Maximum Power Density Research Articles

Fast, variable stiffness-induced braided coiled artificial muscles

Biomimetic actuation technologies with high muscle strokes, cycle rates, and work capacities are necessary for robotic systems. We present a muscle type that operates based on changes in muscle stiffness caused by volume expansion. This muscle is created by coiling a mechanically strong braid, in which an elastomer hollow tube is adhesively attached inside. We show that the muscle reversibly contracts by 47.3% when driven by an oscillating input air pressure of 120 kilopascals at 10 Hz. It generates a maximum power density of 3.0 W/g and demonstrates a mechanical contractile efficiency of 74%. The muscle's low-pressure operation allowed for portable, thermal pneumatical actuation. Moreover, the muscle demonstrated bipolar actuation, wherein internal pressure leads to muscle length expansion if the initial muscle length is compressed and contraction if the muscle is not compressed. Modeling indicates that muscle expansion significantly alters its stiffness, which causes muscle actuation. We demonstrate the utility of BCMs for fast running and climbing robots.

Flexible PVDF-Ba0.97Ca0.03TiO3 polymer-ceramic composite films for energy storage, biosensor, mechanosensor, and UV–visible light protection

Multifunctional piezoelectric devices, which can detect pressure, store electrostatic energy, block UV radiation, and generate electricity from body movements, are highly beneficial for enhancing individual well-being. To achieve these capabilities, polyvinylidene fluoride (PVDF) composite films with Ba0.97Ca0.03TiO3 (BCT3) filler were prepared, varying the BCT3 content from 0 to 50 wt.%. The BCT3 ceramic, prepared using a modified solid-state reaction, exhibits a tetragonal phase at room temperature with a d33 value of 105 pC/N. X-ray diffraction confirms composite formation. The beta phase ranges from 75 to 86.9 %. At 40 wt.% BCT3, the dielectric constant, energy density, and piezoelectric properties peak, yielding maximum Wrec and Wtot of 138.1 and 284.7 mJ/cm3 (@ 250 kV/cm), respectively. PVDF-BCT3-40 (40 wt.%) shows maximum voltage, current, and power density of 25 V, 26.8 nA, and 19.8 μW/cm3 under a 50 N load. Increasing BCT3 content enhances UV–visible absorbance, making the composites effective for light shielding.

The Performance of PEFC with Marimo-like Carbon Considering Relative Humidity

A proton exchange membrane fuel cell (PEMFC) is powered by humidified fuel and air gases supplied to the cells. We evaluated the effect of the relative humidity (RH) of the fuel and air gases on the I-V performance of the Marimo-like carbon (MC). MC is a higher order structure of carbon fibers. The RH increased the proton conductivity of the Nafion, while excessive humidification caused flooding. The highest maximum power density was 303 mW cm-2 (80% RH) for the Pt/MC and 165 mW cm-2 (60% RH) for the Pt/CB (carbon black). At all the RHs, the maximum power density of the Pt/MC was higher than that of the Pt/CB. The fiber structure and I/C (0.1) of the MC increase the mass diffusivity of the Pt/MC. The high mass diffusivity of the Pt/MC found to reduce flooding and promote the wetting of the Nafion by the generated water.

Boosting Electrochemical Performance via Extra-Role of La-Doped CeO2-δ Interlayer for "Oxygen Provider" at High-Current SOFC Operation.

Utilizing rare earth doped ceria in solid oxide cells (SOCs) engineering is indeed a strategy aimed at enhancing the electrochemical devices' durability and activity. Particularly, Gd-doped ceria (GDC) is actively used for barrier layer and catalytic additives in solid oxide fuel cells (SOFCs). In this study, experiments are conducted with La-doped CeO2 (LDC), in which the Ce sites are predominantly occupied by La, to prevent the formation of the Ce-Zr solid solution. This LDC is comparably used as a functional interlayer between the electrolyte and cathode if sintered at lower temperatures to avoid La2Zr2O7 impurity. In addition, the high substitution of La3+ into the ceria lattice improves the oxygen non-stoichiometry of LDC, leading to accelerated electrochemical high performance by the additional role of LDC for oxygen supplier capacitance at high current operation. Thus, it is confirmed that the improved SOFC high performance is achieved at the maximum power density (MPD) of ≈2.15W cm-2 at 800°C when the optimized LDC buffer layer is hired at the anode-supported typed-Samsung's SOFC by lowering the sintering temperature to prevent LDC's impurity reaction.

