Sustainable Energy Applications Research Articles

Tetrafunctional electrocatalyst for oxygen reduction, oxygen evolution, hydrogen evolution, and carbon dioxide reduction reactions

BackgroundThe development of novel electrocatalysts with high efficiency, low cost, and high stability to replace platinum group metal (PGM) electrocatalysts is essential for realizing sustainable energy applications. MethodsIn this study, we synthesized a tetrafunctional electrocatalyst comprising NiFe layered double-hydroxide (LDH) nanosheets anchored on carbon-nanotube-grafted (CNT), Co3O4-embedded, and N-doped porous carbon matrices (NC) derived from zeolitic imidazolate frameworks (NiFe LDHCNT-Co3O4/NC). Significant FindingsThis electrocatalyst exhibited superior performance to PGM electrocatalysts in the oxygen reduction reaction (ORR), oxygen evolution reaction (OER), hydrogen evolution reaction (HER), and carbon dioxide reduction reaction (CO2RR). The linear sweep voltammetry study showed that the NiFe LDHCNT-Co3O4/NC demonstrated superior performance (Eonset = 0.85 V and E1/2 = 0.79 V for ORR; Ej=10 = 1.63 V for OER; overpotential = 0.84 V) comparing to the benchmarks of Pt/C and RuO2. A rechargeable Zn–air battery (ZAB) is used to verify the performance of the developed electrocatalyst in the ORR and OER; the ZAB exhibited an ultralow charge–discharge voltage gap (0.74 V) and excellent stability (104 cycles, >1600 h@10 mA cm−2). Overall water splitting (OWS) is performed to verify the performance of the developed electrocatalyst in the OER and HER. The adopted OWS device exhibited a long and stable process (1.6 V@10 mA cm−1, 700 h). CO2 conversion is investigated for evaluating the HER and CO2RR, and an 80% faradaic efficiency of CO production and high stability are obtained (166 mA cm−2@−1.09 V). We think that the synergistic effect of the NiFe LDHs, Co3O4 nanoparticles, and nitrogen-doped carbon electrocatalyst contributes to the excellent electrocatalytic performance of NiFe LDHCNT-Co3O4/NC in the aforementioned reactions. The hydrophilic NiFe LDHs and highly mesoporous carbon matrices provide a favorable ionic pathway for achieving rapid diffusivity and efficient mass transfer while the CNTs and carbon frameworks enhance the electrical conductivity during redox processes

Phosphorus co-doped reduced graphene oxide embedded flower-like CoS/CoS2 heterostructure as an efficient electrocatalyst for hydrogen evolution reaction in acidic media

The electrochemical efficacy of an electrocatalyst can be improved by an elaborate surface modification. In this study, phosphorus co-doped reduced graphene oxide embedded (rGO) flower like CoS/CoS2 heterostructures have been prepared, via one step hydrothermal process, by taking different mole ratio of phosphorus source for excellent hydrogen evolution reaction (HER) in acid solution. The as-fabricated catalysts are studied by XRD, FT-IR, XPS, SEM, EDS, and HR-TEM analyses. The rGO-CoS/CoS2 @P5 (5 mmol) catalyst exhibits a superior catalytic behavior for HER with a less overpotential (148 mV), low Tafel slope (44 mV dec−1) and enhanced cyclic durability (1000 cycles) in acid condition in comparison with other composition. The synergetic effect of hetero-interface and rapid charge transfer through rGO on the active sites of CoS/CoS2 have improved the HER efficiency. This study demonstrated that the component of rGO and P-incorporation on CoS/CoS2 interface offered an achievable yet easy strategy to synthesize platinum (Pt) free metal-based heterostructured catalyst as the favorable electrode material in sustainable energy applications.

Flat plate and evacuated tube collectors solar water heater system – A comparative study

Renewable energy for the sustainable energy application in the buildings are increasing day-by-day. The aim of this study is to compare flat plate and evacuated tube collectors system in solar water heating of urban building. The two types of solar water heater systems were designed and evaluated based on the requirements of the urban building dwellers. The F-chart method along with commercial software was used to study the performance efficiency of the solar water heater system at an operating temperature of 65 °C. An economic analysis was also carried out using the same tool for both types of collectors with the desired designed parameters. The performance efficiency results of flat plate and evacuated tube collector are 77 % and 67.3 %, respectively. The economic analysis showed that flat plate collector is cost-effective for the solar water heater system due to its steadiness and lower maintenance costs.

