Energy Conversion Applications Research Articles

Advanced approach for active and durable proton exchange membrane fuel cells: Coupling synergistic effects of MNC nanocomposites

AbstractAtomically dispersed metal and nitrogen co‐doped carbon (MNC) is a promising oxygen reduction reaction (ORR) catalyst for electrochemical energy storage and conversion applications but typically suffers from low durability and activity under the acidic conditions of practical polymer electrolyte exchange membrane fuel cells (PEMFCs). Recently, the performance of MNC nanocomposites under acidic ORR conditions has been enhanced by exploiting the synergistic coupling effects of their constituents (single‐atom sites, nanoclusters, and nanoparticles). The unique geometric structures formed by the coupling of diverse sites in these nanocomposites provide optimal electronic structures and efficient reaction pathways, thus resulting in high activity and long‐term durability. This work provides an overview of MNC nanocomposites as ORR electrocatalysts under practical PEMFC conditions, focusing on activity and durability enhancement methods and highlighting the strategies used to prepare electrocatalytically efficient MNC nanocomposites containing no or low amounts of platinum group metals. Progress in the development of advanced MNC nanocomposites as acidic ORR catalysts is discussed, and the pivotal role of synergistic effects resulting from the coupling sites within the nanocomposites is explored together with the characterization methods used to elucidate these effects. Finally, the challenges and prospects of developing MNC nanocomposites as next‐generation electrocatalysts are presented.image

Enhancing Performance and Stability of Perovskite Solar Cells with a Novel Formamidine Group Additive.

Perovskite materials, particularly FAPbI3, have emerged as promising candidates for solar energy conversion applications. However, these materials are plagued by well-known defects and suboptimal film quality. Enhancing crystallinity and minimizing defect density are therefore essential steps in the development of high-performance perovskite solar cells. In this study, 1H-Pyrazole-1-carboximidamide hydrochloride (PCH) is introduced into FAPbI3 perovskite films. The molecular structure of PCH features a pyrazole ring bonded to formamidine (FA). The FA moiety of PCH facilitated the incorporation of this additive into the film lattice, while the negatively charged pyrazole ring effectively passivated positively charged iodine vacancies. The presence of PCH led to the fabrication of an FAPbI3 device with improved crystallinity, a smoother surface, and reduced defect density, resulting in enhanced Voc and fill factor. A record power conversion efficiency of 24.62% is achieved, along with exceptional stability under prolonged air exposure and thermal stress. The findings highlight the efficacy of PCH as a novel additive for the development of high-performance perovskite solar cells.

Stokes and anti-Stokes emission characteristics of Er3+/Yb3+ co-doped zinc tellurite glasses under 377 and 1550 nm excitations for solar energy conversion application

One of the best rare earth combinations for down- and up-converting the solar photons is Er3+/Yb3+. Therefore, at present, by using the traditional melt quench technique, zinc tellurite glasses doped with Er3+ and Er3+/Yb3+ were characterised. Several methods of down-conversion that result in the emission of 1000 nm from the acceptor (Yb3+) under excitation of donor (Er3+) were studied. On the other hand, the impact of acceptor (Yb3+) concentration and excitation pump power on the excited state absorption and its influence on the up-conversion emission (1000 nm) properties were investigated in detail under 1535 nm excitation. The studies on emission and decay results are discovered to be very significant. Suggesting that these glasses when used as conversion layers, can append the conversion efficiency of Si-based solar cells.

Poly-dopamine coated-cellulose/chitosan hybrid carbon aerogel composite phase change materials with efficient photothermal conversion and storage

Solar energy, being both low-cost and renewable, is a viable alternative for thermal storage and can help mitigate the energy crisis. Efficient conversion and storage for solar energy can significantly enhance energy utilization. Phase change materials (PCMs), such as paraffin (PW), are capable of harvesting and converting solar energy into thermal energy, thus playing a crucial role in solar energy utilization. However, PW faces challenges, such as solid–liquid leakage and low photothermal conversion efficiency, which hinder its applications in solar energy storage. In this study, we proposed the construction of a robust poly-dopamine (PDA)/chitosan (CS)/cellulose nanofibers (CNF) carbon aerogel with enhanced photothermal performance. This is achieved by incorporating PDA, known for its excellent light absorption properties, and cross-linking it with low-cost biomass CS and CNF via a Schiff base reaction. The resulting novel composite PCMs exhibit high photothermal conversion efficiency and shape stability by encapsulating PW within the PDA/CS/CNF carbon aerogel. Our findings demonstrate that the composite PCMs have a high melting energy-storage capacity of 209.57 J/g. Notably, the introduction of PDA significantly improved the photothermal conversion efficiency by 94.9 %. These results suggest that composite PCMs hold great potential for applications in photothermal energy conversion and storage.

