs the parameters reported by Pitzer and Mayorga to calculate the Debye–Huckel coefficient and the second and third virial coefficients at 25 °C. The %AAD in predicted equilibrium pressures from experiments is 3.70 when the hydrate formed in NaCl, KCl, MgCl2, and CaCl2 solutions, whereas it is 2.33 in NaBr, KBr, MgBr2, CaBr2, and ZnBr2 solutions. The inhibition effect of any electrolyte on methane hydrate formation at 1 wt % is small, slowly increases at 3 wt %, and then pronounces at 5, 10, and 15 wt %. The cage occupancies have been found to increase and the activity of water has been found to decrease with the increase in electrolytes concentration. The freezing point depression of water in the presence of the strongest inhibitor MgCl2 has been observed to be −12.82 °C, whereas in the presence of the weakest inhibitor ZnBr2 it is −4.22 °C, both at 15 wt % concentration. Based on the phase equilibrium results and the freezing point depression of water, the order of the methane hydrate inhibition effect among all of the electrolytes studied here is MgCl2 > NaCl > CaCl2 > KCl > NaBr > ZnCl2 > MgBr2 > KBr > CaBr2 > ZnBr2.

Transport of hydroxyapatite nanoparticles coated with polyacrylic acid under unsaturated water flow in soil columns

ABSTRACT Phosphorus (P) nanoparticles were hypothesized to exhibit greater mobility in soils than water-soluble P (WSP) and were therefore proposed to be used as a P fertilizer. Unsaturated transport is the main pathway from the application site to plant roots. Though its importance to fertilizer efficacy, quantitative evaluation of unsaturated transport of P nanoparticles has been overlooked to date. Mobility of spherical nano-hydroxyapatite particles coated with polyacrylic acid (PAA-nHAP) suspension and WSP (a mixture of KH2PO4 and K2HPO4) was evaluated in breakthrough column experiments under unsaturated states using three soils: alkaline sand (sandy-alk), acidic sandy clay loam (sandy-ac) and clayey soils. Next, P retention was determined by total P extraction layer-by-layer from the disassembled soil columns. In all soils, PAA-nHAP exhibited faster transport compared to WSP. In the sandy-alk soil, earlier breakthrough but lower plateau of the final relative P concentration of PAA-nHAP (64.0% vs. 100% of the input P concentration) and consistent low P retention with depth after washing with 10 mM KBr solution for the two sources were observed. In the other two soils, PAA-nHAP displayed greater retention near the inlet and decreased retention with depth. In the sandy-ac soil, no WSP and low final relative concentrations of PAA-nHAP (11.6%) were transported through the soil column. The retention of PAA-nHAP was much lower than that of WSP with depth. In the clayey soil, the breakthrough (relative P concentration >1%) occurred earlier (~35 pore volumes vs. ~45 pore volumes) and the eluted P concentration increased more rapidly (~2.6 times) for PAA-nHAP compared to WSP. The difference between the two sources mainly occurred at the soil surface with higher retention of WSP. Soil properties affected the P retention capacity of the two P sources, but for all soils, P mobility was increased by changing from the common soluble fertilizers to nanoparticles. Adsorption and size exclusion effect are suggested as the major factors affecting nHAP mobility. We suggest that the nHAP transport can be improved by modifying its coating with more negative zeta-potential to decrease coagulation and adopting drip flows with short hydraulic retention time. The design of the nanoparticles needs to take into account soil properties.

Facile Preparation of Ag-NP-Deposited HRGB-SERS Substrate for Detection of Polycyclic Aromatic Hydrocarbons in Water

In this study, a surface-enhanced Raman scattering (SERS) substrate based on high-refractive-index reflective glass beads (HRGBs) was prepared by a facile method and successfully applied to the detection of polycyclic aromatic hydrocarbons (PAHs). The HRGB-SERS substrate was prepared by depositing silver nanoparticles (Ag NPs) onto the surface of HRGBs. The preparation procedure of the substrate was simplified by accelerating the hydrolysis of (3-Aminopropyl) trimethoxysilane (APTMS) and increasing the concentration of Ag NPs. Compared with previous methods, the HRGB-SERS substrate prepared with one round of deposition has the same detection performance, a simpler preparation process, and lower cost. Additionally, halide ions were used to modify the substrate to increase the detection sensitivity of PAHs. Adding 10 mM KBr solution to the HRGB-SERS substrate was found to achieve the best modification effect. Under the optimal modification conditions, the detection sensitivity of pyrene was improved by 3 orders of magnitude (10−7 M). Due to the HRGB-SERS substrate’s excellent performance, the rapid identification and trace detection of spiked water samples mixed with anthracene, phenanthrene, and pyrene was realized using a Raman spectrometer with only a volume of 10 μL of the water samples.

