Oxygen Reduction Performance Research Articles

Theoretical inspection of TM-P4C single-atom electrocatalysts: High performance for oxygen reduction and evolution reactions

Developing the cost-effective or even bifunctional electrocatalysts for both oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) with industrially relevant activity is highly desired for metal-air batteries at the current stage. Herein, in this work, the catalytic performances of the single transition metal (TM) atom embeds graphene sheet with the tetra-coordinates Phosphorus (TMP4) for ORR and OER are investigated based on the density functional theory method. The results demonstrate that the most promising ORR and OER catalytic activity can be achieved on the CoP4 with the smallest potential gap ΔE and the lowest overpotential of 0.37 and 0.32 eV among all TMP4 systems, respectively, and the catalytic activity is even better than that of the traditional Pt and IrO2 catalysts. Furthermore, the AIMD and phonon dispersion calculations are conducted to confirm the thermodynamics and dynamics stability of CoP4. This work screens out promising candidates for novel graphene-based bifunctional ORR and OER catalysts and offers detailed microscopic insights into the mechanism of OER/ORR, provides a theoretical guidance for the development of further single-atom catalysts.

Study on oxygen reduction mechanism of S-doped Fe-NC monatomic catalyst

Heteroatom doped Fe-NC catalyst shows excellent performance in oxygen reduction reaction. In this work, density functional theory was used to study the mechanism of S atom doping on the regulation of electronic structure of Fe-NC monatomic catalyst and the promotion of oxygen reduction reaction. The stable configuration of Fe-NC catalyst after sulfur atom doping, the regulation of electronic structure of fen4 active site by S atom, and the mechanism of oxygen adsorption and oxygen reduction reaction were analyzed. The results show that doping a small amount of S atoms around the fen4 active site can improve the stability of the catalyst. The mechanism of S atom doping to improve oxygen reduction performance is as follows: (1) the doping of S atom reduces the band gap of the catalyst, improves the conductivity of the catalyst, and is conducive to the electrocatalytic oxygen reduction reaction; (2) the doping of S atom can improve the ability of the catalyst to adsorb oxygen, which is conducive to oxygen reduction reaction; (3) the introduction of four S atoms into the system can reduce the overpotential of oxygen reduction reaction and improve the catalytic activity of fen4 site for oxygen reduction reaction. This work may provide a new idea for the regulation of heteroatom doping on carbon-based monatomic catalysts.

Tunning the Activity of Silver Alloy Electrocatalysts for the Oxygen Reduction Reaction in Alkaline Media

