Field Of Energy Conversion Research Articles

Size-dependent effects of the thermal transport at gold nanoparticle-water interfaces.

The transfer of heat from a plasmonic nanoparticle to its water environment has numerous applications in the fields of solar energy conversion and photothermal therapies. Here, we use nonequilibrium molecular dynamics to investigate the size dependence of the interfacial thermal conductance of gold nanoparticles immersed in water and with tunable wettability. The interfacial thermal conductance is found to increase when the nanoparticle size decreases. We rationalize such a behavior with a generalized acoustic model, where the interfacial bonding decreases with the nanoparticle size. The analysis of the interfacial thermal spectrum reveals the importance of the low frequency peak of the nanoparticle spectrum as it matches relatively well the oxygen peak in the vibrational spectrum. However, by reducing the nanoparticle size, the low frequency peak is exacerbated, explaining the enhanced heat transfer observed for small nanoparticles. Finally, we assess the accuracy of the continuum heat transfer equations to describe the thermal relaxation of small nanoparticles with initial high temperatures. We show that, before the nanoparticle loses its integrity, the continuum model succeeds in describing with small percentage deviations the molecular dynamics data. This work brings a simple methodology to understand, beyond the plasmonic nanoparticles, thermal boundary conductance between a nanoparticle and its environment.

Highly Efficient Electrocatalytic Oxygen Evolution Over Atomically Dispersed Synergistic Ni/Co Dual Sites

Single-atom catalysts (SACs) are being pursued as economical electrocatalysts. However, their low active-site loading, poor interactions, and unclear catalytic mechanism call for significant advances. Herein, atomically dispersed Ni/Co dual sites anchored on nitrogen-doped carbon (a-NiCo/NC) hollow prisms are rationally designed and synthesized. Benefiting from the atomically dispersed dual-metal sites and their synergistic interactions, the obtained a-NiCo/NC sample exhibits superior electrocatalytic activity and kinetics towards the oxygen evolution reaction. Moreover, density functional theory calculations indicate that the strong synergistic interactions from heteronuclear paired Ni/Co dual sites lead to the optimization of the electronic structure and the reduced reaction energy barrier. This work provides a promising strategy for the synthesis of high-efficiency atomically dispersed dual-site SACs in the field of electrochemical energy storage and conversion.

The Novel Ionic Liquid and Its Related Self‐Assembly in the Areas of Energy Storage and Conversion

Ionic liquids (ILs) are one kind of molten salts, which have been widely used across multiple disciplines in science and engineering. The recent development makes ILs no longer just as the solvent, and more attention has been put to applications of their unique structure and functionalities. This raises the importance to explore advanced IL‐derived materials, which retain most of the characteristics of ILs and are endowed with new features, namely novel ILs. The novel ILs, including deep eutectic solvents (DESs), poly(ionic liquid)s (PILs), ionic liquid crystals (ILCs), and redox‐active ionic liquids (RAILs), have distinct advantages over traditional ILs, such as enhancing the reaction rate, selectivity, and productivity in various chemical reactions. Given the unique physical and chemical properties, electrochemical behavior, and self‐assembled structures, novel ILs have emerged as promising materials in various applications, specifically in energy storage and conversion. Herein, the intrinsic properties of novel ILs and their related self‐assembly behavior in advanced energy storage technology are focused. And the perspectives and challenges of novel ILs in the fields of energy storage and conversion are also proposed.

Tri-functional aerogel photocatalyst with an S-scheme heterojunction for the efficient removal of dyes and antibiotic and hydrogen generation

