Peak Power Density Research Articles

Thermally robust hierarchical nanofiber triboelectric yarns for efficient energy harvesting in firefighting E-textiles

Textile-based triboelectric nanogenerators (TENGs) face challenges in achieving high performance and fulfilling functional requirement for special applications. This paper presents the development of a high-performance, thermally robust hierarchical polyimide (PI) nanofiber triboelectric yarns with a charge-trapping interlayer for application in firefighting E-textiles. The hierarchical nanofiber yarns, comprising a stainless-steel core electrode, a PI/MXene interlayer and PI outer tribo-layer, exhibit enhanced triboelectric performance due to the charge-trapping capabilities of MXene, which preventing the recombination of triboelectric and induced charges. When the MXene content in the charge-trapping interlayer reached 1 wt%, the corresponding TENG achieved its optimal output performance, with an output voltage of 153 V and a current of 13.13 μA and a peak power density of 0.84 W/m2 under optimal conditions. It also demonstrates exceptional thermal stability, maintaining stable output at temperatures up to 400 °C. The integration of the TENG into E-textiles enables real-time monitoring of firefighters’ physical activities and location tracking, significantly enhancing their safety and operational efficiency in fire scenarios. Additionally, the TENG powers electroluminescent yarns, improving visibility in dense smoke and dust environments. This research opens new avenues for the application of smart wearable systems in high-temperature environments, providing effective strategies for ensuring the safety of firefighters in fire rescue operations.

Quaternized poly(aryl imidazolium) containing bulky binaphthyl group as proton exchange membrane for high-temperature fuel cells

The low power output and high phosphoric acid (PA) leakage are the main constraints restricting the commercialization of PA-doped high-temperature proton exchange membranes (HT-PEMs). Ionized imidazoles have been shown to be an effective strategy to improve PA retention, however, less research has been conducted on the fractional free volume (FFV) of the backbone of the main chain on PA loss. Herein, novel imidazolium ions polymer (PQBN-4-IM) material with bulky binaphthyl (BN) group was prepared as PA-doped HT-PEM using a one-step superoxid acid catalyzed polycondensation and subsequent methylation process. The rigidity and hydrophobicity of the BN group promote PQBN-4-IM PEM to produce more obvious microphase separation morphology and large FFV, which is beneficial for forming better ion transport channels and excellent PA interaction. Notably, the PA-doped PQBN-4-IM (PQBN-4-IM/PA) membrane has the highest proton conductivity (90.26 mS cm−1, 180 ℃) and peak power density (PPD) (802.5 mW cm−2, 180 ℃) than PQTP-4-IM/PA and m-PBI/PA HT-PEMs. Moreover, the PQBN-4-IM/PA membrane has higher PA retention at 80 ℃/40 % relative humidity (RH), 40 ℃/60 % RH, or immersed in water due to enhancement on ion-pair interactions by microstructure. Under the accelerated stress test (AST) of the fuel cell (FC), the PQBN-4-IM/PA membrane loses only 12.22 % of PPD after 200 cycles at 80 ℃, which exhibits higher PPD retention than that of the PQBP-4-IM/PA (70.23 %), PQTP-4-IM/PA (74.36 %) and m-PBI/PA (65.25 %) membranes, and shows excellent durability of cell performance for more than 1000 h without significant voltage decay at 160 °C. Thus, the outstanding performance suggests that the microstructure and morphology of imidazolium ions polymer membranes significantly influence proton conductivity, performance, and the durability of a cell.

Development of an efficient bifunctional electrocatalyst based on Co/CoSe2 nanoparticles embedded in N, Se co-doped carbon for AEMFC and rechargeable Zn-air battery

