mW Cm-2 Research Articles

Boron-Doping Engineering in AgCd Bimetallic Catalyst Enabling Efficient CO2 Electroreduction to CO and Aqueous Zn-CO2 Batteries.

The limited adsorption and activation of CO2 on catalyst and the high energy barrier for intermediate formation hinder the development of electrochemical CO2 reduction reactions (CO2RR). Herein, this work reports a boron (B) doping engineering in AgCd bimetals to alleviate the above limitations for efficient CO2 electroreduction to CO and aqueous Zn-CO2 batteries. Specifically, the B-doped AgCd bimetallic catalyst (AgCd-B) is prepared via a simple reduction reaction at room temperature. A combination of in situ experiments and density functional theory (DFT) calculations demonstrates that B-doping simultaneously enhances the adsorption and activation of CO2 and reduces the binding energy of the intermediates by moderating the electronic structure of bimetals. As a result, the AgCd-B catalyst exhibits a high CO Faraday efficiency (FECO) of 99% at -0.8V versus reversible hydrogen electrode (RHE). Additionally, it maintains a FECO over 92% at a wide potential window of 600mV (-0.6 to -1.1V versus RHE). Furthermore, the AgCd-B catalyst coupled with the Zn anode to assemble aqueous Zn-CO2 batteries shows a power density of 20.18mW cm-2 and a recharge time of 33h.

Meso/Microporous Single-Atom Catalysts with Curved Fe-N4 sites Boost the Oxygen Reduction Reaction Activity.

Zeolitic-imidazolate frameworks (ZIFs) are among the most efficient precursors for the synthesis of atomically dispersed Fe-N/C materials, which are promising catalysts for enhancing the performance of Zn-air batteries (ZABs) and proton exchange fuel cells (PEMFCs). However, existing ZIF-derived Fe-N/C electrocatalysts mostly consist of microporous materials, leading to insufficient mass transport and inadequate battery/cell performance. In this study, we synthesize an atomically dispersed meso/microporous Fe-N/C material with curved Fe-N4 active sites, denoted as FeSA-N/TC, through the pyrolysis of hemin-modified ZIF films on ZnO nanorods, obtained from the self-assembly reaction between Zn2+ from ZnO hydrolysis and 2-methylimidazole. Density functional theory calculations demonstrate that the curved Fe-N4 active sites can weaken the intermediate adsorptions, resulting in lower free energy barriers and enhanced performance during oxygen reduction reaction (ORR). Specifically, FeSA-N/TC exhibits exceptional ORR performance with half-wave potentials of 0.925 V in alkaline media and 0.825 V in acidic media. When used as the cathodic catalyst in PEMFCs and ZABs, FeSA-N/TC achieves high peak power densities (H2-O2 PEMFC: 1100 mW cm-2; H2-Air PEMFC: 715 mW cm-2; liquid-state ZAB: 228 mW cm-2; solid-state ZAB: 112 mW cm-2), demonstrating its feasibility and efficiency in practical applications.

Energy-harvesting tile incorporating an origami coupling mechanism.

We present the design and evaluation of a simple, compact and efficient electromagnetic energy harvesting tile that can be used to harness energy from footsteps. The proposed harvester incorporates a translational-rotational origami-inspired coupling mechanism to transform the axial loads exerted by human footsteps into a localized rotation of an electromagnetic generator. The coupling mechanism employs a non-rigid tunable Kresling spring, the restorative behaviour of which is tunable to maximize energy transduction from the applied load to the generator. A computational model is developed to optimize the design parameters of the mechanism, which are then utilized to fabricate a prototype of the energy harvester. The tile is tested under loading conditions that mimic a human step, where it is demonstrated that it is capable of generating 4.18 W of electrical power per step with a surface power density of 2609 μW cm-2.This article is part of the theme issue 'Origami/Kirigami-inspired structures: from fundamentals to applications'.

Boost Electrocatalytic Activity of La0.6Sr0.4Co0.2Fe0.8O3-δ Air Electrode Prepared by High-Temperature Shock for Solid Oxide Electrochemical Cells.

