Electrochemical Active Surface Area Research Articles

Synchronous activation of praseodymium vanadate/graphitic carbon nitride nanocomposite: A promising electrode material for detection of flavonoid– Quercetin

Flavonoids or phenolic compounds are part of the daily intake of every human being. Though they are positive traders for metabolism, excessive intakes bring about detrimental impacts on human health. Herein, the anti-cancer capacitive nature quercetin (Qc) was electrochemically detected through the rare earth metal-based sphere like praseodymium vanadate (PrVO4) entrapped graphitic carbon nitride (g-CN) as electrode modifiers. The nanocomposite was prepared by the one-pot hydrothermal method and characterized by phase compositional and morphology-based techniques. The existing synergistic nature between the PrV@g-CN (praseodymium vanadate@graphitic carbon nitride) makes them have an enhanced electrochemical response towards the Qc than the individual material. The obtained cyclic voltammogram and differential pulse voltammogram profile show one major oxidation peak which is attributed to the conversion of quercetin to quercetin-o-quinone. The PrV@g-CN/GCE (GCE- glassy carbon electrode) shows a good electrochemical active surface area (A = 110 cm2) and linear range between 0.05 and 252.00 μM with a LOD (limit of detection) of 0.002 µM. Moreover, the PrV@g-CN/GCE exhibits good current retention (94.76 %) around 14 days and appreciable repeatability (RSD- 0.5 %) and reproducibility (RSD- 1.3 %) towards the Qc. The real-time implementation of the proposed sensor exhibits a good recovery range towards the black tea (95.00–98.10 %) and green tea (97.80–99.60 %).

Sn doping role in structural modifications and electrochemical performance of Co(OH)2 nanorods for supercapacitors applications

Herein, pristine and Sn–Co(OH)2 nanorods are prepared via hydrothermal method and pseudocapacitive properties are evaluated. The synthesized nanostructures are characterized by various sophisticated techniques including x-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), photoluminescence (PL), scanning electron microscopy (SEM), energy dispersive x-ray spectroscopy (EDS), Brunauer–Emmett–Teller (BET) analysis, transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HRTEM). The SEM analysis discloses the structural modification of Co(OH)2 from nanoparticles to nanorods. Additionally, the presence of Sn in Co(OH)2 significantly influence the electrochemical active surface area which enhances the electrochemical properties as measured through cyclic voltammetry (CV), galvanostatic charge discharge (GCD) and electrochemical impedance spectroscopy (EIS). The SnCo-4 sample indicates high surface area (93.1 m2/g), superior performance with specific capacitance of 1441.8 F/g at 1 A/g and remarkable stability of 84.3 % retention after 5000 GCD cycles. The pseudocapacitive nature (b = 0.799) is observed to increases with scan rate (i.e. 59.1 % at 75 mV/s). This higher performance is mainly due to greater charge transportation and conductivity associated with nanorod morphology and Sn ion. These parameters disclosed that the prepared samples have great potential to be used against energy crisis.

In-situ electrochemical self-reconstruction of permeable Ni(OH)2/Pt hybrid for accelerating alkaline hydrogen evolution

Pt-based hybrid materials are demonstrated to be the most effective catalysts for alkaline hydrogen evolution reactions (HER) due to the synergy effect of heterogeneous interfaces. However, the heterogeneous interfaces are often constructed at the sacrifice of the electrochemical active surface area to cause relatively lower HER activity than expected. Herein, a permeable Ni(OH)2 layer and strained Pt atoms heterogeneous interface with enhanced electrocatalytic activity and minimal loss of active surface sites have been created by using an in-situ electrochemical self-reconstruction strategy. The permeable Ni(OH)2 layer promotes H2O dissociation without blocking proton contact with the active Pt sites. This unique design creates a favorable local acid-like environment that results in an ultra-high mass activity of 17.8 A mgPt−1 at an overpotential of 70 mV, which is 20.5 times superior to that of the commercial Pt/C catalyst and higher than those of the previously reported Pt-based catalysts. Meanwhile, the HER overpotential displays as low as 15 mV at 10 mA cm−2, showing superior HER efficiency and representing one of the optimal Pt-based HER catalysts in alkaline solution. In-situ Raman spectroscopy and DFT calculations prove that the interfacial synergistic interaction between permeable Ni(OH)2 layer and strained Pt atoms can significantly promote the H2O dissociation and the H2 formation. This electrochemical self-reconstruction method provides an effective and facile strategy for optimizing the electronic structure, electrocatalytic activity, and mass activity of active Pt atoms to develop efficient Pt-based heterostructure electrocatalysts.