Numerical modeling of contaminant advection impact on hydrodynamic diffusion in a deformable medium

The self-weight of solid waste or machine-rolled compaction can induce or trigger contaminant migration in the landfill. Although the consolidation-induced hydraulic gradient driving solution transport has been extensively investigated, little attention has been paid to ion migration caused by its concentration gradient variation. It is necessary to more precisely predict the multi-stage contaminant transports in deforming porous material. Based on the modified Cam-clay model, the proposed fluid-solid coupled model can simulate the elastoplastic deformation behavior of layered kaolinite and KBr solution transport/sorption, and its modeling results were validated by published laboratory data. The solid-fluid interactions were analyzed by comparing various transport manners of K + and Br − from excess pore pressure generation to dissipation. Results reveal that the consolidation process can accelerate KBr solute advection from the contaminated layer into the uncontaminated layer, and then affects the subsequent diffusion, mechanical dispersion and sorption for K + and Br − . The simulations also indicate that consolidation-induced solute transport is time-dependent, and therefore the ion diffusion and mechanical dispersion should receive more attention.

Electromagnetic shielding of Optically-Transparent and Electrically-Insulating ionic solutions

High-tech electronic and communication devices require advanced materials for their protection against electromagnetic interference (EMI). Electrically conductive solid materials, such as metals, are typically employed as EMI shields owing to their high shielding performance caused by their high electronic conductivity. Herein, electrically insulative and ionically conducting aqueous ionic solutions of KBr, NaCl, and CaCl2 salts are investigated with a focus on their effective EMI shielding performance, which is mechanistically different from that of conventional solid materials. A 5m KBr solution exhibits an optimal EMI shielding effectiveness of 61.3 dB at 5-mm thickness. Debye and Drude theoretical models, which describe polarization of dipolar water molecules and ionic conduction of mobile ions, respectively, are invoked to elucidate the absorption-dominant EMI shielding mechanism of the optically transparent aqueous ionic solutions in X-band (8.2–12.4 GHz) frequency range. Cost-effective aqueous ionic solutions can be used as efficient and lightweight EMI shielding materials providing strong optical transparency in advanced electronic systems.

Numerical Simulation of the Electrosynthesis of Br2 from a Highly Concentrated KBr Solution

This work is aimed to investigate the electrolysis of a highly concentrated KBr solution on platinum electrodes to produce Br2(l) in a two-electrode cell without separator. The liquid bromine produced on the anode surface increases the local density up to 212% with respect to the 1 M KBr original solution. This increase in density promotes a natural Br2(l) convection flux toward the bottom of the cell with a Grashof number <1x109. The highly dense, slightly soluble, and stable liquid bromine produced at the anode surface absorbs visible light, it exhibits an intense reddish-brown color at high concentrations and a yellowish color at more dilute ones. It facilitates mass transfer studies, diffusion layer monitoring and natural convective flux inspection by video recording. The results presented in this study include a qualitative comparison between the concentration profiles, the current and potential distribution, and the calculated velocity profiles compared with those obtained experimentally.

A singular behavior at the electrolytes solution surfaces: Experimental and simulation investigation over an extended range of temperature

The aqueous electrolytes solutions have an essential role in a variety of systems including natural, biological, and industrial processes. The vital role in human bio-activity and the enhanced oil recovery are two familiar examples with the features that mainly root from the special organization of ions in the solution surface. Despite research works that have been reported on the electrolyte's solution surface, the dependence of surface properties on the thermodynamic state and the chemical nature of constituting phases is still an open field of ongoing research. In this study, the surface properties of halides (NaCl, KBr, and KI) aqueous solutions at the interface with vapor-saturated and at n-octane phase are investigated by surface tension measurement and molecular dynamics simulation. Surface entropy, surface enthalpy, and surface excess concentration (Γ) are explored in a wider range of temperature (up to 343.15 K) than those already have been reported. The surface tension measured under vapor-saturation conditions decreases with temperature and increases with concentration linearly, though shows some characteristics fluctuations. For both (NaCl and KI) systems, variation of Γ versus temperature peculiarly shows a maximum centered in the range of 308.15–313.15 K at all concentrations. These peculiar singularities involve a wealth of information related to the alteration of the surface structure that roots from the nature of Cl− and I− anions at vapor-saturation. To decipher this peculiarity for microscopic details and to account for the factors underlying this singularity, molecular dynamics simulation of NaCl, KBr, and KI aqueous solution was performed over the range 298.15–343.15 K. The simulated bulk and surface molecular structure, as well as the bulk transport properties of 1.0 M (mol/lit) NaCl, KBr, and KI aqueous solution, confirm a singular behavior in the range of 308.15–313.15 K which accounts for the behavior and trend of thermodynamic and surface excess concentration we measured experimentally as a function of temperature. Considering halides salts are taking the main part in the human body intervascular fluid, this discovery also presents a baseline that allows unraveling the effect of temperature fluctuations on the distribution of the excess concentration at the fluid/cell tissue interface.