High-temperature shock (HTS) is an emerging material synthesis technology with advantages, such as rapid processing, low energy consumption, and high controllability. This technology can prepare ultrafine nanoparticles with uniform particle size distribution and introduce additional oxygen vacancies, offering significant potential for the preparation of key materials for solid oxide electrochemical cells (SOCs). In this study, the La0.6Sr0.4Co0.2Fe0.8O3-δ (LSCF) air electrode was successfully prepared using HTS technology. Compared to the conventional muffle furnace calcination, the HTS-prepared LSCF exhibits a larger specific surface area and a higher oxygen vacancy concentration, and it demonstrates significant improvements in performance. The oxygen ion conducting SOC (O-SOC) with the HTS-LSCF air electrode achieved a peak power density (PPD) of 960 mW cm-2 and a current density of 0.38 A cm-2 (at 1.3 V) at 700 °C. Meanwhile, the proton conducting SOC (P-SOC) with HTS-LSCF air electrode reached a PPD value of 1.34 W cm-2 and a current density of 3.43 A cm-2 (at 1.3 V) at 700 °C. Additionally, the P-SOC with HTS-LSCF air electrode showed no significant degradation during over 200 h of long-term testing, reflecting the excellent stability of HTS-LSCF. This work provides a fast, efficient, and economical approach for synthesizing high-performance, high-stability SOC air electrode materials.

High-Entropy Ag-Ru-based Electrocatalysts with Dual-Active-Center for Highly Stable Ultra-Low-Temperature Zinc-Air Batteries.

The development of advanced bifunctional catalysts for oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) is significant for rechargeable zinc-air batteries (ZABs). Herein, a unique dual active center alloying strategy is proposed to achieve the efficient bifunctional oxygen catalysis, and the high entropy effect is further exploited to modulate the structure and performance of the catalysts. The MOF-assisted pyrolysis-replacement-alloying method was employed to construct the CoCuFeAgRu high-entropy alloy (HEA), which are uniformly anchored in porous nitrogen-doped carbon nanosheets. Notably, the obtained HEA catalyst exhibits excellent catalytic performance for both ORR and OER, and a peak power density of 136. 53 mW cm-2 and an energy density of 987.9 mAh gZn-1, surpassing the most of the previously reported bifunctional oxygen electrocatalysts. Moreover, the assembled flexible rechargeable ZAB enables excellent performance even at the ultralow temperature of -40°C, with an energy density of 601.6 mAh gZn-1 and remarkable cycling stability up to 1,650 hours. Combined experimental and theoretical calculation results reveal that the excellent bifunctional catalytic activity of the HEA catalyst originated from the synergistic effect of the Ag and Ru dual active centers, and the optimization of the electronic structure by alloying effect.

Three-Dimensional (3D) Fluoride Molecular Glue to Improve the SnO2/Perovskite Interface for Efficient Perovskite Solar Cells.

Aiming at numerous defects at SnO2/perovskite interface and lattice mismatch in perovskite solar cells (PSCs), we design a kind of three-dimensional (3D) molecular glue (KBF4-TFMSA), which is derived from strong intramolecular hydrogen bonding interaction between potassium tetrafluoroborate (KBF4) and trifluoromethane-sulfonamide (TFMSA). A remarkable efficiency of 25.8 % with negligible hysteresis and a stabilized power output of 25.0 % have been achieved, in addition, 24.57 % certified efficiency of 1 cm2 device is also obtained. Further investigation reveals that this KBF4-TFMSA can interact with oxygen vacancies and under-coordinated Sn(IV) from the SnO2, in the meantime, FA+ (NH2-C=NH2 +) and K+ cations can be well fixed by hydrogen bonding interaction between FA+ and BF4 -, and electrostatic attraction between sulfonyl oxygen and K+ ions, respectively. Thereby, FAPbI3 crystal grain sizes are increased, interfacial defects are significantly reduced while carrier extraction/ transportation is facilitated, leading to better cell performance and excellent stabilities. Non-encapsulated devices can maintain 91 % of their initial efficiency under maximum-power-point (MPP) tracking while continuous illumination (~100 mW cm-2) for 1000 h, and retain 91 % of the initial efficiency after 1000 h "double 60" damp-heat stability testing (60 °C and 60 %RH (RH, relatively humidity)).