A bottleneck to achieve efficient and stable electrocatalysts for Anion Exchange Membrane Fuel Cells (AEMFCs) is the relatively slow kinetics of the oxygen reduction reaction (ORR) taking place at the cathode. The rather mild alkaline conditions in the AEMFC enable the utilization of various PGM-free catalysts, which brings up new possibilities of finding abundant and inexpensive electrocatalysts without compromising the power density. From theory and previous experiments, it is known that Au and Ag bind oxygen weakly, whereas other transition metals (e.g., Pd, Cu, Fe, Ni) bind strongly to oxygenated species1. Therefore, a suitable geometric arrangement between Ag, an abundant metal with relatively high specific activity, and other metals may give rise to optimum binding of oxygen and thus a high activity. A good strategy to improve the activity of Ag-based catalysts could be a rational design of alloys that can enhance the intrinsic activity of Ag by both ensemble and electronic effects2–4. The former is based on the combination of active sites that facilitate the initial oxygen binding together with Ag active sites that help desorb hydroxide anions, whereas the latter is induced by the alloying metal (which binds oxygenated species strongly) on the electronic structure of the overlaying Ag that tunes its binding to oxygen5. Herein, we report the fabrication and characterization of Ag thin-films alloyed with Pd, Ni, Cu and Mo as a tool to investigate the ORR reaction in terms of ensemble and electronic effects and thus relate alloy composition and geometric arrangement with ORR activity. Ag thin-film model catalysts are fabricated by means of physical vapor deposition methods (PVD) with high control over the amount of material deposited. By varying alloy composition and evaluating electrochemical activity and stability, together with detailed physical characterization, the degree and extent of electronic effects are elucidated. In the same way, sputtering of the same amount of Ag on thin-films of different metals evidences the role of the alloying metal on tuning the activity of Ag through an adjustment of its d-band that changes the binding of oxygenated species, as well as through an ensemble effect that provides active sites for the first elementary steps of the reaction. These results provide insights for more tailored design of electrocatalysts in alkaline media by shedding new light on the mechanisms through which the ORR kinetics are improved in alkaline media. Nørskov, J. K. et al. Origin of the overpotential for oxygen reduction at a fuel-cell cathode. J. Phys. Chem. B 108, 17886–17892 (2004).Betancourt, L. E. et al. Enhancing ORR Performance of Bimetallic PdAg Electrocatalysts by Designing Interactions between Pd and Ag. ACS Appl. Energy Mater. 3, 2342–2349 (2020).Slanac, D. A., Hardin, W. G., Johnston, K. P. & Stevenson, K. J. Atomic ensemble and electronic effects in Ag-rich AgPd nanoalloy catalysts for oxygen reduction in alkaline media. J. Am. Chem. Soc. 134, 9812–9819 (2012).Zamora Zeledón, J. A. et al. Tuning the electronic structure of Ag-Pd alloys to enhance performance for alkaline oxygen reduction. Nat. Commun. 12, 1–9 (2021).Stamenkovic, V. et al. Changing the Activity of Electrocatalysts for Oxygen Reduction by Tuning the Surface Electronic Structure. Angew. Chemie 118, 2963–2967 (2006).

Zinc Passivation in Zinc-Slurries Operated Beyond the Zincate Solubility Limit

Recently, zinc-air batteries have received revived interest as one of the proposed post lithium-ion technologies. This revival is driven by the demand for safe and environmentally friendly energy storage solutions for fluctuating renewable energy. These energy storage systems need to address variable power, capacity and profitability requests. Zinc-air-flow batteries with high specific energy density, low-cost, highly available and eco-friendly active materials are suitable to fulfill these requirements. The use of a flow battery type with zinc-particles suspended in an alkaline solution (zinc-slurry) in addition to high performance oxygen-reduction electrodes enables the development of high-power zinc-air batteries. Usually, the energy density of zinc-air-flow cells is limited by the solubility of the oxidation products in the electrolyte. In our cell, the electrolyte is supersaturated with oxidation products, before finally ZnO precipitates from the electrolyte. The cell is therefore operated beyond zincate solubility limit, which allows higher specific capacities than reported in literature, even though the zincate solubility of the electrolyte is much lower than reported [1].The flow cell has an active area of 100 cm² and incorporates a copper plate as current collector for the zinc-suspension electrode and an oxygen reduction electrode with gas-diffusion layer (supplied by Covestro). The zinc-slurry contains zinc-particles (supplied by Grillo) suspended in an alkaline solution (30 wt.-% KOH) and stabilized with polyacrylic acid.One of the main limiting factors of the specific capacity of the zinc-slurry is passivation. While the passivation of stationary electrodes in flowing or quiescent electrolytes is fairly well understood, see e. g. [2], there is no literature on the passivation behaviour of zinc-slurry electrodes. In this study we determined the starting point of ZnO precipitation and the critical factor for the passivation of these anodes by analysing cell voltage, potential of the zinc electrode and the zincate concentration in the liquid phase of the zinc-slurry. Depending on parameters like current density and additive selection, it is possible to reach specific capacities of 287 mAh/gslurry or 574 mAh/gzinc. Appleby, A.J. and M. Jacquier, The C.G.E. circulating zinc/air battery: A practical vehicle power source. Journal of Power Sources, 1976. 1(1): p. 17-34.Bockelmann, M., et al., Electrochemical characterization and mathematical modeling of zinc passivation in alkaline solutions: A review. Electrochimica Acta, 2017. 237: p. 276-298.

