Glassy Carbon Substrate Research Articles

Solid‐Contact Sensor Based on Molecularly Imprinted Polymers (MIPs) for Direct Potentiometric Assessment of 2,4,6‐Trichlorophenol as a Persistent Organic Pollutant

Abstract2,4,6‐trichlorophenol (TCP) is regarded as a very harmful persistent organic pollutant. It is prohibited by the US EPA due to its stability, possible toxicity, and substantial carcinogenicity, which could result in long‐term harm to both the environment and living things. A novel solid‐contact electrode (SCE) is fabricated and characterized for potentiometric determination of 2,4,6‐trichlorophenol (2,4,6‐TCP). Molecularly imprinted trichlorophenol polymer (MIP) beads are used as a recognition receptor for potentiometric determination of this persistent organic pollutant. The MIPs are synthesized using 4‐vinyl pyridine (4‐VP) and N,N′‐Methylene bis(acrylamide) (N,N‐MBAA) as functional monomer and cross‐linking agent, respectively. They are embedded in a selective polyvinyl chloride (PVC) membrane on the top of multi‐walled carbon nanotubes (MWCNTs), which is used as an ion to electron transducer. The SCE exhibits a Nernstian response with a slope of −55.4±2.1 mV/decade (R2=0.999) over the concentration range of 8.0×10−6 to 1.0×10−4 M, a detection limit of 5.0×10−7 M (0.98 μg/mL), and a response time of <10 s. Using electrochemical impedance spectroscopy (EIS) and chronopotentiometry (CP), the suggested SCE′s interfacial capacitance is measured. The interfacial capacitance was increased using MWCNTs and reached 39.7 μF. Also, it prevented the undesirable thin water layer from forming between the conducting glassy carbon (GC) substrate and the sensing membrane. As a result, potential stability is improved, and membrane delamination is avoided. The suggested SCE had a wide range of applications for monitoring TCP in various environmental samples because of the high selectivity, sensitivity, and possible stability that were attained.

Platinum nanoparticles prepared by ion implantation exhibit high durability for fuel cell applications

Proton exchange membrane fuel cells (PEMFCs) have attracted considerable attention as distributed power sources for automotive and residential applications. In PEMFCs, platinum (Pt) nanoparticles supported on carbon materials are used as electrocatalysts for oxygen reduction reactions. However, improved durability of the electrocatalysts is urgently required for commercialization purposes. We describe an ion implantation technique for the preparation of Pt nanoparticles with superior catalytic properties, suitable for fuel cell applications. The Pt nanoparticles were obtained by implanting a glassy carbon (GC) substrate with 100 keV Pt-ions, followed by electrochemical etching and a heat treatment. Electrochemical measurements of the Pt nanoparticles prepared by the proposed implantation technique demonstrated superior durability when compared to those prepared by the conventional magnetron sputtering method. We suggested that the defective structure of the GC substrate, caused by the Pt-ion implantation, has led to the improved electrochemical stability of the GC substrate and Pt-carbon support interactions, thereby enhancing the durability of our Pt nanoparticles.

Elucidation of alkaline electrolyte-surface interaction in SECCM using a pH-independent redox probe

Scanning electrochemical cell microscopy (SECCM) has been used to elucidate the interaction between aqueous alkaline electrolyte and a glassy carbon electrode surface using a free-diffusing Os complex, Os(2,2’-bipyridine)2(N,N’-dimethyl-2,2 ́-biimidazole), as a pH-independent redox probe (Os3+/Os2+). The voltammetric response of the complex showed a significant component of surface-confined behavior, rather than the expected purely sigmoidal nanoelectrode voltammogram. To elucidate and understand the response, we complemented the SECCM experiments with numerical simulations to investigate the impact of the droplet geometry and size on the voltammetric signature. Comparison of experimental and simulated voltammograms reveals a surprisingly large wetted area over the glassy carbon substrate, as confirmed by scanning electron microscopy of droplet residues. By investigating different tip sizes, tip approach rates and pH values, we elucidated the key factors controlling the wetting behavior. Simulations further indicated that the analysis of the peak to limiting current and charge passed provides a route to elucidating the extent of wetting in-situ, although quantitative analysis requires further understanding of evaporation and convective flow. In general, knowledge about droplet geometry and size through this study provides an improved understanding of droplet-surface interactions which is essential for a quantitative interpretation of SECCM measurements.