Enhanced proton transfer in proton exchange membrane fuel cells via novel nanocomposite membrane incorporating (3-Mercaptopropyl)trimethoxysilane-graphene oxide and basic amino ligands: A synergistic acid-base approach

A nanocomposite polymer electrolyte membrane (MGC) was synthesized by blending MPTS (HS(CH2)3Si(OCH3)3) and graphene oxide (GO) nanosheets at varying weight ratios (91.5 to 9.5, respectively) for proton exchange membrane fuel cell (PEMFC) applications. By covalently modifying the GO support with MPTS through a silane modification process, the acidic MGC matrix is formed. The blending process, with ultrasonication and vigorous stirring, initiates two significant reactions in reactive MPTS: first, the conversion of methoxy groups (Si–OCH3) to silanols (Si-OH); second, the potential condensation of silanol groups to form siloxane bonds (Si–O–Si), followed by oxidation of sulfhydryl groups to sulfonic acid (-SO3H) groups by hydrogen peroxide. The resulting -SO3H groups connected to the siloxane network (Si-O-Si) adjacent to the GO. Two basic amino ligands – dopamine, and aminopropyl trimethoxysilane (APTES) were incorporated into the MGC matrix to establish acid-base pairs, promoting swift proton transport. These additions, at weight ratios of (0.5, 1, 2, and 7) wt%, synergistically contributed to the MGC matrix, forming effective proton channels. Various analytical techniques, including field emission-scanning electron microscopy (FE-SEM), atomic force microscopy (AFM), Raman spectroscopy, X-ray diffraction (XRD), and electrochemical impedance spectroscopy (EIS), were employed to assess the impact of functionalized basic amino groups on the MGC matrix. Notably, the MGC membrane containing 2 wt% of PDA as basic amino ligands exhibited optimal performance, showcasing an in-plane proton conductivity of 115.10 mS cm-1 under fully hydrated conditions at 90 °C, and the maximum power density (MPD) of 170.74 mW cm-2 with a current density of 1051.46 mA cm-2 at 60 °C and 100 % relative humidity (RH). In contrast, the MGC membrane, devoid of amino ligands, exhibited a comparatively low in-plane conductivity of 44.32 mS cm⁻¹ under identical conditions at 90 °C. Additionally, it recorded the MPD of 48.5 mW cm⁻², corresponding to a current density of 313.25 mA cm⁻² at 60 °C and 100 % RH. This study introduces an innovative approach for developing high-performance nanocomposite membranes for PEMs and related applications.

Significantly Enhanced Oxidation Resistance and Electrochemical Performance of Hydrothermal Ti3C2Tx MXene and Tannic Acid Composite for High-Performance Flexible Supercapacitors.

The electrochemical performances of Ti3C2Tx MXene are severely restricted by the easy oxidation and restacking. Herein, tannic acid (TA) is introduced into Ti3C2Tx dispersion, and the mixed dispersion is further subjected to a simple hydrothermal treatment to prepare the hydrothermal Ti3C2Tx and TA composite (h-Ti3C2Tx@h-TA). Due to the decomposition of TA into gallic acid (GA), hydrothermal TA (h-TA) is a mixture of TA and GA. The strong interaction between h-TA and MXene mainly involves chemical interaction between the hydroxyl groups in h-TA and the surface/edge Ti atoms, along with numerous hydrogen bonds. The h-TA intercalation weakens MXene restacking and increases interlayer spacing, thereby improving ion transport pathways and accessibility. The chemical interaction between the hydroxyl groups of GA and the Ti atoms significantly enhances oxidation resistance and pseudocapacitive active sites. Therefore, the h-Ti3C2Tx@h-TA film electrode shows significantly enhanced capacitance (848 F·g-1 at 1 A g-1) and cycling stability (100% retention after 20 000 cycles). Moreover, flexible sandwiched supercapacitors with symmetrical h-Ti3C2Tx@h-TA electrodes exhibit a high energy density of 30.1 Wh kg-1 at a high power density of 300 W kg-1, outperforming those of Ti3C2Tx-based film electrodes and sandwiched supercapacitors reported so far. The extrusion-printed microsupercapacitors with h-Ti3C2Tx@h-TA electrodes demonstrate high areal capacitance (135 mF cm-2 at 5 mV s-1) along with energy storage performance (6.74 μWh cm-2 at 506 μW cm-2) and cycling stability (98.8% retention after 41 460 cycles), all while maintaining excellent flexibility. These impressive results indicate the great application potential of the hydrothermal Ti3C2Tx MXene and tannic acid composite in flexible energy storage devices.

Hierarchically Ordered Pore Engineering of Carbon Supports with High-Density Edge-Type Single-Atom Sites to Boost Electrochemical CO2 Reduction.