The Oxygen Reduction Performance of Pt Supported on the Hybrid of Porous Carbon Nanofibers and Carbon Black.

Proton exchange membrane fuel cells (PEMFCs) represent an outstanding clean energy alternative for next-generation power sources. The PEMFC’s performance is mainly determined by the sluggish oxygen reduction reaction (ORR) that occurs in its cathode Therefore, the use of electrocatalysts with high electrocatalytic activity and stability for improving the ORR has been a vital direction for the commercialization of PEMFCs. In this article, porous carbon nanofibers (PCNFs) based on a polyacrylonitrile/polymethyl methacrylate (PAN/PMMA) precursor were fabricated by electrospinning followed by carbonization; then, the PCNFs were mixed together with carbon black (CB) in different mass ratios as a hybrid support for Pt nanoparticles. Pt nanoparticles were deposited on the hybrid support by the ethylene glycol reduction method, and the obtained series of Pt/(PCNF + CB) were used as the oxygen reduction electrocatalyst in the cathode. Their electrocatalytic properties, as well as those of Pt/C as a reference, were investigated by cyclic voltammetry scanning (CV) and linear sweep voltammetry (LSV). The results explained that Pt/(PCNF + CB) showed a higher electrochemical activity area and half-wave potential when the PCNF/CB mass ratio was 3/2 than that of commercial Pt/C. Furthermore, the half-wave potential of Pt/(PCNF + CB) only decreased by 4 mV, which was 86 mV lower than that of commercial Pt/C (90 mV) after 2000 ADT cycles, indicating that the incorporation of PCNFs to form a hybrid support could result in corrosion resistance.

Sodium Borohydride Treatment to Prepare Manganese Oxides with Oxygen Vacancy Defects for Efficient Oxygen Reduction

Manganese oxides are often used as catalysts for oxygen reduction reactions due to their low price and high stability, and they have been extensively studied. However, the poor electrical conductivity and low intrinsic activity of manganese oxides restrict its application in oxygen reduction. In this paper, the manganese oxide octahedral molecular sieve is used as the research object, and the oxygen reduction performance of the material is adjusted by the surface reduction etching treatment of sodium borohydride. After being treated with 8 mmol/L sodium borohydride, the oxygen vacancy content of the manganese oxide octahedral molecular sieve was 26%. The manganese oxide octahedral molecular sieve showed the best performance, and its half-wave potential was 0.821 V. Tests show that the material has excellent electrical conductivity and high oxygen reduction kinetics. The generation of appropriate oxygen vacancies on the surface directly improves the chemical properties of the material surface, regulates the ratio of Mn3+/Mn4+ on the surface of the nanorod, and increases the oxygen reduction adsorption sites on the surface of the material. On the other hand, the electrical conductivity of the material is adjusted to increase the electron transfer rate during the oxygen reduction process, thereby enhancing the oxygen reduction activity.

Wood based quasi-solid-state Zn-air battery with dual honeycomb-like porous carbon and cationic nanocellulose film