The Effects of Contact By the Catalyst Layer and the Gas Diffusion Layer Interface on the Performance of a PEFC with Marimo-like Carbon

When assembling a proton exchange membrane fuel cell (PEMFC), a clamping pressure is applied to all the components. The catalyst layer (CL) and gas diffusion layer (GDL) are compressed to the gasket thickness by the clamping during assembly. This compression increases the conductivity of the protons and electrons while reduces the size of the pores, which are the removal channels for the generated water and the diffusion channels for the fuel and air gases. We evaluated the effect of the CL compression prepared with the Marimo-like carbon (MC) regarding the I-V performance. The MC is a higher order structure of carbon fibers. The maximum power density was the highest (237 mW cm-2) at the 22% compression ratio. The excessive compression was suggested to have a higher effect on blocking the diffusion channels of the fuel and air gases than on improving the conductivity.

Weakening O-Intermediates Adsorption Strength Over the Pd Metallene via Lewis-Acidic Site Modulation for Enhanced Oxygen Reduction.

The reasonable design and modulation of the electronic properties of Pd metallene are acknowledged as a promising avenue for enhancing the oxygen reduction reaction (ORR) in anion exchange membrane fuel cells (AEMFCs), yet they remain a formidable challenge. Herein, a thin-sheet structure of Zr-doped Pd metallene (PdZr metallene) with abundant defects is proposed using a facile wet-chemical approach for efficient and highly durable ORR electrocatalysis. Multiple microstructural analyses uncover that orchestrated electronic and oxophilic regulation of PdZr metallene via Lewis-acidic Zr site modulation could concurrently optimize the electronic configuration of Pd, downshift the d-band center of Pd, and, thus, promote the intrinsic activity. Benefiting from the unique two-dimensional morphology and electronic structure optimization facilitated by the Zr coupling effect, the resultant PdZr metallene demonstrates significantly enhanced ORR electrocatalytic performance in basic solutions, with a high half-wave potential (E1/2) of 0.87 V and commendable stability for 30 000 s, surpassing those of Pd metallene and various advanced Pd-based catalysts reported in the literature. Encouragingly, the PdZr metallene-based AEMFC achieves an increased maximum power density (90.4 mW cm-2) and impressive robustness over 12 h in an alkaline environment, manifesting the practical application of PdZr metallene in AEMFCs. This study showcases the applicability of PdZr metallene via Lewis acid site regulation for fabricating highly active electrocatalysts for high-performance AEMFCs.

A Self-Powered Enzymatic Glucose Sensor Utilizing Bimetallic Nanoparticle Composites Modified Pencil Graphite Electrodes as Cathode.

Enzymatic biofuel cells (EBFC) are promising sources of green energy owing to the benefits of using renewable biofuels, eco-friendly biocatalysts, and moderate operating conditions. In this study, a simple and effective EBFC was presented using an enzymatic composite material-based anode and a nonenzymatic bimetallic nanoparticle-based cathode respectively. The anode was constructed from a glassy carbon electrode (GCE) modified with a multi-walled carbon nanotube (MWCNT) and ferrocene (Fc) as a conductive layer coupled with the enzyme glucose oxidase (GOx) as a sensitive detection layer for glucose. A chitosan layer was also applied to the electrode as a protective layer to complete the composite anode. Chronoamperometry (CA) results show that the MWCNT-Fc-GOx/GCE electrode has a linear relationship between current and glucose concentration, which varied from 1 to 10mM. The LOD and LOQ were calculated for anode as 0.26mM and 0.87mM glucose, respectively. Also the sensitivity of the proposed sensor was calculated as 25.71 A/mM. Moreover, the studies of some potential interferants show that there is no significant interference for anode in the determination of glucose except ascorbic acid (AA), uric acid (UA), and dopamine (DA). On the other hand, the cathode consisted of a disposable pencil graphite electrode (PGE) modified with platinum-palladium bimetallic nanoparticles (Nps) which exhibit excellent conductivity and electron transfer rate for the oxygen reduction reaction (ORR). The constructed EBFC was optimized and characterized using various electroanalytical techniques. The EBFC consisting of MWCNT-Fc-GOx/GCE anode and Pt-PdNps/PGE cathode exhibits an open circuit potential of 285.0mV and a maximum power density of 32.25µWcm-2 under optimized conditions. The results show that the proposed EBFC consisting of an enzymatic composite-based anode and bimetallic nanozyme-based cathode is a unique design and a promising candidate for detecting glucose while harvesting power from glucose-containing natural or artificial fluids.

