Electrochemical Catalytic Activity Research Articles

Pt Loading of Phosphorus-Doped Carbon Nanotube Aerogels in Fuel Cell-Type Gas Sensors for Ultrasensitive H2 Detection.

A phosphorus-doped carbon nanotube (CNT) aerogel as the support material was loaded with Pt nanoparticles in fuel cell-type gas sensors for ultrasensitive H2 detection. The high surface area of the CNT scaffold is favorable to providing abundant active sites, and the high electrical conductivity facilitates the transport of carriers generated by electrochemical reactions. In addition, the CNT aerogel was doped with phosphorus (P) to further enhance the conductivity and electrochemical catalytic activity. As a result, the fuel cell-type gas sensor using the Pt/CNT aerogel doped with the optimal P content as the sensing material shows considerable performance for H2 detection at room temperature. The sensor exhibits an ultrahigh response of -921.9 μA to 15,000 ppm of H2. The sensitivity is -0.063 μA/ppm, which is 21 times higher than that of the conventional Pt/CF counterpart. The sensor also exhibits excellent repeatability and humidity resistance, as well as fast response/recovery; the response/recovery times are 31 and 4 s to 3000 ppm of H2, respectively. The modulation of the structure and catalytic properties of the support material is responsible for the improvement of the sensor performance, thus providing a feasible solution for optimizing the performance of fuel cell-type gas sensors.

YSZ-based mixed-potential acetone sensor with LaBaCo2O5+δ sensitive electrode for diabetic diagnosis

The acetone concentration in exhaled breath can be utilized for the noninvasive diagnosis of diabetes. In this study, to fulfil the requirements of breath analysis for diabetes diagnosis, high-performance mixed-potential acetone sensors based on yttria-stabilized zirconia were successfully developed by employing a novel sensitive electrode (SE) material, namely, LaBaCo2O5+δ. Electrochemical measurement results revealed that the LaBaCo2O5+δ SE, sintered at 1000 ℃, exhibited outstanding electrochemical catalytic activity toward acetone. The device incorporating this SE demonstrated a peak response of −46mV to 100 ppm acetone at 655 ℃. Sensitive performance assessments indicated the capability of the sensor to detect acetone concentrations ranging from 200 ppb to 100 ppm. Based on the mixed-potential model, the sensitivities of the current device were quantified as −1.3 and −53.7mV/decade within the acetone concentration ranges of 0.2−5 and 10−100 ppm, respectively. Furthermore, the fabricated sensor exhibited exceptional selectivity, repeatability, humidity resistance, and long-term stability. In addition, simulated expiratory experiments showed that the developed sensor has substantial potential for application in breath analysis for diabetes diagnosis and noninvasive monitoring of a patient’s physical status.

YSZ-based mixed-potential acetone sensor with LaBaCo2O5+δ sensitive electrode for diabetic diagnosis

The acetone concentration in exhaled breath can be utilized for the noninvasive diagnosis of diabetes. In this study, to fulfil the requirements of breath analysis for diabetes diagnosis, high-performance mixed-potential acetone sensors based on yttria-stabilized zirconia were successfully developed by employing a novel sensitive electrode (SE) material, namely, LaBaCo2O5+δ. Electrochemical measurement results revealed that the LaBaCo2O5+δ SE, sintered at 1000 ℃, exhibited outstanding electrochemical catalytic activity toward acetone. The device incorporating this SE demonstrated a peak response of −46 mV to 100 ppm acetone at 655 ℃. Sensitive performance assessments indicated the capability of the sensor to detect acetone concentrations ranging from 200 ppb to 100 ppm. Based on the mixed-potential model, the sensitivities of the current device were quantified as −1.3 and −53.7 mV/decade within the acetone concentration ranges of 0.2−5 and 10−100 ppm, respectively. Furthermore, the fabricated sensor exhibited exceptional selectivity, repeatability, humidity resistance, and long-term stability. In addition, simulated expiratory experiments showed that the developed sensor has substantial potential for application in breath analysis for diabetes diagnosis and noninvasive monitoring of a patient’s physical status.

