Applications In Energy Devices Research Articles

Topologically Optimized Anode Catalyst Layers of Proton Exchange Membrane Water Electrolyzers

Climate change and global warming are ongoing global problems that will severely impact the environment if they are not addressed seriously. Replacing traditional fossil fuels with clean and sustainable energy from renewable energy sources, such as wind and solar, is necessary to reduce carbon emissions. However, these renewable energy sources are intermittent and thus require a system to help stabilize power generation. In this regard, hydrogen, the most sustainable form of clean energy, is proposed as a potential energy carrier. In such a system, water electrolyzers are used together with fuel cells. This allows hydrogen to be produced and stored in times of excess power generation. When there is demand and insufficient power generation, the produced hydrogen will be converted into electricity using fuel cells, resulting in a stable power grid. Although fuel cells have been improving significantly, water electrolyzers are an essential bottleneck for the widespread commercialization of the hydrogen economy.Due to the intermittency of renewable energy, the water electrolysis system applied to renewable energy should be able to turn on and off depending on renewable energy sources. As a result, low-temperature water electrolysis has gained widespread attention. Due to its potentially high-performance and high-purity hydrogen gas, the proton exchange membrane water electrolyzer (PEMWE) is one of the most promising technology for producing clean hydrogen. However, concerning widespread industrial use, PEMWE is affected by high costs due to its high loadings of expensive iridium-based catalysts. Therefore, it is necessary to improve its performance. As PEMWE technology grows, the working current density is inevitably higher. When the current density is higher, the amount of oxygen and hydrogen that must be removed from the cell must be more significant to deliver water to the reaction site efficiently. To meet the demands of the application, it is crucial to design an efficient electrode, especially at the anode, where the water must be supplied to the catalyst layer, and, at the same time, it is necessary to transfer oxygen gas from the reaction area to the flow channel.Topology optimization, an emerging tool to optimize physical systems, has recently been applied to systems with multi-physics. However, attempts to implement the approach in the system with reactions still lacked in the literature. Only a few studies were interested in utilizing such an approach in electrochemical energy device applications. Roy et al. [1] used topology optimization to develop the porous electrode. According to the findings, the developed electrode outperformed the traditional electrode. However, topology optimization is just a numerical approach. Our research group showed how a topologically optimized structure of porous reactors connected to the situation of the most uniform and minimum entropy generation [2]. To utilize topology optimization with PEMWE, a model for the anode catalyst layer is necessary. Although there are existing models to simulate the phenomena of PEMWE [3,4], to the best of our knowledge, studies have yet to look into how to model the phenomena inside the anode catalyst layer of the PEMWE.Therefore, the main goal of this study is to develop a model to simulate the physics of the anode and utilize it in topology optimization to search for the optimal structure of the anode catalyst layer. The optimization problem was formulated to maximize the cell performance by controlling the volume fractions of ionomer and catalyst materials. Figure 1a-c displays the heterogeneous structure obtained by topology optimization. The electrochemical reaction increased by approximately 40% compared to a case with the homogeneously distributed electrode. The topologically optimized structure was similar to the structure proposed by Dong et al. [5], where their ordered structure with Ir loading of 0.2 mg cm−2 can significantly decrease the overpotentials compared with conventional MEA with an Ir loading of 2 mg cm−2. Therefore, such a structure might be a way forward for high-performance PEMWE system. Acknowledgment The authors would also like to express their gratitude to Office of the Permanent Secretary, Ministry of Higher Education, Science, Research and Innovation (OPS MHESI) (Grant No. RGNS 65-084), Thailand Science Research and Innovation (TSRI) and King Mongkut’s University of Technology Thonburi. This work was partially supported by Grant-in-Aid for JSPS Fellows number 22J20603 and JSPS KAKENHI Grant number 21H04540 References [1] Roy, T., et al., Struct. Multidiscipl. Optim. 65 (2022) 171.[2] Charoen-amornkitt, P., et al., Int. J. Heat Mass Transf. 202 (2023) 123725[3] Lopata, J., et al., J. Electrochem. Soc., 168 (2021) 054518.[4] Lopata, J.S., et al., Electrochim. Acta, 424 (2022) 140625[5] Dong, S., et al., Nano Lett. (2022) (In Press) Figure 1