A novel three-dimensional (3D) S-scheme S-gC3N4/TiO2/SiO2/PAN aerogel heterojunction photocatalyst (denoted as S-gTAHP) is rationally devised and manufactured by combining electrospinning, calcination, hydrothermal and freeze-drying techniques. The synthesized S-gC3N4 molecule is different from traditional g-C3N4, which has a small molecular structure similar to melamine. S-gC3N4 is embedded in the interwoven network structure of TiO2/PAN short fibers, and the catalytic system of the S-scheme heterojunction is formed with SiO2 as a crosslinking agent. S-gTAHP achieves perfect tri-functional photocatalytic capability, including remarkable hydrogen release capacity (806.7 μmol∙h−1∙g−1), efficient removal of three colored dyes with removal efficiencies up to 99.43% (MB, 15 min), 96.13% (RhB, 30 min) and 91.32% (MO, 40 min), and a degradation rate of the colorless antibiotic TCH reaching 84.20% in 40 min driven by simulated sunlight. Meanwhile, the effects of pH values and concentrations of contaminant solutions on the removal rates are explored, and the S-scheme mechanism of S-gTAHP strengthening photocatalytic activity is elucidated. The apparently heightened photocatalytic activities of S-gTAHP can be ascribed to the fact that the 3D hierarchical porous structure of the aerogel endows more active centers and enhanced light-harvesting capacity, and the S-scheme heterojunction supplies effective charge migrating channels, thereby affording the carriers with strong redox capability. Furthermore, S-gTAHP holds prominent reusability and is light weight. Hence, efficient and recyclable 3D aerogel photocatalysts with S-scheme heterojunctions have broad application prospects in practical sewage treatment and energy conversion fields.

Porous carbon framework decorated with carbon nanotubes encapsulating cobalt phosphide for efficient overall water splitting

Exploration of catalysts for water splitting is critical for advancing the development of energy conversion field, but designing bifunctional catalysts remains a major challenge. Herein, we demonstrate the N-doped carbon nanotube (NCNT)-grafted N-doped carbon (NC) framework embedding CoP nanoparticles (CoP@NC/NCNT) as hydrogen and oxygen evolution reaction (HER and OER) catalysts for water splitting. As a result, the CoP@NC/NCNT electrode requires the overpotentials of 106 and 177 mV at 10 mA cm−2 in 0.5 M H2SO4 and 1.0 M KOH solutions for HER, respectively. Moreover, an overpotential of 324 mV for OER can drive 10 mA cm−2 in 1.0 KOH. The CoP@NC/NCNT-based electrolyzer derives a current density of 10 mA cm−2 at a low voltage of 1.72 V in 1.0 M KOH and remains stable for 10 h. The outstanding electrocatalytic performance is mainly attributed to the hierarchical structure with rich branches and highly active component of CoP. The intimate contacts between hierarchical porous NC frameworks by cross-linked NCNTs create a 3D conductive network, which facilitates electron or mass transfer and activates CoP. This work offers a novel route for preparing hierarchical carbon framework encapsulated metal phosphide particles for potential applications in energy conversion field.

Nitrogen-doped hollow carbon polyhedron derived from metal-organic frameworks for supercapacitors

Metal-organic frameworks (MOFs) derived carbon materials have great potential to be utilized as electrode materials in the field of energy storage and conversion. In the present work, nitrogen-doped hollow carbon polyhedron and hollow carbon sphere are synthesized using MOFs coated with carboxylated polystyrene (PS) microspheres as precursors. The morphology evolution of the hollow carbon has been discussed, which are subject to the reactant concentration and solvothermal temperature. The as-prepared hollow carbon has superior electrochemical performances for supercapacitors, owning to the hollow structure, high specific areas and nitrogen doping. The discharge specific capacitances of the hollow carbon polyhedron and hollow carbon sphere are respectively 160.2 F/g and 186.4 F/g under 0.2 A/g current density. Furthermore, the capacitance retentions of the hollow carbon polyhedron and hollow carbon sphere are 96.4 % and 98.9 % after 10,000 cycles, presenting excellent cycling stability. This work could provide new insight into the controllable design and synthesis of hollow carbon materials for energy storage.

An enhanced-performance Al-air battery optimizing the alkaline electrolyte with a strong Lewis acid ZnCl2

Al-air batteries are regarded as the potential energy conversion systems due to the ultra-high theoretical specific capacity of 2980 mAh/g and specific energy of 8100 mWh/g for Al anodes. However, the anodic self-corrosion has severely limited the energy efficiency, which induces a great challenge to the commercial penetration of Al-air batteries. Here, we present an alkaline electrolyte optimization with a single inorganic Zn-compound, where a strong Lewis acid ZnCl2 has the best modification effect for Al-air battery compared with ZnO and ZnCO3. The results demonstrate that the inhibition efficiency of Al anode is up to 83.03% under the adsorption of strong Lewis acid groups on the Zn protective film. The high specific capacity of 2322.91 mAh/g and specific energy of 2457.02 mWh/g for Al-air battery are obtained at the galvanostatic condition of 20 mA/cm2, and the anode efficiency is enhanced to 77.95% after ZnCl2 optimization. Moreover, the optimization mechanism is revealed, which provides a technical basis for the application of the enhanced-performance Al-air batteries in the fields of energy conversion and power supply.