Synthesis of polypyrrole (PPY) functionalized halloysite nanotubes (HNTs): An electrochemical sensor for ibuprofen

Over-the-counter availability of non-steroidal anti-inflammatory drugs (NSAIDs) without prescription, for medicinal use has led to abuse in accidental and intentional suicides. In this context, the present study accentuates on the development of simple and reliable electrochemical sensor based on the HNTs coated with in-situ polymerized polypyrrole (HNT/PPY) for detection of ibuprofen (IBP). Surface functionalization of HNTs with PPY increased the electron rich centres on the electrode surface with an evident ∼8 fold increase in electrochemical active surface area (EASA) as compared to bare electrode, facilitating electron transfer rate. The analytical and electrochemical characterization of the sensor was carried out with TEM, EDX-mapping, FTIR, XPS, XRD, CV and DPV. The proposed sensor exhibited a sensitive response towards oxidation of IBP with linear dynamic range (LDR) of 0.1–100 µM and offers a fairly good limit of detection (LOD) of 0.9 µM. The practical utility of the sensor was tested for real time detection of IBP from biological matrix (urine). Sensitive, selective and stable response of HNT/PPY towards electrochemical oxidation of IBP suggested it is a promising platform for IBP detection and can be used in forensic field and clinical set ups.

Electrochemically selective ammonium recovery from wastewater via coupling hydrogen bonding and charge storage

Electrochemical ammonium (NH4+) storage (EAS) has been established as an efficient technology for NH4+ recovery from wastewater. However, there are scientific difficulties unsolved regarding low storage capacity and selectivity, restricting its extensive engineering applications. In this work, electrochemically selective NH4+ recovery from wastewater was achieved by coupling hydrogen bonding and charge storage with self-assembled bi-layer composite electrode (GO/V2O5). The NH4+ storage was as high as 234.7 mg N g−1 (> 102 times higher than conventional activated carbon). Three chains of proof were furnished to elucidate the intrinsic mechanisms for such superior performance. Density functional theory (DFT) showed that an excellent electron-donating ability for NH4+ (0.08) and decrease of diffusion barrier (22.3 %) facilitated NH4+ diffusion onto electrode interface. Physio- and electro-chemical results indicated that an increase of interlamellar spacing (14.3 %) and electrochemical active surface area (ECSA, 388.9 %) after the introduction of GO were responsible for providing greater channels and sites toward NH4+ insertion. Both non-ionic chemical-bonding (V5+=O‧‧‧H, hydrogen-bonding) and charge storage were contributed to the higher capacity and selectivity for NH4+. This work offers underlying guideline for exploitation a storage manner for NH4+ recovery from wastewater.

Facile fabrication of an enhanced electrodeposited nickel electrode for alkaline hydrogen evolution reaction