Structural and optoelectronic properties of LiYP (Y = Ca, Mg, and Zn) half-Heusler alloy under pressure: A DFT study

By adjusting the lattice geometry through pressure engineering, it is possible to further enhance and customize various properties of materials even at zero pressure. The utilization of pressure allows for the modification of the electronic structure of materials, presenting a relatively new approach to creating essential features for advanced technological applications. These intriguing applications have served as the driving force behind this research, which investigates the behavior of the LiYP (Y = Ca, Mg, and Zn) Half-Heusler (HH) semiconductor. We shed light on the effects of pressure on the optoelectronic and structural characteristics of LiYP (Y = Ca, Mg, and Zn) using the DFT-based Wien2K code. HHs belong to the F 4‾ 3 m space group (No. 216) and are denoted by the chemical symbol XYZ. The calculations were performed by fitting the computed total energy and atomic volume to the Murnaghan equation of state, allowing us to obtain the bulk modulus, first derivatives, and lattice constant. Through the analysis of the partial density of states (PDOS), we evaluated the electronic band structure of LiYP (Y = Ca, Mg, and Zn) under pressures ranging from 0 to 10 GPa. Finally, we examined the optical properties of LiYP and relevant parameters (real part, imaginary part, absorption coefficient and reflectivity coefficient) at different pressure levels. The results obtained from the analysis of optoelectronic properties demonstrate that LiYP (Y = Ca, Mg, and Zn) is suitable for applications in renewable energy devices.

Deep yellow emission and high energy device applications of copper doped orthorhombic zirconium titanate nanoparticles

For the first time, Zirconium titanate doped with copper (1–9 mol %) was synthesized by an aloe vera-mediated combustion route followed by calcination at 700oC. The high crystallinity and pure orthorhombic structure are confirmed through Bragg reflections. The surface morphology consists of larger particles along with agglomeration. The lattice d-spacings and selected area electron diffraction patterns confirm the purity of the sample. The crystallite size increases, whereas the energy band gap determined from Wood and Tauc's relationship decreases. The photoluminescence analysis excited at 471 nm and the Commission Internationale de L'Eclairage (CIE) and color-correlated temperature (CCT) values confirmed that the synthesized sample is a promising candidate for display technology as a yellow nanophosphor. The cyclic voltammetry analysis is performed on the oxidation and redox peaks. Electrochemical impedance spectroscopy (EIS) revealed the ion transport kinetics and supercapacitance values obtained from galvanostatic charge/discharge (GCD) analysis. Specific capacitance values are found to be in the range 290–350 F/g for ZTO:Cu (1–9 mol %) nanoparticles (NPs), respectively. Thus, the present synthesized material might find applications in the fields of display technology and energy storage materials.

Stable and Efficient Dye-Sensitized Solar Cells and Supercapacitors Developed Using Ionic-Liquid-Doped Biopolymer Electrolytes.

An ionic liquid (IL) 1-ethyl, 2-methyl imidazolium thiocyanate incorporated biopolymer system is reported in this communication for applications in dual energy devices, i.e., electric double-layer capacitors (EDLCs) and dye-sensitized solar cells (DSSCs). The solution caste method has been used to synthesize ionic-liquid-incorporated biopolymer electrolyte films. The IL mixed biopolymer electrolytes achieve high ionic conductivity up to the order of 10-3 S/cm with good thermal stability above 250 °C. Electrical, structural, and optical studies of these IL-doped biopolymer electrolyte films are presented in detail. The performance of EDLCs was evaluated using low-frequency electrochemical impedance spectroscopy, cyclic voltammetry, and constant current charge-discharge, while that of DSSCs was assessed using J-V characteristics. The EDLC cells exhibited a high specific capacitance of 200 F/gram, while DSSCs delivered 1.53% efficiency under sun conditions.