Quantum computing and quantum artificial intelligence for renewable and sustainable energy: A emerging prospect towards climate neutrality

Transitioning from fossil fuels to renewable sources and developing sustainable energy materials for energy production and storage are critical factors in achieving climate neutrality. These can be realized through innovative strategies to provide viable, economically competitive, and scalable technologies ranging across various sectors. Quantum computing (QC) has the potential to revolutionize various domains of science and engineering, including macro-energy systems and sustainable energy materials design. Conventional approaches for renewable and sustainable energy systems solely rely on classical computing techniques that may not scale well with the increasing size and complexity of applications. Owing to the advancements in quantum hardware and algorithms, QC and quantum artificial intelligence make promising tools to handle renewable and sustainable energy systems even at larger scales. In this review, we discuss the prospects of QC for various areas of applications in energy sustainability to help address climate change. In addition to providing a brief background on the operations of quantum computers, the constituent segments of widely adopted QC-based techniques that improve the computational efficiency of quantum chemistry calculations for sustainable energy materials along with quantum artificial intelligence methods that can address complex optimization and machine learning problems arising in renewable energy systems are also introduced in this paper. We screen the presented quantum algorithms based on their performance on current quantum devices despite their promising potential. Furthermore, sustainable energy applications that may draw advantages from QC-based strategies are identified in this work while simultaneously setting realistic expectations over the potential improvements offered over classical techniques.

Molecular-Level Control over Ionic Conduction and Ionic Current Direction by Designing Macrocycle-Based Ionomers.

Poor ionic conductivity of the catalyst-binding, sub-micrometer-thick ionomer layers in energy conversion and storage devices is a huge challenge. However, ionomers are rarely designed keeping in mind the specific issues associated with nanoconfinement. Here, we designed nature-inspired ionomers (calix-2) having hollow, macrocyclic, calix[4]arene-based repeat units with precise, sub-nanometer diameter. In ≤100 nm-thick films, the in-plane proton conductivity of calix-2 was up to 8 times higher than the current benchmark ionomer Nafion at 85% relative humidity (RH), while it was 1–2 orders of magnitude higher than Nafion at 20–25% RH. Confocal laser scanning microscopy and other synthetic techniques allowed us to demonstrate the role of macrocyclic cavities in boosting the proton conductivity. The systematic self-assembly of calix-2 chains into ellipsoids in thin films was evidenced from atomic force microscopy and grazing incidence small-angle X-ray scattering measurements. Moreover, the likelihood of alignment and stacking of macrocyclic units, the presence of one-dimensional water wires across this macrocycle stacks, and thus the formation of long-range proton conduction pathways were suggested by atomistic simulations. We not only did see an unprecedented improvement in thin-film proton conductivity but also saw an improvement in proton conductivity of bulk membranes when calix-2 was added to the Nafion matrices. Nafion–calix-2 composite membranes also took advantage of the asymmetric charge distribution across calix[4]arene repeat units collectively and exhibited voltage-gating behavior. The inclusion of molecular macrocyclic cavities into the ionomer chemical structure can thus emerge as a promising design concept for highly efficient ion-conducting and ion-permselective materials for sustainable energy applications.

Energy security assessment of small Pacific Island Countries – Sustaining the call for renewable energy proliferation

Using a contemporary assessment framework, we assess the energy security status of small Pacific Island Countries (PICs) in line with its three broad perspectives. These perspectives – sovereignty, robustness, and resilience encapsulate vulnerabilities and threats to vital energy systems, including their respective political and economic strata. Based on a recently adopted regional energy security framework, we unpack these perspectives and generate a collective evaluative judgment of its impact across small PICs. The results resonate with the commonly held notion that energy security concerns are significant and likely to become more severe if expanding energy needs are not addressed through the proliferation of renewable and sustainable energy applications. Another emerging yet familiar concern is that the energy import bill will become more unsustainable for these cash-strapped islands. The findings demonstrate that PICs have severe constraints to overcome, especially with acquiring appropriate technologies and building institutional capacities to implement their respective energy policies and realise their critical energy targets.

