In this study, three D–A-type trifluoromethylated quinoxaline-based polymers, with different numbers of fluorine (F) atoms on the quinoxaline unit, were developed to clarify the impact of strongly electron-attracting F substituents on the photovoltaic characteristics of polymers. The unfluorinated reference quinoxaline-based polymer PTB-QxCF3, was prepared by coupling an alkylated benzodithiophene donor to a trifluoromethylated quinoxaline acceptor via a thiophene bridge. Subsequently, one and two fluorine atoms were attached to the vacant 6,7-positions of the trifluoromethylated quinoxaline unit to generate the fluorinated polymers PTB-FQxCF3 and PTB-2FQxCF3, respectively. An inverted-type polymer solar cell was constructed with Y6BO as a non-fullerene acceptor, to examine the photovoltaic characteristics of the polymers. Devices made from fluorinated PTB-FQxCF3 and PTB-2FQxCF3 exhibited higher power conversion efficiencies (PCEs) of 11.95% and 13.50%, respectively, than that comprising unfluorinated PTB-QxCF3 (4.80%). This noticeable advancement in the PCEs of devices with fluorinated polymers originates from the rapid increase in their photovoltaic parameters. These results demonstrate the usefulness of the fluorination strategy for promoting photovoltaic responses of trifluoromethylated quinoxaline-based polymers.

We investigated the discharge performance and electrochemical properties of an as-extruded Mg-5Sm-xAl (x=0,1,3) anode for Mg-air batteries. Adding Al modified the phase composition and grain size of the anode. The addition of 1 wt% Al (Mg-5Sm-1Al) induced a high discharge voltage and power density due to the stimulation of the evenly distributed, fine Al11Sm3 particles. However, these particles increased the parasitical anodic hydrogen reaction rate, resulting in a decrease in anodic efficiency. These properties make the anode suitable for high-power density applications. The addition of 3 wt. % Al (Mg-5Sm-3Al) promoted the formation of an aluminium oxide film on the anode surface, which suppressed the anodic hydrogen reaction to improve the anodic efficiency. This film increased the battery's internal resistance resulting in low voltage. This anode is a good candidate for heavy-duty battery applications, where a steady voltage output and long service life are desired. By controlling the Al content, the tailoring of discharge performance of the Mg-Sm-Al anode is feasible to satisfy different battery load requirements.

The tunable bandgap of quantum dot (QD)-based solar cells is their greatest advantage, providing control over light absorption region. However, the investigation of the effect of bandgap variation on QD-based photovoltaic properties is insufficient, in contrast to well-defined material properties. In this study, we analyze the electrical properties of solar cells fabricated with bandgap-tuned lead sulfide (PbS) QDs to examine the effect of bandgap variation on photovoltaic properties. We find that reducing the thickness of the QD active layer is necessary to achieve high power conversion efficiency mainly because the doping concentration of the QD film increases as the QD bandgap decreases. We suggest that QD photovoltaic device structures should be designed with consideration of their electrical characteristics in relation to the bandgap.

Lithium-sulfur batteries are plagued by the shuttle effect and sluggish kinetics in the redox reaction of lithium polysulfides (LiPSs) to Li2S, resulting in a limited capacity and shortened lifetime. To address these issues, it is crucial to develop an efficient catalytic sulfur host by creating active sites that can both confine LiPSs and accelerate their conversion. Herein, we developed carbon-coated mesoporous Fe3O4 (C@M−Fe3O4) nanospindles and applied them as sulfur host material to improve the electrochemical performance of Li–S batteries. Besides, the conductive C@M−Fe3O4 particles with rich sites of electrolyte/Fe3O4/carbon ‘‘triple-phase’’ can also accelerate the conversion of LiPSs and promote the nucleation and growth of Li2S. With these merits, our C@M-Fe3O4/S electrode shows good cycling stability with a remaining capacity of 1064.3 mAh/g at 0.2 C after 100 cycles and delivers an initial capacity of 712.0 mAh/g at 2 C. The proposed synthetic method could pave the way for designing similar porous transition metal-based compounds with different precursors (e.g. carbonates, hydroxides, oxalates) for other electrochemical applications.