Conversion of low-value biomass to hierarchically porous carbon-based materials for oxygen reduction reactions (ORR), without using conventional template methods, is of particular significant for energy storage technology. Herein, dual honeycomb-like porous carbon inspired by multiscale structure of wood was assembled with cationic nanocellulose film into Zn-air battery. Nitrogen-doped hierarchically porous carbon was obtained by a simple two-step process involving alkaline extraction and pyrolysis with NH4Cl. Alkaline extraction was utilized for partially degrading lignin and heterosaccharide from unprocessed wood to create a porous wood with numerous nanopores and 3D loose structure. The inner and outer parts of obtained porous wood were further pore-optimized and doped with NH4Cl by a consequent pyrolysis step. The resulting carbon-based material (AHWC) possessed high specific surface area (1601.8 m2 g−1), well-developed hierarchical porosity, and high N content enabled excellent electrocatalytic oxygen reduction performance. Compared with commercial Pt/C catalysts in KOH electrolyte, AHWC exhibits nearly two times higher kinetic currents in the low overpotential region, comparable number of transferred electrons, and significantly higher operating stability. This carbon-based material also showed an excellent capacity and energy density equal to 792 mA h g−1 and 927 W h kg−1, together with superior long-term durability (200 h at the current density of 10 mA cm−2) when assembled as the active electrode material into a Zn-air battery. Additionally, cationic modified nanocellulose film (C-CNF-M), acting as a solid electrolyte, was assembled with AHWC for a quasi-solid-state Zn-air battery which exhibited excellent specific capacity (672.2 mA h g−1), energy density (644.11 W h kg−1) and cycling stability (500 min at 1 mA cm−2). The AHWC establish a bridge between papermaking and the field of energy storage by green conversion of biomass and fabrication of porous carbon-based materials and cellulose based electrolyte with excellent properties applicable to electrochemical energy devices.

A template approach to designing and synthesizing hierarchical porous carbon with tri-modal pore structure and its application for high performance oxygen reduction electrocatalyst support

A new type of hierarchical porous carbon with tri-modal pore structure (Tri-PC), i.e., ordered micropores (1.3 nm), uniformly distributed mesopores (2–10 nm) and “earthworm-shaped” mesochannels (with a diameter of 20 nm) running through the whole particle was successfully realized via a novel and facile template approach, in which zeolite Y was firstly gone through a pore expansion using oxalic acid-ammonium fluoride mixture to prepare hierarchical porous zeolite. The hierarchical porous zeolite was subsequently used as the template to catalytically grow carbon via CVD technique. Tri-PC was then obtained after the removal of the template. The as synthesized Tri-PC showed great potential as the catalyst support. We evaluated the ORR catalytic activity of Tri-PC supported platinum nanoparticles (Pt/Tri-PC) in alkaline electrolyte, which exhibits 20 mV higher onset potential (0.95 V) and 30 mV higher half-wave potential (0.87 V) than commercial 10 wt% Pt/C catalyst. Meanwhile, the electrochemical impedance spectroscopy measurement showed that Pt/Tri-PC had lower charge transfer resistance. High performance benefits from a collaborative hierarchical architecture. Micropores offer a large specific surface area and sufficient active sites, mesopores increase the accessibility of active sites and shorten the diffusion path of fuels and products, and mesochannels further enhance the connectivity of the entire pore network. The present work highlights the significance of the hierarchical porous structure for enhancing the catalytic performance of catalysts and suggests that Tri-PC could be used as an advanced catalyst support in many fields.

Bulky Thiolate-Protected Silver Nanocluster Ag 213 (Adm-S) 44 Cl 33 with Excellent Electrocatalytic Performance toward Oxygen Reduction

Bulky Thiolate-Protected Silver Nanocluster Ag ₂₁₃ (Adm-S) ₄₄ Cl ₃₃ with Excellent Electrocatalytic Performance toward Oxygen Reduction

Silver based single atom catalyst with heteroatom coordination environment as high performance oxygen reduction reaction catalyst

Silver based single atom catalyst with heteroatom coordination environment as high performance oxygen reduction reaction catalyst

Metal-organic framework-erythrocytic hybrid surfaces with enhanced oxygen reduction performance for enzymatic biofuel cells–An updated strategy

