High Peak Power Density Research Articles

Octahedral distortion enhances exceptional oxygen catalytic activity of calcium manganite for advanced Zn-Air batteries

Calcium manganite (CMO) holds great potential for OER/ORR catalysis. But, the weak interaction between the oxygen intermediates and reaction sites leads to sluggish catalytic kinetics. Herein, to trigger the exceptional catalytic activity of CMO, we propose a thermal-induced MnO 6 octahedral distortion strategy to advance the absorption capability of intermediate reactants. Refined structural analysis and theoretical calculation reveal that the strong Jahn-Teller distortion of MnO 6 is capable of optimizing the surface electron redistribution and accelerating the electron transfer between the oxygen and Mn sites, which significantly boosts the intrinsic oxygen catalytic activities of the distorted CMO (D-CMO). Notably, the D-CMO functions as excellent bifunctional oxygen electrocatalysts and enables a high-performance solid-state Zn-air battery with satisfactory mechanical strength. Specifically, the as-assembled battery displays a remarkable open circuit voltage of 1.46 V and high peak power density of 149 mW cm −2 , even outstripping noble-metal-based counterparts. Modulating the octahedral units to ignite the intrinsic oxygen catalytic activity provides enlightening clues to design perovskite-type air cathodes. • A thermal-induced MnO 6 octahedral distortion strategy is proposed. • The octahedral distortion can optimize electron density and e g electron-filling states. • The octahedron-distortion CaMnO 3 (D-CMO) owns excellent oxygen catalytic activity. • The solid-state ZAB exhibits a high peak power density of 149 mW cm −2 .

Molten NaCl‐Assisted Synthesis of Porous Fe‐N‐C Electrocatalysts with a High Density of Catalytically Accessible FeN4 Active Sites and Outstanding Oxygen Reduction Reaction Performance

AbstractIron single atom catalysts (FeN4) hosted in the micropores of N‐doped carbons offer excellent performance for the oxygen reduction reaction (ORR). Achieving a high density of FeN4 sites accessible for ORR has proved challenging to date. Herein, a simple surface NaCl‐assisted method towards microporous N‐doped carbon electrocatalysts with an abundance of catalytically accessible FeN4 sites is reported. Powder mixtures of microporous zeolitic imidazolate framework‐8 and NaCl are first heated to 1000 °C in N2, with the melting of NaCl above 800 °C creating a highly porous N‐doped carbon product (NC‐NaCl). Ferric (Fe3+) ions are then adsorbed onto NC‐NaCl, with a second pyrolysis stage at 900 °C in N2 yielding a porous Fe/NC‐NaCl electrocatalyst (Brunauer–Emmett–Teller surface area, 1911 m2 g−1) with an excellent dispersion and high density of accessible surface FeN4 sites (26.3 × 1019 sites g−1). The Fe/NC‐NaCl electrocatalyst exhibits outstanding ORR performance with a high half‐wave potential of 0.832 V (vs reversible hydrogen electrode) in 0.1 m HClO4. When used as the ORR cathode catalyst in a 1.0 bar H2‐O2 fuel cell, Fe/NC‐NaCl offers a high peak power density of 0.89 W cm−2, ranking it as one of the most active M‐N‐C materials reported to date.

Direct UV written waveguides and Bragg gratings in doped planar silica using a 213 nm laser

In this paper, the first demonstration of simultaneous UV written Bragg gratings and waveguides in germanium and boron‐doped planar silica is presented using a 5th harmonic solid‐state nanosecond laser operating at 213 nm wavelength. The fabrication of high‐quality gratings by using a high peak power density, yielding sufficient uniformity and without any surface damage is demonstrated. The photosensitivity of the doped silica layer is investigated by measuring the local effective refractive index of the optical modes. The written gratings are used to measure grating refractive index modulation, grating detuning bandwidth and the waveguide propagation loss with a minimum value of 0.28 ± 0.07 dB cm−1. This paper shows that this new generation of pulsed UV lasers is a promising alternative for conventional longer wavelength CW laser sources used in small spot direct grating writing in doped silica.