Sn-Doping-Induced Biphasic Structure Advances Ductile Ag2S-Based Thermoelectrics.

Due to its inherent ductility, Ag2S shows promise as a flexible thermoelectric material for harnessing waste heat from diverse sources. However, its thermoelectric performance remains subpar, and existing enhancement strategies often compromise its ductility. In this study, a novel Sn-doping-induced biphasic structuring approach is introduced to synergistically control electron and phonon transport. Specifically, Sn-doping is incorporated into Ag2S0.7Se0.3 to form a biphasic composition comprising (Ag, Sn)2S0.7Se0.3 as the primary phase and Ag2S0.7Se0.3 as the secondary phase. This biphasic configuration achieves a competitive figure-of-merit ZT of 0.42 at 343 K while retaining exceptional ductility, exceeding 90%. The dominant (Ag, Sn)2S0.7Se0.3 phase bolsters the initially low carrier concentration, with interfacial boundaries between the phases effectively mitigating carrier scattering and promoting carrier mobility. Consequently, the optimized power factor reaches 5 µW cm-1 K-2 at 343 K. Additionally, the formation of the biphasic structure induces diverse micro/nano defects, suppressing lattice thermal conductivity to a commendable 0.18Wm-1K-1, thereby achieving optimized thermoelectric performance. As a result, a four-leg in-plane flexible thermoelectric device is fabricated, exhibiting a maximum power density of ≈49 µW cm-2 under the temperature difference of 30 K, much higher than that of organic-based flexible thermoelectric devices.

In-situ observation of defects evolution of graphene nanoflakes in Pt/C catalyst for boosting ORR performance

The structural stability of supported metal nanoparticles determines the activity and longevity of heterogeneous catalysts. Unfortunately, the chemical/thermal working environment inevitably accelerates metal sintering to larger crystallites that leads to the degradation of catalytic performance. Here, we demonstrate that the distribution of defects in carbon support as an inherent parameter plays a crucial role in catalyst sintering. Based on in-situ transmission electron microscopy studies, the strong metal-support interaction between platinum (Pt) nanoparticles and defect-rich graphene nanoflakes largely suppresses metal sintering up to 700 °C. Particularly, the optimal carbon support can be achieved in the annealing process, in which the mass transfer and charge transport can be enhanced by accurately manipulating the distribution of defects in carbon matrix and graphitization degree. It is worth noting that the screened Pt/GNs-300 exhibits impressive oxygen reduction reaction performance with high half-wave potential (0.91 V), mass activity (108.1 A g–1Pt) and excellent stability. By its ascendancy in ORR, the Pt/GNs-300 exhibits a high open-circuit voltage of 1.41 V and a maximum power density of 198.6 mW cm−2 in Zn-air battery, implying its brilliant practicability. This work paves a pathway for achieving sinter-resistant metal-loaded catalysts in energy electrocatalysis.

Study on the synthesis of CoFe/CoFe2O4@NCNTs derived from ZnFeCo-ZIF with abundant heterostructures and oxygen vacancies as bifunctional catalyst for ORR/OER in zinc-air batteries