Electrodeposited nickel (Ni) electrode for alkaline hydrogen evolution reaction (HER) has low cost and high stability advantages, but its catalytic performance is unsatisfactory. In this study, a Ni electrode with a pentagonal pyramid microstructure was first fabricated by electrodeposition, and then the surface microstructure and chemical composition of the electrode were elaborately modified by a simple acid etching treatment which significantly enhanced the HER catalytic performance. The HER over-potential at 10 mA cm−2 on the electrode which was etched for 60 min was reduced from 238 mV to 60 mV compared to the un-etched one. The fabricated electrode could maintain stable catalytic stability at a current density of 100 mA cm−2 beyond 360 h. The surface microstructures and chemical compositions of the electrodes were characterized and the catalytic kinetics were investigated by electrochemical methods. The steps on the pentagonal pyramids on the Ni electrode were preferentially dissolved in the etching treatment and the surface became undulating, which efficiently increased the electrochemically active surface area (ECSA). The etching treatment improved the surface wettability and accelerated the hydrogen bubble detachment speed on the electrode. Meanwhile, the electrode surface was further oxidized in the etching treatment. Metallic Ni and crystal NiO were alternately presented on the electrode surface. The generated NiO could facilitate the Volmer step in the HER, which led to the change of the rate-controlling step from the Volmer step to the Heyrovsky step. Further, the synergistic effect between Ni and NiO with a suitable ratio improved the HER catalytic performance of the electrode.

Synergistic effect of morphology and Co+2/Co+3 ratio on supercapacitor performance of Co3O4/vertical graphene nanosheets binder-free hybrid electrodes

Cobalt oxide (Co3O4) nanostructures decorated vertical graphene nanosheets (VGN) based hybrid electrodes are synthesized to fabricate binder-free high-performance supercapacitors. Tuning of microstructure, morphology, and stoichiometry of Co3O4 nanostructures is endeavoured by growing them in an oxygen medium using the pulsed laser deposition (PLD) technique. The variation in background oxygen pressure transformed the growth morphology of Co3O4 nanostructures from smooth film to nano-particulate caterpillar, flower, and cloud-like. Additionally, the variation in background oxygen pressure significantly influences the Co+2/Co+3 ratio. Moreover, the morphology variation led to a significant change in electrochemical active surface area (ECSA), and the electrochemical impedance characteristics varied from highly capacitive to nearly diffusive nature. These Co3O4/VGN hybrid electrodes exhibited an areal capacitance value of 32 mF/cm2 (1900 F/g) @ 20 mV/s with cyclic stability of 87 % after 3000 charge-discharge (CD) cycles in 1 M KOH electrolyte. Herein, a correlation between morphology, ECSA, and Co+2/Co+3 ratio with areal capacitance values is established. Finally, an asymmetric coin-cell device is fabricated using the Co3O4/VGN as a positive electrode and oxygenated VGN as a negative electrode, respectively. The coin-cell device exhibited a 4 mF/cm2 capacitance with energy and power densities of about 1.8 μWh/cm2 and 218.8 μW/cm2, respectively. Additionally, the coin-cell device displayed excellent cyclic stability of 92% after 5000 CD cycles. The potential utilization of this device is demonstrated by lighting an LED.

Facile fabrication of bismuth vanadate grafted carbon nanotubes composite for enhanced oxygen evolution reaction

The increasing demand of maintainable energy boosts researchers to develop reliable electrocatalysts for enhanced water splitting mechanisms. All thesynthesized materials, including CNTs, BiVO4, and BiVO4/CNTs, were characterized utilizing a variety of methodologies to assist the structural, configurational, morphological, and topographical investigations. This work aims to create unique BiVO4/CNTs nanocomposite, which may have higher electrocatalytic activity then previous materials (81 mV dec−1 tafel slope and overpotential of 237 mV at 10 mAcm−2). The composite exhibits notable qualities, including extended stability lasting up to 100 h, a substantial electrochemically active surface area (ECSA) of 586.5 cm2, minimal charge transfer resistance (Rct) of 1.3 Ω, a low onset potential, a reasonably reduced overpotential, and a relatively modest Tafel slope. The synergistic interaction between CNTs and BiVO4 is responsible for electrocatalyst's exceptional catalytic efficiency and unique stability for 100-hour retaining both morphological and structural features, showcasing structural integrity of BiVO4/CNTs nano-composite. The objective of this research is to split water into its componentmolecules using a nano-composite made, and may also useful for future applications.