Nanoscopic Silicon Oxide Overlayers Improve the Performance of Ruthenium Oxide Electrocatalysts Toward the Oxygen Evolution Reaction

RuO2 is a highly active electrocatalyst for the oxygen evolution reaction (OER) but is unstable in acidic environments. Herein we investigate the encapsulation of RuO2 nanoparticles with semipermeable, nanoscopic silicon oxide (SiOx) overlayers as a strategy to improve their stability. SiOx encapsulated RuO2 (SiOx|RuO2) electrodes were prepared by drop-casting RuO2 nanoparticles onto glassy carbon substrates followed by deposition of SiOx overlayers of varying thickness by a room temperature photochemical deposition process. The best-performing SiOx|RuO2 electrodes consisted of 2–3 nm thick SiOx overlayers on top of RuO2 particles and 3–7 nm thick SiOx on the glassy carbon substrate. Such electrodes exhibited lower overpotentials relative to bare RuO2 due to an improved electrochemically active surface area while also demonstrating an ability to retain OER activity over time, especially at higher overpotentials. Surprisingly, it was found that the SiOx coating was unable to prevent Ru dissolution, which was found to be proportional to the charge passed and independent of the presence or thickness of the SiOx coating. Thus, other possible explanations for the improved current retention of SiOx|RuO2 electrodes are discussed, including the influences of the overlayer on bubble dynamics and the stability of the underlying glassy carbon substrate.

Optimization of Pd–Co–Cu and Pd–Co–Au catalysts for the oxidation of formic acid using scanning electrochemical microscopy

This study uses scanning electrochemical microscopy (SECM) to screen ternary metal catalyst arrays for the oxidation of formic acid. Pd–Co–Au and Pd–Co–Cu ternary metal catalyst arrays are prepared using a piezoelectric dispensing system and then reduced on a glassy carbon substrate by hydrogen reduction. For the catalyst arrays, the optimal ratio of ternary alloy catalysts for the oxidation of formic acid is Pd2Co6Au2 and Pd2Co6Cu2 catalysts in Pd–Co–Au and Pd–Co–Cu ternary metal catalyst arrays, respectively. The surface morphology of Pd2Co6Au2 and Pd2Co6Cu2 catalysts is more complex and diverse than that of a pure Pd catalyst. A Pd2Co6Au2 catalyst is mainly composed of heterostructures of Au and PdCoO2, and a Pd2Co6Cu2 catalyst is mainly composed of heterostructures of CuPdO2, CuCoO2 and Co. The XPS results roughly matches with the XRD results. Cyclic voltammograms show that these two catalysts have a higher oxidation current in formic acid than that for a pure Pd catalyst. The onset potential for the oxidation of formic acid by a Pd2Co6Cu2 catalyst is lower than that for a Pd2Co6Au2 catalyst. Electrochemical impedance spectroscopy analysis shows that these catalysts exhibit pseudo inductive behavior. For an equivalent circuit, a Pd2Co6Cu2 catalyst has the smallest charge transfer resistance and removes the intermediate adsorbate at the lowest overpotential.

Hydrogen Evolution from Metal Nanoparticles Synthesized in a Deep Eutectic Solvent

In the present work, Pd, Rh and PdRh nanoparticles (NPs) were synthesized in a deep eutectic solvent (DES) by electrodeposition onto a glassy carbon substrate. The NPs were evaluated for the hydrogen evolution reaction (HER, Hydrogen Evolution Reaction), in an acid medium. The results showed that the highest catalytic activity for HER was the metallic Rh.