Metal sites at the edge of the carbon matrix possess unique geometric and electronic structures, exhibiting higher intrinsic activity than in-plane sites. However, creating single-atom catalysts with high-density edge sites remains challenging. Herein, the hierarchically ordered pore engineering of metal-organic framework-based materials to construct high-density edge-type single-atomic Ni sites for electrochemical CO2 reduction reaction (CO2RR) is reported. The created ordered macroporous structure can expose enriched edges, further increased by hollowing the pore walls, which overcomes the low edge percentage in the traditional microporous substrates. The prepared single-atomic Ni sites on the ordered macroporous carbon with ultra-thin hollow walls (Ni/H-OMC) exhibit Faraday efficiencies of CO above 90% in an ultra-wide potential window of 600mV and a turnover frequency of 3.4×104h-1, much superior than that of the microporous material with dominant plane-type sites. Theory calculations reveal that NiN4 sites at the edges have a significantly disrupted charge distribution, forming electron-rich Ni centers with enhanced adsorption ability with *COOH, thereby boosting CO2RR efficiency. Furthermore, a Zn-CO2 battery using the Ni/H-OMC cathode shows an unprecedentedly high power density of 15.9mW cm-2 and maintains an exceptionally stable charge-discharge performance over 100h.

Carbothermal Reduction-Assisted Synthesis of a Carbon-Supported Highly Dispersed PtSn Nanoalloy for the Oxygen Reduction Reaction.

Exploring high-performance and low-platinum-based electrocatalysts to accelerate the oxygen reduction reaction (ORR) at the air cathode of zinc-air batteries remains crucial. Herein, by combining electroless deposition and carbothermal reduction, a nitrogen-doped carbon-supported highly dispersed PtSn alloy nanocatalyst (PtSn/NC) was prepared for a high-efficiency ORR process. Electrochemical measurements show that PtSn/NC exhibits excellent electrocatalytic ORR activity with a half-wave potential of 0.850 V versus reversible hydrogen electrode (RHE), which is higher than that of commercial Pt/C (0.815 V). The PtSn/NC-based (20 μgPt cm-2) rechargeable Zn-air battery exhibited astonishing performance with a maximum power density of up to 150.1 mW cm-2, as well as excellent rate performance and charge/discharge stability. Physical characterization reveals that carbothermal reduction could compel the transformation of Sn oxide into metallic Sn, which then alloys with the deposited Pt atoms to form the PtSn nanoalloy, in which electrons are transferred from Sn atoms to neighboring Pt atoms, thereby improving the ability of Pt-based active sites to catalyze the ORR process in PtSn/NC by optimizing the unoccupied d-band of Pt atoms. This work provides a reliable and innovative route for the rational design of highly dispersed Pt-based alloy ORR electrocatalysts.

Highly asymmetrically configured single atoms anchored on flame-roasting deposited carbon black as cathode catalysts for ultrahigh power density Zn-air batteries

Iron group element-based single atom (SA) catalysts are highly regarded as promising alternatives to commercial Pt/C for catalysis of oxygen reduction reaction (ORR). For applications in rechargeable zinc-air batteries (ZABs), achieving the necessary high catalytic efficiency of the SAs toward oxygen evolution reaction (OER) however remains a significant challenge. Here, highly asymmetrically configured Fe SAs created with N,S co-coordination and anchored on flame-roasting deposited carbon black (CB), Fe-N3S1/CB, are developed, achieving outstanding bifunctional oxygen catalytic efficiency, with an ultra-small potential gap of 0.661 V at 10 mA cm-2 (ΔE10), outperforming the (Pt/C+RuO2) composite catalyst (0.697 V). With a newly proposed binder-free composite air cathode design, the Fe-N3S1/CB based ZAB achieves an ultrahigh power density of 365.7 mW cm-2 at a current density of 511.3 mA cm-2, largely outperforming the (Pt/C+RuO2) based ZAB (225.9 mW cm-2 at 344.7 mA cm-2). Furthermore, the Fe-N3S1/CB based ZAB demonstrates excellent long-term stability, with only 8.2% decay in round-trip efficiency over 1000 (333.3 h) charge-discharge cycles at 10 mA cm-2. Density functional theory calculations elucidate that incorporation of sulfur into the coordination sphere of Fe facilitates the electrochemical dehydroxylation step for ORR and accelerates the electrochemical O2 desorption step for OER, thereby reducing the corresponding free energy differences on Fe SAs for largely enhanced catalytic efficiency.1. A large size hetero-atom element, sulfur, is introduced to create highly asymmetrically configured Fe single atoms for enhancements in catalytic efficiency toward both oxygen reduction reaction and oxygen evolution reaction, and a binder-free composite air cathode design is proposed to improve electrochemical performances of zinc-air batteries.2. An ultra-small potential gap of 0.661 V at 10 mA cm-2 (ΔE10) is achieved for the air cathode, and an ultrahigh discharge power density of 365.7 mW cm-2 at a current density of 511.3 mA cm-2 is acquired for the zinc-air battery.