We suggest a hollow-structured N, Se dual-doped carbon framework embedded with Co/CoSe2 nanoparticles (Co/CoSe2@NSeC) as highly efficient bifunctional electrocatalyst for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). The prepared electrocatalyst exhibits high electrochemical active surface area attributed to its unique hollow/porous structure and defective heteroatom doping sites. Furthermore, the strongly coupled heterojunction between Co and CoSe2 species not only provides abundant and highly active sites but also generates built-in electric field, thereby promoting electron transfer during the electrocatalytic reaction. Based on the above considerations, the prepared catalyst shows excellent bifunctional electrocatalytic performance. Leveraging the excellent ORR activity of Co/CoSe2@NSeC, alkaline exchange membrane fuel cells (AEMFC) with the Co/CoSe2@NSeC as air cathode exhibits high power density of 171.23 mW cm2. Furthermore, the rechargeable Zn-air battery employing the Co/CoSe2@NSeC shows high specific capacity (729.4 mAh gZn−1), peak power density (192.88 mW cm2), and sustained stability over 300 cycles.

Gd3Ga5O12: a wide bandgap semiconductor electrolyte for ceramic fuel cells, effective at temperatures below 500 °C

Searching for compatible electrolytes with Ni0.8Co0.15Al0.05LiO2 (NCAL) electrodes with high ionic conductivity at low operational temperatures (<550 °C) is essential for the research on ceramics fuel cells (CFCs). In this work, the experimental and theoretical analyses demonstrate that the highly stable single-phase Gd3Ga5O12 (GGO) garnet structure, composed of Gd-O octahedrons and Ga-O tetrahedrons, provides more active sites for ion transport, resulting in enhanced peak power density (PPD) and stable open circuit voltage (OCV) at low operational temperature. The unique internal garnet structure effectively reduces the interfacial impedance of the prepared fuel cell device, provides many active sites at triple-phase boundaries and increases the electrochemical stability. As a result, the constructed cell can deliver a superior peak power density of 770 mW/cm2 at 490 °C. In addition, X-ray photoelectron spectroscopy, electrochemical impedance spectroscopy and theoretical calculations further demonstrate electrolyte effectiveness of GGO, enabling stable OCV even at a low temperature of 370 °C under a H2/air environment. This work can help in improving the understanding of the underlying mechanisms of a single-layer fuel cell device, which is essential to further develop this potential energy technology even at a very low temperature of 370 °C.

S-N co-doped porous carbon as metal-free ORR electrocatalysts in zinc-air batteries

The implementation of zinc-air batteries (ZABs) requires the creation of economically feasible electrocatalysts for the oxygen reduction reaction (ORR) process. In this work, sulfur-nitrogen co-doped porous carbon materials (S-N-PC) were synthesized using a straightforward approach including ball milling followed by calcination without solvent. The optimized S-N-PC 1000 demonstrates exceptional ORR performance in 0.1 M KOH, with a half-wave potential of 0.870 V that outperforms commercial Pt/C. Furthermore, it exhibits remarkable durability and exceptional methanol resistance. The S-N-PC 1000 performs excellent performance as an air cathode in ZABs, exhibiting a peak power density of 159.26 mW cm−2 and outstanding stability for up to 720 h. Additionally, the energy efficiency decreases by only 2.52 % after undergoing more than 2000 cycles of charging and discharging at 5 mA cm−2. This study offers a novel concept for the development of eco-friendly porous carbon catalysts for ZABs.

Co/CoTe heterostructure internal hairy fibers as high-efficiency oxygen electrocatalyst for Zn-air batteries

The design of highly efficient catalysts to enhance the kinetics of oxygen reduction (OER) and oxygen evolution (ORR) reactions is the key issue for the development of high-performance Zn-air battery. In this work, we report the design of Co-CoTe heterostructured fibers as the bifunctional oxygen catalyst for Zn-air battery. Firstly, the theoretical analysis was carried out on Co-CoTe heterostructure. The large work function difference is favorable to construct strong interfacial built-in electric field (BIEF), and the low energy barrier endows high catalytic activities. Moreover, the in-situ grown carbon shell was designed to build “core–shell” Co-CoTe/C unit to realize its high performance. They assemble the Co-CoTe@HFS fiber with good self-supporting and flexible features. Taken the advantages of the strong BIEF, the “core–shell” basic unit, and the freestanding substrate, the Co-CoTe@HFS fiber achieves the good electrocatalytic properties and high reliability. The full Zn-air battery (ZAB) with the Co/CoTe@HFS air cathode achieves the high peak power density and cycling stability over long-term cycling. Therefore, this work provides a clue to design bifunctional oxygen catalysts for high-performance ZABs.