The formation of solid electrolyte interphase at the first cycle has raised technical issues of capacity loss in anode materials for lithium-ion batteries. As one solution, using Li-excess Li2NiO2 as a cathode additive aims to compensate for the initial Li+ consumption by anode materials using some of the high irreversible capacity. However, Li2NiO2 is insufficient for satisfying atmospheric stability, which induces spontaneous side reactions (e.g. Li2CO3 and LiOH), resulting in an increase of interfacial resistance for Li+ migration. In addition, the small but significant evolution of oxygen (O2) gas during the charge process over 3.8 V vs. Li/Li+ brings an extra caution for safety concerns. There is no doubt that structural stabilization of Li2NiO2 is a prerequisite for practical use in lithium-ion batteries. In this study, we propose a surface coating of amorphous niobium oxycarbide (NbOxCy) onto Li2NiO2 particles to improve their atmospheric stability, together with suppression of O2 gas evolution. Owing to its distinctive physicochemical properties, NbOxCy is beneficial for enhancing vulnerability to moisture as well as scavenging any residual O2 gas. In practice, the adoption of NbOxCy-coated Li2NiO2 improved electrochemical performance in full cells and was verified as a strategic solution to two fundamental challenges.

Solar cells have penetrated many cities as Building Integrated Photovoltaic (BIPV) or the energy source for standalone Internet of Things (IoT) devices. Traditionally, photovoltaic (PV) cells are evaluated using 1 sun irradiance. However, in a city, factors such as air pollution, cloudiness and cell installation orientation may attenuate the receivable solar energy. Also, the power conversion efficiency (PCE) of a PV cell is highly irradiance-dependent. Evaluating urban outdoor PV cells using 1 sun irradiance could lead to inaccurate prediction of PCE and overestimated output power in actual usage. Herein, we analyzed daytime irradiances of 11 cities located across the globe. Our results show that realistic irradiance (RI) in most cities is between 0.01 and 0.5 sun, reflecting the irradiance under a cloudy to mostly sunny sky. Under such an RI window, the PCEs of 9 different PV technologies were compared. 7 PV technologies have compromised performance. 2 PV technologies, organic and perovskite PVs, show enhanced PCE under the RI window and are favorable for urban outdoor applications. The potential of powering IoT devices by these PV technologies under sub-optimal irradiance conditions in cities is also highlighted.

The lithium-sulfur (Li–S) battery has emerged as one of the most promising candidates for next-generation energy storage systems due to its high specific capacity and potential low cost. However, the shuttle effect of lithium polysulfide (LiPS) is problematic because it results in the irreversible loss of active materials and rapid capacity decay. In this study, we developed a potent separator that overcomes the limitations posed by LiPS shuttling and improves the selectivity of Li-ions. The interior of a polypropylene separator was filled with self-assembled supramolecules comprising tetrabutyl ammonium, 18-Crown-6, and Ni(dmid)2, which exhibited high selectivity for Li-ions and facilitates their rapid transmission. Utilizing the hard and soft acid-base effect between the supramolecule and LiPS, the proposed separator renders LiPS unstable upon contact with the separator. This promotes the transformation of LiPS and ensures smooth pathways for Li-ion migration, thereby inhibiting LiPS shuttling and enhancing Li-ion selectivity. As a result, experimental results demonstrated a Li–S battery with a remarkable lifetime of over 1000 cycles, an initial specific capacity of 1228 mAh/g at a current density of 0.5 C, and a cycle decay as low as 0.028% per cycle. Overall, by optimizing the sulfur redox kinetics, the separator presented in this work provides a rational design strategy for suppressing LiPS shuttling, enhancing Li-ion transport, and promoting highly efficient and durable Li–S batteries.