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.

High-Performing Flexible Mg3Bi2 Thin-Film Thermoelectrics.

With the advances in bulk Mg3Bi2, there is increasing interest in pursuing whether Mg3Bi2 can be fabricated into flexible thin films for wearable electronics to expand the practical applications. However, the development of fabrication processes for flexible Mg3Bi2 thin films and the effective enhancement of their thermoelectric performance remain underexplored. Here, magnetron sputtering and ex-situ annealing techniques is used to fabricate flexible Mg3Bi2 thermoelectric thin films with a power factor of up to 1.59 µW cm-1 K-2 at 60°C, ranking as the top value among all reported n-type Mg3Bi2 thin films. Extensive characterizations show that ex-situ annealing, and optimized sputtering processes allow precise control over film thickness. These techniques ensure high adhesion of the films to various substrates, resulting in excellent flexibility, with <10% performance degradation after 500 bending cycles with a radius of 5mm. Furthermore, for the first time, flexible thermoelectric devices are fabricated with both p-type and n-type Mg3Bi2 legs, which achieve an output power of 0.17 nW and a power density of 1.67 µW cm-2 at a very low temperature difference of 2.5°C, highlighting the practical application potential of the device.

MOF-on-MOF Derived Co2P/Ni2P Heterostructures for High-Performance Supercapacitors.

Metal-organic frameworks (MOFs) have been widely used as versatile precursors to fabricate functional nanomaterials with well-defined structures for various applications. Herein, the presynthesized Ni-MOF nanosheets were grown on a Ni foam (NF) substrate, which then guided the nucleation and further growth of Prussian blue analogues (PBA) nanocubes to form MOF-on-MOF of the PBA/Ni-MOF film. This film was subsequently converted into a Co2P/Ni2P heterostructure. The NF-supported Co2P/Ni2P composites exhibited excellent supercapacitor performance, delivering a high specific capacity of 5124.2 mF cm-2 at 1 mA cm-2 and a remarkable capacity retention of 80.69% after 3000 cycles at 10 mA cm-2. An asymmetric supercapacitor assembled using Co2P/Ni2P/NF as the cathode and activated carbon as the anode yielded a maximum energy density of 0.34 mWh cm-2 at a power density of 1.50 mW cm-2. The enhanced supercapacitor performance is attributed to the synergistic effects of the Ni2P and Co2P components with multiple valence states as well as the unique hierarchical structure, which provides efficient pathways for electron and ion transport while mitigating volume expansion during energy storage. This synthetic strategy demonstrates an effective approach to fabricate phosphide-based hybrid materials for high-performance supercapacitor applications.

Recycling of spent heat pack towards Fe-Fe3O4@NC based cathode for electrocatalytic ORR in direct methanol fuel cells and Al-air batteries

The effective repurposing of waste materials is crucial for sustainable development. The widespread use of disposable iron-based chemical warmers (IBCW) generates substantial solid waste annually. In this study, IBCWs were repurposed as raw materials to synthesize different electrocatalyst composites comprising metallic and oxide forms of iron embedded in nitrogen-doped carbon (NC). The composites were evaluated as oxygen reduction reaction (ORR) catalysts. The optimized Fe-Fe3O4@NC demonstrated enhanced ORR kinetics, with an onset potential of 0.92 V and a half-wave potential of 0.86 V vs. RHE. As an air cathode, Fe-Fe3O4@NC achieved a power density of 33.3 mW cm−2 at 88 mA cm−2, demonstrating its practical applicability. Additionally, a quasi solid-state aluminium-air battery (SAAB) was assembled using this catalyst as the air cathode with a PVA-KOH gel electrolyte as the separator. The quasi SAAB exhibited an open circuit voltage (OCV) of 1.46 V, a power density of 40 mW cm-2, and good rate capability compared to Pt/C. The combined effect of metallic and oxide iron with nitrogen doping enhances the overall catalytic activity. This study demonstrates that IBCWs can be effectively transformed into valuable catalysts for renewable energy applications, enabling clean and sustainable utilization of waste materials.

Two-Dimensional MOF Constructed by a Binuclear-Copper Motif for High-Performance Electrocatalytic NO Reduction to NH3.