Transition Metal-Based Polyoxometalates for Oxygen Electrode Bifunctional Electrocatalysis

Polyoxometalates (POMs) with transition metals (Co, Cu, Fe, Mn, Ni) of Keggin structure and lamellar-stacked multi-layer morphology were synthesized. They were subsequently explored as bifunctional electrocatalysts for oxygen electrodes, i.e., oxygen reduction (ORR) and evolution (OER) reaction, for aqueous rechargeable metal-air batteries in alkaline media. The lowest Tafel slope (85 mV dec−1) value and the highest OER current density of 93.8 mA cm−2 were obtained for the Fe-POM electrocatalyst. Similar OER electrochemical catalytic activity was noticed for the Co-POM electrocatalyst. This behavior was confirmed by electrochemical impedance spectroscopy, where Fe-POM gave the lowest charge transfer resistance of 3.35 Ω, followed by Co-POM with Rct of 15.04 Ω, during the OER. Additionally, Tafel slope values of 85 and 109 mV dec−1 were calculated for Fe-POM and Co-POM, respectively, during the ORR. The ORR at Fe-POM proceeded by mixed two- and four-electron pathways, while ORR at Co-POM proceeded exclusively by the four-electron pathway. Finally, capacitance studies were conducted on the synthesized POMs.

Enhancing Electrochemical Efficiency of Solid Oxide Electrolysis Cells for Carbon Dioxide Reduction Through Nickel‐Doped Titanate‐Based Cathode with Doped Ceria Electrolyte

AbstractSolid oxide electrolysis cell (SOEC) is a potential technology for converting the principal greenhouse gas, carbon dioxide (CO2), into carbon monoxide (CO) by employing renewable energy. SOECs have great potential, including high‐energy efficiency, fast electrode kinetics, and competitive cost; however, this technology still has challenges in developing highly active, robust CO2 cathode electrocatalysts. In this work, we report the Ni‐doped lanthanum strontium calcium titanate (La0.20Sr0.25Ca0.45Ni0.05Ti0.95O3−δ) cathode for application as the cathode of CO2 electrolysis with gadolinia‐doped ceria (Gd0.1Ce0.9O1.95) electrolyte in SOEC. The exsolution of Ni nanoparticles is achieved by a simple in situ growth method at 800 °C. The Ni doping in LSCT significantly improved the electrochemical activity of the catalyst by increasing oxygen vacancies, and the Ni metallic nanoparticles can afford much more active sites for CO2 reduction. The CO2 electrolysis mechanism is studied by the distribution of relaxation time analysis of impedance spectroscopy. Ni‐LSCT renders a higher activity for electrolysis of CO2 with an exceptionally high reduction current density of 3.89 A cm−2 at 2.5 V potential applied and 800 °C temperature with GDC (Gd0.1Ce0.9O1.95) electrolyte. Ni doping is a crucial factor in controlling the electrochemical performance and catalytic activity in SOEC and GDC electrolytes, which is further helped by the high ionic conductivity.

Controlled synthesis of quasi-single-crystal lead dioxide by polyvinylpyrrolidone for enhanced electrochemical ozone production

The crystal facet of PbO2 has been proved to be a key factor affecting its electrochemical ozone production (EOP) performance. However, PbO2 with smooth and uniform crystal surface and single-crystal nature, which is the basis and prerequisite for PbO2 crystal facet engineering, has not yet been reported. In this study, by adding polyvinylpyrrolidone (PVP) as a facet modifier during the hydrothermal synthesis, a quasi-single-crystal PbO2 (PVP:Pb(CH3COO)2·3H2O=48:100, PVP-48) with (110) and (101) exposed facets was successfully synthesized. Compared with commercial PbO2 prepared by electrochemical deposition, PVP-48 exhibits excellent electrochemical catalytic activity due to its special crystal structure, and achieves the highest current efficiency of 11.9 % at a current density of 0.83 A/cm2. Further calculations show that PVP prefers to adsorb onto the (110) facet of the lead dioxide and reduces its surface energy, thereby exposing the (110) facet more readily. This work demonstrates the importance of PbO2 facets composition and provides new ideas for further controllable synthesis of PbO2 with specific facet structure and higher EOP efficiency.