Coupling boron-modulated bimetallic oxyhydroxide with photosensitive polymer enable highly-active and ultra-stable seawater splitting

Seawater photoelectrolysis is showing huge potential in green energy conversion field, yet it is still a formidable challenge to develop one catalyst that can drive the electrolysis reaction stably, economically and efficiently. Motivated by this point, the inorganic–organic hybridization strategy is proposed to in-situ construct one hierarchical electrode via concurrent electroless plating and polymerization, which assures the growth of boron-modulated nickel–cobalt oxyhydroxide nanoballs and photosensitive polyaniline nanochains on the self-supporting Ti-based foil (B-CoNiOOH/PANI@TiO2/Ti). Upon inducing photoelectric effect (PEE), the designed target electrode delivers overpotentials as low as 196 and 398 mV at 100 mA cm−2 for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), respectively, corresponding to an activity enhancement by about 15% as compared to those without PEE. Inspiringly, when served as bifunctional electrocatalysts for overall seawater electrolysis, it can stably maintain at 200 mA cm−2 with negligible decay over 72 h. Further analysis reveals that the exceptional catalytic performance can be credit to the B-CoNiOOH, polyaniline (PANI) and TiO2 subunit coupling-induced physically and chemically synergistic catalysis effect such as admirable composition stability, photoelectric function and adhesion capability. The finding in this contribution may trigger much more broad interest to the novel hybrid catalysts consisting of photosensitive polymer and transition metal-based electrocatalysts.

A novel infrared electrochromic device based on Ti3C2Tx MXene

Due to its unique two-dimensional structure, MXene has attracted extensive attention in the fields of electrochemical energy storage and conversion, photothermal conversion, and electromagnetic shielding. With the capacitive and photoelectric properties combined, an infrared electrochromic device based on Ti3C2Tx MXene is created and employed for dynamic thermal radiation regulation. The device exhibits dynamic emissivity variations of 0.31, 0.24, and 0.23 in the wavelength bands of 3–5 μm, 8–14 μm, and 2.5–18 μm, respectively. However, the regulation mechanism of MXene’s infrared emissivity is not clear. In this work, the morphology, structures, and electrochemical properties of MXene were characterized and analyzed. The results reveal that the reason for MXene's emissivity variation is related to the changes in the free O-terminal groups caused by Li-ion intercalation/deintercalation. This paper creates a new application of MXene in the field of dynamic regulation of thermal radiation.

Emerging Investigators in Electrochemical Energy Conversion and Storage 2022

Abstract This special issue features the 2022 Emerging Investigators in Electrochemical Energy Conversion and Storage. Eleven emerging investigators were invited to this special issue to showcase up-and-coming scientists and engineers in the field of electrochemical energy conversion and storage. Emerging investigators are typically in the early stages of their independent careers (within about 12 years following graduation with a doctorate degree), and have demonstrated potential for high impact in the field. The purpose of this special issue will be to highlight emerging engineers and scientists who are internationally recognized for making outstanding contributions to the electrochemical energy conversion and storage field. The JEECS associate editors and guest editors have contributed to the suggestion of invitees and to the review of invited manuscripts for this special issue. We also thank the reviewers for their careful and diligent review of the invited work.

Manganese and cobalt bimetallic-doped Prussian blue analogs as a bifunctional electrocatalyst for zinc-air batteries

Zinc-air battery is a novel safe and environment-friendly energy storage device, but the noble-metal electrocatalysts at the air electrode urge people to search for new substitutes. Herein, different ratios of manganese (Mn) and cobalt (Co) are doped into the iron Prussian blue analogs (PBAs) and used as bifunctional electrocatalysts. The Mn1.33Co0.67-PBA shows the outstanding electrocatalytic properties that the half-wave potential is 0.79 V, the Ej=10 of OER is 1.54 V, and the ΔE is as low as 0.75 V, which is superior to that of Pt/C + RuO2 system (0.78 V). Benefiting from the bimetallic-doping advantage, the Mn1.33Co0.67-PBA has good stability in alkaline solutions. Besides, the Mn1.33Co0.67-PBA was assembled into ZAB, possessing a high maximum power density of 161 mW cm−2 and a large specific capacity of 617 mAh g−1, as well as excellent cycle stability. The as-prepared bimetallic-doped PBA has the potential for applications in the energy storage and conversion field.