A microscopic view on the electrochemical deposition and dissolution of Au with scanning electrochemical cell microscopy – Part I

The nucleation and dissolution of gold nanoparticles (NPs) on a glassy carbon substrate have been studied with a local electrochemical approach based on Scanning Electrochemical Cell Microscopy (SECCM). By performing hundreds of locally-resolved voltammograms, a distribution of responses for nucleation was found when scanning multiple regions of the substrate, addressing experimentally the statistical nature of the nucleation and growth process at the micro-scale. Moreover, the confinement of the electrochemical cell to the SECCM meniscus enables us to resolve a diversity of events during the electrochemical dissolution of previously electrodeposited NPs, characterized as current spikes during the voltammetric scans. These current events do not manifest in the macro-scale due to the averaging of the electrochemical response over the large electrode area and reveal previously untapped information from the electrochemical nucleation, growth, and dissolution of supported metal nanoparticles. This approach opens up new opportunities for the rational design (electrodeposition) of functional nanostructured materials and the evaluation of their durability under electrochemical polarization (resistance to electrodissolution). The ability to study these considering the heterogeneous nature of the supports and the differences within nanomaterial ensembles is essential for applications in electrochemical conversion and storage.

Study of the Silicon Electrochemical Nucleation in LiCl-KCl-CsCl-K2SiF6 Melt

In this work, we studied the kinetics of the cathodic process and the regularities of the initial stages of silicon electrodeposition with methods of cyclic voltammetry, square-wave voltammetry, and chronoamperometry on a glassy carbon substrate from a LiCl-KCl-CsCl melt with K2SiF6 at a temperature of 545 ± 5°C. It is shown that the cathodic process of silicon reduction proceeds in one stage, and it is not electrochemically reversible. The diffusion coefficient of silicon ions found by CV and chronoamperometry was 8.44·10−11 and 1.00·10−10 m2 s−1, respectively. It was also found that the nucleation of silicon on glassy carbon is progressive; the formation of new nuclei proceeds continuously against the background of the growth of existing ones. Based on electrochemical measurements, various modes of silicon electrodeposition in the form of thin films were chosen: potentiostatic, pulse, reverse and galvanostatic with preliminary anodizing. As a result of electrolysis, silicon films were obtained, which were analyzed by SEM and XRD methods. The thickness of such deposits during electrolysis reaches several microns, and it consists of many spherical nuclei up to 0.7 microns in diameter. The content of impurities in deposits is extremely low, and the main contaminant is oxygen (0.4–1.2 wt%).

Multiscale Electrochemistry of Lithium Manganese Oxide (LiMn2O4): From Single Particles to Ensembles and Degrees of Electrolyte Wetting.

Scanning electrochemical cell microscopy (SECCM) facilitates single particle measurements of battery materials using voltammetry at fast scan rates (1 V s-1), providing detailed insight into intrinsic particle kinetics, otherwise obscured by matrix effects. Here, we elucidate the electrochemistry of lithium manganese oxide (LiMn2O4) particles, using a series of SECCM probes of graded size to determine the evolution of electrochemical characteristics from the single particle to ensemble level. Nanometer scale control over the SECCM meniscus cell position and height further allows the study of variable particle/substrate electrolyte wetting, including comparison of fully wetted particles (where contact is also made with the underlying glassy carbon substrate electrode) vs partly wetted particles. We find ensembles of LiMn2O4 particles show voltammograms with much larger peak separations than those of single particles. In addition, if the SECCM meniscus is brought into contact with the substrate electrode, such that the particle-support contact changes from dry to wet, a further dramatic increase in peak separation is observed. Finite element method modeling of the system reveals the importance of finite electronic conductivity of the particles, contact resistance, surface kinetics, particle size, and contact area with the electrode surface in determining the voltammetric waveshape at fast scan rates, while the responses are relatively insensitive to Li+ diffusion coefficients over a range of typical values. The simulation results explain the variability in voltammetric responses seen at the single particle level and reveal some of the key factors responsible for the evolution of the response, from ensemble, contact, and wetting perspectives. The variables and considerations explored herein are applicable to any single entity (nanoscale) electrochemical study involving low conductivity materials and should serve as a useful guide for further investigations of this type. Overall, this study highlights the potential of multiscale measurements, where wetting, electronic contact, and ionic contact can be varied independently, to inform the design of practical composite electrodes.