Enzymatic biofuel cells (EBFCs), which can use oxygen in the body as a cathode fuel to generate electricity, have broad application prospects. For air cathode of EBFCs, the most important factors affecting the electrocatalytic performance are the inherent fragile nature, poor oxygen enrichment performance and low activity of enzyme catalysts. Herein, based on the natural oxygen enrichment performance of red blood cells (RBCs) and its electrocatalytic activity for oxygen reduction reaction, we fabricate the hybrid surfaces of metal–organic framework-nanocoated RBCs (RBC@ZIF-8) using an in situ synthesis method. Versus native RBCs, the electrocatalytic activity and stability of RBC@ZIF-8 are enhanced by 50% and 35%, respectively, when explored as a biocathode catalyst for implantable biofuel cells. And compared with enzyme catalysts, RBC@ZIF-8 has better stability and handleability. Mechanistic studies show that the coating surface increases the O2-enriched capacity of RBCs and then provides more reaction raw materials for the hemoglobin with catalytic active. Moreover, direct electron transfer capability of RBC@ZIF-8 is found on carbon cloth electrode without promoters and mediators. Our research expands the types of air cathode catalyst for EBFCs and suggests a promising strategy to enhance the electrocatalytic performance of gas-based biocatalysts, such as bioelectrocatalytic reduction of CO2 and N2.

Highly Selective Oxygen Reduction to Hydrogen Peroxide on a Carbon-Supported Single-Atom Pd Electrocatalyst

Selective electrochemical two-electron oxygen reduction is a promising route for renewable and on-site H2O2 generation as an alternative to the anthraquinone process. Herein, we report a high-performance nitrogen-coordinated single-atom Pd electrocatalyst, which is derived from Pd-doped zeolitic imidazolate frameworks (ZIFs) through one-step thermolysis. High-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) combined with X-ray absorption spectroscopy verifies atomically dispersed Pd atoms on nitrogen-doped carbon (Pd-NC). The single-atom Pd-NC catalyst exhibits excellent electrocatalytic performance for two-electron oxygen reduction to H2O2, which shows ∼95% selectivity toward H2O2 and an unprecedented onset potential of ∼0.8 V versus revisable hydrogen electrode (RHE) in 0.1 M KOH. Density functional theory (DFT) calculations demonstrate that the Pd-N4 catalytic sites thermodynamically prefer *–O bond breaking to O–O bond breaking, corresponding to a high selectivity for H2O2 production. This work provides a deep insight into the understanding of the catalytic process and design of high-performance 2e– ORR catalysts.

Self-supporting nitrogen-doped reduced graphene oxide@carbon nanofiber hybrid membranes as high-performance integrated air cathodes in microbial fuel cells

The traditional air cathode in microbial fuel cell (MFC) usually consists of catalyst layer (CL), supporting layer (SL) and conductive gas diffusion layer (GDL), the overall MFC performance is inevitably affected by the additional and expensive adhesives and conductive agents. Here, we developed an integrated air cathode in MFC without any additional SL, GDL or adhesives. The integrated air cathode was self-supporting nitrogen-doped reduced graphene oxide@carbon nanofiber (N-rGO@CNF) hybrid membranes fabricated by electrospinning with subsequent heat-treatment under ammonia atmosphere. The as-fabricated N-rGO@CNFs possessed far superior MFC performance and oxygen reduction reaction (ORR) activity to the pristine nitrogen-doped carbon nanofibers (NCNF) and commercial activated carbon (CAC). The amount of rGO embedded into CNF had prominent influence on their ORR activities and MFC performances. N-5-rGO@CNF had the lowest resistance and the maximal exchange current density, exhibiting desirable oxygen reduction performance via a four-electron pathway. The maximum power density of N-5-rGO@CNF can reach 826 mW m−2 in MFC, which is approximately 9, 2.53 and 1.82 times of pristine NCNF, CAC and Pt/C with values of 91, 327 and 454 mW m−2. The outstanding performance of the integrated air-cathodes originates from the integrality, brevity and hybrid composition of the electrospun nanofiber membrane. The appropriate embedded rGO not only improves the bulk conductivity of the rGO@CNF to promote ion adsorption, but also provides vacancies to accommodate ions, the doped nitrogen atoms facilitate O2 adsorption and/or subsequent O–O bond breaking, thus improving the electrochemical performance of N-rGO@CNF in MFC.

Exploring the Effect of Pd on the Oxygen Reduction Performance of Pt by In Situ Raman Spectroscopy.