Superior Piezo-/Ferro-Electricity in Antiferroelectric AgxNbO3-δ Thin Films by Nanopillar Local Structure Design.

Antiferroelectrics are fundamental mother compounds critical in developing innovative lead-free piezoelectrics and ferroelectrics and hold great promise for wide-ranging applications in energy conversion and electronic devices. However, harnessing their superior properties presents a significant challenge due to the delicate balance required between their various states. In this study, through the unique design of nanopillar structures to alleviate the local polar heterogeneity, we have achieved significantly improved piezo-/ferro-electricity in classic lead-free antiferroelectric AgxNbO3-δ (x = 1, 0.9, and 0.8) epitaxial thin films. The effective piezoelectric coefficient reaches 440 pm V-1, 1 order of magnitude larger than the stoichiometric AgNbO3, rivaling classic lead zirconate titanate piezoelectrics. Atomic-scale electron microscopy investigations unravel the underlying mechanisms. The nanopillars, characterized by antisite occupancy of both Ag and Nb atoms and forming out-of-phase boundaries with the matrix, reduce the local crystal symmetry via interphase strain. This leads to the creation of flexible multinanodomain structures that significantly facilitate polarization rotation, thus substantially enhancing the piezoelectric performance. This study demonstrates the feasibility of engineering local heterogeneity through nanopillar design, offering a generally applicable method for property improvement of a wide range of antiferroelectrics.

Ce-doped ZnO nanonails synthesized by a simple thermal evaporation method for photocatalytic degradation

One-dimensional (1D) nanomaterials have garnered significant scientific and technological attention due to their potential applications in electronics devices, gas sensing, energy conversion, and photocatalysis. However, the development of a simple and low-cost technique for 1D nanostructure synthesis remains a challenge. The doping of ZnO nanostructures has proven to be an effective way to improve their internal properties. In this work, one-dimensional ZnO and Ce-doped ZnO nanorods and nanonails were synthesized by a simple thermal evaporation method using different weight ratios of ZnS and CeO2 precursor powders in a catalyst-free process. The effects of cerium doping concentration on the structural, morphological, and optical properties of the as-prepared samples were investigated. XRD analysis confirmed that the crystal structure was converted from the cubic ZnS phase to the hexagonal ZnO phase with increasing annealing temperatures. The UV–Vis spectra showed that the optical absorption edge of Ce-doped ZnO samples was slightly red-shifted. Additionally, the band gap energy decreases with increasing cerium concentration. SEM images showed that the morphology of the structures obtained changed from nanorods to nanonails as the Ce content increased. The incorporation of Ce ions into the ZnO matrix has been successfully confirmed by HRTEM, Raman, and EDX analysis. Photocatalytic activity studies showed that Ce-doped ZnO samples exhibited significantly enhanced photocatalytic performance compared to pure ZnO for the degradation of rhodamine B under UV radiation. These results may suggest the use of heterogeneous photocatalysis as an efficient, cheap, and environment-friendly alternative for the removal of pollutants from water and the use of Ce-doped ZnO as a promising candidate.

Fabrication of bacteriorhodopsin-embedded hydrogel construct for biocompatible photosensitive device