La and Yb were incorporated as co-doping elements into Zr-doped ceria to investigate the influence of doping ions by means of ionic radius and valence on the ceria crystal lattice and potentially on thermodynamic and kinetic properties relevant to solar-driven two-step thermochemical CO2 splitting. Both Zr–La and Zr–Yb co-doped ceria clearly exhibited better reduction capability than ceria and partial molar enthalpy and entropy that were in between those of Zr-doped ceria and undoped ceria. In the case of CO2 splitting kinetics, Zr-doped ceria was the slowest in accordance with relevant literature, but La-doped samples were much faster than Yb-doped counterparts suggesting that extrinsic oxygen vacancy formation, even though important, does not primarily determine the CO2 splitting kinetics unlike the hypothesis postulated by previous works. This work elucidates the role of dopant's ionic radius, lattice constant and valence on thermodynamics and CO2 splitting kinetics via experimental demonstration, and provides a new doping strategy not based on the extrinsic oxygen vacancy formation but based on the dopant ionic radius and valence with an insight for the further doped ceria-based redox material discovery.

The formation of Li dendrites and dead Li, which causes short circuits, continuous side reactions, low Coulombic efficiency (CE) and thermal runaway, severely hinders the development of anode-free lithium metal batteries. Here, Cu-based current collector with super-three-dimensional lithiophilic modification layer is developed by the pyrolysis of resorcinol formaldehyde on 3D engineered copper mesh (a-RF@3D CM). The modification layer, consisting of highly dispersed CuOx sites in the O-containing defective carbon, together with the super-three-dimensional microstructure exhibits excellent lithiophilicity and capability to effectively reduce the nucleation overpotential, accommodate the uniform dendrite-free lithium deposition, promote stable and inorganic-rich solid electrolyte interphase formation, and improve the cycle stability. As a result, the a-RF@3D CM current collector exhibits reduced nucleation overpotential of 14.2 mV and prolonged cycling life over 400 cycles with average CE >98.5%. In the LiFePO4||a-RF@3D CM anode-free cell, average CE of 99.50% and capacity retention of 60.66% are successfully achieved after 100 cycles. Meanwhile, average CE 99.78% and capacity retention of 64.43% are successfully achieved in LiFePO4||Li@a-RF@3D CM cell (N/P = 1.6) after 200 cycles. The work provides feasible way to realize the fabrication of anode-free lithium metal batteries and also enhance the understanding of solid electrolyte interface evolution and regulation strategy of Li plating–stripping in advanced Li metal-based batteries.

The Lab-to-Fab transfer from cell to large-area flexible semitransparent organic photovoltaic (OPV) module by the slot-die coating based on halogen-free host solvent and under ambient air environment is developed. The bulk heterojunction structure (BHJ) and formation mechanism of slot-die-coated active layer on flexible substrate are different from those usually reported. The relationship among processing, film thickness/BHJ morphology, transmittance and performance for the slot-die-coated module, and the optimum strategy are studied in this article. The flexible semitransparent modules with active areas of 45 and 22.5 cm2 have the average visible transmittance of 21.3%–16.7%. The corresponding average power conversion efficiency (PCE) values are 4%–6.2%. The highest PCE can achieve 7.8%. Compared to all large-area flexible semitransparent slot-die-coated OPV modules reported with PCEs (usually ≤5%), the modules prepared here have the best PCE. The electric behavior and stability of these OPV modules and a Si-PV panel under the greenhouse test are studied. Among the stability data (usual T80 lifetime ≤100 days) reported for semitransparent flexible OPV modules under greenhouse test, the T80 lifetime of the OPV modules prepared here can reach 200 days and also remain the highest PCE with the least burn-in loss.