Controllable Sulfurization of MXenes to In‐Plane Multi‐Heterostructures for Efficient Sulfur Redox Kinetics

AbstractAlthough in‐plane heterostructure with high ion transport pathway and unique interfacial atomic structure offers endless possibilities in the catalysis field, it is still challenging to directly synthesize MXene‐based in‐plane heterostructure due to the differences in crystal structures and growth conditions. Here, Mo2C–MoS2 in‐plane multi‐heterostructures are synthesized by topological conversion of sandwich‐like mesoporous Mo2C–SiO2 layers in sulfur vapor and subsequent removal of SiO2. During the conversion process, the exposed Mo2C will efficiently converted to 2H phase MoS2, meanwhile, the covered Mo2C remained stable, affording metallic Mo2C MXene and semiconducting MoS2 in‐plane multi‐heterostructures compatible in one layer. The resultant Mo2C–MoS2 layer has multiple heterointerfaces, build‐in electric fields as well as abundant defects. Such structural features enable to improve of the electrochemical active surface area (16.4 mF cm−2), which not only facilitates the bidirectional sulfur electrochemistry between solid Li2S and soluble lithium polysulfides, but also enhances the transfer kinetics of electrons and ions, giving rise to a high‐rate performance (642 mAh g−1 at 5 C) and a long‐term cycle life (1000 cycles at 5 C) in lithium–sulfur batteries.

Agri-waste derived electroactive carbon-iron oxide nanocomposite for oxygen reduction reaction: an experimental and theoretical study.

Herein, we have utilized agri-waste and amalgamating low Fe3+, to develop an economic iron oxide-carbon hybrid-based electrocatalyst for oxygen reduction reaction (ORR) with water as a main product following close to 4e- transfer process. The electrocatalytic activity is justified by electrochemical active surface area, synergetic effect, and density functional theory calculations.

Electrochemical control of the morphological evolution of PEDOT on a Ni-Co(OH)2/carbon cloth surface to modulate the performance of wearable H2O2 sensors.

The slow redox rate of hydrogen peroxide (H2O2) in neutral environments makes the H2O2 sensor inadequate for the detection of low levels of signalling molecules. The aim of this study is to fabricate a flexible sensing electrode by hydrothermally loading micro-nanometer Ni and Co(OH)2 on carbon cloth (CC) and electrochemically depositing poly(3,4-ethylenedioxythiophene) (PEDOT) on the surface of the electrode. The sensor presented high sensitivity (10.43 mA mM-1 cm-2), a wide detection range (0.033-120.848 mM), a low detection limit (0.92 nM), high stability, and excellent anti-interference performance in neutral solutions. Ni-Co(OH)2 provides abundant active sites while CC solves their agglomeration phenomenon and conductivity. The PEDOT film offers heightened conductivity, hydrophilicity, interfacial stability, and an electrochemically active surface area (ECSA). The side area of the chrysanthemum petal like PEDOT is 39 ± 7 times the bottom area, and PEDOT increases the ECSA of the composite to six times that of CC. Electrochemical precise control of PEDOT morphology to improve sensor performance provides a new strategy for the application of PEDOT in sensors.

An on-site and portable electrochemical sensing platform based on spinel zinc ferrite nanoparticles for the quality control of paracetamol in pharmaceutical samples.