Bacteriorhodopsin (br) is a promising photosensitive material with applications in energy conversion, biosensors, and optoelectronic devices due to its bio-sourced origin and photoelectrical properties. Despite advancements in recent years, the integration of br-based devices necessitates the use of materials with little biocompatibility and fabrication techniques with restricted customizability, limiting potential applications such as optocontrol of cell behavior, implants with 3D patterning for retinal disease treatment, and light-sensitive cell robots. To solve this limitation, this study presents a novel approach by embedding br into a hydrogel matrix. It utilizes an extrusion-based and 3D bioprinting technique, showcasing its light-sensitive characteristics within a fully biocompatible construct. The hydrogel, comprising gelatin and sodium alginate, offers excellent printability for generating structured designs with versatile patterns. Photoelectrical properties of the fabricated br-embedded hydrogel construct, such as differential response, light intensity sensitivity, and br concentration sensitivity, are identified through electrochemical characterization. The temporal and spatial pattern recognition ability, based on the photoelectrical characteristics, is demonstrated through modulated light illumination and different patterns of printed hydrogel construct. Pattern recognition ability was then applied to reconstruct images containing different Latin letters. This research presents a novel method for the fabrication of patterned hydrogel constructs with high biocompatibility and distinctive light-responsive properties, expanding the potential applications of br in bio-related scenarios.  

Chiral Au@CeO2 Helical Nanorods with Spatially Separated Structures for Polarization-Dependent N2 Photofixation.

Chiral photocatalytic nanomaterials possess numerous unique properties and hold promise for various applications in chemical synthesis, environmental protection, energy conversion, and photoelectric devices. Nevertheless, it is uncommon to develop effective means to enhance the asymmetric catalytic performances of chiral plasmonic nanomaterials. In this study, a type of L/D-Au@CeO2 helical nanorods (HNRs) was fabricated by selectively growing CeO2 on the surface of Au HNRs via a facile wet-chemistry construction method. Chiral Au@CeO2 HNRs, featuring Au and CeO2 with spatially separated structures, exhibited the highest photocatalytic performance for N2 fixation, being 50.80±2.64 times greater than that of Au HNRs. Furthermore, when L-Au@CeO2 HNRs were exposed to left circularly polarized light (CPL) and D-Au@CeO2 HNRs were exposed to right CPL, their photocatalytic efficiency was enhanced by 3.06±0.06 times compared to the samples illuminated with the opposite CPL, which can be attributed to the asymmetrical generation of hot carriers upon CPL excitation. This study not only offers a simple approach to enhance the photocatalytic performance of chiral plasmonic nanomaterials but also demonstrates the potential of chiral plasmonic materials for application in specific photocatalytic reactions, such as N2 fixation.

Chiral Au@CeO2 Helical Nanorods with Spatially Separated Structures for Polarization‐dependent N2 Photofixation

Chiral photocatalytic nanomaterials possess numerous unique properties and hold promise for various applications in chemical synthesis, environmental protection, energy conversion, and photoelectric devices. Nevertheless, it is uncommon to develop effective means to enhance the asymmetric catalytic performances of chiral plasmonic nanomaterials. In this study, a type of L/D‐Au@CeO2 helical nanorods (HNRs) was fabricated by selectively growing CeO2 on the surface of Au HNRs via a facile wet‐chemistry construction method. Chiral Au@CeO2 HNRs, featuring Au and CeO2 with spatially separate structures, exhibited the highest photocatalytic performance for N2 fixation, being 50.80 ± 2.64 times greater than Au HNRs. Furthermore, when L‐Au@CeO2 HNRs corresponded left circularly polarized light (CPL) and D‐Au@CeO2 HNRs corresponded right CPL, their photocatalytic efficiency was enhanced by 3.06 ± 0.06 times in contrast with the samples illuminated with the opposite CPL, which can be attributed to the asymmetrical generation of hot carriers upon CPL excitation. This study not only offered a simple approach to enhance the photocatalytic performance of chiral plasmonic nanomaterials but also demonstrated the potential of chiral plasmonic materials for application in specific photocatalytic reactions, such as N2 fixation.

Enhanced photoelectrochemcial activity of TiO2 nanoparticles by graphene intercalation

The photoelectronchemical (PEC) activity of the photocatalyst is largely dependent on the concentration and lifetime of the photogenerated carriers, however, these carriers are easily and quickly neutralized within the photocatalyst. To address this issue, we designed a superstructure of graphene-intercalated TiO2 nanoparticles (TiO2/G) by pyrolyzing octylamine-intercalated hexafluorotitanic acid hybrids. The inserted graphene accelerates photoelectron transfer and reduces the recombination of photogenerated carriers in the body, while maintains the structural stability. The TiO2/G hybrid composite exhibits a low carbon content of only 1.3 wt.%, a strong Ti-C chemical interaction between TiO2 and intercalated graphene, and a large surface area of 38.88 m2/g, nearly five times that of bare TiO2 (7.96 m2/g). The findings from the photocatalytic experiments indicate that the photocatalytic efficiency and photocurrent response of TiO2/G are twice and 4.22 times higher, respectively, compared to standard TiO2 nanoparticles. This indicates a substantial promise for the superstructure in photoelectrochemistry and energy conversion applications.