The rational design of bifunctional catalysts for oxygen reduction reaction (ORR)/oxygen evolution reaction (OER) in alkaline electrolyte is of great significance for zinc-air batteries (ZABs). In this study, different types of Fe/Co compounds and nitrogen-doped carbon-based composite catalysts from trimetallic zeolitic-imidazole-framework-derived (ZnFeCo-ZIF) were synthesized by adjusting the ratio of Zn/Fe/Co. Among them, the synthesized CoFe/CoFe2O4-N-doped carbon nanotubes (CoFe/CoFe2O4@NCNTs) have abundant Fe-Nx and Co-Nx activity sites, heterostructures and oxygen vacancies. The experimental results reveal that the electrons of CoFe are transferred to CoFe2O4 at the interface of CoFe/CoFe2O4, which not only enhances the electron transfer ability, but also induces oxygen vacancies to improve the adsorption/desorption capacity of O2 and intermediates. Meanwhile, metal atoms are uniformly dispersed in the N-doped carbon nanotubes to form metal–N sites with high catalytic activity. Therefore, the CoFe/CoFe2O4@NCNTs exhibit excellent electrocatalytic performance, possessing a half-wave potential (E1/2) of 0.878 V and a prominent limiting-current densities (JL) of 6.281 mA cm−2 for ORR, and a low overpotential of 344 mV at 10 mA cm−2 for OER. In particular, the CoFe/CoFe2O4@NCNTs-equiped ZAB possesses a higher open-circuit voltage (1.50 V), a greater maximum power density (193.42 mW cm−2) and a longer cycling performance (160 h). The density functional theory (DFT) calculations show that the CoFe/CoFe2O4 heterostructure can induce the rapid transfer of electrons at the CoFe/CoFe2O4 interface, which promotes the change of the surface electronic structure of the catalyst, and thus helps to enhance the ability of the catalyst to transfer electrons.

Triboelectric Nanogenerators Based on Transition Metal Carbo-Chalcogenide (Nb2S2C and Ta2S2C) for Energy Harvesting and Self-Powered Sensing.

With burgeoning considerations over energy issues and carbon emissions, energy harvesting devices such as triboelectric nanogenerators (TENGs) are developed to provide renewable and sustainable power. Enhancing electric output and other properties of TENGs during operation is the focus of research. Herein, two species (Nb2S2C and Ta2S2C) of a new family of 2D materials, Transition Metal Carbo-Chalcogenides (TMCCs), are first employed to develop TENGs with doping into Polydimethylsiloxane (PDMS). Compared with control samples, these two TMCC-based TENGs exhibit higher electric properties owing to the enhanced permittivity of PDMS composite, and the best performance is achieved at a concentration of 3wt. ‰ with open circuit voltage (Voc) of 112V, short circuit current (Isc) of 8.6µA and charge transfer (Qsc) of 175nC for Nb2S2C based TENG, and Voc of 127V, Isc of 9.6µA, and Qsc of 230nC for Ta2S2C based TENGs. These two TENGs show a maximum power density of 1360 and 911mWm-2 respectively. Moreover, the tribology performance is also evaluated with the same materials, revealing that the Ta2S2C/PDMS composite as the electronegative material presented a lower coefficient of friction (COF) than the Nb2S2C/PDMS composite. Their applications for energy harvesting and self-powered sensing are also demonstrated.

NiMnO nanoparticle-activated carbon anodes for efficient urea oxidation and energy production in wastewater-driven direct urea fuel cells

The growing concern over urea-containing wastewater from industrial sources necessitates innovative treatment solutions that also offer sustainable energy production. In this study, a novel anode material is developed by decorating activated carbon with NiMnO nanoparticles through thermal treatment under an inert atmosphere. The resulting NiMnO NPs-decorated activated carbon was evaluated for its electrocatalytic performance in the electrooxidation of urea and its application in a direct urea fuel cell (DUFC). X-ray diffraction patterns confirmed the formation of nickel metal and Mn(II) oxide, with activated carbon showing representative peaks. Scanning electron microscopy images revealed well-dispersed nanoparticles on the activated carbon surface, corroborated by uniform elemental distribution from mapping results. Electrochemical measurements using cyclic voltammetry demonstrated that the 30 wt% MnAc sample exhibited the highest electrocatalytic activity among the tested samples (0, 5, 10, 20, 30, 40 and 50 wt% MnAc) with a maximum current density of 123 mA/cm2 at 3.0 M urea concentration and an onset potential of −0.02 V versus Ag/AgCl. Linear sweep voltammetry of the assembled DUFC showed promising open circuit potentials of 0.82 V and maximum power densities reaching 4.9 W/m2, achieved using industrial wastewater from the Egyptian Chemical Industries Company (KIMA) in Aswan, Egypt. The results highlight the efficacy of NiMnO NPs-decorated activated carbon in both urea oxidation and electrical energy generation. This study not only provides a viable method for treating urea-rich industrial wastewater but also presents a sustainable approach to energy production. The findings underscore the potential of this material for future applications in DUFCs, offering significant environmental and economic benefits.