In this study, crystalline spinel zinc ferrite nanoparticles (ZnFe2O4 NPs) were successfully prepared and proposed as a high-performance electrode material for the construction of an electrochemical sensing platform for the detection of paracetamol (PCM). By modifying a screen-printed carbon electrode (SPE) with ZnFe2O4 NPs, the electrochemical characteristics of the ZnFe2O4/SPE and the electrochemical oxidation of PCM were investigated by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), chronoamperometry (CA), and differential pulse voltammetry (DPV) methods. The calculated electrochemical kinetic parameters from these techniques including electrochemically active surface area (ECSA), peak-to-peak separation (ΔEp), charge transfer resistance (Rct), standard heterogeneous electron-transfer rate constants (k0), electron transfer coefficient (α), catalytic rate constant (kcat), adsorption capacity (Γ), and diffusion coefficient (D) proved that the as-synthesized ZnFe2O4 NPs have rapid electron/mass transfer characteristics, intrinsic electrocatalytic activity, and facilitate the adsorption-diffusion of PCM molecules towards the modified electrode surface. As expected, the ZnFe2O4/SPE offered excellent analytical performance towards sensing of PCM with a detection limit of 0.29 μM, a wide linear range of 0.5-400 μM, and high electrochemical sensitivity of 1.1 μA μM-1 cm-2. Moreover, the proposed ZnFe2O4-based electrochemical nanosensor also exhibited good repeatability, high anti-interference ability, and practical feasibility toward PCM sensing in a pharmaceutical tablet. Based on these observations, the designed electrochemical platform not only provides a high-performance nanosensor for the rapid and highly efficient detection of PCM but also opens a new avenue for routine quality control analysis of pharmaceutical formulations.

Insights of the efficient hydrogen evolution reaction performance in bimetallic Au4Cu2 nanoclusters.

The design of efficient electrocatalysts for improving hydrogen evolution reaction (HER) performance using atomically precise metal nanoclusters (NCs) is an emerging area of research. Here, we have studied the HER electrocatalytic performance of monometallic Cu6 and Au6 nanoclusters and bimetallic Au4Cu2 nanoclusters. A bimetallic Au4Cu2/MoS2 composite exhibits excellent HER catalytic activity with an overpotential (η10) of 155 mV vs. reversible hydrogen electrode observed at 10 mA cm-2 current density. The improved HER performance in Au4Cu2 is due to the increased electrochemically active surface area (ECSA), and Au4Cu2 NCs exhibits better stability than Cu6 and Au6 systems and bare MoS2. This augmentation offers a greater number of active sites for the favorable adsorption of reaction intermediates. Furthermore, by employing X-ray photoelectron spectroscopy (XPS) and Raman analysis, the kinetics of HER in the Au4Cu2/MoS2 composite were elucidated, attributing the favorable performance to better electronic interactions occurring at the interface between Au4Cu2 NCs and the MoS2 substrate. Theoretical analysis reveals that the inherent catalytic enhancement in Au4Cu2/MoS2 is due to favorable H atom adsorption over it and the smallest ΔGH* value. The downshift in the d-band of the Au4Cu2/MoS2 composite influences the binding energy of intermediate catalytic species. This new catalyst sheds light on the structure-property relationship for improving electrocatalytic performance at the atomic level.

Estimation of the electrochemical active site density of a metal-free carbon-based catalyst using phosphomolybdate (PMo12) as an adsorbate.

A method to estimate the electrochemical active site density (SD) of carbon (C) and nitrogen-doped carbon (N/C-900) using phosphomolybdate (PMo12) as a probe molecule is proposed. The complete coverage of the active sites by the probe molecules is established irrespective of the adsorbate concentration (1, 5, or 10 mM), potential cycling (1 or 10 cycles) and cleaning time (2, 5, or 10 min). A conversion factor derived from a smooth and polished glassy carbon disk of known geometrical area is used to estimate the electrochemical active surface area (ECSA) of the carbon catalyst from the SD. The relatively higher SD values estimated from DC voltammetry than from large-amplitude Fourier-transform alternating-current voltammetry (FTacV) is indicative of the contribution of capacitive charge in the former. Adsorbed probe molecules (PMo12) can readily be desorbed from the catalyst surface by cycling the electrode to lower potentials. The active site density of N/C-900 (∼0.36 × 1019 sites g-1) is higher than that of C (∼0.17 × 1019 sites g-1).