Boron monosulfide as an electrocatalyst for the oxygen evolution reaction

The current energy crisis and environmental problems associated with the use of fossil fuels necessitate a transition to clean and sustainable energy carriers like hydrogen produced by electrocatalytic water splitting. Hence, the development of robust, low-cost, and high-performance oxygen evolution reaction (OER) electrocatalysts has attracted considerable attention. Herein, an OER electrocatalyst for use in alkaline media is prepared by hybridising rhombohedral boron monosulfide with graphene to provide electronic conductivity. The catalytic activity of the electrocatalyst (overpotential of 250 mV at 10 mA cm−2) is higher than those of most previously reported counterparts. Our results pave the way for the design of electrocatalysts composed of abundant elements with a wide range of applications in renewable energy devices.

Systematic Conversion of Photoinduced Intramolecular Electron Transfer in Trinuclear M-Ir-M (M = Re, Ir) Complexes to Intersystem Charge Transfer by Coupling to Gold Nanoclusters

Two trinuclear cyclometalated iridium(III)-based complexes of M-Ir-M (M = Re, Ir) type were strategically designed with characteristically different electron distributions based on the electronegativities of Re and Ir. Photoinduced intramolecular electron transfer (PIIET) is readily observed in these complexes with different lifetimes of the radicals. The free amine ends of these symmetric complexes act as the electron donor for PIIET. These ends, on the other hand, can also act as centers for reducing gold (Au) salt (HAuCl4·3H2O) to generate Au atomistic nanoclusters (AuNCs) protected and templated by the trinuclear complexes. Formation of the AuNCs completely stops the PIIET and induces excited state intersystem charge transfer (ESICT) from the surrounding complexes to the AuNC core on exciting the system with radiation of the same wavelength. The trinuclear cyclometalated complexes were synthesized by chelation of the transition metal units, such as Re(CO)3Cl and Ir(ppy)2, to thiosemicarbazone (TSC) appended with cyclometalated ligands of the precursor Ir(III) complex. Such a phenomenon of conversion of PIIET in a trinuclear cyclometalated coordination complex completely to ESICT on coupling to a noble metal nanocluster is unique and promising for applications in energy devices.

Colossal Ionic Conductivity in Interphase Strain-Engineered Nanocomposite Films.

Owing to their wide application in oxide-based electrochemical and energy devices, ion conductors have attracted considerable attention. However, the ionic conductivity of the developed systems is still too low to satisfy the low-temperature application. In this study, by developing the emergent interphase strain engineering method, we achieve a colossal ionic conductivity in SrZrO3-xMgO nanocomposite films, which is over one order of magnitude higher than that of the currently widely used yttria-stabilized zirconia below 673 K. Atomic-scale electron microscopy studies ascribe this superior ionic conductivity to the periodically well-aligned SrZrO3 and MgO nanopillars that feature coherent interfaces. Wherein, a tensile strain as large as +1.7% is introduced into SrZrO3, expanding the c-lattice and distorting the oxygen octahedra to decrease the oxygen migration energy. Combining with theoretical assessments, we clarify the strain-dependent oxygen migration path and energy and unravel the mechanisms for strain-tuned ionic conductivity. This study provides a new scope for the property improvement of wide-range ion conductors by strain engineering.

Proton Conducting Organic-Inorganic Composite Membranes for All-Vanadium Redox Flow Battery.

The quest for a cost-effective, chemically-inert, robust and proton conducting membrane for flow batteries is at its paramount. Perfluorinated membranes suffer severe electrolyte diffusion, whereas conductivity and dimensional stability in engineered thermoplastics depend on the degree of functionalization. Herein, we report surface-modified thermally crosslinked polyvinyl alcohol-silica (PVA-SiO2) membranes for the vanadium redox flow battery (VRFB). Hygroscopic, proton-storing metal oxides such as SiO2, ZrO2 and SnO2 were coated on the membranes via the acid-catalyzed sol-gel strategy. The membranes of PVA-SiO2-Si, PVA-SiO2-Zr and PVA-SiO2-Sn demonstrated excellent oxidative stability in 2 M H2SO4 containing 1.5 M VO2+ ions. The metal oxide layer had good influence on conductivity and zeta potential values. The observed trend for conductivity and zeta potential values was PVA-SiO2-Sn > PVA-SiO2-Si > PVA-SiO2-Zr. In VRFB, the membranes showcased higher Coulombic efficiency than Nafion-117 and stable energy efficiencies over 200 cycles at the 100 mA cm-2 current density. The order of average capacity decay per cycle was PVA-SiO2-Zr < PVA-SiO2-Sn < PVA-SiO2-Si < Nafion-117. PVA-SiO2-Sn had the highest power density of 260 mW cm-2, while the self-discharge for PVA-SiO2-Zr was ~3 times higher than Nafion-117. VRFB performance reflects the potential of the facile surface modification technique to design advanced membranes for energy device applications.