Enhanced membrane electrode assembly performance by adding PTFE/Carbon black for high temperature polymer electrolyte membrane fuel cell

Phosphoric acid used as a proton-conductive medium in high-temperature polymer electrolyte membrane fuel cells (HT-PEMFCs) poisons the Pt surface and prevents oxygen transport in the cathode catalyst layer. The hydrophobic binders in the catalyst not only maintain the catalyst layer structure but also control the phosphoric acid distribution. In this study, polytetrafluoroethylene (PTFE)/carbon black (Vulcan XC-72R) added to the catalyst layer generates an oxygen transport channel. The catalyst layers coated on the gas diffusion layer by the bar-coating method serve as the cathode. High PTFE content causes hydrophobicity in the catalyst layer. The membrane electrode assembly (MEA) with 6 wt% PTFE/Vulcan results in the highest peak power density (0.347 W cm−2) and voltage (0.653 V) at 0.2 A cm−2. A critical reason for its high performance is having the lowest Rct + Rmt values measured at 0.6 V and 0.4 V. These results could contribute to improving the MEA performance for HT-PEMFCs.

Enhanced Reliability of Ni-Fe Alloys Supported SOFCs with Ex-Situ Sintered La0.8Sr0.2MnO3−δ Coated Ba0.5Sr0.5Co0.8Fe0.2O3–δ Cathode

A critical issue for massive production of metal-supported solid oxide fuel cell is cathode processing due to the contradicting of the metal support and the cathode with regard to the sintering atmosphere. Herein, LSM-BSCF (La0.8Sr0.2MnO3-δ coated Ba0.5Sr0.5Co0.8Fe0.2O3-δ ) cathodes on Ni-Fe alloys supported SOFCs (NF-SOFCs) are fabricated by an ex situ sintering approach and electrochemical evaluation in humidified H2 fuel. The ex situ sintering of cathodes on NF-SOFCs are performed at 1050 °C in air with metal oxide support consisted of NiO and 10 at% Fe2O3, and then the oxide support is reduced in situ into Ni-Fe alloys during testing. Cross-section microstructure analysis shows clear evidence that each layer is well adhered to each other after reduction and the suitable microstructure of ex situ sintered cathode is observed after sintering at 1050 °C. In the single-cell test, a higher peak power density is achieved for NF-SOFC with ex situ sintered LSM-BSCF in comparison with in situ sintered cells, revealing a beneficial effect of ex situ sintered cathode on cell performance. The durability measurement and post-test analysis confirm the sufficient adherence and mechanical stability between ex situ sintered LSM-BSCF cathode and GDC (Ce0.9Gd0.1O1.95) electrolyte. The successful electrochemical characterizations of NF-SOFCs with ex situ sintered LSM-BSCF cathode confirm the applicability of the novel sintering procedure.

Carbon nanotube supported bifunctional electrocatalysts containing iron-nitrogen-carbon active sites for zinc-air batteries

Bifunctional electrocatalysts with high activity toward both oxygen reduction and evolution reaction are highly desirable for rechargeable Zn-air batteries. Herein, a kind of carbon nanotube (CNT) supported single-site Fe-N-C catalyst was fabricated via pyrolyzing in-situ grown Fe-containing zeolitic imidazolate frameworks on CNTs. CNTs not only serve as the physical supports of the Fe-N-C active sites but also provide a conductive network to facilitate the fast electron and ion transfer. The as-synthesized catalysts exhibit a half-wave potential of 0.865 V for oxygen reduction reaction and a low overpotential of 0.442 V at 10 mA·cm−2 for oxygen evolution, which is 310 mV smaller than that of Fe-N-C without CNTs. The rechargeable Zn-air batteries fabricated with such hybrid catalysts display a high peak power density of 182 mW·cm−2 and an excellent cycling stability of over 1,000 h at 10 mA·cm−2, which outperforms commercial Pt-C and most of the reported catalysts. This facile strategy of combining single-site Metal-N-C with CNTs network is effective for preparing highly active bifunctional electrocatalysts.