Anion-intercalation pseudocapacitance in oxygen vacancy-rich spinel-perovskite NiFe2O4-LaFeO3 nanocomposite for high energy density asymmetric supercapacitor application

Oxide nanomaterials have attracted significant attention as energy storage materials. The combination of spinel-perovskite oxides as nanocomposites creates dense oxygen vacancies (VO) at the hetero-interface. VO present in the complex oxides are indispensable for energy conversion applications. Herein, we demonstrated the one pot synthesis of spinel-perovskite NiFe2O4-xLaFeO3 nanocomposite and investigated the phase formation using variable temperature powder X-ray diffraction of the gel precursor. The role of oxygen-vacancy mediated tuneable redox transitions in NiFe2O4-xLaFeO3 nanocomposite has been understood. The anion-intercalation-based pseudocapacitance and the oxygen intercalation have been exploited for high-performance electrochemical energy storage. The NiFe2O4–2LaFeO3 exhibited a high specific capacity of 652 C g−1 at a current density of 2 A g−1. The fabricated NiFe2O4–2LaFeO3||NiCo2O4 asymmetric supercapacitor device (ASC) exhibited excellent cyclability over 20,000 cycles with superior capacity retention and high Coulombic efficiency (92 %) and achieved a high energy density of 42.5 Wh kg−1 at a power density of 1500 W kg−1. The presence of VO and the mixed-valence states of Fe2+/3+ were confirmed by XPS-depth profiling. The tuneable redox transition of Fe2+/3+ and VO contribute to the higher pseudocapacitance response.

Modulating the Conductivity of Light-Responsive Ionic Liquid Crystals.

In this work, we describe the phase behaviour and the dielectric and conductivity response of new light-responsive ionic liquid crystals, ILCs, which can be applied as controllable electrolytes. The materials include two different dicationic viologens, the asymmetric 6BP18 and the symmetric EV2ON(Tf)2, containing bistriflimide as the counterions, mixed with 5% and 50% molar, respectively, of one new photoresponsive mesogen called CNAzO14. These mixtures exhibit liquid crystal behaviour, light responsiveness through the E-Z photoisomerisation of the azobenzene groups in CNAzO14, and strong dielectric responses. The 5%-CNAzO14/Ev2ON(Tf)2 mixture displays direct current conductivities in the 10-7 S·cm-1 range, which can be increased by a two-fold factor upon the irradiation of UV light at 365 nm. Our findings set the grounds for designing new smart ionic soft materials with nanostructures that can be tuned and used for energy conversion and storage applications.

Piezo-photocatalysis synergy in γ-GeSe for highly efficient oxygen evolution reaction

Solar-driven semiconductor photocatalysts are highly appealing in applications of environmental remediation and energy conversion. However, photocatalytic reactions, particularly oxygen evolution reaction (OER), are often constrained by the swift recombination of electron–hole pairs, thereby resulting in low reaction efficiency. Although it is effective to separate charge carriers by constructing heterojunctions to form built-in electric field, the lattice mismatch and inefficient interlayer charge transfer of heterojunctions in the photocatalysts limit their further development. Here, we propose a new strategy by constructing an internal electric field for OER through an individual piezoelectric two-dimensional material. The results indicate that the piezoelectric effect regulates the electronic structure, reduces bandgap, improves light absorption efficiency, and that the displacement of positive and negative charge centers is the key factor in the enhanced OER. This research indicates the feasibility of combining piezoelectric properties of two-dimensional materials with OER (1.19 eV), providing new insights and guidance for applying the piezoelectric effect in the OER and opening up a way to promote efficient separation of charge carriers.