Shifting Oxygen Evolution Reaction Pathway via Activating Lattice Oxygen in Layered Perovskite Oxide

AbstractDeveloping high‐performance oxygen evolution reaction (OER) catalysts are critical for the practical application of many electrochemical energy devices. In this study, taking layered perovskite oxide thin films as the model system, it is demonstrated that the OER pathway can be effectively shifted by activating lattice oxygen, leading to strongly enhanced intrinsic activity. The OER performance of Ruddlesden‐Popper (RP)‐phase cobaltite is significantly enhanced as Sr doping at the A site increases, which is attributed to the shift of the reaction pathway from adsorbate evolution mechanism (AEM) to lattice oxygen‐mediated mechanism (LOM). Advanced spectroscopic techniques and density functional theory calculations reveal that the Sr dopant effectively facilitates oxygen ligand hole formation, charge transfer from the oxygen sites, and the formation and migration of oxygen vacancy, hence promoting lattice oxygen to participate in surface reactions. The results provide critical insight into the role of oxygen activity and offer a potential way for constructing highly active electrocatalysts.

A DFT investigation of mechanical, optical and thermoelectric properties of double perovskites K2AgAsX6 (X = Cl, Br) halides

Focusing on renewable energy device applications, we explored double perovskites K2AgAsX6 (X = Cl, Br) halides for the first time. We used WIEN2k (all-electron method) and BoltzTrap code to investigate optoelectronic and thermoelectric properties for renewable energy device applications. For structural and elastic calculations, we employed PBEsol generalized gradient approximations and found that both halides in the cubic phase are structurally stable. Further, Pugh's and Poisson's predicted values indicate that both halides are ductile. Furthermore, we also calculate the formation energy to check the thermodynamical stability of both halides. For accurate calculations of optoelectronic properties, we applied Tran-Bhala modified Becke and Johnson potential (TB-mBJ). Electronic band structure calculations indicate both halides are indirect bandgap nature having values of 2.1 eV and 1.6 eV, respectively, and might be potential candidates for solar cell applications. We also discussed the optical parameters within the incident photon energy range of 0–12 eV. We found strong absorption in the visible region for K2AgAsX6 (X = Cl, Br) halides indicating both halides are appropriate solar cell devices. Lastly, we calculate thermoelectric parameters against temperature and chemical potential. A probing figure of merit shows halides is also potential candidates for thermoelectric device applications.

Thermal conductivity of yttria‐stabilized zirconia thin films grown by plasma‐enhanced atomic layer deposition

AbstractZirconia doped with yttrium, widely known as yttria‐stabilized zirconia (YSZ), has found recent applications in advanced electronic and energy devices, particularly when deposited in thin film form by atomic layer deposition (ALD). Although ample studies reported the thermal conductivity of YSZ films and coatings, these data were typically limited to Y2O3 concentrations around 8 mol% and thicknesses greater than 1 μm, which were primarily targeted for thermal barrier coating applications. Here, we present the first experimental report of the thermal conductivity of YSZ thin films (∼50 nm), deposited by plasma‐enhanced ALD (PEALD), with variable Y2O3 content (0–36.9 mol%). Time‐domain thermoreflectance measures the effective thermal conductivity of the film and its interfaces, independently confirmed with frequency‐domain thermoreflectance. The effective thermal conductivity decreases from 1.85 to 1.22 W m−1 K−1 with increasing Y2O3 doping concentration from 0 to 7.7 mol%, predominantly due to increased phonon scattering by oxygen vacancies, and exhibits relatively weak concentration dependence above 7.7 mol%. The effective thermal conductivities of our PEALD YSZ films are higher by ∼15%–128% than those reported previously for thermal ALD YSZ films with similar composition. We attribute this to the relatively larger grain sizes (∼23–27 nm) of our films.