SrCo0.8Ti0.1Ta0.1O3-δ perovskite: A new highly active and durable cathode material for intermediate-temperature solid oxide fuel cells

Reducing the operating temperatures of solid oxide fuel cells (SOFCs) to the intermediate-temperature range (IT, 400–650 °C) can bring about several benefits including cost effectiveness, prolonged lifetime and flexible sealing. Nevertheless, the accompanying deterioration of cathodic activity for oxygen reduction reaction (ORR) introduces a large obstacle for commercial applications of IT-SOFCs. Herein, a new perovskite SrCo0.8Ti0.1Ta0.1O3-δ (SCTT) is developed by co-doping titanium and tantalum into the B-site of parent SrCoO3 oxide, which may tackle this problem. At 400–650 °C, SCTT shows high electrical conductivities (65–142 S cm−1), appropriate oxygen vacancy concentrations (0.23–0.27) and high bulk diffusion capability due to a synergy between the two dopants in SCTT. Consequently, SCTT exhibits a favorable ORR activity with an area-specific resistance of only 0.17 Ω cm2 at 500 °C on samaria-doped ceria electrolyte, and the corresponding cell generates a high peak power density (PPD) of 0.90 W cm−2 at 500 °C with negligible performance decay for 180 h. Additionally, SCTT performs well in protonic ceramic fuel cells, achieving a PPD of 0.78 W cm−2 at 650 °C and a high durability for ~176 h at 550 °C. This work provides a new promising cathode material that may accelerate the commercialization of IT-SOFC technology.

Ultrastable FeCo Bifunctional Electrocatalyst on Se-Doped CNTs for Liquid and Flexible All-Solid-State Rechargeable Zn-Air Batteries.

The rechargeable Zn-air batteries as an environmentally friendly sustainable energy technology have been extensively studied. However, it is still a challenge to develop non-noble metal bifunctional catalysts with high oxygen reduction as well as oxygen evolution reaction (ORR and OER) activity and superior durability, which limit the large-scale application of rechargeable Zn-air batteries. Herein, we synthesized an ultrastable FeCo bifunctional oxygen electrocatalyst on Se-doped CNTs (FeCo/Se-CNT) via a gravity guided chemical vapor deposition (CVD) strategy. The catalyst exhibits excellent ORR (E1/2 = 0.9 V) and OER (overpotential at 10 mA cm-2 = 340 mV) properties simultaneously, surpassing commercial Pt/C and RuO2/C catalysts. More importantly, the catalyst shows an unordinary stability, that is, is no obvious decrease after 30K cycles accelerated durability test for ORR and OER processes. The small potential gap (0.75 V) represents superior bifunctional ORR and OER activities of the FeCo/Se-CNT catalyst. The FeCo/Se-CNT catalyst possesses outstanding electrochemical performance for the rechargeable liquid and flexible all-solid-state Zn-air batteries, for example, a high open circuit voltage (OCV) and peak power density of 1.543 and 1.405 V and 173.4 and 37.5 mW cm-2, respectively.

Metal-Free Bifunctional Ordered Mesoporous Carbon for Reversible Zn-CO2 Batteries.

The fabrication of Zn-CO2 batteries is a promising technique for CO2 fixation and energy storage. Herein, nitrogen-doped ordered mesoporous carbon (NOMC) is adopted as a bifunctional metal-free electrocatalyst for CO2 reduction and oxygen evolution reaction in the near-neutral electrolyte. The ordered mesoporous structures and abundant N-dopings of NOMC facilitate the accessibility and utilization of the active sites, which endow NOMC with excellent electrocatalysis performance and outstanding stability. Especially, a nearly 100% CO Faradaic efficiency is achieved at an ultralow overpotential of 360 mV for CO2 reduction. When constructed as an aqueous rechargeable Zn-CO2 battery using NOMC as the cathode, it yields a high peak power density of 0.71mW cm-2 , a good cyclability of 300 cycles, and excellent energy efficiency of 52.8% at 1.0mA cm-2 .