Water structures and anisotropic dynamics at Pt(211)/water interface revealed by machine learning molecular dynamics

Abstract Water molecules at solid–liquid interfaces play a pivotal role in governing interfacial phenomena that underpin electrochemical and catalytic processes. The organization and behavior of these interfacial water molecules can significantly influence the solvation of ions, the adsorption of reactants, and the kinetics of electrochemical reactions. The stepped structure of Pt surfaces can alter the properties of the interfacial water, thereby modulating the interfacial environment and the resulting surface reactivity. Revealing the in situ details of water structures at these stepped Pt/water interfaces is crucial for understanding the fundamental mechanisms that drive diverse applications in energy conversion and material science. In this work, we have developed a machine learning potential for the Pt(211)/water interface and performed machine learning molecular dynamics simulations. Our findings reveal distinct types of chemisorbed and physisorbed water molecules within the adsorbed layer. Importantly, we identified three unique water pairs that were not observed in the basal plane/water interfaces, which may serve as key precursors for water dissociation. These interfacial water structures contribute to the anisotropic dynamics of the adsorbed water layer. Our study provides molecular-level insights into the anisotropic nature of water behavior at stepped Pt/water interfaces, which can influence the reorientation and distribution of intermediates, molecules, and ions—crucial aspects for understanding electrochemical and catalytic processes.

Fabrication of boron nitride/copper oxide@multi-walled carbon nanotubes composites for enhancing heat transfer and photothermal conversion of phase change materials

To realize the efficient storage and conversion of solar energy by phase change materials (PCMs), low photothermal conversion efficiency and poor heat transfer performance remain great challenges. Herein, polyethylene glycol (PEG)-based composite PCMs with excellent photothermal conversion performance and exceptional thermal management capability were obtained by using boron nitride/copper oxide@multi-walled carbon nanotubes (BN/CuO@MWCNTs) as the thermal conductive and photothermal conversion enhancement fillers. The results indicate that owing to the bridging effect, the introduction of CuO and MWCNTs on the BN surface can construct additional heat transfer paths, resulting in a high thermal conductivity of up to 2.35 W/(m·K) for the as-prepared PEG/BN/CuO@MWCNTs composite, which is about 9-folds enhancement than pristine PEG. Simultaneously, the supercooling degree of PEG in PEG/BN/CuO@MWCNTs is effectively suppressed due to the synergistic nucleation effect of BN, CuO and MWCNTs. Additionally, the PEG/BN/CuO@MWCNTs composites not only exhibit a high latent-heat capacity of 154.5 J/g and a high photothermal conversion efficiency of 92.2 %, but also show favorable shape stability and durable reliability. This work offers a workable solution for the synergistic enhancement of photothermal conversion and thermal management, which can effectively promote the practical application in solar energy conversion and storage.

Computational insights into structural, electronic, optical and thermoelectric features of ternary chalcogenide Ca2GeX4 (X=S, Se, Te) compounds

The advancements in materials engineering for clean energy and greenhouse gas reduction has attracted global attention. Furthermore, the distinct electrical and optical properties of ternary chalcogenides are critical for their application in solar energy conversion. In this study, the electronic, optical, thermodynamic, and thermoelectric transport properties of the ternary chalcogenide Ca2GeX4 (X = S, Se, and Te) compounds are comprehensively investigated using the density functional theory-based WIEN2k package. The findings indicate that ternary chalcogenide Ca2GeX4 compounds possess substantial band gaps and display strong covalent bonding characteristics. Analysis of the density of states reveals minimal impact from S-s and S-p states, while highlighting the significance of Ca-s and Ge-s states. The investigated materials show significant UV absorption with reflectance between 30 and 40 % which peaks at 13.5 eV at about 65 %, confirming the optical properties of the ternary chalcogenide Ca2GeX4. The positive Seebeck coefficient suggests that holes are the primary charge carriers in tested materials, with thermal energy rising in accordance with the chalcogenide's atomic number. Several thermoelectric properties that demonstrate the suitability of these materials for thermoelectric applications were also discussed. Overall, the findings confirm the thermoelectric and optoelectronic properties of Ca2GeX4 materials, which may facilitate the creation and development of effective optoelectronic devices.