Fluoroborate ionic liquids as sodium battery electrolytes.

High-voltage sodium batteries are an appealing solution for economical energy storage applications. Currently available electrolyte materials have seen limited success in such applications therefore the identification of high-performing and safer alternatives is urgently required. Herein we synthesise six novel ionic liquids derived from two fluoroborate anions which have shown great promise in recent battery literature. This study reports for the first time the electrochemically applicable room-temperature ionic liquid (RTIL) N-ethyl-N,N,N-tris(2-(2-methoxyethoxy)ethyl)ammonium (tetrakis)hexafluoroisopropoxy borate ([N2(2O2O1)3][B(hfip)4]). The RTIL shows promising physical properties with a very low glass-transition at -73 °C and low viscosity. The RTIL exhibits an electrochemical window of 5.3 V on a glassy carbon substrate which enables high stability electrochemical cycling of sodium in a 3-electrode system. Of particular note is the strong passivation behaviour of [N2(2O2O1)3][B(hfip)4] on aluminium current-collector foil at potentials as high as 7 V (vs. Na+/Na) which is further improved with the addition of 50 mol% Na[FSI]. This study shows [B(hfip)4]- ionic liquids have the desired physical and electrochemical properties for high-voltage sodium electrolytes.

Boosted formic acid electro-oxidation on platinum nanoparticles and "mixed-valence" iron and nickel oxides.

The modification of Pt nanoparticles (nano-Pt, assembled electrochemically onto a glassy carbon (GC) substrate) with hybrid multivalent nickel (nano-NiOx) and iron (nano-FeOx) oxide nanostructures was intended to steer the mechanism of the formic acid electro-oxidation (FAO) in the desirable dehydrogenation pathway. This binary modification with inexpensive oxides succeeded in mediating the reaction mechanism of FAO by boosting reaction kinetics "electron transfer" and amending the surface geometry of the catalyst against poisoning. The sequence of deposition was optimized where the a-FeOx/NiOx/Pt/GC catalyst (where "a" denotes a post-activation step for the catalyst at -0.5 V in 0.5 mol L-1 NaOH) reserved the best hierarchy. Morphologically, while nano-Pt appeared to be spherical (ca. 100 nm in average diameter), nano-NiOx appeared as flowered nanoaggregates (ca. 56 nm in average diameter) and nano-FeOx (after activation) retained a plate-like nanostructure (ca. 38 nm in average diameter and 167 nm in average length). This a-FeOx/NiOx/Pt/GC catalyst demonstrated a remarkable catalytic efficiency (125 mA mgPt-1) for FAO that was ca. 12.5 times that of the pristine Pt/GC catalyst with up to five times improvement in the catalytic tolerance against poisoning and up to -214 mV shift in the FAO's onset potential. Evidences for equipping the a-FeOx/NiOx/Pt/GC catalyst with the least charge transfer resistance and the highest stability among the whole investigated catalysts are provided and discussed.

Evaluation of polycrystalline cerium oxide electrodes for electrochemiluminescent detection of sarcosine

Prostate cancer (PCa) is widely spread in male population, especially over 65 years. Currently used medical methods of PCa diagnosis often lead to false-positive results thus new non-invasive methods for PCa detection, such as urine tests for cancer metabolites, are actively studied. Herein, nanostructured polycrystalline cerium oxide thin films (CeO2/GC) prepared by magnetron sputtering on a glassy carbon substrate are tested for electrochemiluminescent (ECL) detection of sarcosine exploiting the oxidative-reduction mechanism using Ru(bpy)32+ as luminophore. Non-functionalized CeO2/GC electrodes revealed a higher ECL signal stability compared to bare glassy carbon electrodes. Moreover, CeO2/GC electrodes were successfully applied for rapid and sensitive detection of different sarcosine concentrations ranging from 50 to 5000 µM. These results open new possibilities for developing sensing platforms for sarcosine detection based on the CeO2/GC working electrode via surface modification and functionalization, aiming to further investigate and improve their sensitivity and selectivity.

