Materials For Energy Applications Research Articles

In-silico realization of YX (X = N, P, As) pnictide monolayers as highly efficient thermoelectric materials

Exploiting the changes in the electronic and vibrational properties accompanying the reduction of dimensionality from 3D to 2D has now become a widely established strategy for developing materials breaking the figure of merit (ZT) ∼ 1 barrier that was experienced in much of the last century. Several studies have suggested the possibility of developing rare earth pnictides into a new family of prospective thermoelectric (TE) materials owing to the strong p-d hybridization in these materials, leading to dispersive band edges and, consequently, high carrier mobilities in these semiconductors. Motivated by the above developments, we explored the electronic and transport properties of three yttrium pnictide monolayers. We present a detailed investigation highlighting the merit of YX (X = N, P, As) monolayer-based materials for TE applications. We found a high power factor for p-type (n-type) YX monolayers in the y-direction (x-direction). This, in conjunction with low to moderate lattice thermal conductivities 3.335, 1.779, and 1.648 Wm-1K-1 of the YN, YP, and YAs monolayers, respectively, at 500 K, leads to high ZTs in optimally doped YN, YAs and YP of 2.02, 1.39, and 1.18. The finding of high TE performance adds further evidence in support of the conjecture that dimensionality reduction in semiconducting materials with strong p-d hybridization can lead to particularly high electrical conductivities (reaches up to 217.84 × 106 Ω-1m-1 for YN), thereby resulting in excellent ZT. The high TE performance of these materials at 500 K suggests the prospect of developing rare-earth-based materials for energy applications.

Harnessing Quantum Materials for Enhanced Energy Efficiency and Storage: A Comprehensive Study of Electronic Properties and Performance Optimization

This research explores the exciting potential of various quantum materials to enhance energy efficiency and storage capabilities, filling in a crucial gap in our understanding of their electronic properties and interactions. A major hurdle in this field is the lack of empirical data on key factors such as conductivity, charge mobility, and thermal stability—elements that are vital for optimizing the performance of these materials in energy applications. Our study aims to blend experimental data with computational simulations to create a robust framework for modelling how quantum materials behave under different conditions. This comprehensive approach helps lay a solid foundation for their practical use in energy technologies. We focus on an array of fascinating quantum materials, including topological insulators, transition metal dichalcogenides, and superconductors. To investigate these materials, we employ advanced techniques like scanning tunnelling microscopy and spectroscopy, which allow us to delve deep into their unique properties. While pursuing this research, we do encounter challenges. Variations in sample quality, environmental factors during experimentation, and the complexities of theoretical modelling can affect the consistency of our results and the interpretation of our data. Despite these obstacles, our findings suggest that certain quantum materials hold remarkable potential for enhancing energy storage and conversion systems through improved charge mobility and thermal stability. In fact, some materials have demonstrated conductivity levels that surpass those of traditional options, hinting at transformative applications in energy technologies. These insights highlight the importance of continuing our exploration of quantum materials, positioning them as promising candidates for tackling today’s energy challenges and paving the way for advancements in sustainable energy solutions.

The deformation mechanism of low symmetric Ti–Pt intermetallic compounds containing high density of planar defects

Intermetallic compounds typically exhibit limited plastic deformation capacity due to challenges in activating dislocation slip and deformation twinning, coupled with a lack of alternative deformation mechanisms. Ti–Pt alloys are a prevalent type of intermetallic compound utilized in high-temperature shape memory alloys and as materials for energy applications in electric fields. However, they often exhibit poor deformation capability. Here, we prepared a low-symmetry intermetallic phase, Ti4Pt3, which demonstrates significant plastic deformation capability. This phase features a high density of parallel planar defects, resulting in an exceptionally large lattice periodicity perpendicular to these defects. Through in-situ scanning electron microscope compression tests, we observed substantial plastic deformation in this new phase. Analysis of the deformed Ti4Pt3 phase revealed that the dense planar defects create uniformly distributed sites of internal stress concentration, enabling a rapid increase in back stress within crystals. This phenomenon leads to notable lattice rotation and localized order-disorder transitions, both crucial mechanisms facilitating plastic deformation and enhancing deformation capacity. Our research underscores the potential of leveraging structural asymmetry to enable unconventional deformation mechanisms, thereby enhancing the plasticity of intermetallic materials.