Power absorption and flow-field characteristics analysis for oscillating coaxial twin-buoy wave energy converter by using CFD

The energy conversion capacity of wave energy conversion devices highly depends on the hydrodynamic characteristics of the energy-harvesting structure. To investigate the effect of hydrodynamic performance on the power conversion characteristics, a twin-buoy wave energy converter (WEC) was investigated by using a three-dimensional numerical wave pool based on the Computational Fluid Dynamics (CFD) method. Several factors are examined, including the elasticity coefficient of the anchor chain, the bottom configuration of the floating body, and the power take-off (PTO) damping coefficient. The heave displacement, heave velocity, and heave force of the converter are calculated under specific wave parameters, and the flow field cloud diagram during the heave motion is analyzed. The results indicate that a wave energy converter with a hemispherical floating body exhibits the best kinematic performance. The influence of the mechanical damping coefficient on the energy conversion performance of the device is studied. By appropriately reducing the mechanical damping coefficient, the energy capturing capability of the device can be increased to a certain extent. These findings can serve as a theoretical basis for the application of deep-water wave energy conversion in engineering and the optimization of future WEC designs.

High Performance and Selective Sequestration of Cd(II) from Water by Layered Thiophosphate.

The extensive use of toxic cadmium (Cd) in energy conversion and industrial applications ranging from solar cells and battery appliances to paints and pigments contaminates water bodies. However, the upper limit of Cd contamination in drinking water is to be only 3 ppb by the WHO and 5 ppb by the USA-EPA, which underscores the need for cost-effective, efficient, and ppb level capture of Cd from contaminated water. Leveraging the selectivity due to Lewis's hard-soft acid-base (HSAB) theory, we have achieved swift and highly selective capture of Cd(II) ions from aqueous mediums using layered potassium manganese thiophosphate (K-MnPS3). K-MnPS3 effectively removes Cd(II) ions from extremely dilute aqueous solutions (ppb levels), achieving a maximum sorption capacity of 405.43 mg/g and a removal rate exceeding 97% within 20 min. Even in the presence of competing ions such as Na+, Mg2+, Ca2+, and Pb2+, K-MnPS3 remains selective. Additionally, it operates efficiently across a wide pH range (1.78-11.19) with a high distribution coefficient (∼104 mL/g). Breakthrough experiments using a 1 wt % K-MnPS3 and 99 wt % sand column showed complete breakthrough of Cd(II) after 62 h, leading K-MnPS3 as a promising candidate for Cd(II) removal from industrial effluents.

Piezoelectricity in NbOI2 for piezotronics and nanogenerators

2-dimensional (2D) piezoelectric materials have gained significant attention due to their potential applications in flexible energy harvesting and storage devices. Recently, niobium oxide dihalides NbOI2 stands out as a multifunctional anisotropic semiconductor family with an exceptionally high lateral piezoelectric constant (~21.8 pm/V), making it a promising candidate for energy conversion applications. Here we report the experimental observation of anisotropic in-plane piezoelectricity in multilayer NbOI2. Current-voltage relationships reveal a significant piezotronic effect in two typical crystalline orientations. Additionally, cyclic tensile and release experiments demonstrate an intrinsic current output of up to 140 pA when subjected to a tensile strain of 0.51%. A flexible piezoelectric nanogenerator prototype is demonstrated on the human finger and wrist, which opens up new avenues for the development of wearable electronic devices and provides valuable insights for further exploration in this field.

Rational design of Er2O3/ZnS as highly competent electrocatalyst for OER application

The fabrication of an extremely productive, inexpensive and prominent electrocatalyst is required to improve the slow oxygen evolution reaction (OER). Here, a hydrothermal approach was utilized to fabricate Er2O3/ZnS composite as a competent electrode material for the purpose of efficient water splitting. The various analytical tools were used to evaluate morphology, crystallinity, functionality, surface area, and thermal stability of the reported materials. The large surface area of the Er2O3/ZnS composite (61.06 m2 g−1), makes it a suitable candidate for carrying out the OER process. Moreover, the electrochemical study for Er2O3/ZnS composite was conducted on nickel foam (NF) as a substrate to determine the electrolytic nature. The electrochemical study showed that the synthesized composite responds to an impressive overpotential (260 mV) and low Tafel value (40 mV dec−1) at an ideal current density (j) of 10 mA cm−2. The Er2O3/ZnS composite exhibits a reduced onset potential of approximately 1.31 V and exceptional durability of about 30 h. The electrochemical observation suggests that incorporating Er2O3 into ZnS resulted in an enlarged surface area and enhanced active regions which reduce the resistance and promote the rapid binding of electrolyte ions. The composite (Er2O3/ZnS) developed by this approach can be utilized in various energy conversion and storage applications.