Novel space-confinement synthesis of two-dimensional Fe, N-codoped graphene bifunctional oxygen electrocatalyst for rechargeable air-cathode

The 2D Fe, N-codoped graphene (2D Fe-NG) with high oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) performances for Zn-air batteries (ZABs) is prepared by a facile synthesis method, which used nitrogen-containing polymer (2,5-benzimidazole) (ABPBI), Fe salts and the cationic surface-active agent treated montmorillonite (CMMT) layer template. The vacuum assist and heat treatment of ABPBI/CMMT at 350 °C are the keys of Fe3+ addition. The characterization analysis demonstrates that added Fe3+ exists in the form of Fe-Nx bonds formed by coordination with N species of ABPBI in MMT. Owing to the existed Fe-Nx sites in 2D Fe-NG, it possesses excellent ORR performance better than 2D NG and 20 wt% Pt/C in O2-saturated 0.1 M KOH electrolyte. For OER, the performance of 2D Fe-NG is close to that of RuO2. The self-made ZAB based on 2D Fe-NG exhibits high peak power density, excellent rechargeable performance, and higher D-C cycling stability.

Polymer-coating-induced synthesis of FeNx enriched carbon nanotubes as cathode that exceeds 1.0 W cm−2 peak power in both proton and anion exchange membrane fuel cells

We reported an interface-induced synthesis of iron nitrogen (FeNx) enriched carbon nanotubes (FeNx-CNTs) with high activity in alkaline and acidic environment for oxygen reduction reaction (ORR) by coating polypyrrole (PPy) thin layers on iron-doped zeolitic imidazolate framework-8 (Fe-ZIF). The constructed polymer/metal-organic framework (MOF) interface suppresses the agglomeration of iron (Fe) atomic sites during the thermal activation, and thus facilitates carbon nanotubes (CNTs) formations with FeNx coordination in carbon matrix. The produced FeNx-CNTs catalyst shows excellent ORR activities with extremely high peak power density of 1.15 and 1.16 W cm−2 in anion and proton exchange membrane fuel cells, respectively.

Preparation of 3D structure high performance Ba0·5Sr0·5Fe0·8Cu0·2O3-δ nanofiber SOFC cathode material by low-temperature calcination method

The electrospinning and sol-gel methods are used to prepare a Ba0·5Sr0·5Fe0·8Cu0·2O3-δ (BSFC) cathode material with good chemical compatibility with the traditional electrolyte Ce0.8Gd0.2O2−δ (GDC). Systematic experiments are performed to investigate the effect of sintering temperature on BSFC fibers microstructure, morphology and electrochemical properties. The results show that the three dimensional (3D) BSFC-F800 prepared by the low-temperature calcination method (800 °C) has a well-organized porous structure and larger specific surface area and porosity. In addition, the fibers are connected to each other to form a continuous electrode path, which provides an uninterrupted channel for charge transmission, and the low-temperature calcination can efficiently reduce the surface Sr segregation and increase ORR activity. At 700 °C, the 3D nanofiber cathode material BSFC-F800 has lower area specific resistance (ASR = 0.128 Ω cm2) and higher peak power density (PPD = 0.51 W cm−2). The voltage decay rate in the 100 h long-term stability test is only 0.0342% h−1.

Harnessing Interfacial Electron Transfer in Redox Flow Batteries

Summary Redox flow batteries (RFBs) have garnered increasing attention for their potential to enable the widespread adoption of renewable electricity. However, a critical need associated with the continued development of this technology involves designing electrode-electrolyte interfaces that exhibit rapid, stable electron transfer kinetics. This targeted review outlines key challenges associated with measuring and enhancing the electron transfer kinetics of established and emerging flow battery active materials. We discuss several promising opportunities for advancing flow battery science and technology using the tools of applied electroanalysis and catalysis science. These challenges and opportunities are broadly relevant for future research directed at advancing the commercial adoption of RFBs for grid-scale energy storage.

Numerical Study on the Evolution Mechanism of the Crater under a Millisecond Laser

A two-dimensional numerical model considering recoil pressure and Hertz-Knudsen ablation rate was established on the foundation of the laser remelting model to investigate the influence of laser processing parameters on crater feature and melted zone, and it was verified through experiments. The temperature and flow velocity distribution of the molten pool during the formation of the crater were analyzed. The results showed that the ablation velocity could be considered under a higher laser peak power density or higher pulse width due to the metal evaporation caused by heat accumulation. The depth and diameter of the crater were significantly affected by laser peak power density and laser pulse duration. Simultaneously, the height of the edge bulge decreased with the increase in pulse duration after 1.5 ms, and the growth rate of central depth was more rapid than that of edge bulge height with the increase of laser peak power density. In the texture with the same depth, a larger melted zone could be obtained with a longer laser duration than the higher peak power density.