Space charge effects in mixed ionic-electronic conducting electrodes for solid-state batteries.

Mixed ionic-electronic conductors are widely used as electroactive materials in energy applications. The contact of a mixed conductor with another phase plays a crucial role in charge storage and transport in energy devices. However, the interfacial chemistry at the heterojunctions comprising mixed conductors and its interplay with the bulk chemistry remains imperative yet inadequately understood. This study addresses the fundamentals of space charge effects by exploring the equilibrium situations for contacts consisting of mixed conductors. From the perspective of defect chemistry, and by unifying the bulk and interfacial conditions with the electrochemical potential, our treatment allows for predicting the built-in potential at heterojunctions, profiling the space charge distributions, and evaluating the resulting interfacial charge storage and transport. The treatment can be related to experimental characterization, including coulometric titration, conductivity, and capacitance measurements at electrochemical interfaces in all-solid-state batteries. Besides, our treatment also highlights the significance of size and doping effects in nanocrystalline electrodes. This work provides a comprehensive framework for understanding and engineering the heterojunctions in electrochemical devices.

Enhanced catalytic performance of M-doped SnS2 (M: Ni, Cu, Fe, and Co) and graphene nanocomposite for oxygen reduction reaction in alkaline media

In this study, the electrocatalytic behavior of tin sulfide doped with various metallic elements (copper, cobalt, nickel, and iron) for the oxygen reduction reaction was investigated. Our findings reveal cobalt as the most effective dopant in enhancing ORR efficiency. The graphene nanosheets were introduced to form a G/Co-SnS2 nanocomposite, which significantly improved ORR performance, surpassing Pt/C in current density. Our findings underscore the positive impact of chemical doping and the synergistic effect of SnS2 with graphene nanosheets, improving the onset potential and facilitating the ORR. Through comprehensive characterization including XRD, XPS, FESEM, and BET analysis, the structural and surface properties of the materials were evaluated. Employing the Rotating Disk Electrode technique, we observed that G/Co-SnS2 exhibited a superior onset potential of 0.88 V vs. RHE and high current density of 6.12 mA cm−2, indicating enhanced ORR facilitation. Furthermore, Electrochemical Impedance Spectroscopy revealed lower resistance in the G/Co-SnS2 nanocomposite compared to other samples, highlighting its enhanced durability. Additionally, G/Co-SnS2 nanocomposite demonstrated significantly enhanced durability in comparison to the costly Pt/C catalyst, further underscoring its potential as a robust alternative for catalyzing the oxygen reduction reaction. These comprehensive characterizations provide insights into the enhanced electrocatalytic performance observed. Overall, this study highlights the promising potential of Co-doped SnS2 in combination with graphene nanosheets for efficient oxygen reduction reactions, opening avenues for advanced electrocatalytic materials in energy applications.

Banana Stem Waste as a Sustainable Modifier for Microstructure Modification of Protonic Ceramic Fuel Cell Cathode