Elastomeric Sensor-Triboelectric Nanogenerator Coupled System for Multimodal Strain Sensing and Organic Vapor Detection.

Stretchable, flexible sensors are one of the most critical components of smart wearable electronics and Internet of Things (IoT), thereby attracting multipronged research interest in the last decades. Following miniaturization and multicomponent development of several sensors in one could further propel the demand for wireless, multimodal platforms. Greener substitutes to conventional sensors that can operate in a self-powered configuration are highly desirable in terms of all-in-one sensor utilities. However, fabrication of composite-based ultrastretchable, self-powered sensors with multifunctionality, robustness, and conformability is still only partially achieved and, therefore, demands further investigation. In this work, we report a triboelectric nanogenerator (TENG)-based multifunctional strain and organic vapor sensor using cross-linked ethylene propylene diene monomer (EPDM) elastomer and conducting carbon black as active fillers in the presence of an ionic liquid. The resulting piezoresistive sensor demonstrates ultrahigh gauge factor (GF > 220k) and wide range strain sensitivity and is, therefore, suitable for subtle-to-high frequency motion detection devices. Supported by excellent triboelectric outputs (force sensitivity 0.5 V/N in the range of 50-300 N, maximum output voltage VOC ∼ 178 V, short circuit current ISC ∼ 18 μA, maximum power density 0.11 mW/cm2), the hybrid sensors offer remarkable mechanical toughness and seamless voltage generation under contact-separation, even after several thousand cycles of operations. Furthermore, the sensor substrates exhibited reproducible organic vapor-sensing behavior, with high responsivity of 1.92 and 1 for ethanol and acetone, respectively, under flowing vapor conditions. This work lays a strong foundation for developing a truly multimodal, TENG-based, self-powered organic vapor and strain sensors.

Versatile Ultrahigh‐Output Bilayer Hydrogel for Electricity Generation and Passive Cooling

AbstractThe gradient concentration in nature has garnered significant attention as a promising source for energy harvesting. Researchers have explored various methods to harness electricity from gradient‐concentration‐induced flows, including evaporation‐driven nanogenerators and humidity‐gradient‐based power generators. However, their low current and power density are the main obstacles toward practical applications. Herein, a Bilayer Hydrogel Electricity Generator (BHEG) is presented to enable efficient energy harvesting through the synergy between ion gradient concentration and galvanic effects. A BHEG unit employing identical materials for both electrodes demonstrates an open‐circuit voltage of 0.7 V and a short‐circuit current of 4.34 mA—surpassing the currently reported average by over 73 times—and achieves a maximum power density of 72.2 mW m−2. Moreover, another BHEG unit using Zn─C electrode materials exhibit an open‐circuit voltage of 1.86 V and a short‐circuit current of 92 mA. Furthermore, the versatility of the BHEG extends beyond power generation, effectively providing passive thermal management for electronics, resulting in a maximum temperature reduction of ≈20 °C. Consequently, the study contributes insights into the design and fabrication of efficient hydrogel‐based power generators, providing a promising avenue for leveraging natural‐flow‐induced energy for various applications.

Anionic and cationic co-doping to enhance the oxygen transport property of Bi0.5Sr0.5FeO3-δ as a high-performance air electrode for reversible solid oxide cells