An investigation on the structure and group vibrations of balenine molecule by matrix isolation IR spectroscopy, DFT and MP2 based calculations

Stable conformers of neutral balenine were scanned through molecular dynamics simulations and energy minimizations using Allinger’s MM2 force field. For each of the found minimum-energy conformers, geometry optimization and thermochemistry calculations were performed by using B3LYP, MP2, G3MP2B3 methods, 6-31G(d), 6–311++G(d,p) and aug-cc-pvTZ basis sets. The calculation results have indicated that balenine has about twenty stable conformers whose relative energies are in the range of 0–9.5 kcal/mol. Three of these are thought to provide the major contribution to matrix isolation IR spectra of the molecule. Our solvent calculations using the polarized continuum model revealed the stable zwitterion structures which are predicted to dominate IR spectra of balenine in water and heavy water (D2O) solvents. Pulay’s SQM-FF method was used in scaling of the harmonic force constants and vibrational spectral data calculated for the neutral and zwitterion structures. These refined calculation data together with those obtained from anharmonic frequency calculations enabled us to correctly interpret the matrix isolation IR spectrum of balenine and the tautomerism-based changes observed in its KBr IR and solution (D2O) IR spectra. The results revealed the crucial role of conformation and zwitterionic tautomerism on the structure and vibrational spectral data of the molecule.

A Versatile Cationic Organic Network Adsorbent for the Highly Efficient Removal of Diverse Water Contaminants

AbstractWater decontamination is of great importance to address the increasing shortage of water resources, ion‐exchange‐driven adsorption being one of the most efficient approaches to this aim. Despite the advances achieved in this field, particularly with the emergence of ionic organic networks as a new class of adsorbents for water treatment, the development of adsorbents with high performance is still highly desired. This paper describes the facile preparation of a new cationic organic network, denoted as CON‐LDU3, via a quaternization reaction between 1,2,4,5‐tetra(pyridin‐4‐yl)benzene and 1,4‐bis(bromomethyl)benzene. The cationic framework and abundant exchangeable Br− anions render CON‐LDU3 as a suitable adsorbent to capture anionic contaminants from water. CON‐LDU3 displays fast kinetics and high capacity for the removal of CrO42−, reaching the kinetic constant and maximum capacity values of 0.0539 g mg−1 min−1 and 232 mg g−1, respectively. Moreover, this adsorbent can be regenerated by simple washing with KBr solution, and it can be recycled for at least eight times. CON‐LDU3 also exhibits excellent performance in the adsorption of some emerging organic water contaminants such as orange G and diclofenac sodium. Therefore, this study demonstrates the high potential of CON‐LDU3 as a versatile adsorbent for water remediation.

UHMWPE Modified by Halogenating Reagents: Study on the Improvement of Hydrophilicity and Tribological Properties

Three groups of ultra-high-molecular-weight polyethylene (UHMWPE) with optimum hydrophilicity were obtained by halogenation modification. They were immersed in a 15% KBr solution for 30 h, a 10% NH4Cl solution for 60 h, or a 15% NH4Cl solution for 60 h. The mechanism of hydrophilicity enhancement by halogenation modification was investigated by combining surface morphologies and energy spectrum analysis. Friction and wear tests were carried out to measure the friction coefficients of modified UHMWPE under different test conditions, and the wear volume and morphologies of the worn surfaces were studied to explore the friction and wear mechanism. The results showed that the best tribological properties were obtained when immersed in the 15% KBr solution for 30 h. Furthermore, the synergistic optimization effect of hydrophilicity enhancement on tribological properties was explained by the lubrication mechanism, as well as the influence of interfacial properties change on the wear mechanism. This study provides an experimental and theoretical basis for using halogenated UHMWPE.