This study investigates the feasibility of utilizing banana stem waste (BSW) as a pore former to modify the microstructure of the PCFC composite cathode. The microstructure of the La0.6Sr0.4Co0.2Fe0.8O3-α-Ba(Ce0.6Zr0.4)0.9Y0.1O3-δ (LSCF-BCZY64) composite cathode was modified by varying the amounts of the incorporated banana stem waste. The samples underwent sintering at 1000 ˚C, and their microstructural and physical properties were analyzed using X-ray diffraction, scanning electron microscopy, and densimeter. The results indicate that the incorporation of BSW enhances the porosity of the cathode without significantly affecting its crystalline structure. As the amount of BSW increased from 10 to 40 wt.%, the porosity level increased from 7.0% to 32.7%, and the density of the samples decreased from 1.3 to 0.9 g/cm3, thereby supporting the results of the porosity analysis. Increased cathode porosity can enhance reactant accessibility to active sites, potentially resulting in improved cell performance and durability. Moreover, the utilization of BSW as a sustainable and cost-effective pore former aligns with the growing emphasis on environmentally friendly materials in energy applications.

Recent advances in porous organic cages for energy applications.

In recent years, the energy and environmental crises have attracted more and more attention. It is very important to develop new materials and technologies for energy storage and conversion. In particular, it is crucial to develop carriers that store energy or promote mass and electron transport. Emerging porous organic cages (POCs) are very suitable for this purpose because they have inherent advantages including structural designability, porosity, multifunction and post-synthetic modification. POC-based materials, such as pristine POCs, POC composites and POC derivatives also exhibit excellent energy-related properties. This latest perspective provides an overview of the progress of POC-based materials in energy storage and conversion applications, including photocatalysis, electrocatalysis (CO2RR, NO3RR, ORR, HER and OER), separation (gas separation and liquid separation), batteries (lithium-sulfur, lithium-ion and perovskite solar batteries) and proton conductivity, highlighting the unique advantages of POC-based materials in various forms. Finally, we summarize the current advances, challenges and further perspectives of POC-based materials in energy applications. This perspective will promote the design and synthesis of next-generation POC-based materials for energy applications.

Measuring the ionic conductivity of solid polymer electrolyte powders

Ex-situ characterization of solid polymer electrolytes plays an important role in their development as materials for energy applications, with ionic conductivity being a crucial parameter to quantify. Conventional measurements of ionic conductivity often require the formation of a free-standing polymer film which in many instances is difficult to fabricate, thus there may be a need to quantify their ionic conductivity in powder form. In this work, we present a practical and reproducible method for measuring the ionic conductivity of solid polymer electrolytes (SPEs) in their powder form. By using a modified configuration of a through-plane cell, demonstrated with both a proton conducting- and an anion conducting-solid polymer electrolyte powder (SPEP), we are able to obtain ionic conductivity values under variable conditions in order to explore the influence of external parameters on the ionic conductivity of powders. Two types of SPEs in insoluble powder form were employed in this work: (1) a proton-exchange material (SPEP-H+) based on a hyperbranched, sulfo-phenylated poly(phenylene) SPEP (HB-sPPT-H+), with measured ionic conductivity of ⁓ 210 mS cm−1 at 80 °C and 95 % of relative humidity (RH); (2) an anion-exchange conducting polymer in its chloride form (SPEP-Cl-), consisting of a radiation-grafted ultra-high density polyethylene insoluble SPEP containing covalently-bonded benzyltrimethylammonium (BTMA) head-groups, with measured ionic conductivity of ⁓ 53 mS cm−1 at 80 °C and 95 % RH.

Evaluation and Optimization of Tour Method for Synthesis of Graphite Oxide with High Specific Surface Area

Many of the graphene-based structures exhibit an adsorption capacity due to their high specific surface area (SSA) and micropore volume. This capacity makes them competent materials for applications in energy and environmental sectors where efficiency is highly dependent on these properties for applications, such as water decontamination, solar cells or energy storage. The aim of this work is to study graphene-related materials (GRM) for applications where a high SSA is a requirement, considering the ideal SSA of graphene ≅ 2600 m2g−1. For the synthesis of most of the GRMs, some oxidation method such as the Tour method is used to oxidize graphite to graphite oxide (GrO) as an initial step. Our work studies the optimization of this initial step to evaluate the best conditions to obtain GrO with the maximum possible SSA. The different parameters influencing the process have been evaluated and optimized by applying an experimental design (ED). The resulting materials have been characterized by Brunauer–Emmett–Teller (BET), elemental analysis (EA), X-ray diffraction (XRD) and Raman and scanning electron microscopy (SEM). The evaluation of the results shows a maximum SSA of GrO of 67.04 m2g−1 for a temperature of 60 °C, a time of 12 h, a H2O2 volume of 50 mL and 4 g of KMnO4.