Insights on the activity-selectivity trade-off in iron-containing nitrogen-doped carbon catalyst via cobalt addition for oxygen reduction reaction in alkaline medium

Iron-based noble-metal-free electrocatalysts exhibit impressive performance and stability for the Oxygen reduction reaction (ORR) in alkaline media, but face challenges. This study investigates the impact of Co addition to Fe in nitrogen(N)-doped carbon (Fe/NC) catalysts prepared via one-pot synthesis involving direct pyrolysis of the metal (M) and 2,4,6-tris(2-pyridyl)-s-triazine complexes (M-TPTZ) on carbon. Comprehensive characterization reveals N-doped carbon structures with single-atom sites and metal oxides, with M-Nx centers mainly in carbon pores and metal oxides on the carbon surface. N2 adsorption/desorption experiments and electrochemical surface area (ECSA) reveals that Co introduction enhances the catalyst surface area. Moreover, Co addition alters nitrogenated species distribution, affecting catalytic activity. Electrochemical studies rank catalytic activity as Fe/NC < Co/NC < CoFe/NC, while rotating ring-disk electrode (RRDE) investigations show mixed 2 and 4 electrons pathways. Fe/NC follows a 4e- pathway with minimal HO2− production, while Co-containing catalysts suggest a mixed (2e- + 2e-) pathway with an average of 3.75 electrons involved. This divergence highlights nuanced electrochemical characteristics of Fe- and Co-based materials, emphasizing the need for in-depth characterization.

Effects of Pt Loading onto SnO2 Ordered Porous Thin Films on Potentiometric Hydrogen Sensing Properties

Ordered Pt/SnO2 composite porous thin films were prepared for fabrication of planar mixed-potential hydrogen sensors. Characterization of the Pt/SnO2 films revealed that Pt elements were primarily loaded in Pt° form on the SnO2 film surface and did not significantly change the morphology of the film electrodes. The potentiometric response of Pt/SnO2 thin films to hydrogen varied with the Pt loading contents. Compared to the pristine SnO2 film, the 1 at% and 2 at% Pt-loaded SnO2 composite films exhibited 1.6 and 2.0 times higher potentiometric response to 300 ppm hydrogen at 500 °C, with a similar response time of 6–10.5 s. By assembling an array of sensors composed of SnO2 films loaded with 1 at% and 2 at% Pt, and using principal component analysis, discrimination of hydrogen and four interfering gases (ammonia, carbon monoxide, nitrogen dioxide, and propane) in the concentration range of 100–300 ppm was achieved. The sensing behaviors of the Pt/SnO2 composite thin films were discussed in relation to the competitive promotion effects for the heterogeneous and electrochemical catalytic activities by Pt loading.

A novel Sr7Mn4O15 incorporated F-MWCNT nanocomposite: synthesis, characterization, and its electrochemical catalytic activity towards l-tryptophan detection

The present study investigates the facile construction of heptastrontium manganate (Sr7Mn4O15) decorated functionalized-multiwalled carbon nanotube (F-MWCNT) nanocatalyst and its utilization as a catalyst for the quantification of l-tryptophan (Trp). Prepared Sr7Mn4O15 and Sr7Mn4O15/F-MWCNT nanocomposites were confirmed to exhibit high crystallinity and extraordinary electrical conductivity (minimum resistance of 31.01 Ω). Sr7Mn4O15/F-MWCNT-modified platinum electrode exhibited the highest irreversible oxidation peak potential of Trp at + 0.80 V (vs Ag/AgCl) in pH 6.0 analyte solution. Upon raising the sweep rate, the oxidation potential moved to more positive potential due to the formation of a complex between Trp and Sr7Mn4O15/F-MWCNT. The linear correlation between Trp concentration and the anodic current intensity was attained in the span of 2–400 µM. The detectable limit of Trp was calculated to 23 nM and a sensitivity of 17 μA μM−1cm−2 with high selectivity.