Effect of non-local hybrid functional on electronic band structure, manipulation of photocatalytic properties and optical response of Cu alloyed NaMgF3

In the context of eco-friendly renewable hydrogen energy production, it is imperative to compute the band edges positions and the effect of dopant concentration on the energy-harnessing capability of a designed photocatalyst. Ergo we investigated NaMgF3 fluoro-perovskite due to its novel and intriguing optical properties using Density functional theory (DFT). The impact of Cu on the band edge positions of NaMgF3, structural, electronic, and optical features is explored herein using Perdew-Burke-Ernzerhof generalized gradient approximation (GGA-PBE) and Ultrasoft pseudo potential (USSP) method. Electronic properties have been computed with Heyd–Scuseria– Ernzerhof (HSE03) hybrid functional to get experimentally comparable results, when sodium was replaced by Cu in NaMgF3 fluoro-perovskite up to 100%. The lattice parameters (a = b) show a quasi-linear increasing trend while alloying with Cu unlike the c-lattice parameter, which first increases and then decreases for Cu concentration above 40%. A cubic to pseudocubic tetragonal transition was also seen as a result of Cu inclusion at the Na site. The Bandgap enhancement of 7.393 eV is observed for HSE03 hybrid potential for pristine NaMgF3, in contrast with its GGA-PBE counterpart (5.75 eV). In addition, the band gap topology is found to be consistent for local and nonlocal hybrid potentials and shows decreasing trend upon alloying with Cu. The reduction in band gap infers the location of CBE just below the reduction edge of NHE for 33% Cu inclusion in NaMgF3 and hence is considered a suitable alloying concentration for the photodegradation of chemical dyes. Optical properties such as absorption, reflectivity, refractive index, dielectric function, and energy loss function were computed and an apparent red shift was observed after Cu inclusion. The static refractive index and dielectric function for pure NaMgF3 were found to be 1.45 and 1.95 respectively, and a linear behavior was observed after alloying in all optical parameters. Hence Cu alloyed NaMgF3 can possess possible future applications in optoelectronic and energy devices.

Novel Co-doped nickel hydroxyfluorides with rapid electron transfer for high-performance supercapacitors

Transition metal electrode materials are promising for applications in high-energy and power-density rechargeable energy devices. However, their poor intrinsic conductivities and limited redox kinetics hinder the rapid energy supply at high current densities. Herein, a series of Co-doped nickel hydroxyfluorides (Co-Ni(OH)F) was constructed as new electrode materials to maximize the charge storage ability at different current densities. The introduction of Co did not only induce abundant defects for regulating the electronic structure but also fine-tuned the surface morphology and shortened the ion/electron diffusion distance. The coexistence of multiple oxidation states of Ni and Co species provided abundant redox processes and effectively enhanced the electrochemical activities. The relationship between Co2+ doping and the increase in conductivity of the system was further confirmed by the calculated density of states (DOS). The optimized Co-Ni(OH)F (Co=20%) electrode material exhibited an ultrahigh specific capacity of 3380.2 F g−1 at a current density of 1 A g−1. Even at an enhanced current density of 20 A g−1, the optimized electrode showed a superior capacity retention rate of 78.4%. After 5000 cycles at a high current density of 30 A g−1, the electrode retained 76.3% of its original capacity. Furthermore, the Co-Ni(OH)F (Co=20%)//Bi2O3 asymmetric device delivered an ultrahigh density of 139.8 Wh kg−1 at a power density of 800 W kg−1, suggesting superior energy density than previously reported systems. Overall, new insights into the rational design of novel high-capacity and high-rate electrode materials were provided, promising for the construction of advanced energy devices.

Unraveling Thermal Transport Correlated with Atomistic Structures in Amorphous Gallium Oxide via Machine Learning Combined with Experiments.