Enhanced electrocatalytic activity by NiCu-LDH/CoS as dual co-catalysts on g-C3N4 nanosheets in NiCu-LDH@CoS/g-C3N4 nanostructure for oxygen evolution reactions

The development of highly efficient electrocatalysts is crucial for realizing efficient oxygen evolution reactions (OERs). Herein, a novel strongly coupled ternary electrocatalyst of NiCu-layered double hydroxide (NiCu-LDH) on cobalt sulfide (CoS) and the material graphitic carbon nitride (g-C3N4) was synthesized. In OER tests, NiCu-LDH@CoS/g-C3N4 electrocatalyst exhibited excellent performance using 1 M KOH alkaline electrolyte. In the present study, the electrode potential was only 290 mV for a current density of 10 mA/cm2 and a Tafel slope of 75 mV/dec. The improved electrocatalytic activity was ascribed to the strong interaction and electronic coupling with efficient charge transfer at the CoS/g-C3N4 heterojunction interface and the enhanced electronic effects of NiCu-LDH at the NiCu-LDH@CoS/g-C3N4 interface. The optimized NiCu-LDH@CoS/g-C3N4 nanostructure was stable, with a 99.7% remarkable efficiency for the OER. This work presents a novel approach to maximize the efficiency through the synergetic effect of CoS and NiCu-LDH as dual co-catalysts for sustainable energy applications.

Type‐II van der Waals Heterostructures Based on AsP and Transition Metal Dichalcogenides: Great Promise for Applications in Solar Cell

As an effective means to adjust the properties of 2D materials, type‐II van der Waals (vdW) heterostructures have been under extensive research due to their significantly reduced carrier recombination probability and extended carrier lifetime. Herein, stable vdW heterostructures based on arsenic phosphorus (AsP) and transition metal dichalcogenides are designed. The geometry, electronic, and optical properties for type‐II AsP/MX2 heterostructures (M = Mo, W; X = S, Se) by first‐principle calculations are systematically explored and their application in solar cell materials is predicted. AsP/MX2 heterostructures are indirect semiconductors with the quasiparticle bandgap ranging from 1.49 to 2.02 eV. They effectively widen the light absorption of AsP monolayers in visible and ultraviolet regions. It is worth noting that AsP/WSe2 heterostructure can form a built‐in electric field (0.832 eV Å−1) and have a minor exciton binding energy (0.22 eV), suggesting that it is a potential solar cell material. The power conversion efficiency is more than 15%. The results will provide a theoretical basis for sustainable energy applications of AsP‐based vdW heterostructures in the future.

Toward a New Era of Sustainable Energy: Advanced Triboelectric Nanogenerator for Harvesting High Entropy Energy.

Widely distributed across the environment, irregular micro-nano mechanical high entropy energy (HEE) is a new promising recoverable energy, in which the development of matched harvesting technology is imperative to fit in with the requirements of booming sustainable energy in the new era. The triboelectric nanogenerator (TENG) is a very efficient technology for harvesting micro-nano HEE, especially when converting irregular, low-frequency, weak mechanical energy into electricity. Here, the latest advancements are comprehensively reviewed in using TENGs for sustainable energy, sensing, and other applications. The fundamental theory and overwhelming superiority of TENG is systematically analyzed as a sustainable energy with four representative domains: micro-nano distributed power sources, self-powered sensing systems, direct high-voltage power sources, and large-scale blue energy. The review is concluded with a discussion of the challenges of leveraging TENGs for sustainable energy engineering. The striving directions of TENG technologies are proposed with a concentration on basic research and commercialization for the new ear of 5G and Internet of Things.

Surface Science in the Research and Development of Hydrate-Based Sustainable Technologies

Compact gas inclusion in hydrates presents not only fascinating science but also wide-ranging applications in sustainable energy and environmental technologies. The surface of hydrates dictates many essential phenomena underlying hydrate-based processes such as hydrate nucleation and growth, mass transfer, heat transfer, agglomeration, adhesion, and adsorption. Thus, surface science falls within the core of hydrate science and engineering. This paper covers an insight perspective on surface science related to the research and development of hydrate-based sustainable technologies. We present insightful molecular views of hydrate surfaces with a focus on the interfacial premelting, and discuss how new fundamental advances benefit the sustainable engineering in the areas of greener and chemical-free flow assurance, energy-efficient gas storage, carbon capture and storage, and recovery of methane (low-carbon energy) from natural hydrates. We highlight the prospects and challenges as well as stimulate future studies on this important topic.

Thermoelectric and stress distributions around a smooth cavity in thermoelectric material