An enhanced electrochemical catalytic activity towards arsenic (III) detection based on FTO electrode modified with gold nanoparticles by irradiation and electrophoretic deposition

An enhanced electrochemical catalytic activity towards arsenic (III) detection based on FTO electrode modified with gold nanoparticles by irradiation and electrophoretic deposition

Emergence of electrochemical catalytic activity via an electrochemical-probe on defective transition metal dichalcogenide nanosheets

Two-dimensional transition metal dichalcogenides (2D TMDs) have shown exceptional electrochemical catalytic activity for the efficient generation of hydrogen through electrochemical water splitting. In the case of molybdenum disulfide (MoS2), a prominent member of 2D TMDs, the electrochemically active sites primarily reside at the edges, while the basal plane, which constitutes the majority of the MoS2 structure, remains relatively inactive. In this study, we aimed to activate the inert sites of the basal plane with some defective structure for hydrogen evolution reaction (HER) by employing an electrochemical-probe in combination with voltage sweeping. The initiation of HER at these previously inactive sites was visualized and confirmed using scanning electrochemical cell microscopy (SECCM). Our findings reveal that the enhanced HER activity originates from surface defects induced by the probing process.

Calcination-induced enhancement of Cd2+ and Pb2+ electrochemical detection capabilities of nano-ag-supported CoZn bi-metal ZIFs

The electrochemical properties of CoZn bi-metal ZIF were improved by calcination at high temperature. Ag@ZIF-1000 exhibited the best detection capabilities for Cd2+ and Pb2+ with a low limit of detection and high sensitivity.

Facile and Low Temperature Synthesis of Nd1.8Sr0.2NiO4-δ Cathode Nanofibers for Intermediate Temperature Solid Oxide Fuel Cells