Amendment of palladium nanocubes with iron oxide nanowires for boosted formic acid electro−oxidation

To quickly move the formic acid (FA) fuel cells closer to a real commercialization, an inexpensive, efficient, and durable electrocatalyst for the direct FA electro-oxidation (FAEO) was developed. This involved a sequential modification of a glassy carbon (GC) substrate with palladium nanocubes (ca. 70 nm, nano-Pd) and iron oxide nanowires (nano-FeOx, ca. 40 nm and 150 nm in average diameter and length, respectively). The deposition sequence and loading level of nano-FeOx in the catalyst were optimized to minimize the catalyst's poisoning with CO that might probably release from a parallel dehydration of FA or from CO2 reduction. Surprisingly, the FeOx/Pd/GC catalyst exhibited a high (21.6 mA cm−2) specific activity for FAEO, which denoted ca. 7 times that of the “pristine” Pd/GC catalyst. This was synchronized with a better (up to fivefold increase in turnover frequency) “long-termed” stability that extended for 90 min of continuous electrolysis at room temperature. A successful effort was dedicated to improving more the catalyst's stability by activating the catalyst electrochemically at –0.5 V vs Ag/AgCl/KCl (sat.) in 0.2 mol L−1 NaOH. The CO stripping agreed perfectly with the impedance analysis in appending the observed enhancement in the catalytic efficiency of FAEO to a favorable electronic modulation at the Pd surface that boosted the oxidative desorption of poisoning CO species at a lower potential.

Nanostructured gold thin film electrode derived from surfactant-free gold nanoparticles for enhanced electrocatalysis

Electrodes composed of nanostructured surfaces have been shown to be promising electrocatalysts, offering enhanced catalytic activity. Gold nanoparticles (AuNPs) are often used to produce such a nanostructured surface. However, these are commonly prepared using a reductant and surfactant, often hindering the electrocatalytic application of the surface. In the present study, we fabricated a nanostructured gold thin film electrode derived from a solution of AuNPs containing only Au, H, and O, which was prepared by solution plasma processing in the presence of hydrogen peroxide. The concentrated AuNP dispersed aqueous solution was dropped onto the glassy carbon substrate and then dried to form a AuNP thin film at room temperature. The resultant gold film was nanostructured owing to the presence of the AuNPs, could be used directly in electrochemical reactions without pre-treatment (such as surfactant/reductant removal), and gave stable voltammetric responses, indicating its suitability as an electrode material. In addition, the AuNP thin film electrode exhibited enhanced electrocatalytic activity compared with conventional planar gold electrodes, which can be attributed to its surface nanostructure. In particular, the electrocatalytic current in the hydrogen evolution reaction was more than 10 times larger at the nanostructured AuNP thin film electrode than at a planar gold electrode. Further, the AuNP thin film electrode enabled direct electron transfer (DET) between a redox enzyme, neuroglobin, and the electrode surface, while the planar electrode showed no DET response. The results indicate the usefulness of the present AuNP thin film electrode, prepared by a reagent-free process, for various electrocatalytic applications.