Ambient electrochemical NO reduction presents a dual solution for sustainable NO reduction and NH3 synthesis. However, their complex kinetics and energy demands necessitate high-performance electrocatalysts to ensure effective and selective process outcomes. Herein, we report that a two-dimensional Cu-based metal-organic framework (MOF), {[Cu(HL)]·H2O} n , (Cu-OUC, H3L = 5-(2'-carboxylphenoxy)isophthalic acid) acts as a stable electrocatalyst with high efficiency for NO-to-NH3 conversion. Electrochemical experimental studies showed that in 0.1 M K2SO4 solution, the as-prepared Cu-OUC achieved a peak Faradaic efficiency of 96.91% and a notable NH3 yield as high as 3415.82 μg h-1 mg-1. The Zn-NO battery in aqueous solution can produce electricity possessing a power density of 2.04 mW cm-2 while simultaneously achieving an NH3 yield of 616.92 μg h-1 mg-1. Theoretical calculations revealed that the surface of Cu-OUC effectively facilitates NO activation through a two-way charge transfer mechanism of "electron acceptance and donation", with the *NO formation step being the potential-determining stage. The study pioneers the use of a MOF as an electrocatalyst for ambient NO-to-NH3 conversion.

Meta-substituted thienoviologen with enhanced radical stability via π-π interaction modulation for neutral aqueous organic flow batteries

The aqueous organic redox flow batteries (AORFBs) are recognized as the most promising large-scale storage technology for long-duration energy storage (LDES). Although viologen derivatives are widely used as anolyte materials for AORFBs, their practical application is strongly limited by weak conjugation and unstable radicals. Here, we present a novel thienoviologen derivative, [(NPr)2SV]Cl4, achieved utilizing a meta-substitution approach based on the pristine viologen derivatives ( [(NPr)2V]Cl4). Compared to other ortho- and para-substitution methods, this strategy features a locked plane configuration (0.14°), effectively regulating π-π interactions and suppressing reactivity between radical and oxygen, which is confirmed via X-ray single-crystal structural analyses, spectroscopy techniques, molecular dynamics simulation accompanied by linear ion trap mass spectrometry experiments. Additionally, the meta-substituted [(NPr)2SV]Cl4 significantly improves water solubility (2.39 M), enhances aromaticity, and extends radical lifetime compared with para-substituted [(NPr)2TV]Cl4. Consequently, the cycling stability of the [(NPr)2SV]Cl4-based AORFB over 2500 cycles is 4.1 times higher than that of [(NPr)2TV]Cl4. Furthermore, the 0.5 M battery delivers an impressive 99.83% capacity retention during 200 cycles and a power density of 147 mW cm-2.

Charge Transfer Kinetics and Thermodynamics Control the Energy Conversion Efficiency of a Gallium Phosphide Solar Hydrogen Photocathode.

P-type gallium phosphide (GaP) photocathodes for hydrogen evolution from water have a theoretical energy conversion efficiency of 12% based on the 2.4 eV optical band gap of the material. The performance of actual GaP photocathodes is much lower, for reasons not entirely clear. Here we use vibrating Kelvin probe surface photovoltage (VKP-SPV), open circuit potential (OCP) measurements, and photoelectrochemical (PEC) experiments to evaluate the kinetic and thermodynamic factors that control energy conversion with GaP photocathodes for the hydrogen evolution reaction (HER). We find that the open circuit photovoltage of the bare GaP-H2O junction is limited by recombination at surface states and that an CdS overlayer increases both photovoltage and photocurrent due to formation of a n-p-junction. An optimized GaP/CdS/Pt photocathode drives hydrogen evolution with a quantum efficiency of 62% at 400 nm and 0.0 V RHE and an open circuit photovoltage of 0.43 V at 250 mW cm-2. The Pt cocatalyst increases the photocurrent due to improve HER kinetics but reduces the photovoltage by promoting recombination. Added hydrogen or oxygen gas raise or lower the photovoltage by modifying the electrostatic barrier (band bending) in GaP. This shows that the GaP/CdS junction is not "buried" but behaves like a Schottky junction whose charge separating properties are controlled by the electrochemical potential of the electrolyte. The dynamic junction properties need to be considered in the design of optimized hydrogen evolution photoelectrodes and photocatalysts. Additionally, the work reveals that PEC or OCP measurements tend to underestimate the photovoltage because they do not account for changes in the electrochemical potential at the electrode-liquid contact. In contrast, the VKP-SPV method provides the open circuit photovoltage value directly. By combining the photovoltage data with OCP data, the minority carrier electrochemical potential at the electrode-liquid contact can be measured in a contactless way. This provides an improved understanding of illuminated photoelectrodes for the production of solar fuels.

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.

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.