Enhancement in the performance of a vanadium-manganese redox flow battery using electrospun carbon metal-based electrode catalysts

This study investigates the performance of both a vanadium/manganese redox flow battery (V/Mn RFB) and an all-vanadium redox flow battery (VRFB), employing carbon metal fabrics (CMFs) prepared through electrospinning followed by carbonization. Noteworthy advancements are observed in both systems upon coupling CMFs with thermally treated graphite felt (GF) electrodes. Nearly doubled peak power density and 50 % higher capacity utilization over 150 charge/discharge cycles at 75 mA cm−2 are achieved for the V/Mn RFB with the incorporation of CMFs alongside graphite felt as catalysts. The VRFB demonstrates notable enhancements too, achieving approximately 200 cycles at a current density of 80 mA cm−2, with high efficiencies (85 %) and electrolyte utilization (79 %) when CMFs are used in combination with graphite felts. These advancements may facilitate pilot-scale testing and integration of the V/Mn RFB for the employment in the renewable energy storage sector and grid-balancing studies.

High-performance rechargeable zinc-air batteries enabled by cobalt iron anchored on nitrogen-doped carbon matrix as bifunctional electrocatalyst

Developing efficient bifunctional oxygen reduction reaction (ORR)/oxygen evolution reaction (OER) electrocatalysts is potential ways for achieving high rechargeable zinc-air (Zn-air) battery performance. Herein, we report an iron (II) acetate-assisted strategy to synthesize Co3Fe7-NC-OAc catalyst with cobalt iron (Co3Fe7) alloy anchored on nitrogen-doped carbon (NC) matrix, which can serve as efficient ORR/OER bifunctional electrocatalysts for rechargeable Zn-air batteries. Apart from alloying with Co to form ORR/OER active Co3Fe7 nanoparticles, the incorporation of iron (II) acetate has expanded the pore size inside the Co3Fe7-NC-OAc catalyst to serve as gas transfer channels, and has induced synergetic electronic coupling between Co3Fe7 nanoparticles and NC matrix for boosting catalytic activity. Therefore, Co3Fe7-NC-OAc exhibits favorable ORR activity with a most positive half-wave potential of 0.90 V vs. RHE, fast ORR kinetics with a highest kinetic current density of 57.4 mA cm−2 at 0.85 V vs. RHE, and fast O2 diffusion and transport that enables smaller mass transport overpotential at high current density up to 800 mA cm−2. Additionally, Co3Fe7-NC-OAc can catalyze OER with low overpotential of 310 mV at 10 mA cm−2. When employed as air electrode for Zn-air batteries, Co3Fe7-NC-OAc achieve high peak power densities of 193 mW cm−2 and 587 mW cm−2 in liquid and solid-state Zn-air batteries. The liquid battery also exhibits high specific capacity and remarkable cycling performance. This work opens up a new opportunity for developing highly efficient bifunctional electrocatalysts for Zn-air battery applications.

Self-Powered Traffic Lights Through Wind Energy Harvesting Based on High-Performance Fur-Brush Dish Triboelectric Nanogenerators.

Traffic lights play vital roles in urban traffic management systems, providing clear directional guidance for vehicles and pedestrians while ensuring traffic safety. However, the vast quantity of traffic lights widely distributed in the transportation system aggravates energy consumption. Here, a self-powered traffic light system is proposed through wind energy harvesting based on a high-performance fur-brush dish triboelectric nanogenerator (FD-TENG). The FD-TENG harvests wind energy to power the traffic light system continuously without needing an external power supply. Natural rabbit furs are applied to dish structures, due to their outstanding characteristics of shallow wear, high performance, and resistance to humidity. Also, the grid pattern of the dish structure significantly impacts the TENG outputs. Additionally, the internal electric field and the influences of mechanical and structural parameters on the outputs are analyzed by finite element simulations. After optimization, the FD-TENG can achieve a peak power density of 3.275Wm-3. The portable and miniature features of FD-TENG make it suitable for other natural environment systems such as forests, oceans, and mountains, besides the traffic light systems. This study presents a viable strategy for self-powered traffic lights, establishing a basis for efficient environmental energy harvesting toward big data and Internet of Things applications.