Investigation on the performance of proton exchange membrane water electrolyzer coupled with a catalyst layer pore network model

Improvement of performance and cost reduction are urgent issues for proton exchange membrane water electrolyzers (PEMWEs). This study explored ways to improve electrolyzer performance from the perspective of the catalyst layer (CL) microstructures. The pore network model of the CL was established, and the obtained structural, mass transfer and electrochemical parameters were coupled with the macroscale performance model of PEMWE to get the multi-scale performance model. The mass transfer, heat transfer, and electrochemical processes inside the electrolyzer were considered to improve the model's accuracy. The maximum error between the simulated results by this multi-scale performance model and the experimental data was verified to be only 3.1%. The verified model was then used to predict the electrolyzer performance with various cathode/anode catalyst layer (CCL/ACL) microstructures. The predicted results showed that the electrochemical activity surface area affects the performance of PEMWE to a much greater extent than the conductivity. The performance of PEMWE gradually deteriorated as the catalyst particle radius or pore diameter of the CCL/ACL increased by the same degree, and the catalyst particle radius had a relatively more significant impact on the performance of the electrolyzer. Overall, the variation of ACL structure had a more substantial effect on the electrolyzer performance than that of CCL.

Enhanced Electrocatalytic Nitrate Reduction to Ammonia Using Functionalized Multi-Walled Carbon Nanotube-Supported Cobalt Catalyst.

Ammonia (NH3) is vital in modern agriculture and industry as a potential energy carrier. The electrocatalytic reduction of nitrate (NO3-) to ammonia under ambient conditions offers a sustainable alternative to the energy-intensive Haber-Bosch process. However, achieving high selectivity in this conversion poses significant challenges due to the multi-step electron and proton transfer processes and the low proton adsorption capacity of transition metal electrocatalysts. Herein, we introduce a novel approach by employing functionalized multi-walled carbon nanotubes (MWCNTs) as carriers for active cobalt catalysts. The exceptional conductivity of MWCNTs significantly reduces charge transfer resistance. Their unique hollow structure increases the electrochemical active surface area of the electrocatalyst. Additionally, the one-dimensional hollow tube structure and graphite-like layers within MWCNTs enhance adsorption properties, thus mitigating the diffusion of intermediate and stabilizing active cobalt species during nitrate reduction reaction (NitRR). Using the MWCNT-supported cobalt catalyst, we achieved a notable NH3 yield rate of 4.03 mg h-1 cm-2 and a high Faradaic efficiency of 84.72% in 0.1 M KOH with 0.1 M NO3-. This study demonstrates the potential of MWCNTs as advanced carriers in constructing electrocatalysts for efficient nitrate reduction.

How microstructures, oxide layers, and charge transfer reactions influence double layer capacitances. Part 1: impedance spectroscopy and cyclic voltammetry to estimate electrochemically active surface areas (ECSAs).

Varying the electrode potential rearranges the charges in the double layer (DL) of an electrochemical interface by a resistive-capacitive current response. The capacitances of such charge relocations are frequently used in the research community to estimate electrochemical active surface areas (ECSAs), yet the reliability of this methodology is insufficiently examined. Here, the relation of capacitances and ECSAs is critically assessed with electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) data on polished (Au, Ti, Ru, Pt, Ni, glassy carbon, graphite plate) and porous (carbon fleeces) electrodes. By investigating this variety of electrodes, the frequency-dependencies observed in the measured capacitances are shown to arise from the inherent resistive-capacitive DL response, charge transfer reactions, and resistively damped capacitive currents in microstructures (such as pores, pinholes, or cracks). These frequency-dependencies are typically overlooked when capacitances are related to ECSAs. The capacitance at the specimen-characteristic relaxation frequency of the resistive-capacitive DL response is proposed as a standardized capacitance-metric to estimate ECSAs. In 1 M perchloric acid, the polished gold electrode and the high-surface area carbon fleeces show ratios of capacitance-metric over surface-area of around 3.7 μF cm-2. Resistively damped currents in microstructures and low-conducting oxide layers are shown to complicate trustworthy capacitance-based estimations of ECSAs. In the second part of this study, advanced equivalent circuits models to describe the measured EIS and CV responses are presented.