High Oxide‐Ion Conductivity through the Interstitial Oxygen Site in Sillén Oxychlorides

AbstractOxide‐ion conductors are gaining attention as future materials in energy applications, such as solid oxide fuel cells. Many Bi‐containing compounds exhibit high oxide‐ion conductivity via conventional vacancy mechanism. However, interstitial oxide‐ion conduction is rare in Bi‐containing materials. Herein, high oxide‐ion conductivity is reported through interstitial oxygen sites in Sillén oxychlorides, LaBi2−xTexO4+x/2Cl (Bi2LaO4Cl‐based oxychlorides). Oxide‐ion conductivity of LaBi1.9Te0.1O4.05Cl is 20 mS cm−1 at 702 °C, and higher than best oxide‐ion conductors as Bi2V0.9Cu0.1O5.35 below 201 °C. Despite of the presence of Bi and Te species, LaBi1.9Te0.1O4.05Cl shows extremely high chemical and electrical stability at 400 °C from oxygen partial pressure 10−25 to 0.2 atm and high chemical stability under CO2 flow, wet 5% H2 in N2 flow, and air with natural humidity. Neutron scattering length density analysis, DFT calculations, and ab initio molecular dynamics simulations indicate that the extremely high oxide‐ion conduction is attributed to cooperative diffusion through interstitial oxygen sites (interstitialcy diffusion mechanism) in triple fluorite‐like layers. The present findings demonstrate the ability of LaBi2−xTexO4+x/2Cl as superior oxide‐ion conductors, which can open new horizons for oxide‐ion conductors.

Editorial of Special Issue “Materials for Energy Applications 2.0”

Energy is a key factor in determining the growth of human society [...].

Janus γ-GeSSe Monolayer as a High-Performance Material for Photocatalysis and Thermoelectricity

Two-dimensional Janus materials have attracted increasing attention in recent years because of their potential as materials for energy applications, such as photocatalysis and thermoelectricity (TE). Here, for the first time, we propose a monolayer Janus structure with the Mexican-hat band, γ-GeSSe, by replacing the S atoms on one side of the synthesized γ-GeS with Se atoms. Using first-principles calculations based on density functional theory (DFT), we show that γ-GeSSe is mechanically, dynamically, and thermally stable. The mechanical, electronic, optical, and transport properties of monolayer Janus γ-GeSSe are also investigated in the DFT calculations. We find that the ideal strengths of the Janus γ-GeSSe are 6.08, 8.6, and 10.08 GPa for the armchair, zigzag, and biaxial directions, respectively. The Janus γ-GeSSe is an indirect-gap semiconductor with a band gap of 1.131 eV. Our results show the Janus γ-GeSSe as a photocatalysis material for water splitting with a high solar-to-hydrogen efficiency of up to 28.78%. This is because the combination of features includes an intrinsic electric field, high optical absorption coefficient, and carrier mobility. In addition, with the γ-structure, the Janus γ-GeSSe shows an intrinsic low lattice thermal conductivity of 3.33 W/mK at room temperature, which will contribute to obtaining high TE efficiency. By using the Boltzmann transport theory, we find that the maximum TE power factor and figure of merit of the Janus γ-GeSSe reach 55–85 mW/mK2 and 0.7–0.9 in the temperature range from 300 to 900 K, respectively. Thus, our findings not only contribute to proposing a Janus material but also suggest that it can be used as an energy material with high-performance photocatalysis and TE.