Architecting side chain grafted poly (vinylidene fluoride) based graphene oxide composite polyelectrolyte membranes for hydrogen and direct methanol fuel cells

Chemically modified poly (vinylidene fluoride) (PVDF) as polyelectrolyte has generated immense interest due to its high efficiency in electrochemical energy devices. Herein, the design of a polymer electrolyte membrane (PEM) is formulated by the synergistic fusion of graphene oxide (GO) into chemically grafted PVDF with 2-acrylamido-2-methylpropane sulfonic acid (AMPS) by solution phase intercalation producing GO@PVDF-g-PAMPS composite membranes. Ozone-induced graft copolymerization technique is employed to prepare PVDF-g-PAMPS with 18.3% (w/w) degree of grafting. Incorporation of GO into the polymeric membrane generates appropriate hydrophilic-hydrophobic phase separation and constructs well-organized sub-nano slit-like pathways that elevate the proton conduction. PAG-0 membrane without any filler shows a proton conductivity (κ) of 15.1 mS/cm at 80°C whereas PAG-2 membrane (with 2% w/w GO loading) shows a κ of 25.9 mS/cm under similar conditions. The presence of a perfluorinated backbone furnishes excellent oxidative stability to the PEMs by retaining 95% of total mass and 97.3% of κ after dipping in harsh Fenton's reagent at 60°C for 6 h. Representative PAG-2 shows a peak power density of 152.9 mW/cm2 with a maximum current density of 480.6 mA/cm2 (fuel cell operating conditions: 75°C at 100% RH) in hydrogen fuel cell and a peak power density of 37.7 mW/cm2 in methanol fuel cell. Moreover, PAG-2 retains 91% of its initial OCV after 50 h of the durability test.

Synthesis of poly(terphenyl-co-dibenzo-18-crown-6 methylimidazole) copolymers for high-performance high temperature polymer electrolyte membrane fuel cells

This study focuses on the development of high temperature polymer electrolyte membranes (HT-PEMs), which are essential components for HT-PEM fuel cells (HT-PEMFCs). While phosphoric acid (PA) doped polybenzimidazole (PBI) has been recognized as a successful HT-PEM, it faces several challenges, including the use of carcinogenic monomer, complex synthesis processes, and poor solubility in organic solvents. To produce more cost-effective, easily synthesized, and high-performance alternatives, this study utilizes a straightforward superacid-catalyzed Friedel-Crafts reaction to synthesize a series of poly(terphenyl-co-dibenzo-18-crown-6 methylimidazole) copolymers, referred to as Co-x%TP-y%CE-Im, using p-terphenyl, dibenzo-18-crown-6 and 1-methyl-1H-imidazole-2-formaldehyde as monomers. The copolymerized hydrophilic and bulky crown ether units introduce substantial free volume and multiple interaction sites with PA molecules, as indicated by theoretical calculations. Additionally, the formation of microphase separation structures, confirmed by atomic force microscope (AFM) and transmission electron microscope (TEM), contributes to the enhanced performance of these membranes. For instance, after immersion in 85 wt% and 75 wt% PA solutions, the Co-90%TP-10%CE membrane achieves PA doping contents of 200 % and 169 %, achieving high conductivities of 0.092 S cm−1 and 0.054 S cm−1 at 180 °C, while maintaining tensile strengths of 6.5 MPa and 7.5 MPa at room temperature. Without the need for humidification or backpressure, the peak power density of an H2-O2 cell equipped with Co-90%TP-10%CE/169%PA membrane with a thickness of 79 μm reaches an impressive 1018 mW cm−2 at 210 °C. These results demonstrate new materials and insights for the development of high-performance HT-PEMs.