Co‐N‐doped hierarchically ordered macro/mesoporous carbon as bifunctional electrocatalyst toward oxygen reduction/evolution reactions

SummaryExploring progressed activity and stability, electrocatalyst toward oxygen reduction reaction (ORR) and oxygen evolution reaction (OER), has been the most considerable factor in extensive commercialization of metal‐air batteries and fuel cells. Herein, Co/N co‐doped 3D hierarchical porous bifunctional oxygen electrocatalyst was synthesized using F127 as soft template and PMMA nanosphere as hard template to build hierarchically ordered macro/mesoporous porous nanostructure. The as‐obtained macro/mesoporous Co‐N‐doped carbon endowing its 3D ordered hierarchical porosity and satisfactory surface area, leading to superior performance for ORR, OER, and rechargeable Zn‐air battery. For ORR, the catalyst showed superior ORR activity with an attractive half‐wave potential of 0.85 V (vs RHE), remarkable methanol tolerance, and robust long‐term stability under alkaline electrolyte. For OER, the as‐synthetized electrocatalyst exhibited low overpotential of 1.67 V (vs RHE) under the current density of 10 mA/cm2. Moreover, the Zn‐air battery assembled from the hierarchical porous catalyst displayed a high peak power density of 146 mW/cm2.

Hollow Co9S8 spheres-derived polyhedrons uniformly anchored on N, S-doped graphene for efficient oxygen electrocatalysts

Exploring highly efficient and low-cost bifunctional electrocatalysts for the oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) is significant for the development of renewable energy. Here, Co9S8 nanospheres with hollow structure anchored on N and S dual-doped graphene oxide (Co9S8-NSGO) are synthesized by solvothermal strategy. After pyrolyzed, advanced bifunctional electrocatalysts with feature of sea-island architecture of Co9S8 polyhedrons evenly dispersed on N and S co-doped graphene sheets (Co9S8-NSG) are obtained, in which Co9S8 polyhedrons stem from the derivative of Co9S8 nanospheres. Ascribed to large surface area, sea-island structure of uniform dispersion of Co9S8 nanoparticles on graphene, synergistic effect between Co9S8 and graphene and more active sites based N and S doping, the as-prepared Co9S8-NSG catalyst exhibits excellent OER performance with a small overpotential (240 mV at 10 mA cm−2) and satisfactory ORR performance with half-wave potential (0.79 V). Notably, a zinc-air battery using Co9S8-NSG as air cathode shows high peak power density (120 mW cm−2) and outstanding cycling stability (120 h at 10 mA cm−2).

Enhanced oxygen reduction and evolution in N-doped carbon anchored with Co nanoparticles for rechargeable Zn-air batteries

In this study, a facile surface treatment on polypyrrole (PPy) nanofiber with ZnCl2 solution is employed to fabricate N-doped carbon anchored with metallic Co (denoted as Co/N-CZn) via gas-transport approach. Structural characterizations reveal that the intrinsic structure of Co/N-CZn in terms of its morphology, pore structure and defects have been greatly modulated by such a surface treatment, resulting in a higher loading amount of metallic Co, larger surface area and increased pyridinic N and Co-N species as efficient active sites. Benefiting from the structural modulation, Co/N-CZn exhibits outstanding ORR activity and kinetics with a positive half-wave potential of 0.88 V vs. RHE, a high kinetic current density (Jk) value of 36.6 mA cm−2 at 0.85 V vs. RHE, and a small Tafel slope of 55.9 mV dec−1, which even outperforms commercial Pt/C. Moreover, enhanced OER performance is also achieved in Co/N-CZn, with an overpotential of 280 mV at 10 mA cm−2, surpasses that of commercial RuO2 (295 mV). Finally, Co/N-CZn shows promise for substitution of commercial Pt/C and RuO2 to drive both liquid and solid-state rechargeable Zn-air batteries with high peak power densities of 196 mW cm−2 and 130 mW cm−2.