Directly monitoring the oxygen reduction reaction (ORR) process in situ is very important to deeply understand the reaction mechanism and is a critical guideline for the design of high-efficiency catalysts, but there is still lack of definite in situ evidence to clarify the effect between adsorbed intermediates and the strain/electronic effect for enhanced ORR performance. Herein, in situ surface-enhanced Raman spectroscopy (SERS) was employed to detect the intermediates during the ORR process on the Au@Pd@Pt core/shell heterogeneous nanoparticles (NPs). Direct spectroscopic evidence of the *OOH intermediate was obtained, and an obvious red shift of the *OOH frequency was identified with the controllable shell thickness of Pd. Detailed experimental characterizations and density functional theory (DFT) calculations demonstrated that such improved ORR activity after inducing Pd into Au@Pt NPs can be attributed to the optimized adsorbate-substrate interaction due to the strain and electronic effect, leading to a higher Pt-O binding energy and a lower O-O binding energy, which was conducive to O-O dissociation and promoted the subsequent reaction. Notably, this work illustrates a relationship between the performance and strain/electronic effect via the intermediate detected by SERS and paves the way for the construction of ORR electrocatalysts with high performance.

Surface functionalization of polyaniline and excellent electrocatalytic performance for oxygen reduction to produce hydrogen peroxide

We have developed the CNT@PANI-NO electrocatalyst that is significantly different from the conventional electrocatalyst previously reported. • Polyaniline (PANI) can be changed into PANI-NO with the functional group of –NO. • Introducing PANI-NO on the surface of CNT obtains the CNT@PANI-NO. • PANI-NO has promoted selectivity of H 2 O 2 than PANI. • CNT@PANI-NO exhibits excellent electrochemical performance for H 2 O 2 production. Electrochemical two-electron oxygen reduction is an environmental-friendly and promising method to generate H 2 O 2 . However, a great challenge remains to develop more economic and effective electrocatalysts for practical application. Here, we have developed a CNT@PANI-NO electrocatalyst that is significantly different from the conventional electrocatalyst previously reported (such as metal, alloy, carbon materials doped with heteroatoms, metal single-atom catalysts). We firstly find that the polyaniline (PANI) treated by dilute nitric acid can be changed into the PANI-NO product with the functional group of –NO. Then we introduce the PANI-NO on the surface of carboxylated carbon nanotubes to obtain the CNT@PANI-NO nanocomposites, which exhibit excellent electrochemical performance to H 2 O 2 production. The H 2 O 2 selectivity of the typical CNT@PANI-NO is between 87% and 94% at the potential of 0.2–0.68 V (vs. RHE), the faradaic efficiency is close to 95% and the current density is up to 2.9 mA/cm 2 (at 0.3 V) in alkaline condition. The DFT results give the origin of the catalytic activity. This study provides a new idea for the application of polymer in electrocatalysis and a new way to develop the high-performance 2e-ORR electrocatalyst.

Green Synthesis of Flowerball-like MoS2/VC Nanocomposite and Its Efficient Catalytic Performance for Oxygen Reduction Either in Alkaline or Acid Media

Opening up electrocatalysts for oxygen reduction reaction (ORR) is essential for practical application in fuel cells and metal-air batteries; however, how to make the catalysts with both good performance and low cost is difficult. Recently, research on the ORR of molybdenum disulfide-based catalysts in alkaline electrolytes has been on the rise. However, the development of MoS2 catalyst for acidic ORR is still in its infancy. Herein, without using reductant and morphology control reagent, we firstly obtained flowerball-like MoS2/Vulcan XC-72R (VC) nanocomposites via hydrothermal method. The designed composite exhibits a nearly 4e− ORR process with 0.78 and 0.92 V onset potentials in 0.1 M KOH and HClO4, respectively. Furthermore, the flowerball-like composite shows utmost electrochemical stability judging by 87 and 80% current retention for about 5.5 h either in alkaline or acid media, long term durability for continuous 10,000 cycles, and stronger resistance to methanol than the commercial Pt/C catalyst. The abundant Mo edges as catalytic active centers of flowerball-like structure, high electron conductivity, and enhanced mass transport in either alkaline or acidic electrolyte are favorable for catalytic performance. The prepared catalyst provides great potential for the substitution of noble metal based catalysts in fuel cells and metal-air batteries.