Novel Intercalation Approach in MXene Using Modified Silica Nanospheres to Enhance the Surface Charge Density for Superior Triboelectric Performance

AbstractThis paper proposes a novel intercalation approach to address the challenges of surface triboelectric charge dissipation and self‐restacking of MXene layers in triboelectric nanogenerators (TENGs). The proposed strategy significantly improves the performance of TENGs, as it prevents the loss of surface charges and enhances the structural stability of MXene. First, the modified silica nanospheres (MSNs) of specific dimensions are synthesized, followed by their intercalation between MXene layers. This not only resolves the restacking issue but also dramatically increases the interlayer distance and MXene's surface area. The MSNs, acting as effective charge storage sites, significantly enhance surface charge density, whereas their high dielectric permittivity generates a synergistic effect that modulates the dielectric constant via polarization. Ultimately, the proposed MSN‐intercalated MXene‐based TENG demonstrates outstanding output performance (output voltage of ≈461 V, output current of ≈19 µA, and maximum peak power density of ≈691.2 µW cm−2) at a 2 wt.% MSN‐intercalated MXene concentration. This study paves a new pathway for the structural design of tribonegative and charge storage layers in TENGs for energy harvesting.

Conductivity-enhanced Poly(biphenyl piperidine) anion exchange membranes with organic tubes

Anion exchange membrane fuel cells (AEMFCs) present an economically efficient alternative to proton exchange membrane fuel cells because of the use of non-precious metals. The development of high-performance and durable AEMFCs necessitates the use of highly conductive and robust anion exchange membranes (AEMs). In this study, a novel organic-organic composite AEM was synthesized by preparing poly(arylene piperidinium) polymer through Friedel-Crafts acid condensation and incorporating one-dimensional organic tubes as reinforcing materials. The composite AEM exhibits high conductivity (235 mS cm−1 at 80 °C) due to the chain orientation within the organic tubes and the availability of abundant transport sites. Furthermore, in contrast to the incompatibility of inorganic materials with polymers, the flexible nature of organic tubes enhanced polymer entanglement, significantly boosting the mechanical strength (120 MPa) of the AEM. Crosslinking the polymer backbone with the organic tubes facilitated simultaneous swelling, effectively mitigating interfacial compatibility issues, result in high dimensional stability. The H2–O2 fuel cell employing the developed AEM demonstrated a peak power density of 1018 mW cm−2 at 80 °C. This study provides a comprehensive synthetic strategy for producing stable AEMs with high hydroxide ion conductivity and outstanding mechanical properties tailored for alkaline membrane fuel cell applications.

Enhanced performance of polydimethylsiloxane-based triboelectric nanogenerator using BaTiO3/MWCNTs

Triboelectric nanogenerators (TENGs) that operate in the contact-separation mode are widely utilized for energy harvesting owing to their simple structure, excellent durability, and high energy-conversion efficiency. This study investigated the enhanced performance of TENGs using polydimethylsiloxane (PDMS) incorporating barium titanate (BTO) and multiwalled carbon nanotubes (MWCNTs). The negative triboelectric layer, comprising PDMS with BTO and MWCNTs, and aluminum foil as both the positive triboelectric layer and electrode, were optimized to improve the TENG performance. The optimal composition of PDMS incorporating 0.01 wt% MWCNTs and 10 wt% BTO yielded output voltage and current of 394.75 V and 28.24 µA, respectively. Further enhancement was realized via the application of radio frequency plasma treatment, which increased the surface roughness and fluorine incorporation. Consequently, the output voltage and current improved to 421.06 V and 32.33 µA, respectively, with a peak power density of 4.76 W/m2 at 10 MΩ. The optimized TENG maintained consistent performance over 2000 cycles and successfully illuminated commercial LEDs, thereby demonstrating its potential for practical energy-harvesting applications.