• In this paper the thermoelectric coupling problem of an infinite homogeneous isotropic thermoelectric material with a smooth cavity and exerting a uniform current density and/or uniform energy flux is studied. • New analytical solutions are completely exact, and operable for complex shapes. • New solutions have a finite form for cavity characterized by Laurent polynomial. • The curvature of the cavity contour affects the distribution of the fields. • The maximum stress concentration appears near the points with extremal curvature. Thermoelectric materials have attracted more and more attention since they are friendly to the environment and have potentials for sustainable and renewable energy applications. As typically brittle semiconductors with low mechanical strength and always subjected to defects and damages, to clarify the stress concentration is very important in the design and implement of thermoelectric devices. The two-dimensional thermoelectric coupling problem due to a cavity embedded in an infinite isotropic homogeneous thermoelectric material, subjected to uniform electric current density or uniform energy flux, is studied, where the shape of the cavity is characterized by the Laurent polynomial, and the electric insulated and adiabatic boundary around the cavity are considered. The explicit analytic solutions of Kolosov-Muskhelishvili (K-M) potentials and rigid-body translation are carried out through a novel tactic. Comparing with the reported results, the new obtained are completely exact and possess a finite form. Some results of three typical cavities are presented to analyze the electric current densities (energy fluxes) and stresses around the tips. The main conclusions include: the distribution of thermoelectric field and stress at the tip obviously depends on the curvature of the contour and load directions; for triangle and square with symmetrical tips, the thermoelectric and stress concentration reach the maximum or minimum when the load direction is parallel to or perpendicular to the symmetry axis of the tip, which is distinct to the extremum characteristics of pentagram with bimodal of curvature around the tip; the maximum thermoelectric and stress concentration appear near the maximum curvature point for most load directions, but not at the maximum curvature point.

Aromatic Schiff Base-Based polymeric phase change materials for Safe, Leak-Free, and efficient thermal energy management

Polymeric phase change materials (PCMs) have garnered enduring interest owing to no leakage and considerable latent heat in thermal management. However, the flammability, poor recyclability, and low energy storage density of typical polymeric PCMs have long-term constraint on their applications in sustainable energy. Herein, we fabricated a novel linear polymeric solid–solid PCM (HPPEG-PU) with facile recyclability, fire safety, and simultaneous high heat transition capacity via introducing aromatic Schiff base structure into the hard segment of HPPEG-PU and meanwhile using high-molecular-weight polyethylene glycol as energy-storage soft segment. HPPEG8000-PU achieved the latent heat of 131.1 J g−1, higher than the reported polymeric solid–solid PCMs, and realized thermal reprocessing at 80 ℃ and fire extinguishment once being ignited. Mechanisms for safe, leak-free, and highly efficient thermal energy storage/release were discussed deeply, in which aromatic Schiff base structure induced network confinement, crystallization, and self-crosslinking charring are highly responsible for shape stability, high thermal storage capacity, and fire safety, respectively. Based on the phase change characteristic of HPPEG-PU, thermosensitive imaging and convenient thermal management applications were developed in this work. Cunningly targeting aromatic Schiff base structure to polymeric PCMs may provide a promising route for safe, leak-free, and efficient thermal energy management.

Laser fragmentation in liquid synthesis of novel palladium-sulfur compound nanoparticles as efficient electrocatalysts for hydrogen evolution reaction

One promising way to tune the physicochemical properties of materials and optimize their performance in various potential applications is to engineer material structures at the atomic level. As is well known, the performance of Pd-based catalysts has long been constrained by surface contamination and their single structure. Here, we employed an unadulterated top-down synthesis method, known as laser fragmentation in liquid (LFL), to modify pristine PdPS crystals and obtained a kind of metastable palladium-sulfur compound nanoparticles (LFL-PdS NPs) as a highly efficient electrocatalyst for hydrogen evolution reaction (HER). Laser fragmentation of the layered PdPS crystal led to a structural reorganization at the atomic level and resulted in the formation of uniform metastable LFL-PdS NPs. Noteworthy, the LFL-PdS NPs show excellent electrocatalytic HER performance and stability in acidic media, with an overpotential of –66 mV at 10 mA⋅cm−2, the Tafel slope of 42 mV⋅dec−1. The combined catalytic performances of our LFL-PdS NPs are comparable to the Pt/C catalyst for HER. This work provides a top-down synthesis strategy as a promising approach to design highly active metastable metal composite electrocatalysts for sustainable energy applications.

Photocatalytic transition-metal-oxides-based p–n heterojunction materials: synthesis, sustainable energy and environmental applications, and perspectives

Photocatalytic transition-metal-oxides-based p–n heterojunction materials: synthesis, sustainable energy and environmental applications, and perspectives

Fabrication and Characterization of Semi-Crystalline and Amorphous Dielectric Polymer Films for Energy Storage

Dielectric polymer films are energy storage materials that are used in pulse power operations, power electronics and sustainable energy applications. This paper reviews energy storage devices with focus on dielectric film capacitors. Two prominent examples of polymer dielectrics Polyetherimide (PEI) and Poly (tetrafluoroethylene-hexafluoropropylene-vinylidene fluoride) (THV) have been discussed. Polyetherimide (PEI) is an amorphous polymer recognized for its high-temperature capability, low dielectric loss and high dielectric strength. THV is a semi-crystalline polymer with high dielectric constant, high-temperature capability and charge-discharge efficiency. The primary focus of this paper is to introduce the reader to the fabrication procedures and characterization techniques used in research labs for processing of dielectric polymers. The fabrication and characterization process of both polymers has been discussed in detail to shed the light on experimental process in this area of research.