Promising water splitting applications of synergistically assembled robust orthorhombic CoSe2 and 2D Ti3C2Tx MXene hybrid

In prospect to the unrelenting energy demand, the hunt for clean,green, sustainable and renewable energy sources has been the focal research area in the fast few decades. Hydrogen energy can be an impeccable substitute for non-renewable fossil fuels and the concern of energy crunch can be circumvented. The production of oxygen and hydrogen from water electrolysis (otherwise known as hydrogen evolution reaction-HER and oxygen evolution reaction-OER, the half-cell reactions) is one of the most clean and green energy productions. Cost-effective, noble metal free, efficient and robust electrocatalysts are needed to address the aforementioned stumbling. Herein, we have synergistically designed a robust-interface involving orthorhombic CoSe2 nanorods and two dimensional Ti3C2Tx MXene sheets for promising overall water splitting application. The above-mentioned catalyst was characterized comprehensively through XRD, FESEM, EDAX, HRTEM, XPS and BET surface area analysis. In terms of electrocatalytic activity, the catalyst performance was incredible in both HER and OER. The amalgamated catalyst exhibited a rapid charge transfer kinetic metrics and attained an overpotential of 230 mV and 65 mV/dec of Tafel value for effectual HER application whereas for OER, the catalyst revealed 270 mV of overpotential and 71 mV/dec of Tafel slope at 10 mA/cm2. In both cases the catalyst withstands a long-term stability test for more than 12 h and the after-stability polarization curves just matched with the before stability LSV curves conveying the idea of the robustness of the material. We hope this catalyst can be turned out to be a frontier in the field of energy conversion owing to its better charge transfer characteristics, lager surface area, ample electrochemical active sites and high hydrogen binding along with high dissociations which can be ascribed to the synergistic effect.

Promising N, P Co‐doped Porous Carbon Materials as Metal‐Free Electrocatalyst for Oxygen Reduction Reaction in Alkaline Medium

AbstractDeveloping an efficient metal‐free electrocatalyst to compete with the noble metal‐based catalysts for oxygen reduction reaction (ORR) is of great significance in the field of energy storage and conversion. We have designed a metal‐free electrocatalyst via dual doping of nitrogen and phosphorus in a porous carbon structure from a cyclotripolyphosphazene (CTP)‐based polymer. The optimized material (CTP‐800) demonstrates an excellent ORR catalytic performance with an onset potential of 0.89 V, a high limiting current density of 4.58 mA cm−2, and a favorable 4‐electrons mediated reaction mechanism in the KOH electrolyte. Moreover, the electrochemical stability, as well as methanol compatibility of CTP‐800, are superior to the commercially available Pt/C catalyst. The remarkable electrocatalytic performance of CTP‐800 can be credited to the high surface area with rich micropores/mesopores and homogenous distribution of heteroatoms.

Low-Dimensional Nanomaterial Systems Formed by IVA Group Elements Allow Energy Conversion Materials to Flourish

In response to the exhaustion of traditional energy, green and efficient energy conversion has attracted growing attention. The IVA group elements, especially carbon, are widely distributed and stable in the earth’s crust, and have received a lot of attention from scientists. The low-dimensional structures composed of IVA group elements have special energy band structure and electrical properties, which allow them to show more excellent performance in the fields of energy conversion. In recent years, the diversification of synthesis and optimization of properties of IVA group elements low-dimensional nanomaterials (IVA-LD) contributed to the flourishing development of related fields. This paper reviews the properties and synthesis methods of IVA-LD for energy conversion devices, as well as their current applications in major fields such as ion battery, moisture electricity generation, and solar-driven evaporation. Finally, the prospects and challenges faced by the IVA-LD in the field of energy conversion are discussed.