Solid oxide fuel cells (SOFCs) are usually operated at high temperatures (800-1000 °C). As the overall efficiency of SOFC is governed by thermodynamics and kinetics during operation, reducing the operating temperature to 500-650 °C causes significant increase in the electrode polarization losses especially at cathode due to high activation energy towards oxygen reduction reaction (ORR) at cathode, which eventually reduces the overall cell performance. Addressing increased polarization losses at relatively low temperatures (500-650 °C) has been the key issue and a focus of many groups over past couple of decades. Conventional cathode materials lose their ORR activity and so discarded for intermediate temperature (IT)-SOFC application. In this regard, mixed ionic-electronic conductors (MIECs) offer high thermal and chemical stability along with high oxygen diffusion and good electronic conductivity at IT [1,2]. In addition, Ruddlesden-Popper (RP) type MIECs with A2BO4 structure have been demonstrated as promising cathode for IT- SOFCs due to their unique structure, rapid oxygen surface exchange kinetics, and excellent stability in atmosphere. Particularly Nd2NiO4+δ oxides offer an excellent oxygen diffusion coupled with high surface exchange coefficients and comparable thermal expansion coefficients with those of oxygen-ion conductors (YSZ and CGO) [2]. Enhanced electronic conductivity and electrochemical performance have been demonstrated for partial replacement of Nd with Sr in our previous reports [3].Albeit, the intrinsic material properties such as electrochemical catalytic activity and electrical conductivity are of primary importance, an actual electrode performance strongly depends on its microstructure. Therefore, in addition to using high catalytic and conductive materials, achieving an extremely high-power density, thus, requires a finely controlled electrode microstructure, to expand the electrochemically active triple-phase boundary (TPB). Recently, electrospinning has been considered as an efficient, cost effective and promising method for synthesis of ceramic nanofibers. Pertinent literature suggests that SOFC with cathode nanofiber has superior/better performance (nearly doubled power density and significant reduced polarization resistance) compared to powder type electrodes. Selection of suitable cathode materials with modified microstructure (nanofibers) would facilitate more electrochemically active sites for the oxygen reduction at relatively low temperatures <650 °C.In this paper we synthesized Nd1.8Sr0.2NiO4-δ (NSNO) cathode nanofibers using electrospinning technique and compared its electrochemical performance with NSNO nanopowder. Practically, 10 wt.% Polyvinylpyrrolidone (PVP) solution was prepared by dissolving it in ethanol, to which stoichiometric amounts of Nd-nitrate, Sr-nitrate, Ni-nitrate (total weight percentage of metal salts- 3 wt%) were added, together with some deionized water. The mixture was then stirred for 10 h at room temperature on a magnetic stirrer to obtain a homogeneous sol. The sol was loaded into the electrospinning syringe. Distance between the spinneret and the collector was fixed at 25 cm and the high-voltage supply was maintained at 30 kV. The spinning rate was controlled at 5 ml h- 1 by a syringe pump. The obtained nanofibers were dried at 80 °C for 12 h, then sintered at 900 °C for 2 h in air to obtain single-phase NSNO.The obtained nanofibers were characterized using room temperature XRD, XPS, SEM and dc electrical conductivity (400-650 °C). In addition, electrochemical impedance spectroscopy studies on symmetric cells were carried out as a function of temperature (400-650 °C). Improved electrochemical performance is attributed to enhanced electrochemical active sites for ORR due to nanofibers and optimum porosity.

NiSe2-CoSe2 hollow polyhedron as counter electrode catalyst for high-efficiency dye-sensitized solar cells

The design of efficient counter electrode (CE) materials for dye sensitized solar cells (DSSCs) strongly depend on the microstructure construction and the effective combination of different active components. In this study, a hollow polyhedral structured NiSe2-CoSe2 composite electrode was synthesized through the direct selenization of the hollow nanocage morphology nickel-cobalt layered double hydroxide (NiCo-LDH) ultrathin nanosheets, which was derived from ZIF-67 nanocrystals. Notably, owing to the unique hollow structure and synergistic effect of the Ni-Co bimetallic selenides, the hollow polyhedral NiSe2-CoSe2 CE exhibited the expected electrochemical catalytic activity in the reduction of triiodide, as revealed by electrochemical impedance spectroscopy, cyclic voltammetry and Tafel polarization measurements. The photovoltaic results revealed that the PCE of the NiSe2-CoSe2 CE reached 8.21 %, which was higher than those of the Pt and CoSe2 CEs (7.62 % and 6.78 %, respectively). Moreover, the hollow NiSe2-CoSe2 CE exhibited a favourable photocurrent response upon light on-and-off cycling and improved stability over multiple start. This study provides a meaningful reference for the construction of hollow polymetallic transition-metal selenides for DSSC devices.

Hyphae Carbon Coupled with Gel Composite Assembly for Construction of Advanced Carbon/Sulfur Cathodes for Lithium-Sulfur Batteries.