Anaerobic self-assembly of a regenerable bacteria-quantum dot hybrid for solar hydrogen production.

Inorganic-biological hybrid systems (bio-hybrids), comprising fermentative bacteria and inorganic semiconductor photosensitizers for synergistic utilization of solar energy and organic wastes, offer opportunities for sustainable fuel biosynthesis, but the low quantum efficiency, photosensitizer biotoxicity and inability for self-regeneration are remaining hurdles to practical application. Here, we unveil a previously neglected role of oxygen in suppressing the biosynthesis of cadmium selenide quantum dots (CdSe QDs) and the metabolic activities of Escherichia coli, and accordingly propose a simple oxygen-regulation strategy to enable the self-assembly of bacterial-QD hybrids for efficient solar hydrogen production. Shifting from aerobic to anaerobic biosynthesis significantly lowered the intracellular reactive oxygen species level and increased NADPH and thiol-protein production, enabling a two-order-of-magnitude higher bio-QD synthesis rate and resulting in CdSe-rich products. Bacteria with abundant biocompatible intracellular bio-QDs naturally formed a highly active and self-regenerable bio-hybrid and achieved a quantum efficiency of 28.7% for hydrogen production under visible light, outperforming all the existing bio-hybrids. It also exhibited high stability during cyclic operation and robust performance for treating real wastewater under simulated sunlight. Our work provides valuable new insights into the metallic nanomaterial biosynthesis process to guide the design of self-assembled bio-hybrids towards sustainable energy and environmental applications.

Reversible assembly of silica nanoparticles at water-hydrocarbon interfaces controlled by SDS surfactant.

Achieving reversible and tunable assembly of silica nanoparticles at liquid-liquid interfaces is vital for a wide range of scientific and technological applications including sustainable subsurface energy applications, catalysis, drug delivery and material synthesis. In this study, we report the mechanisms controlling the assembly of silica nanoparticles (dia. 50 nm and 100 nm) at water-heptane and water-toluene interfaces using sodium dodecyl sulfate (SDS) surfactant with concentrations ranging from 0.001-0.1 wt% using operando ultrasmall/small-angle X-ray scattering, cryogenic scanning electron microscopy imaging and classical molecular dynamics simulations. The results show that the assembly of silica nanoparticles at water-hydrocarbon interfaces can be tuned by controlling the concentrations of SDS. Silica nanoparticles are found to: (a) dominate the interfaces in the absence of interfacial SDS molecules, (b) coexist with SDS at the interfaces at low surfactant concentration of 0.001 wt% and (c) migrate toward the aqueous phase at a high SDS concentration of 0.1 wt%. Energetic analyses suggest that the van der Waals and electrostatic interactions between silica nanoparticles and SDS surfactants increase with SDS concentration. However, the favorable van der Waals and electrostatic interactions between the silica nanoparticles and toluene or heptane decrease with increasing SDS concentration. As a result, the silica nanoparticles migrate away from the water-hydrocarbon interface and towards bulk water at higher SDS concentrations. These calibrated investigations reveal the mechanistic basis for tuning silica nanoparticle assembly at complex interfaces.

The progress toward more sustainable energy, water and environmental systems approaches and applications

This editorial provides an overview of ten scientific articles published as the Special paper selection in Thermal Science. The papers were selected from almost six hundred contributions, presented at the 16th Conference on Sustainable Development of Energy, Water and Environment Systems (SDEWES 2021), held on October 10-15, 2021 in Dubrovnik, Croatia. The topics covered in the Special paper selection include economics of electricity markets, nuclear technology, repowering of the coal-based power plant, hybrid renewable energy system, sustainable biomass handling and conversion, post-combustion emissions control, and efficient cooling technology. The editorial also emphasised the papers recently published in the Special Issues of leading scientific journals dedicated to the series of SDEWES Conferences.

Role of Computational Science in Materials and Systems Design for Sustainable Energy Applications: An Industry Perspective

Role of Computational Science in Materials and Systems Design for Sustainable Energy Applications: An Industry Perspective

Design and Implementation of a Soft Switching Quadratic High-Gain Converter for Sustainable Energy Applications

Design and Implementation of a Soft Switching Quadratic High-Gain Converter for Sustainable Energy Applications