An Efficient Electrocatalyst (PtCo/C) for the Oxygen Reduction Reaction

The oxygen reduction reaction (ORR) is paid much more attention because of the high overpotential required for driving the four-electron process in the field of storage and sustainable energy conversion, including fuel cell applications. In this paper, PtCo nanoparticles encapsulated on carbon supports were prepared by a simple modified polyol method with ethylene glycol. Structural as well as electrochemical characterizations illustrated that the PtCo/C electrocatalysts had a minimum particle size of 4.8 nm, which is close to the commercial 40 wt% Pt/JM. Moreover, the electrochemical measurements indicated that ORR activity was competitive with the commercial 40 wt% Pt/JM catalyst. The synthesis method is a critical way to produce PtCo/C catalysts for use in polymer electrolyte membranes in fuel cells (PEMFCs).

Iridium‐Doped 10H‐Phase Perovskite BaCo0.8Fe0.15Ir0.05O3–δ as an Efficient Oxygen Evolution Reaction Catalyst

Comprehensive SummaryDesigning low‐cost and high‐performance catalysts of electrocatalytic oxygen evolution reaction (OER) has always been one of the hot topics in current research. Hexagonal perovskite materials show great application potential in this field. Here, we synthesized 5% Iridium (Ir)‐doped hexagonal phase perovskite BaCo0.8Fe0.15Ir0.05O3–δ (BCFI). Using the Rietveld method to refine the structure, combining with the spherical aberration corrected high‐angle annular dark‐field scanning transmission electron microscopy (HAADF‐STEM) atomic imaging, we found that BCFI is a ten‐layer hexagonal (10H) structure, which belongs to the Pm2 space group. In addition, BCFI shows excellent OER catalytic effect and good stability in 1 mol/L KOH solution, and the overpotential reaches 294 mV at a current density of 10 mA cm–2. The reduction of Cobalt (Co) valence state induced by Ir doping significantly enhances the OER activity of BCFI. Meanwhile, density functional theory (DFT) calculations show that the 2p‐band center of oxygen (O) in BCFI is closer to the Fermi level than that in undoped BaCo0.8Fe0.2O3‐δ (BCF), which is beneficial to the OER. This work reveals a novel 10H‐BCFI material with excellent OER performance, and provides a basis for the design of hexagonal perovskite materials in OER and other energy conversion fields.

FeS2 Nanoparticles Encapsulated in S/N Co-Doped Carbon Nanofibers With a Three-Dimensional Multi-Channel Structure for Lithium-Ion Batteries.

Pyrite (FeS2) is one of the potential candidates for advanced rechargeable Li-ion batteries (LIBs) owing to its inherent capacity (849 mAh g-1), environmental friendliness, and abundant natural resources. However, the volume expansion of FeS2 and the dissolution of polysulfide in the electrochemical reaction severely limit its application in the field of energy conversion and storage. Herein, FeS2 nanoparticles are encapsulated in S/N co-doped three-dimensional multi-channel structural carbon nanofibers (FeS2@CNFs) through the electrospinning method. As a cathode material for LIBs, FeS2@CNFs demonstrated excellent rate property and cyclic stability. The 3FeS2@CNFs (weight ratio of FeS2 is 30%) present the initial capacity of 1,336.7mAh g-1 and the remaining 856.5 mAh g-1 at 0.02Ag-1 after 100 circles. The favorable electrochemical properties have confirmed that carbon nanofibers can enhance the electroconductivity of electrodes, reduce the volume collapse of FeS2, and remit the dissolution of polysulfide during the Li+ ions insertion/de-insertion process. In addition, co-doped S/N can supply abundant active sites for electrochemical reactions, providing enough space for Li+ ion storage. The results indicate that 3FeS2@CNFs is a cathode with a developmental prospect for LIBs.