Thermal transport properties of amorphous materials are crucial for their emerging applications in energy and electronic devices. However, understanding and controlling thermal transport in disordered materials remains an outstanding challenge, owing to the intrinsic limitations of computational techniques and the lack of physically intuitive descriptors for complex atomistic structures. Here, it is shown how combining machine-learning-based models and experimental observations can help to accurately describe realistic structures, thermal transport properties, and structure-property maps for disordered materials, which is illustrated by a practical application on gallium oxide. First, the experimental evidence is reported to demonstrate that machine-learning interatomic potentials, generated in a self-guided fashion with minimum quantum-mechanical computations, enable the accurate modeling of amorphous gallium oxide and its thermal transport properties. The atomistic simulations then reveal the microscopic changes in the short-range and medium-range order with density and elucidate how these changes can reduce localization modes and enhance coherences' contribution to heat transport. Finally, a physics-inspired structural descriptor for disordered phases is proposed, with which the underlying relationship between structures and thermal conductivities is predicted in a linear form. This work may shed light on the future accelerated exploration of thermal transport properties and mechanisms in disordered functional materials.

Analysis of wave energy device dynamics and power optimization

As an important renewable resource, wave energy has considerable development value and application prospects. How to design a wave energy conversion device to maximize the output power is an urgent problem in its practical application. In this paper, we mainly study the principle of wave energy device capacity, the motion and power model of the constructed wave energy device, and finally design a specific scheme to achieve the maximum output power of wave energy through kinetic analysis, the fourth-order ordinary differential equation solved by the Longacurta method, and the Simpson integral method. At the end of the paper, the developed model is objectively evaluated and the potential value of the developed model in practical wave energy device applications is illustrated.

Metal Oxide-Supported Metal Catalysts for Electrocatalytic Oxygen Reduction Reaction: Characterization Methods, Modulation Strategies, and Recent Progress.

The sluggish kinetics of the oxygen reduction reaction (ORR) with complex multielectron transfer steps significantly limits the large-scale application of electrochemical energy devices, including metal-air batteries and fuel cells. Recent years witnessed the development of metal oxide-supported metal catalysts (MOSMCs), covering single atoms, clusters, and nanoparticles. As alternatives to conventional carbon-dispersed metal catalysts, MOSMCs are gaining increasing interest due to their unique electronic configuration and potentially high corrosion resistance. By engineering the metal oxide substrate, supported metal, and their interactions, MOSMCs can be facilely modulated. Significant progress has been made in advancing MOSMCs for ORR, and their further development warrants advanced characterization methods to better understand MOSMCs and precise modulation strategies to boost their functionalities. In this regard, a comprehensive review of MOSMCs for ORR is still lacking despite this fast-developing field. To eliminate this gap, advanced characterization methods are introduced for clarifying MOSMCs experimentally and theoretically, discuss critical methods of boosting their intrinsic activities and number of active sites, and systematically overview the status of MOSMCs based on different metal oxide substrates for ORR. By conveying methods, research status, critical challenges, and perspectives, this review will rationally promote the design of MOSMCs for electrochemical energy devices.

Optimizing the thermal performance of the thermosyphon heat pipe for energy saving with graphene oxide nanofluid

A thermosyphon heat pipe (THP) involves a vacuum tube with a specific quantity of liquid. Due to its simplicity of design and structure, THP has many applications in heat recovery and renewable energy devices. Prior studies showed that using stable nanofluids can improve THPs' energy efficiency. In this evaluation, the effect of working fluid type, input heat, two types of surfactants, and nanoparticle concentration on the energy efficiency and thermal resistance of a THP was investigated and optimized. A magnetic stirrer and ultrasonic waves were used to create stability. Imaging and spectrophotometric analysis showed that graphene oxide (GO) nanofluid with SDS surfactant is more stable. The most notable decrease in thermal resistance at an input power of 100 W with GO nanofluids compared to distilled water at an F.R. of 50% was 12%. The highest decrease in the evaporator temperature section was achieved with GO and SDS surfactant at a weight ratio of 0.3% wt, equal to 12.3 °C. This was also confirmed by measuring the contact angle. The highest percentage increase in thermal efficiency of THP with the mixture of GO nanoparticles and SDS surfactant in distilled water with 0.3 wt percent and input heat of 200 W was 18% compared to distilled water. In the optimum condition, the highest percentage increase in thermal efficiency of THP with the mixture of GO nanoparticles and SDS surfactant in distilled water with 0.3 wt percent and input heat of 200 W was 18% compared to distilled water.