Green hydrogen production via water electrolysis is crucial to the strategic path toward carbon neutrality. Therefore, exploration of efficient and low-cost electrocatalysts for oxygen evolution reaction (OER) is essential due to the sluggish OER kinetics, where cobalt-iron-layered double hydroxides (CoFe-LDHs) represent a class of promising OER catalysts. Herein, a systematic study gives insights into the Co/Fe intrinsically assembled structures in CoFe-LDHs on their catalytic performances in OER, representing a new route for rational design of catalysts. Theoretical calculations suggest that the electron structure at exposed active sites can be modulated by varying the Co/Fe assembled structure and introducing oxygen vacancy. The structural characterizations of the as-synthesized CoFe-LDHs with varied Co/Fe assembled structures indicate that Co1Fe3-LDHs-Vo induces the suitable distortion in the octahedral unit structure of [CoO6] with a shorter cobalt–oxygen bonding distance and hence leads to the favorable Co active sites exposed for the formation of oxygenated intermediates. Consequently, the Co1Fe3-LDHs-Vo exhibits the unprecedented OER activity with an overpotential of 253 mV at 50 mA/cm2 and Tafel value of 26.8 mV/dec. The overall water splitting is driven by a voltage of 1.47 V at 10 mA/cm2 in 1.0 M KOH electrolyte.

Transparent conductive oxide (TCO) films are widely used for semi-transparent perovskite solar cells (st-PSCs) and perovskite-based tandem solar cells due to their high optical transparency and good electrical conductivity. However, the high-power sputtering damage during the deposition of TCO film is a vital factor to prevent the perovskite-based solar cells from achieving high efficiency. In this work, we develop an ultrathin chromium oxide (CrOx) buffer layer between the hole transporting layer (HTL) and indium-doped tin oxide (ITO) by trace-oxygen reactive thermal deposition (to-RTD). The experimental results show that the CrOx buffer layer can hinder the sputtering damage of ITO deposition and ensure a high-performance device, which can be attributed to the improved conductivity of the HTL/CrOx/ITO structure together with the tailored energy level alignment. In addition, this buffer layer with a thickness of 4 nm displays a high optical transmittance (>95%) in the interested wavelengths, meaning a limited optical parasitic absorption loss. As a result, the st-PSC with CrOx buffer layer achieves a champion power conversion efficiency (PCE) of 19.06%, which is one of the highest PCEs for the n-i-p st-PSCs. Moreover, a four-terminal perovskite/silicon tandem solar cell featuring a CrOx buffer layer realizes a relatively high PCE of 27.48%.

Nickel-rich cathode materials preparation requires a timewise lengthy and complicated chemical reaction, which results in challenges in determining a suitable sintering schedule to obtain a high-quality product. In this article, a multiparticle cellular automaton modeling method is proposed to capture and track the complex grain dynamics evolution process. According to the chemical reaction mechanism, the sintering process is divided into three main reactions, with each reaction's starting and ending temperature points determined based on thermal hysteresis. Then multiparticle state transition rules based on the Arrhenius formula and experiments data are constructed to obtain a multiparticle cellular automaton with kinetic properties. To realize dynamic simulation under multiple heating rates, a kinetic parameter transfer method is designed, in which particle swarm optimization and least squares estimation algorithms are adopted. Based on the above model, the final Li/Ni cation mixing parameter of the preparation is predicted by combining X-ray diffraction experiments analysis with the Li/Ni cation mixing law in reactions. The simulation results show that the proposed modeling method can accurately simulate the grain dynamics evolution of the cathode materials, which can provide a valuable reference for optimizing the sintering schedule in the sintering process of the cathode materials.

The efficiency of Bi2Te3 thermoelectric generators is strongly constrained by the fact that n-type alloys always perform poorly thermoelectrically compared to their p-type counterparts. Here, we report an efficient method for improving the thermoelectric performance of n-type Bi2Te2.69Se0.33Cl0.03 by incorporating Ag8SnSe6. The incorporation of Ag8SnSe6 increases the carrier effective mass as a result of dissolved Ag and Sn atoms in Bi2Te2.69Se0.33Cl0.03, which in turn enhances the Seebeck coefficient. The thermal conductivity of Bi2Te2.69Se0.33Cl0.03 also decreases due to multiscale phonon scattering from both the residual Ag8SnSe6 second phase and point defects. Consequently, we achieve a high ZT of 1.24 at 353 K and a high average ZT of 1.12 for temperatures in the range of 300–433 K in Bi2Te2.69Se0.33Cl0.03 + 1 wt% Ag8SnSe6, which are respectively ∼ 27.42% and ∼ 26.78% larger than those of Bi2Te2.69Se0.33Cl0.03. Furthermore, a device with two couples of n-p thermoelectric legs based on 1 wt% Ag8SnSe6 n-type legs shows a greater cooling temperature drop (28%) than that of the Bi2Te2.69Se0.33Cl0.03 n-type legs device. The high thermoelectric and mechanical performance (83.4 HV) of Ag8SnSe6 incorporation in n-type Bi2Te3 makes them strong candidates for practical applications.