The design and fabrication of novel carbon hosts with high conductivity, accelerated electrochemical catalytic activities, and superior physical/chemical confinement on sulfur and its reaction intermediates polysulfides are essential for the construction of high-performance C/S cathodes for lithium-sulfur batteries (LSBs). In this work, a novel biofermentation coupled gel composite assembly technology is developed to prepare cross-linked carbon composite hosts consisting of conductive Rhizopus hyphae carbon fiber (RHCF) skeleton and lamellar sodium alginate carbon (SAC) uniformly implanted with polarized nanoparticles (V2O3, Ag, Co, etc.) with diameters of several nanometers. Impressively, the RHCF/SAC/V2O3 composites exhibit enhanced physical/chemical adsorption of polysulfides due to the synergistic effect between hierarchical pore structures, heteroatoms (N, P) doping, and polar V2O3 generation. Additionally, the catalytic conversion kinetics of cathodes are effectively improved by regulating the 3D carbon structure and optimizing the V2O3 catalyst. Consequently, the LSBs assembled with RHCF/SAC/V2O3-S cathode show exceptional cycle stability (capacity retention rate of 94.0% after 200 cycles at 0.1 C) and excellent rate performance (specific capacity of 578mA h g-1 at 5 C). This work opens a new door for the fabrication of hyphae carbon composites via fermentation for electrochemical energy storage.

Heteroatom co-doped biomass carbon modified electrodes for all-vanadium redox flow batteries with ultra-low decay rate of energy efficiency

The intermittent nature of renewable energy calls for advanced energy storage systems, of which all-vanadium redox flow batteries (VRFBs) are recognized as the most promising long-duration energy storage devices. The most common electrode for VRFBs is graphite felt (GF), however with poor hydrophilicity and weak electrochemical activity, making it difficult to be a perfect electrode. In this work, we report a nitrogen-phosphorus co-doped biomass carbon modified GF (NP-GF), in which the introduction of cross-linking agents enhances the linkage between the carbon material and the GF. With excellent electrolyte wettability and electrochemical catalytic activity, the NP-GF electrode exhibits enhanced electrochemical activity and reversibility for VO2+/VO2+ and V2+/V3+ in electrochemical tests. The coulombic efficiency (CE), voltage efficiency (VE), and energy efficiency (EE) are all boosted at current densities of 80–280 mA cm−2 in VRFB single cell tests assembled with NP-GF. The power density of the VRFB reaches a peak of 757.0 mW cm−2. Furthermore, the VRFB has an extremely low EE decay rate per cycle (0.0018 %), demonstrating superior electrochemical performance stability.

Reduced graphene oxide-supported palladium oxide-MOx for improving the performance of air-cathode microbial fuel cells: Influence of the Sn, Ce, Zn, and Fe precursors

Over the past few decades, microbial fuel cells (MFCs) have attracted significant interest within the realm of renewable energy technologies owing to their capability to generate electricity from low-grade substrates. However, their commercialization and scaling-up are impeded by significant obstacles, including high capital costs, limited durability, and sluggish oxygen reduction reaction (ORR). Here, we demonstrate an environmentally-friendly approach for developing highly efficient electrocatalysts consisting of palladium oxide (PdO) and different transition metal oxides (i.e., tin (IV) oxide (SnO2), ceric oxide (CeO2), iron (III) oxide (Fe2O3), and zinc oxide (ZnO)) embedded within reduced graphene oxide (rGO) framework for improving the efficiency of ORR in neutral medium and MFCs. Among the as-prepared electrocatalysts, the PdO–SnO2/rGO possesses the highest ORR electrochemical catalytic activity in a neutral medium (pH ∼ 7.2) following a four-electron ORR pathway, with a current density slightly lower than that of benchmark Pt/C electrocatalyst. The assessment of MFC performance is conducted by employing activated sludge as the inoculum and glucose as the sole electron donor in the anode chamber of single-chamber, air-cathode MFCs. Consistent with electrochemical performance, the maximum power output of an MFC equipped with PdO–SnO2/rGO as an air cathode is significantly higher than other tested MFCs, reaching 84.6 ± 2.8 mW m−2, which represents ∼ 91 % of the power output of an MFC with Pt/C air cathode. Our results reveal that the incorporation of PdO into transition metal reduced graphene oxide framework has the potential to facilitate their long-term application as air cathodes in MFCs that possess easy fabrication, relatively affordable cost, and outstanding electrochemical catalytic oxygen reduction capability, for enhancing electricity generation from wastewater.