Activated Lone-Pair Electrons Lead to Low Lattice Thermal Conductivity: A Case Study of Boron Arsenide.

Reducing thermal conductivity (κ) is of great significance to lots of applications, such as thermal insulation, thermoelectrics, etc. In this study, we propose an effective approach for realizing low κ by introducing lone-pair electrons or making the lone-pair electrons stereochemically active through bond nanodesigning. By cutting at the (111) cross section of the three-dimensional cubic boron arsenide (c-BAs), the κ is lowered by more than 1 order of magnitude in the resultant two-dimensional graphene-like BAs (g-BAs). The underlying mechanism of activating lone-pair electrons is analyzed based on the comparative study on the thermal transport properties and electronic structures of g-BAs, c-BAs, graphene, and diamond (c-BAs → g-BAs vs diamond → graphene). The proposed approach for realizing low κ and the underlying mechanism uncovered in this study would largely benefit the design of advanced thermal functional materials, especially in future research involving novel materials for energy applications.

Impact of hybridization on specific capacitance in hybrid NiO/V2O5@graphene composites as advanced supercapacitor electrode materials

Currently, hybrid composites are considered promising materials in energy applications. Among various approaches for synthesizing hybrid composites, the solution combustion approach has attracted significant research interest worldwide due to its high versatility, efficiency, simplicity, scalability, reproducibility, and cost-effectiveness. Further, solution combustion synthetic techniques have recently been regarded as one of the more facile methods for developing effective supercapacitor electrodes. This paper provides the synthesis of vanadium pentoxide (V2O5), nickel oxide-vanadium pentoxide (NiO/ V2O5), and nickel oxide-vanadium pentoxide-Graphene (NiO/ V2O5@Graphene) nano-composites using solution combustion method. The importance of the hybridization of transition metal oxide with other-transition metal oxide and carbon derivatives is studied systematically. The obtained materials are characterized by X-ray diffraction, UV-Visible spectroscopy, Fourier transform infrared spectroscopy, Field emission scanning electron microscopy, Energy-dispersive X-ray analysis, Cyclic voltammetric analysis, Galvanostatic charge-discharge, and Electrochemical impedance. The average crystalline sizes are calculated as 27 nm, 24 nm, and 14 nm for V2O5, NiO/ V2O5, and NiO/ V2O5@Graphene nano-composites. The UV-Visible, Fourier transform infrared, and Energy-dispersive X-ray spectroscopy analysis confirms the formation of synthesized materials. Field emission scanning electron microscopy provides the distribution of NiO/ V2O5 nano-composite over the graphene sheet. The electrochemical performance of V2O5 is improved drastically with the simultaneous hybridization of two metal oxides. Further, the addition of graphene makes a small enhancement in the specific capacitance of the nano-composites. The order of specific capacitance is V2O5 (328 F/g) ˂ NiO/V2O5 (918 F/g) ˂ NiO/V2O5@Graphene (939 F/g). The solution resistance and charge transfer resistance of the modified electrodes are in the order of V2O5 (1.59 Ω) ˃ NiO/V2O5 (0.85 Ω) ˃ NiO/V2O5@Graphene (0.73 Ω) and V2O5 (5.66 Ω) ˃ NiO/V2O5 (1.35 Ω) ˃ NiO/V2O5@Graphene (0.17 Ω) respectively, which supports the enhancement in specific capacitance upon hybridization. The obtained materials are cost-effective, low-toxic, and efficient, hence would be appropriate for industrial use.