N, S co-doped carbon film wrapped Co nanoparticles for boosting oxygen reduction reaction

Electrochemical energy (e.g., fuel cell and metal-air batteries) is featured by large theoretical energy density, high conversion efficiency, safe operation and pollution-free emission. However, the sluggish dynamics of oxygen reduction reaction (ORR) and high cost of noble metals hinder their widespread commercial applications in electrochemical energy devices. Herein, we present a method for the preparation of the N, S co-doped carbon film wrapped Co nanoparticles (Co/NSC) for ORR by aging and then pyrolyzing the mixture of cobalt salt and 1-(p-Toluenesulfonyl)imidazole. The co-doping of N and S facilitates the electron rearrangement of the carbon film, resulting in a rapid electron transfer. The core-shell structure enhances the interaction between N, S co-doped carbon film and Co nanoparticles. These features endow the Co/NSC catalyst an excellent ORR with a half-wave potential of 0.860 V and limiting current density of 6.2 mA cm-2, besides the superior anti-methanol. The Co/NSC catalyst as the air cathode grants the assembled zinc-air battery high open circuit voltage (1.467 V), large peak power density (156.2 mW cm-2), great specific capacity (747.9 mAh gZn-1), and excellent stability. Thus, the prepared Co/NSC catalyst exhibits a promising application in zinc-air battery. This work provides an approach for the synthesis of the carbon-shell coated non-noble metal catalyst and its subsequent applications in oxygen electrocatalysis.

Scalable and Controllable Synthesis of Pt‐Ni Bunched‐Nanocages Aerogels as Efficient Electrocatalysts for Oxygen Reduction Reaction

AbstractDeveloping efficient and stable Pt‐based oxygen reduction reaction (ORR) electrocatalysts via both economical and controllable routes is critical for the practical application of electrochemical energy devices. Herein, a scalable, controllable, and general ambient‐O2‐involved aqueous‐solution cultivating strategy to prepare PtxMy (M = Ni, Fe, Co) bunched‐nanocages aerogels (BNCs AG) is demonstrated, based on a newly established high‐M‐to‐Pt‐precursor‐ratio‐and‐B‐incorporation‐facilitated M‐rich core and Pt‐rich shell hydrogel formation process. The Pt83Ni17 BNCs AG shows prominent ORR performance with a mass activity (MA) of 1.95 A mgPt−1 and specific activity of 3.55 mA cm−2, which are 8.9‐times and 9.6‐times that of Pt supported on carbon (Pt/C), respectively. Particularly, the Pt83Ni17 BNCs AG displays greatly enhanced durability (MA 82.6% retention) compared to Pt/C (MA 31.8% retention) after a 20 000‐cycles accelerated durability test. Systematic studies including density functional theory calculations uncover that the excellent activity is closely related to the optimized ligand and strain effects with the optimized Ni content in this aerogel; the outstanding durability is endowed by the lowered‐down Ni leaching with the optimized Pt/Ni ratio and the inhibited sintering due to its appropriate porosity. This work provides new perspectives on the development of electrocatalysts with both high performance and low cost.

Enhancing solar energy harvest by Cu2S/CuCl heteroarrays with enriched sulfur vacancies for photo-rechargeable pseudocapacitors

The use of broadband light energy is important for enhancing photoenergy conversion. However, bifunctional materials that can efficiently harvest solar energy to assist electrochemical energy storage are difficult to prepare. Herein, copper foam (CF)-supported cuprous sulfide (Cu2S) heteroarrays (CS HAs) with enriched sulfur (S) vacancies (VS) were designed for photo-rechargeable pseudocapacitors. A direct hydrothermal sulfurization of CF first resulted in the growth of CS HAs with leaf-like heterostructures. Subsequent partial oxidation of S2− in FeCl3 aqueous solution enriched the VS within the leaf-like structures. In addition, CuCl and Cu2O were formed from Cu2S during FeCl3 treatment to derive a bifunctional photoelectrode with ternary components, thus further broadening the light absorption region. Thus, the optimal CS HAs have demonstrated areal capacitances of 1440−1048 mF cm−2 with the assistance of the photoelectric/thermal effects of light energy, delivering remarkable photoenhancements of 25%–35%. The asymmetrical pseudocapacitors fabricated from the optimal photoelectrodes delivered a high areal capacitance of 670 mF cm−2 after 6000 cycles, suggesting a promising application in transparent light-driven energy devices.