Reversible solid oxide cells (RSOCs) have attracted considerable interest due to their efficient energy conversion. However, the low catalytic activity of air electrodes limits the application of RSOCs. Bi0.5Sr0.5Fe0.9Ta0.1O3-δ developed in our previous work exhibits a comparatively desirable performance and is expected to be further optimized. Herein, a novel strategy of anionic F and cationic Ta co-doped Bi0.5Sr0.5Fe0.9Ta0.1O3-δ-xFx (x = 0, 0.05, 0.10, 0.15, denoted as, BSFTF0, BSFTF5, BSFTF10, BSFTF15) materials are obtained to enhance the oxygen transport property of Bi0.5Sr0.5FeO3-δ for RSOCs. The polarization resistance (Rp) of BSFTF10 (0.017 Ω cm2) decreases by 66 % compared with that of BSFTF0 (0.051 Ω cm2) at 800 °C. In fuel cell mode, the single cell with BSTF10 reaches the maximum power density of 908 mW cm−2, which is approximately 72 % higher than the only Ta-doped BSFTF0 (527 mW cm−2) at 800 °C. In electrolysis mode, the single cell with BSFTF10 exhibits a high electrolysis current density of 1679 mA cm−2, indicating an approximately 90 % increase compared to that of BSFTF0 at 800 °C and 1.5 V with 70 % CO2-30 % CO feed gas. The bulk chemical diffusion (Dchem) of BSFTF10 is up to 5.12 × 10−4 cm2 s−1, which is 4.3 times higher than that of BSFTF0. The superior oxygen transport property of BSFTF10 is attributed to the high electronegativity of F− (4.0) and low electronegativity of Ta5+(1.8), which may weaken the chemical bonding between B-site ions and O2−, generating more oxygen vacancies and accelerating the rate of oxygen transfer. The results indicate that F and Ta co-doping is an effective strategy to develop a highly catalytically active air electrode for RSOCs featuring oxygen transport properties.

Next‐Generation Ultrathin Lightweight Electrode for pH‐Universal Aqueous Flow Batteries

AbstractAqueous flow batteries (AFBs) are promising long‐duration energy storage system owing to intrinsic safety, inherent scalability, and ultralong cycle life. However, due to the thicker (3–5 mm) and heavier (300–600 g m−2) nature, the current used graphite felt (GF) electrodes still limit the volume/weight power density of AFBs. Herein, a lightweight (≈50 g m−2) and ultrathin (≈0.3 mm) carbon microtube electrode (CME) is proposed derived from a scalable one‐step carbonization of commercial cotton cloth. The unique loose woven structure composed of carbon microtube endows CME with excellent conductivity, abundant active sites, and enhanced electrolyte transport performance, thereby significantly reducing polarization in working AFBs. As a consequence, CME demonstrates excellent cycling performance in pH‐universal AFBs, including acidic vanadium flow battery (maximum power density of 632.2 mW cm−2), neutral Zn‐I2 flow battery (750 cycles with average Coulombic efficiency of 99.6%), and alkaline Zn‐Fe flow battery (energy efficiency over 70% at 200 mA cm−2). More importantly, the estimated price of CME is only 5% of GF (≈3 vs ≈60 $ m−2). Therefore, it is reasonably anticipated that the lightweight and ultrathin CME may emerge as the next generation electrode for AFBs.

Promoting Electricity Production and Cr (VI) Removal Using a Light–Rutile–Biochar Cathode for Microbial Fuel Cells

Microbial fuel cell (MFC) technology holds significant promise for the production of clean energy and treatment of pollutants. Nevertheless, challenges such as low power generation efficiency and the high cost of electrode materials have impeded its widespread adoption. The porous microstructure of biochar and the exceptional photocatalytic properties of rutile endow it with promising catalytic potential. In this investigation, we synthesized a novel Rutile–Biochar (Rut-Bio) composite material using biochar as a carrier and natural rutile, and explored its effectiveness as a cathode catalyst to enhance the power generation efficiency of MFCs, as well as its application in remediating heavy metal pollution. Furthermore, the impact of visible light conditions on its performance enhancement was explored. The X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) analysis validated the successful fabrication of rutile composites loaded with biochar. The maximum current density and power density achieved by the MFCs were 153.9 mA/m2 and 10.44 mW/m2, respectively, representing a substantial increase of 113.5% and 225% compared to the control group. In addition, biochar-supported rutile MFCs showed excellent degradation performance of heavy metal pollutants under light conditions. Within 7 h, the Cr6+ degradation rate reached 95%. In contrast to the blank control group, the removal efficiency of pollutants exhibited increases of 630.8%. The cyclic degradation experiments also showcased the remarkable stability of the system over multiple cycles. This study successfully integrated natural rutile and biochar to fabricate highly efficient cathode photocatalyst composites, which not only enhanced the power generation performance of MFCs but also presented an environmentally sustainable and economically viable method for addressing heavy metal pollution.