Oxophilic Low‐Coordination Gd‐N3 Single Atom Sites With P‐Enhanced Second Coordination for High‐Performance Al‐Air Batteries

AbstractThe development of efficient rare earth single‐atom (SA) catalysts for the oxygen reduction reaction (ORR) is essential yet challenging for high‐performance aluminum‐air batteries (AABs). This study introduces a concept‐to‐proof strategy for synthesizing a hollow carbon‐supported gadolinium (Gd) SA catalyst using low‐coordination and second‐coordination sphere engineering. In this design, Gd atoms are coordinated to three nitrogen (N) atoms in N‐doped carbon and surrounded by six phosphorus (P) atoms, forming Gd‐N3‐P6 sites. These catalysts demonstrated exceptional ORR performance, achieving a half‐wave potential of 0.895 V and superior durability compared to the commercial Pt/C benchmark. When integrated into AABs, they delivered impressive performance, with a peak power density of 257 mW/cm2 and an energy density of 2916 Wh/kg, alongside enhanced cycling stability. In situ characterization and theoretical calculations revealed that the strategic placement of P atoms in the second coordination sphere significantly enhanced the valence state of the Gd site. This enhancement improved the adsorption capacity for O2 and H2O while facilitating the rapid desorption of *OH intermediates during the ORR. This study offers valuable insights into the development of cost‐effective ORR catalysts, emphasizing the significance of modulating the local coordination environment of metal SA sites.

Impact of side chain length on the properties and alkaline fuel cell performance of OEG-grafted poly(terphenyl piperidinium) anion exchange membranes

In designing comb-shaped anion exchange membranes (AEMs), replacing alkyl side chains with ethylene glycol (EG)-based ones significantly enhances membrane properties and boosts AEM fuel cell performance. Although much research has focused on optimizing the placement of EG segments within the polymer matrix, the effect of EG chain length remains less explored. In this work, a series of poly(terphenyl piperidinium) AEMs with N-oligo(ethylene glycol) (OEG) terminal pendants having two to five EG repeating units were prepared by simple post-polymerization quaternization. The membrane properties showed a strong correlation with the length of the OEG side chains, influenced by both chemical composition and phase behavior. Among the OEG-grafted AEMs, PTP-OEG3 with moderate three EG repeating units, exhibited the best properties due to a careful balance between EG and cationic groups, leading to a favorable microphased separation. It achieved high hydroxide conductivity (114 mS cm−1 at 80 °C in water), robust mechanical strength (tensile strength >52 MPa), and good ex situ alkaline stability. As a result, the AEM fuel cells with the property-balanced PTP-OEG3 membrane achieved the highest peak power density of 976 mW cm−2. The in situ stability of these AEMs was also investigated. Evidently, understanding the optimal EG side chain length is an important criterion for designing AEM materials for alkaline fuel cells.

Robust branched Poly(p-terphenyl isatin) anion exchange membranes with enhanced microphase separation structure for fuel cells

Anion exchange membrane fuel cells (AEMFCs) are gradually becoming the focus of sustainable hydrogen energy research due to the advantages of clean by-products, faster oxidation-reduction dynamics and allowing cheap platinum-free base materials. As the key components of AEMFCs, anion exchange membranes (AEMs) are required to have high ionic conductivity and dimensional stability. This study focused on the design and preparation of branched AEMs for AEMFCs. The b-PTIN-x membranes were generated by incorporating 1,3,5-triphenylbenzene (TPB) units into rigid poly(p-terphenyl isatin) (PTI) polymer backbones. This innovative approach aimed to induce microphase separation structures by exploiting TPB with high FFV, as well as to enhance the tensile strength of AEMs with the help of branched structures. SAXS and AFM images revealed that the AEMs achieved enhanced microphase separation structures, resulting in the formation of ion transport channels with dimensions in the range of a few nanometers (3.36–3.70 nm). The branched b-PTIN-11 membranes displayed significant OH− conductivity (153.9 mS cm−1 at 80 °C) while having a low ion exchange capacity (IEC) (1.73 mmol g−1). The b-PTIN-11 membranes displayed improved tensile strength (56.69 MPa) and exceptional dimensional stability, with swelling ratio (SR) of 18.5 % at 80 °C. They also showed great chemical stability with 89.64 % conductivity remaining, lasting for more than 1200 h in 3 M NaOH solution at 80 °C. Ultimately, the b-PTIN-11 membrane underwent testing to evaluate its performance in a fuel cell using H2–O2. It demonstrated a peak power density (PPD) of 566 mW cm−2 when subjected to a current density of 1339 mA cm−2.