Substituting Ni for Co in high-Ni layered oxide cathodes is highly effective in enhancing the range of delithiation and reducing production costs, but the reactive Ni3+ and unavoidable residual surface impurities critically limit the cycleability of lithium-ion batteries (LIBs). Although the wet-coating method is one solution suitable for widespread industrial production, wet-coating of high-Ni layered oxides is complicated due to chemical delithiation, corrosion, and the inhomogeneous coating caused by their instability. Herein, we applied wet-coating chemistry to coat LiNi0.88Co0.06Mn0.06O2 (NCM88) with a thin boron–aluminum oxide layer using eco-friendly aqueous solutions. Under acidic H3BO3 conditions, Al(OH)3 is critical in preserving the fragile surface of Ni-rich layered oxides and forming a homogeneous coating. Furthermore, structural characterization reveals the formation of an amorphous Li2O–LiAlO2–LiBO2 (LABO) coating layer. A highly homogeneous LABO-coated NCM88 exhibits significantly improved cyclability, retaining 75.5% of its capacity after 250 cycles of charging/discharging. This is a much higher capacity retention rate than those of bare NCM88 (7%) and NCM88 coated with Al(OH)3 (64.4%) or H3BO3 (65.2%). The LABO-coated layer also demonstrates improved rate capability with charge voltages of 4.25 and 4.5 V.

Among the various liquid metals, Ga has unique properties, such as a low melting temperature, fluidity, and non-toxicity. In addition, Ga can alloy with Li to form a Li2Ga phase, which can be applied to high-capacity anodes for Li-ion batteries (LIBs). However, Ga-based materials readily melt and agglomerate during lithiation/delithiation owing to their low melting temperature and high surface energy, resulting in poor cycling stability. In this study, two structural types of Ga, crystalline and amorphous, were selected and electrochemically investigated as LIB anodes. Subsequently, to address the melting and agglomeration issues of the Ga anode, an optimized Ga-based nanocomposite was developed using a novel synthetic concept, namely a solid-state alloying–dealloying process. This process involves an alloying reaction of Ga and Ti to form various Ga–Ti compounds, such as Ga3Ti, Ga2Ti, and Ga3Ti2, and a dealloying reaction with amorphous C to form a nanocomposite comprising evenly dispersed amorphous Ga and Li-inactive TiC in the amorphous C matrix. The Li-inactive TiC and amorphous C matrix in the nanocomposite effectively confined amorphous Ga, thereby preventing the problems caused by its melting and agglomeration during cycling. In addition, an interesting transformation behavior of amorphous Ga into electrochemically stabilized Ga nanocrystallites (approximately 2–3 nm) was demonstrated during cycling, contributing to the high electrochemical performance. The Ga-based nanocomposite exhibited a superior electrochemical performance. This study proposes a better understanding of high-performance Ga-based anodes for LIBs as well as an effective fabrication method for high-performance nanocomposites by solid-state alloying–dealloying.