High energy efficiency of Al-based anodes for Al-air battery by simultaneous addition of Mn and Sb

• Mn and Sb were added to increase the energy efficiency of Al anode. • The activation mechanism of Mn and Sb was clarified. • Al-Mn-Sb anode exhibited high energy efficiency as anode for Al-air cell. In this work, an Al-Mn-Sb anode has been prepared for the alkaline Al-air battery. The energy efficiency and corrosion behaviors are investigated in details. The results indicate that the prepared Al-Mn-Sb anode exhibits high discharge voltage and peak power density of 1.206 V and 96 mW∙cm −2 , respectively, with a small degree of polarization at high discharge rate (80 mA∙cm −2 ). It can also output high energy density and considerable anodic utilization of 3236 mWh∙g −1 and 90.0%, respectively. Such high discharge performance should be attributed to the micro-nano scale precipitates generated by the simultaneous addition of Mn and Sb, effectively activating the grain boundaries. The Al-Mn-Sb anode can be a desirable candidate for high energy efficiency anodes dedicated to high-performance Al-air battery cells meeting the demands of high-power/energy applications.

High-Performance Packaged 3D Lithium-Ion Microbatteries Fabricated Using Imprint Lithography.

Fabrication of high-energy-density and high-power-density packaged long-cycle-life rechargeable microbatteries remains a considerable challenge. Here, high-performance microbatteries with high active volume fraction, thick, 3D-structured electrodes (V2 O5 cathode and Li metal anode) are realized through a combination of imprint lithography, self-assembly, and electrodeposition. To assist the critical challenge of hermetic packaging, the microbattery is infilled with a gel electrolyte. The packaged cell exhibits high areal energy and power densities of 1.24 J cm-2 and 75.5mW cm-2 , respectively, and can be cycled 550 times in argon or 200 times in air with 75% capacity retention of the initial discharge capacity. An unpackaged cell, using a liquid electrolyte, provides a power density of 218mW cm-2 . As far as it is known, the microbatteries have the highest peak power density among all reported microbatteries.

(Invited) Ruthenium/Samaria-Doped Ceria Cermet Anode through Plasma Enhanced Atomic Layer Deposition

Direct methane-fueled solid oxide fuel cells (DM-SOFCs) operating at low temperature range (<450 C) are promising next-generation energy conversion devices, in which, however, anode reactions should be facilitated for high performance even at low temperatures. Obtaining catalyst with high activity, thermal stability and carbon coking resistance is essential for high-performance SOFC operating with hydrocarbon fuel. Noble metal catalyst, e.g., Ru, can be effective for direct methane oxidation in DM-SOFC anode. However, their high costs prevent them from being extensively applied to such devices as SOFCs, and, therefore, significant efforts have been made to lower the noble metal loading in designing fuel cell electrodes.Herein, we report the design and fabrication of heterogeneous catalyst with ultra-low-loading Ru nanostructures via plasma enhanced atomic layer deposition (PEALD) on SDC backbone anode. We confirmed the presence of highly dispersed PEALD Ru particles over the SDC backbone compared to sputtered Ru deposited on only porous sputtered SDC surface. We found out that PEALD Ru of 100 ALD cycles, or approximately 5nm in thickness with Ru loading of only 0.004 mg/cm2, was sufficient for the use of anode catalyst with methane fuel. Furthermore, compared to the cell with 100 nm-thick sputtered Ru/sputtered SDC anode, the cell with PEALD Ru/sputtered SDC anode showed 45 % higher peak power density with only 1/20 of Ru loading. Moreover, after 4 hours operation with dry methane at 450 C, the activation resistance of the cell with the sputtered Ru composite anode increased by 7 times, while that of the cell with the PEALD Ru composite anode increased by only 2 times. This result suggests that, using PEALD, one can simultaneously reduce Ru loading, thereby reducing cost, and improve the performance and the thermal stability of the anode for DM-SOFC.