Editorial: Special Issue on Materials for Extreme Environments, Part 2

Abstract The response of materials to extreme conditions of heat flux, stresses, strain rates, and corrosive environments provides an insight into new phenomena, reveals failure modes that limit technological possibilities, and presents novel routes for making new and improved materials. Exposing materials to extreme environments induces new physical phenomena, which are central to the challenges of science. Understanding and exploiting these extreme environments is critical for facing many of the future energy challenges, as materials for these usually operate at extremes of pressure, temperature, and chemical reactivity. Identifying materials that not only survive but also perform under extreme conditions to the design requirements is a major concern in energy research. It is in this context that this special issue on materials for extreme environment becomes relevant and useful for readers in their research endeavors. It has been a pleasure to be guest editors for the two-part special issue on Materials for Extreme Environments for Materials Performance and Characterization. The first part of special issue covered 16 papers, essentially covering the areas of materials for cryogenic applications and ultrahigh temperature, advanced materials, and manufacturing technologies. The second part of the special issue contains the remaining 18 papers, essentially showcasing recent advances in materials for energy applications. There are two review articles in this volume. The first is by Prasad Reddy et al. from the Indira Gandhi Centre for Atomic Research, India, on “Core Materials for Sodium Cooled Fast Reactors: Past to Present and Future Prospects,” which reviews materials that are subjected to extreme conditions of intense fast-spectrum neutron irradiation, high temperatures, and mechanical/chemical fuel-cladding interactions. The second article, by Patil et al., “A Review on the Material Development and Corresponding Properties for Power Plant Applications,” brings out the recent advances in materials for power plants. These are followed by six papers each on corrosion/oxidation and welding of advanced materials for use in extreme environments. We sincerely thank both the authors and reviewers for their hard work and dedication. We wholeheartedly thank the ASTM International staff dealing with the special issues for all their efforts. We sincerely hope that you enjoy the papers in this special issue.

Versatile Graphitized Carbon Nanofibers in Energy Applications

Graphitized carbon nanofibers (CNFs) are the allotropic forms of carbon that offer exceptional electrical conductivity, high aspect ratio, large surface-to-volume ratio, flexibility, mechanical robustness, and structural stability. These properties render CNFs as useful materials in energy applications, including water electrocatalysis and electrochemical energy storage devices (EESDs). Graphitized CNFs manifest huge versatility in EESDs and have been employed as electrode materials, as supports for other electrode materials, and conductive additives. This perspective summarizes the production methods, structural aspects, and energy applications of graphitized CNFs. Different design strategies have been employed to produce CNFs with diverse and distinct morphologies and structures. Their fabrication methods, along with precursors and dopants or cocatalysts, impact the overall structural, functional, and topographical properties. Recent developments on the state-of-the-art interests of graphitic CNFs in lithium-ion batteries (LIBs), lithium–sulfur (Li–S) batteries, vanadium redox flow batteries (VRFBs), supercapacitors, and water splitting have explored the many possibilities in energy sectors. The assembly and functioning of CNFs in water splitting and EESDs as well as primary challenges are discussed in this perspective.

Two-Dimensional Boron-Rich Monolayer BxN as High Capacity for Lithium-Ion Batteries: A First-Principles Study.

Owing to lightweight, abundant reserves, low cost, and nontoxicity, B-based two-dimensional (2D) materials, e.g., borophene, exhibit great potential as new anode materials with higher energy density for Li-ion batteries (LIBs). However, exfoliation of borophene from the Ag substrate remains the most daunting challenge due to their strong interfacial interactions, significantly restricting its practical applications. In this study, through first-principles swarm-intelligence structure calculations, we have found several Boron-rich boron nitride BxN materials (x = 2, 3, 4, and 5) with increased stability and weakened interactions with the Ag(111) substrate compared with δ6-borophene. A high cohesive energy and superior dynamical, thermodynamic, and mechanical stability provide strong feasibility for their experimental synthesis. The obtained BxN materials exhibit a high mechanical strength (94-226 N/m) and low interfacial bonding with the Ag substrate, from -0.043 to -0.054 eV Å-2, significantly smaller than that of δ6-borophene. Among them, B3N and B5N exhibit not only a remarkably high storage capacity of 1805-3153 mAh/g but also a low barrier energy and open-circuit voltage. Moreover, B2N showed a cross-sheet motion with a low barrier of 0.24 eV, which is unique compared with the in-plane diffusion in most other 2D electrode materials restricted by their quasi-flat geometry. BxN also exhibits excellent cyclability with improved metallic conductivity upon Li-ion intercalation, showing great potential in LIB applications. This study opens up a new avenue to explore B-rich 2D electrode materials in energy applications and provide instructive insights into borophene functionalization and exfoliation.