Ni-Doped SFM Double-Perovskite Electrocatalyst for High-Performance Symmetrical Direct-Ammonia-Fed Solid Oxide Fuel Cells.

Ammonia has emerged as a promising fuel for solid oxide fuel cells (SOFCs) owing to its high energy density, high hydrogen content, and carbon-free nature. Herein, the electrocatalytic potential of a novel Ni-doped SFM double-perovskite (Sr1.9Fe0.4Ni0.1Mo0.5O6-δ) is studied, for the first time, as an alternative anode material for symmetrical direct-ammonia SOFCs. Scanning and transmission electron microscopy characterization has revealed the exsolution of Ni-Fe nanoparticles (NPs) from the parent Sr2Fe1.5Mo0.5O6 under anode conditions, and X-ray diffraction has identified the FeNi3 phase after exposure to ammonia at 800 °C. The active-exsolved NPs contribute to achieving a maximal ammonia conversion rate of 97.9% within the cell's operating temperatures (550-800 °C). Utilizing 3D-printed symmetrical cells with SFNM-GDC electrodes, the study demonstrates comparable polarization resistances and peak power densities of 430 and 416 mW cm-2 for H2 and NH3 fuels, respectively, with long-term stability and a negligible voltage loss of 0.48% per 100 h during ammonia-fed extended galvanostatic operation. Finally, the ammonia consumption mechanism is elucidated as a multistep process involving ammonia decomposition, followed by hydrogen oxidation. This study provides a promising avenue for improving the performance and stability of ammonia-based SOFCs for potential applications in clean energy conversion technologies.

Biomass carbon with defective structures as effective ORR catalyst for DMFC

Oxygen reduction reaction (ORR), as an important reaction carried out on the cathode of direct methanol fuel cells (DMFC), directly affects the performance of the cell. Previous experimental studies have shown that there are some interactions between the defect structure and N doping to promote the ORR performance of the catalysts. In this work, the binder was first utilized to reduce the lignin content in the cotton straw (CS) system, thereby increasing the defective structure of the carbon substrate. Here, we obtained 5C-NP-Fe catalysts by increasing the defectivity of the carbon substrate through binder. The coordination environment surrounding the Fe-N4 sites is optimized by the synergistic action of the N and P atoms and the faulty structure, as shown by DFT theoretical calculations. In alkaline medium, half-wave potentials as high as 0.88 V in the three-electrode system and a peak power density of 10.8 mW cm−2 in a direct methanol fuel cell at 60℃. Compared to a 20 wt% commercial Pt/C catalyst (0.84 V, 7.5 mW cm−2), 5C-NP-Fe showed good ORR activity. The binder modification strategy provides a simple and green approach to the structural optimization of biomass-based catalysts.

A CO2-emission free direct methanol fuel cell for simultaneous production of electrical energy and value-added chemicals

It remains challenges to efficiently convert carbon-based fuels such as methanol from CO2 into electrical energy while without CO2 greenhouse gas emission. Herein, a CO2-emission free direct methanol fuel cell (DMFC) has been realized through using unique Pt-CoOOH/nickel foam anode with high electro-catalytical selectivity, activity and stability. The DMFCs demonstrate simultaneous production of 18 mol of formate for every 1 kWh of electricity output with peak power density of 49.3 mW cm−2 and high selectivity of formate value-added chemicals up to 96 %. Moreover, this simple procedure does not consume energy while output electricity compared to the traditional formate production. It either does not use the toxic feedstock of CO and the reaction conditions are very mild. The in-situ Raman test indicates that CoOOH acts as an auxiliary active site to promote the conversion of *HCO to *HCOOH and improve the selectivity of formate. In-situ IR tests and density functional theory (DFT) calculations confirm that methanol tends to be oxidized selectively into formate rather than complete-oxidizing into CO2. This study achieves clean and efficient utilization of carbon-based fuels to co-generate electrical energy and value-added chemicals while no CO2 greenhouse emission, even realize the “negative carbon” cycle.