Stimulation of ethylene glycol electrooxidation on electrodeposited Ni–PbO2–GN nanocomposite in alkaline medium

In this work, a novel system composed of non-precious nickel-based metal oxide/reduced graphene oxide nanocomposite (Ni–PbO2–GN) is used for electrooxidation of ethylene glycol (EG) in 1.0 M NaOH solution and compares its activity with that of Ni, Ni–GN, and Ni–PbO2. The facile electrodeposition technique is used to prepare the catalysts on glassy carbon (GC) substrates. The outcomes of electrochemical measurements show a high performance towards EG oxidation is obtained for Ni-nanocomposite electrodes compared to that of Ni mainly due to their higher surface areas. The excellent electrocatalytic properties of the Ni-nanocomposite could be ascribed to the synergistic contributions of PbO2 and graphene (GN) nano-sheets that help the reduction of Ni grains. A smaller charge transfer resistance value of 34.5 Ω cm2 for EG oxidation reaction at + 360 mV is recorded for GC/Ni–PbO2–GN compared to the other prepared electrodes. Moreover, it exhibits higher kinetic parameters of EG such as diffusion coefficient (D = 3.9 × 10–10 cm2 s−1) and charge transfer rate constant (ks = 32.5 mol−1 cm3 s−1). The overall performance and stability of the prepared catalysts towards EG electrooxidation have been estimated to be in the order of GC/Ni–PbO2–GN > GC/Ni–GN > GC/Ni–PbO2 > GC/Ni.Graphical abstract

Surface Conductivity of Bi, Ga, In, and Sb Nanocrystals Condensed on Glassy Carbon Substrates

Surface Conductivity of Bi, Ga, In, and Sb Nanocrystals Condensed on Glassy Carbon Substrates

Morphology and chemical state of platinum ions implanted into glassy carbon substrates

Glassy carbon substrates were implanted with 100 keV platinum ions. The implanted samples were analyzed using cross-sectional transmission electron microscopy (TEM) and x-ray photoelectron spectroscopy. Ion beam sputtering significantly affected the depth profile during platinum-ion implantation. Cross-sectional TEM revealed that the implanted platinum atoms were in the amorphous state and did not aggregate. Chemical state analysis of the platinum-ion-implanted glassy carbon substrates suggested that lattice defects in the substrates owing to the platinum-ion implantation caused the platinum–carbon interaction with electron transfer from platinum to carbon.

Electrochemically-grown Chloride-free Cu2O nanocubes favorably electroreduce CO2 to Methane: The interplay of appropriate electrochemical protocol

Nowadays, electrochemical CO2 reduction reaction (CO2RR) to value-added products represents one of the major challenges in electrocatalysis. Copper-based nanocubes (Cu NCs) have been proposed as the front-runner's catalyst for the production of C2+ products at the industrial level. However, their selectivity (C1 vs. C2 product distribution) is rather complex depending on the dynamic structural transformations, the presence of mixed Cu+/Cu0 states, the microenvironment, and nanocatalyst-support interactions. Commonly, electrochemically-grown Cu NCs are prepared in the presence of chlorides that acts as a shaping agent. In this study, an optimized electrodeposition method for the synthesis of Cl−-free Cu2O nanocubes on a glassy carbon substrate with uniform size, shape, and loading is established. The successful preparation of chloride-free cuprous oxide nanocubes (Cu2O NCs) was confirmed with X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS) analyses. We report how the electrochemical double-layer capacitance (EDLC) method for electrochemical surface area (ECSA) determination with(out) subsequent return to the open-circuit potential (OCP) conditions before electrolysis influences the CO2RR activity/selectivity. When Cu2O NCs are subjected to the EDLC method (often considered a non-invasive method) and exposed to the OCP before electrolysis, they become active for methane (CH4) formation. Moreover, the influence of the potential window width (i.e. 200 and 400 mV) in which the EDLC-ECSA is employed and its correlations with the selectivity is presented. We underline the importance of the ECSA determination method and OCP on/off state as a triggering factor for reactivity/selectivity of particular Cu2O NCs for CO2RR and further emphasize the reconstructive nature of Cu2O NCs under CO2RR relevant conditions.