The Value of Watching How Materials Grow: A Multimodal Case Study on Halide Perovskites

AbstractMaterial synthesis is one of the most important aspects in humankinds’ endeavor to discover and create new materials for energy applications. One strategy to tailor materials with desired functions in a rational way is by knowing how functions relate to structure, synthetic variables, arrangement of atoms and molecules, and how functions evolve during synthesis. In order to accelerate materials synthesis, discovery, and optimization by 10 times it is the right time now to integrate computational tools, synthesis, and characterization. One particular barrier to realizing this concept is the understanding of when and how phases form in real time during synthesis, which is challenging to asses by existing theoretical frameworks. In addition, transient or metastable phases with positive free energy above the lowest‐free energy ground state can be revealed by such real time (in situ) measurements. Metastable materials are ubiquitous in condensed matter and can show superior properties compared to their equilibrium form. This essay discusses the value of emerging multimodal in situ characterizations exemplified on hybrid halide perovskites. Finally, the ways in which the implementation of in situ measurements can advance the materials science synthesis field as well as their role to enable close‐loop feedback control and autonomous synthesis are discussed.

Effect of TiO2 content on Ni/TiO2 composites electrodeposited on SS316L for hydrogen evolution reaction

Composite Ni/TiO2 catalysts have gained enormous interest in recent years in both electrocatalysis and photoelectrocatalysis for the generation of hydrogen. However, there are no systematic studies of the synthesis and characterization of these materials for applications in energy storage.In this work, three Ni/TiO2 catalysts were synthesized starting from nickel electrodeposition on AISI 316 L stainless steel with a modified Ni Watts bath, where different TiO2 contents have been added (0.1, 0.3, and 0.5% w/v). The mechanism of composite formation was studied at different electrodeposition times, in order to analyze the early periods of synthesis, reaching a chemically and structurally stable material after 45 min. It was found that all Ni/TiO2 catalysts present catalytic activity towards hydrogen generation, higher than that found by plating with a conventional Ni Watts. Particularly, the Ni/TiO2(0.3) catalyst presents increases in hydrogen formation efficiency of 75.3% and 67.8% at 298 K and 323 K, respectively.

Bifunctional electrocatalysts derived from cluster-based ternary sulfides for oxygen electrode reactions

Applying metal sulfides in the electrochemical systems is a currently emerging field owing to the unique physicochemical properties and low-cost. Although ternary sulfides have been explored as oxygen electrocatalysts, they are usually mono-functional and undergo a complicated preparation process. Herein, via a facile and mild self-assembly method induced by electrostatic interaction, a series of novel ternary sulfide hybrids (denoted as MInS/NH2-CNT, M=Co, Fe or Mn) were fabricated as bifunctional oxygen electrocatalysts using supertetrahedral metal sulfide nanoclusters (T4 clusters) with uniformly distributed ternary component as precursors. The synergistic effect between T4 clusters-aggregated nanoparticles and amino carbon nanotubes (i.e., NH2-CNT) endows the hybrids with oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) catalytic activity. Among the as-synthesized MInS/NH2-CNT, CoInS/NH2-CNT reveals superior electrocatalytic performance for the OER (overpotential of 398 mV at 10 mA cm−2) and ORR (half-wave potential of 0.76 V vs. RHE). The strategy developed here can be easily adopted to construct other cluster-based hybrid materials for electrocatalysts, thus providing more promising non-noble-metal materials for energy application.