Bifunctional electrode materials: Enhancing microbial fuel cell efficiency with 3D hierarchical porous Fe3O4/Fe-N-C structures

The rational development of high-performance anode and cathode electrodes for microbial fuel cells (MFCs) is crucial for enhancing MFC performance. However, complex synthesis methods and single-performance electrode materials hinder their large-scale implementation. Here, three-dimensional hierarchical porous (3DHP) Fe3O4/Fe-N-C composites were prepared via the hard template method. Notably, Fe3O4/Fe-N-C-0.04-600 demonstrated uniformly dispersed Fe3O4 nanoparticles and abundant Fe-Nx and pyridinic nitrogen, showing excellent catalytic performance for oxygen reduction reaction (ORR) with a half-wave potential (E1/2) of 0.74 V (vs. RHE), surpassing Pt/C (0.66 V vs. RHE). Moreover, Fe3O4/Fe-N-C-0.04-600 demonstrated favorable biocompatibility as an anode material, enhancing anode biomass and extracellular electron transfer efficiency. Sequencing results confirmed its promotion of electrophilic microorganisms in the anode biofilm. MFCs employing Fe3O4/Fe-N-C-0.04-600 as both anode and cathode materials achieved a maximum power density of 831.8 ± 27.7 mW m−2, enduring operation for 38 days. This study presents a novel approach for rational MFC design, emphasizing bifunctional materials capable of serving as anode materials for microorganism growth and as cathode catalysts for ORR catalysis.

Synergistic effect of Ru single atoms and MnO2 to boost oxygen reduction/evolution activity via strong electronic interaction

Ru-based single-atomic catalysts have shown great potential application in sustainable electrochemical energy conversion/storage devices. Herein Ru single atoms anchored on the surface of MnO2 nanorods (Ru SAs@MnO2) have been successfully constructed by a facile low-temperature solid-phase reaction, which has been confirmed by X-ray adsorption spectra. The synthesized Ru SAs@MnO2 catalyst exhibits a comparable ORR performance with half-wave potential of 0.83 V and a limiting current density of 7.1 mA cm−2 to commercial Pt/C, and high OER performance with the overpotential of 320 mV at 10 mA cm−2. Theoretical calculation results indicate that Mn sites and Ru sites of Ru SAs@MnO2 act as the catalytic ORR and OER sites, respectively, and the synergistic effect between Ru SAs and MnO2 contributes to the improved catalytic performance via strong electronic interaction. When assembled zinc-air batteries, a maximum power density 230.0 mW cm−2 could be delivered at 318.5 mA cm−2.

Solution infiltrated lanthanum nickelate–GDC composite cathode via flash-light sintering for intermediate temperature solid oxide fuel cells

Solid oxide fuel cells (SOFCs) require high operating temperatures to minimize the oxygen reduction reaction resistance at cathode and increase the ionic conductivity of oxygen. However, at high operating temperatures, their stability during long-term operation degrades because of material deterioration and the mutual chemical reactions occurring at the interfaces. Herein, an electrode–electrolyte composite is fabricated by solution infiltration of lanthanum nickelate (LNO) electrode material into a GDC electrolyte layer to ensure more reaction sites compared with the conventional powder mixing of the electrode and electrolyte material. Further, the conventional thermal sintering process is replaced with the flash-light sintering process. Thus, the performance of the LNO–GDC cathode cell manufactured by flash-light sintering improves owing to suppression of grain growth of the infiltrated LNO particles. The microstructures of the infiltrated solution and composite layer of the electrolyte material are analyzed using field-emission scanning electron microscopy, and the crystallinity of the LNO nanoparticles is analyzed using high-resolution transmission electron microscopy. A maximum power density of 1.1 W/cm2 is achieved, an improvement of 58 % over the LSCF cell without infiltration at 750 ℃. This study is expected to contribute to the commercialization of SOFCs by replacing conventional thermal sintering.