Two-Dimensional Metal–Organic Frameworks with Unique Oriented Layers for Oxygen Reduction Reaction: Tailoring the Activity through Exposed Crystal Facets

Two-Dimensional Metal–Organic Frameworks with Unique Oriented Layers for Oxygen Reduction Reaction: Tailoring the Activity through Exposed Crystal Facets

Preparation and oxygen reduction performance of nitrogen-doped cotton stalk-derived carbon

Abstract Oxygen reduction reaction (ORR) is a key step in the operation of fuel cells and metal air cells, which needs some economic and efficient catalysts to improve its reaction kinetics process. In this work, nitrogen-doped carbon (N-C) catalyst material was prepared by one-step high-temperature pyrolysis with biomass waste cotton stalk as carbon/nitrogen precursor material and urea as auxiliary nitrogen source. The effect of temperature on the structure and performance of the prepared N-C catalyst was investigated. The experimental results show that a small temperature change of 25°C will cause a significant change in the structure of N-C material. N-C-900 samples prepared at 900°C had a larger specific surface area of 620 m2 g−1, significantly improved graphitization degree and nitrogen content (7.30 at%) and showed significantly better ORR performance than other samples in alkaline medium. The ORR activity of N-C-900 sample is the best, indicated by the highest Eonset (0.92 V) and E1/2 (0.85 V) of ORR, which are positively shifted by 20 and 30 mV compared with commercial Pt/C. Its ORR initial potential and half-wave potential are similar to those of commercial Pt/C, and it shows better ORR stability and methanol resistance than Pt/C.

Hollow iron carbides via nanoscale Kirkendall cavitation process for zinc-air batteries

Hollow structured nanoparticles, especially metal carbides, are of great interest because of their wide applications, unique morphologies and superior catalytic properties. The Kirkendall cavitation process is a typical method of producing hollow structured nanoparticles. It should be noted that only precursors with proper diffusion couples can guarantee a successful preparation. In this work, based on a matching diffusion rate of graphene with that of iron atoms, hollow iron carbides nanoparticles anchoring on N-doped reduced graphene oxides (hollow Fe3C/N-rGO) are designed via a simple carbonization synthesis method. As expected, the obtained Fe3C/N-rGO exhibits excellent electrocatalytic performance both in oxygen reduction (E1/2 = 0.829 V) and evolution reactions. Rechargeable Zn-air batteries are assembled based on the composite, which can also deliver a notable peak power density (160.2 mW cm−2), long cycle life (over 300 cycles) and deformable property.

Interface engineering of polyaniline-functionalized porous Pd metallene for alkaline oxygen reduction reaction

Engineering the interface between two-dimensional materials and polymers is of great importance to improve their catalytic performance for oxygen reduction reaction (ORR). Hence, polyaniline (PANI)-functionalized porous Pd metallene (Pd@PANI metallene) is prepared via a two-step strategy. Due to the ultrathin porous nanosheets and interfacial structure, the Pd@PANI metallene possesses sufficient active sites and optimized electronic structure, which exhibits superior oxygen reduction performance in alkaline electrolyte. The mass and specific activities for Pd@PANI metallene are measured to 1.79 A mgPd−1 and 2.96 mA cm−2, which are 11.9 and 9.30 times those of Pt/C (0.15 A mgPd−1 and 0.32 mA cm−2), respectively. Additionally, the ORR performance and morphology of Pd@PANI metallene can be maintained after long-term stability testing, making it an excellent ORR catalyst. This work provides an effective interface engineering strategy to construct efficient two-dimensional ORR electrocatalysts to improve the performance.