Fabrication of Block Copolymer Templated Extended Surface Model Electrocatalysts By Atomic Layer Deposition and Physical Vapor Deposition

Templating platinum group metal (PGM) nanostructures from microphase separated block copolymers (BCPs) allows for electrocatalytic activity to be studied on highly ordered, model surfaces with precisely controlled feature sizes and morphologies, thereby allowing catalyst electroactivity and stability to be probed as a function of nanoscale geometry. In our previous work [1], BCP templated electrocatalysts fabricated via incipient wetness impregnation of PGM precursors were tested for hydrogen oxidation/evolution and water-splitting activity on interdigitated electrodes using liquid and solid polymer electrolytes. This talk presents the fabrication of such electrocatalysts via Atomic Layer Deposition (ALD) and Physical Vapor Deposition (PVD) techniques (e-beam evaporation and sputtering). Self-assembled lamellae of poly-(styrene-block-methylmethacrylate) (PSbPMMA) thin films on Si wafer and glassy carbon substrates were subjected to 5 - 15 ALD cycles with trimethylaluminium (TMA) precursor to induce selective growth of alumina in the PMMA domains via Sequential Infiltration Synthesis. Thereafter, the polymer template was removed via Reactive Ion Etching (RIE) with oxygen plasma. The resultant alumina nanostructures templated from self-assembled PSbPMMA was then used as a substrate either for Platinum ALD with (trimethyl)methylcyclopentadienylplatinum(IV) precursor atop a Titanium Nitride adhesive layer, or for sputtering of Pt atop a Ti adhesive layer to obtain conformal Pt coatings of up to 20 nm in thickness. When e-beam evaporation was used, The PMMA domains were selectively removed by successive wet and dry etch steps, followed by deposition and lift-off. The PGM electrocatalyst nanostructures were characterized via a combination of electron microcopy, X-ray diffraction, and X-ray photoelectron spectroscopy, and the Pt content of the catalysts were determined via microwave leaching and digestion of the electrocatalyst thin film followed by Inductively Coupled Plasma Mass Spectroscopy. The nanostructured electrocatalysts were tested for oxygen reduction (ORR) activity in a conventional rotating disk electrode setup using 0.1 M perchloric acid electrolyte, and the ORR mass activities and active surface area were obtained.[1] Bhattacharya, D., Arges, C. G., et al., Small, 2021, 17, 2100437

Surface engineering of Pt surfaces with Au and cobalt oxide nanostructures for enhanced formic acid electro-oxidation

A novel n-CoOx/n-Au/n-Pt nanocatalyst assembled onto a glassy carbon (GC) substrate is recommended for efficient formic acid electro-oxidation (FAEO), the principal anodic reaction in the direct formic acid fuel cells (DFAFCs). • A catalyst composed of Pt nanoparticles was engineered with Au and cobalt oxide nanostructures. • It showed a promising catalytic performance toward the formic acid electro-oxidation. • Adjusting its loading hierarchy drove the reaction mechanism to the desirable dehydrogenation pathway. • Geometric and electronic enhancements were elucidated and quantified. This study aims to mitigate the CO poisoning of platinum (Pt) surfaces during formic acid electro-oxidation (FAEO), the essential anodic reaction in the direct formic acid fuel cells (DFAFCs). For this purpose, a glassy carbon (GC) electrode was amended sequentially with Pt (n-Pt), gold (n-Au), and cobalt oxide (n-CoOx) nanostructures. Fascinatingly, the ternary modified n-CoOx/n-Au/n-Pt/GC catalyst (for which n-Pt, n-Au, and n-CoOx were sequentially and respectively assembled onto the GC surface) exhibited a remarkable electrocatalytic enhancement toward FAEO, which surpassed ca. 53 times that of the Pt/GC catalyst. Additionally, it exhibited a much (ca. 18 times) higher stability after 3000 s of continuous electrolysis. The observed enhancement was proven to originate from driving the reaction mechanism principally to the desirable direct dehydrogenation pathway on the expense of the poisoning dehydration path. The impedance and CO stripping measurements confirmed the prevailing of both the electronic and third body effects in the catalytic enhancement.