Energy conversion from chemical to electrical energy through electrochemical processes using fuel cells is a promising advanced technology to address global environmental issues. However, the development of cathode materials for proton exchange membrane fuel cells (PEMFCs) still faces challenges due to their practical requirements for activity and stability. Introducing oxides into the electrocatalysts is an important way to improve performance. Here, we propose a one-pot hydrothermal synthesis to load Pt and TiO2 nanoparticles (NPs) onto the treated carbon (TC). Through the TiO2 reconciliation between the Pt NPs and the carbon support, the tightly bound Pt–TiO2–TC electrocatalyst shows excellent activity and stability in the oxygen reduction reaction (ORR) due to the strong electronic interaction. At 0.9 V vs. reversible hydrogen electrode, the Pt–TiO2–TC electrocatalyst has about twice the specific activity (SA) and mass activity (MA) of commercial Pt/C. Moreover, the decline of Pt- SA and MA in Pt–TiO2-TC after the accelerated durability test (ADT) was 4.2% and 12.3%, respectively. Therefore, we strongly recommend hybrid metal-oxide-carbon materials with high conductivity, electronic interaction, and carbon corrosion resistance as support materials for Pt NPs to develop Pt-based electrocatalysts for fuel cell applications.

Conversion-type cathodes have a higher theoretical capacity compared to intercalation-type cathodes due to the use of more transition metal cations. However, their sluggish kinetics and low operation voltage hinder their practical application in the industry, resulting in low specific capacity. To address these issues, we prepare an amorphous carbon-coated Cu(PO3)2 nanocomposite, and evaluate its electrochemical performance under rechargeable Na-ion battery system. At a current density of 24 mA/g, it achieves a large specific capacity of ∼232 mAh/g with an average operation voltage of ∼2.0 V (vs. Na+/Na). Furthermore, the amorphous carbon-coated Cu(PO3)2 nanocomposite exhibits a cycle retention of ∼90% compared to the initial capacity after 100 cycles. In contrast, bare Cu(PO3)2 shows poor electrochemical performance under the same conditions. Various experimental measurements have demonstrated that the amorphous carbon-coated Cu(PO3)2 nanocomposite exhibits a reversible and smooth conversion reaction of Cu(PO3)2 phase in the rechargeable Na-ion battery system.

Graphite anode for potassium-ion batteries suffers poor rate capability because of the sluggish diffusion kinetics of K+. According to the rate law of chemical reactions, enrichment of K+ on the outer layer of graphite anode is expected to improve the rate capability. However, the surface of graphite is too smooth to adsorb adequate K+ to enhance rate capability. Herein, MoS2 is coated on exfoliated graphite to enrich the concentration of K+ on the surface of EG by forming K2S in high-voltage region, leading to an extremely high diffusion coefficient of up to 1000 times than that of bare graphite at the bottleneck stage, which accelerates the reaction rate of electrochemical intercalation process. Consequently, the EG/MoS2 electrode exhibits superior rate performances (125 mAh/g at 3.2 A/g), which is 11 times higher than that of EG. Moreover, the specific capacity of EG/MoS2 is 169 mAh/g at 1.6 A/g below 0.36 V, which is almost 25 times higher than that of bare EG (7 mAh/g). Our study provides new fundamental insights to boost power density of the anodes for PIBs without trading off energy density.

Solar-driven water purification is considered as an efficient and green method to solve water scarcity. However, creating a hydrogel evaporator with both long-lasting evaporation performance and an efficient reduction in water vaporization enthalpy remains a significant challenge. Herein, a hydrogel with low water vaporization enthalpy was prepared by introducing β-cyclodextrin (β-CD) to polyacrylamide. The three-dimensional network structure was obtained via a simple freeze-drying process, and the addition of β-CD enhanced its hydrophilicity. Due to the hydration of hydroxyl groups on β-CD, the hydrogel facilitated the formation of intermediate water, substantially reducing the water vaporization enthalpy to 1428 J/g. It enabled the hydrogel to achieve a high evaporation rate of 2.65 kg/m2/h under 1 sun irradiation. Furthermore, the hydrogel demonstrated excellent hydration properties and abundant water transport channels for salt rejection in long-term desalination. After 50 cycles of testing in 3.5% brine, the evaporation rate remained high at 2.38 kg/m2/h. This work provides a sustainable way to develop a highly efficient solar evaporator for clean water production.