Enhancement of Stability of Bi2O3-Based Ionic Conductor Via Microstructural Tuning

Oxygen-ion conductors with superior performance have been sought in the fields of energy conversion and storage.[1] Bi2O3-based ionic conductors which exhibit the highest known oxygen-ion conductivity have got attention for the next-generation solid electrolytes.[2] However, at intermediate temperatures below ~ 600 °C, their conductivity degrades rapidly owing to the cubic-to-rhombohedral phase transformation. Here, we demonstrate that grain boundary engineering can preserve the superior ionic conductivity of stabilized Bi2O3. To investigate the microstructural effect on stability, epitaxial and nano-polycrystalline model films of Er0.25Bi0.75O1.5 were fabricated by pulsed laser deposition. Interestingly, the grain boundary-free epitaxial film significantly improved the stability of the cubic phase while severe degradation is observed in conductivity of its polycrystalline counterpart. First-principles calculations revealed that thermodynamic stability of the cubic phase with respect to the rhombohedral counterpart is reduced near grain boundaries. These findings suggest novel aspects into the development of highly durable superionic conductors via physical manipulation of microstructure.

(Invited) Charge Attachment–Induced Transport: Toward New Paradigms in Solid State Electrochemistry

Modern applications in solid state electrochemistry, e.g. in the field of energy storage and conversion, involve the transport of charge carriers through surfaces or interfaces as a key aspect. Many of the electrochemical concepts in fact originate from the field of liquid state electrochemistry. The transfer of concepts from the liquid to the solid state causes some problems which have been addressed in a recent review [1]. This contribution coveres some of the topics from ref. [1] e.g. (i) electrode potentials and half-cell potentials, (ii) charge carrier blocking and dielectric breakdown, and (iii) activities versus particle densities. Additional topics to be discussed are transfer of charge carriers across interfaces, work functions and electrodeposition.Many of these topics can be addressed by the charge attachment–induced transport technique developed in the authors group. The discussion involves modifying some of the paradigms we became acquainted to in the liquid state.[1] K.-M. Weitzel, Current opinion in electrochemistry, 26:100672, (2021)

(Keynote) Bioelectrocatalytic Systems Based on Microcapsules, Glyconanoparticles and Microcavities

For four decades, the functionalization of electrodes by biomaterials based on electrogenerated polymers, carbon nanotubes and / or nano-objects, was widely used in the field of analytical chemistry and energy conversion. Recently, we redesigned enzymatic bioelectrodes in order to produce original objects. An innovative concept of reagentless biosensors based on enzymatic reduction of oxygen was developed by trapping and releasing the substrate of the enzyme (catechol) from the structure of the biosensor. A polyurethane support modified by two perforated microcapsules filled with catechol was easily transformed into a bioelectrode by the successive deposition of multiwalled carbon nanotubes and a mixture of laponite clay and tyrosinase enzyme [1].On the other hand, the development of glyconanoparticles resulting from the self-assembly of block copolymers composed of polystyrene and cyclodextrin as an inclusion site will be reported. These glyconanoparticles, which are stable in suspension in aqueous media, have an outer layer composed of cyclodextrin [2]. The latter allows a post-functionalization of the nanoparticle by hydrophobic molecules through host-guest interactions. It appears that it is possible to modulate the site density of βCD at the surface of the shell of the hybrid glyconanoparticles while maintaining its inclusion properties. Moreover, the anchoring of glyconanoparticles to the surface of electrodes has been carried out by host-guest interactions with electrogenerated polymers. The efficient immobilization of the nanoparticles allows the anchoring of multilayers of biotinylated glucose oxidase.Finally, a new generation of bioelectrodes for oxygen reduction and electrical energy production will be described. This approach is based on the design of flat electrodes made of permeable and conductive materials defining a very thin microcavity with a large surface area containing, in a microvolume, enzymes in powder form. The concept has been demonstrated with bilirubin oxidase (BOD) for the electroenzymatic reduction of oxygen in water. Besides the influence of the amount of enzyme trapped in the microcavity on the performance of the bioelectrode, the functionalization of the electrodes by adsorption of redox mediators or compounds allowing an orientation of the BOD favorable to electron transfer was also explored. After 5 months of storage in an aqueous buffer, the bioelectrode exhibits 20% of its initial electro-enzymatic activity. Y. Nedellec, C. Gondran, K. Gorgy, S. MC Murtry, O. El Mazria, P. Agostini, S. Cosnier. Biosens. Bioelectron., 180, 113137-113141(2021).M. Carrière, P. H. M. Buzzetti, K. Gorgy, M. Mumtaz, C. Travelet, R. Borsali, S. Cosnier. Nanomaterials 11 (2021) 1162. doi.org/10.3390/nano11051162.