Electrochemical Valorization of Glycerol via Electrocatalytic Reduction into Biofuels: A Review.

Electrochemical conversion of underutilized biomass-based glycerol into high-value-added products provides a green approach for biomass and waste valorization. Plus, this approach offers an alternative to biofuel manufacturing procedure, under mild operating conditions, compared to the traditional thermochemical routes. Nevertheless, glycerol has been widely valorized via electrooxidation, with lower-value products generated at the cathode, ignoring the electroreduction. Here we study and establish a review of the efficient glycerol reduction into various products via the electrocatalytic reduction (ECR) process. This review has been built upon the background of glycerol underutilization and theoretical knowledge about the state-of-the-art ECR. The experimental understanding of the processing parameter influences towards electrochemical efficiency, catalytic activity, and product selectivity are comprehensively reviewed, based on the recent glycerol ECR studies. We conclude by outlining present issues and highlighting potential future research avenues for enhanced ECR application.

Enhancing electrocatalytic performance and Stability: A novel Prussian Blue-Graphene quantum dot nanoarchitecture for H2O2 reduction

The reduction reaction of hydrogen peroxide (H2O2) stands as a pivotal electrochemical process holding the promise of revolutionizing energy conversion and water treatment applications. Realizing this potential hinges on the development of electrocatalysts that not only exhibit exceptional activity but also demonstrate unwavering stability. Herein, we propose a pioneering electrocatalyst composed of Prussian blue (PB)-graphene quantum dot (GQD) (PB-GQD) nanoarchitecture fabricated through an in-situ electrochemical method. The PB-GQD nanoarchitecture boasts precisely crafted PB nanoparticles (NPs) that exhibit remarkable electrochemical catalytic activity and stability, offering a substantial advancement over conventional PB NPs structure used as a control. The augmentation of electrocatalytic performance in the PB-GQD nanoarchitecture can be attributed to the symbiotic relationship between PB NPs and GQD. This synergy is engendered through electrostatic attraction and/or coordination interactions between PB precursor’s iron cations and GQD’s multivalent polyanions. This unique arrangement accelerates heterogeneous electron transport, endows the structure with abundant electrochemically active sites, and shortens mass transfer lengths. Notably, GQD’s presence, rich with hydroxyl (–OH) and carboxylic (–COOH) groups, mitigates the decomposition of PB NPs into Fe(OH)3 in neutral or higher pH solutions. This preservation mechanism ensures sustained, elevated electrocatalytic performance for H2O2 reduction.

Ultra-fine Fe3C nanoparticles decorated in the Fe–N co-doped carbon networks with hierarchical nanoarchitectonics towards efficient oxygen reduction electrocatalysis

The iron-nitrogen co-doped carbon (Fe–N–C) materials have considered one of the oxygen reduction reaction catalysts with the best potential. Unfortunately, their insufficient intrinsic activity and low active sites result in thick cathode catalytic layers of fuel cell, which has limited discharge performance of the Fe–N–C catalysts in the fuel cells. Herein, a supramolecular assembly strategy is designed to prepare accessible Fe-Nx sites and ultra-fine Fe3C nanoparticles in porous carbon nanosheet with optimized pore structure toward oxygen reduction electrocatalysis. It is found that supramolecular assembly strategy has significantly increased the specific surface area and Fe-Nx site content, and induced the formation of highly dispersed Fe3C nanoparticles, which contributes to the high electrochemical active surface area and catalytic activity. The obtained FeNC-900-S catalyst exhibits a high half-wave potential of 0.860 V and a current density of up to 8.28 mA/cm2 (Jk at 0.85 V) in 0.1 M KOH, outperforming the those of commercial Pt/C. More importantly, when the FeNC-900-S is employed as an air cathode catalyst towards zinc-air batteries, it obtains an open-circuit voltage of 1.548 V, a power density of 188.8 mW/cm2 and a specific capacity of 790.5 mAh/g.