Engineering highly selective CO2 electroreduction in Cu-based perovskites through A-site cation manipulation.

Perovskites exhibit considerable potential as catalysts for various applications, yet their performance modulation in the carbon dioxide reduction reaction (CO2RR) remains underexplored. In this study, we report a strategy to enhance the electrocatalytic carbon dioxide (CO2) reduction activity via Ce-doped La2CuO4 (LCCO) and Sr-doped La2CuO4 (LSCO) perovskite oxides. Specifically, compared to pure phase La2CuO4 (LCO), the Faraday efficiency (FE) for CH4 of LCCO at -1.4 V vs. RHE (reversible hydrogen electrode) is improved from 38.9% to 59.4%, and the FECO2RR of LSCO increased from 68.8% to 85.4%. In situ attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy spectra results indicate that the doping of A-site ions promotes the formation of *CHO and *HCOO, which are key intermediates in the production of CH4, compared to the pristine La2CuO4. X-ray photoelectron spectroscopy (XPS), electron paramagnetic resonance (EPR), and double-layer capacitance (Cdl) outcomes reveal that heteroatom-doped perovskites exhibit more oxygen vacancies and higher electrochemical active surface areas, leading to a significant improvement in the CO2RR performance of the catalysts. This study systematically investigates the effect of A-site ion doping on the catalytic activity center Cu and proposes a strategy to improve the catalytic performance of perovskite oxides.

Sn-based film electrodeposited on Ag foil for selective electrochemical CO2 reduction to CO.

Electrochemical CO2 reduction (ECR) to valuable chemicals and fuels using renewable energy is a promising way to reduce carbon emission. Herein, Sn-based films were electrodeposited on Ag foil surfaces (Sn/Ag-y) for selective ECR to CO, where y represented the concentration of SnCl2 in the electrodeposition bath. The Sn/Ag-20 electrode achieved a high CO faradaic efficiency of 96.0% with a current density of 69.3 mA cm-2. The enhanced catalytic performance could be attributed to appropriate superficial properties, large electrochemical active surface areas, low charge transfer resistance, efficient stabilization capacity of the CO2˙- intermediates, and suitable combination with electrolytes.

Electrochemical preparation and features of newly cross-stacking multi-layered reduced graphene oxide (rGO) and polyaniline (PANI) modified carbon-based electrode

Carbon-based electrode as an economically benign choice is widely used in electrochemical or bio-electrochemical systems. However, its poor electrical conductivity that leading high overpotential and energy loss, especially in large scale facilities, remains a bottleneck for its application. Herein, a unique cross-stacking multi-layered reduced graphene oxide (rGO) and polyaniline (PANI) modified carbon brush is fabricated via one-step electro-depositing. In particular, the top-most layer of the modified electrode is orientated controlled to be rGO or PANI layer by adjusting the initial CV scanning in the positive or negative direction. As was indicated by cyclic voltammetry, the improved electrochemical activity is achieved by coupling the advantages of the highly conductive network offered by graphene with desirable stability provided by the well-dispersed deposition of nanoscale PANI particles. In comparison, the modified electrode with rGO on the top-most layer (LrGO) showed higher degree of sp2-hybridized -C-C- ordered structure in Raman profile, lower O/C ratio in XPS analysis, higher Zeta potential (−2.05 mV) and more hydrophilic than unmodified one. Moreover, benefiting from the unique cross-stacking multi-layered matrix of rGO and PANI, the best electrochemical performance was achieved on the electrode LrGO with high exerted electrochemical active surface area (ECSA) of 0.85 mF cm−2, and the charge transfer resistance as low as 0.32 Ω. The findings of this study provide a guidance for the modification and application of carbon-based electrode using rGO and PANI, which potentially enables the scaling-up of carbon-based electrode in various (bio-) electrochemical systems with high electrochemical performance.