Low-Resistance silver bromide electrodes for recording fast ion channel kinetics under voltage clamp conditions

BackgroundTwo-electrode voltage clamp is a widely used technique for studying ionic currents. However, fast activation kinetics of ion channels are disguised by the capacitive transient during voltage clamp of Xenopus oocytes. The limiting factors of clamp performance include, but are not limited to, amplifier gain, membrane capacitance, and micropipette resistance. Previous work has focused on increasing amplifier gain (e.g.; high performing two-electrode amplifiers) or reducing the membrane capacitance (e.g.; the cut-open technique). New methodThe use of an Ag-AgBr electrode with saturated KBr solution to reduce micropipette resistance. ResultsThe conductivity of 4 M KBr was 37 % higher compared to 3 M KCl and the micropipette resistance was reduced by 19 % when 4 M KBr was used, compared to the standard 3 M KCl solution. Micropipette resistances correlated positively with capacitive transient durations. Neither the current-voltage relationship of the voltage-gated sodium channel, Nav1.7, nor Xenopus oocyte stability were affected by bromide ions. Comparison with existing methodsThe de facto standard for two-electrode voltage clamp is 3 M KCl and Ag-AgCl electrodes, which are associated an unnecessarily high micropipette resistance. Elsewise, cut-open voltage clamp techniques are technically demanding and require manipulation of the intracellular environment. ConclusionsThe use of an Ag-AgBr electrode with saturated KBr as micropipette solution reduces the capacitive transient in two-electrode voltage clamp recordings. Moreover, the exchange of chloride against bromide ions does not seem to affect oocyte physiology and ion channel kinetics.

Dissolution of Metals in Different Bromide-Based Systems: Electrochemical Measurements and Spectroscopic Investigations.

The dissolution of the main metals (Cu, Zn, Sn, Pb and Fe) found in waste printed circuit boards (WPCBs) was investigated by electrochemical corrosion measurements (potentiodynamic polarization and electrochemical impedance spectroscopy (EIS)) in different bromide-based systems that could be used as lixiviants in hydrometallurgical route of metals recovery. The analysis of the corrosion products was carried out by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) measurements. All measurements showed that the addition of bromine in the electrolyte favors to great extents the dissolution process of all studied metals as compared to bromine-free electrolytes. In the investigated experimental conditions, the highest dissolution rates of the metals were obtained in acidic KBr solution containing 0.01 mol/L bromine and they decreased in the following order: Zn >> Sn > Pb > Fe > Cu. The XRD and XPS chemical assessment allowed the identification of the dissolution products formed on the metallic surfaces after exposure to the electrolytes. They consisted mainly of oxides in the case of Cu, Zn, Sn and Fe, while the presence of PbBr2 was also noticed on the lead surface. Based on the results of EIS and surface investigations, several models explaining the corrosion behavior of the metals were proposed and discussed. The obtained results demonstrate that all studied metals could be successfully leached using brominated solutions, providing a viable alternative for the selective and efficient recovery of the base metals from WPCBs through a multi-step hydrometallurgical processing route.

Study of solute-solvent interactions using volumetric properties for the ternary {L-Serine +H2O+NaBr, KBr, LiBr} solutions at different temperatures and ambient pressure

Abstract Volumetric properties for L‑serine in aqueous LiBr, NaBr and KBr solutions, are reported by using the measured density values for these systems. The apparent molar volume at infinite dilution (Vφ0) is evaluated by fitting the Redlich-Meyer type equation to apparent molar volume values (Vφ). In the following, the expansibility and hydration number for L‑serine are appraised. The results revealed that, by increasing concentration and temperature, the apparent molar volume values enhanced for all solutions. It is indicated that the calculated hydration number for L‑serine increased by growing the salt concentration in studied solutions while decreased when rising the temperature. Also solute–solvent interactions are discussed in detail. It is shown that L‑serine has structure maker role in considered ternary solutions.

A scalable method for preparing Cu electrocatalysts that convert CO2 into C2+ products

Development of efficient catalysts for selective electroreduction of CO2 to high-value products is essential for the deployment of carbon utilization technologies. Here we present a scalable method for preparing Cu electrocatalysts that favor CO2 conversion to C2+ products with faradaic efficiencies up to 72%. Grazing-incidence X-ray diffraction data confirms that anodic halogenation of electropolished Cu foils in aqueous solutions of KCl, KBr, or KI creates surfaces of CuCl, CuBr, or CuI, respectively. Scanning electron microscopy and energy dispersive X-ray spectroscopy studies show that significant changes to the morphology of Cu occur during anodic halogenation and subsequent oxide-formation and reduction, resulting in catalysts with a high density of defect sites but relatively low roughness. This work shows that efficient conversion of CO2 to C2+ products requires a Cu catalyst with a high density of defect sites that promote adsorption of carbon intermediates and C–C coupling reactions while minimizing roughness.