NiO, an anodic electrochromic material, has applications in energy-saving windows, intelligent displays, and military camouflage. However, its electrochromic mechanism and reasons for its performance degradation in alkaline aqueous electrolytes are complex and poorly understood, making it challenging to improve NiO thin films. We studied the phases and electrochemical characteristics of NiO films in different states (initial, colored, bleached and after 8000 cycles) and identified three main reasons for performance degradation. First, Ni(OH)₂ is generated during electrochromic cycling and deposited on the NiO film surface, gradually yielding a NiO@Ni(OH)₂ core–shell structure, isolating the internal NiO film from the electrolyte, and preventing ion transfer. Second, the core–shell structure causes the mode of electrical conduction to change from first- to second-order conduction, reducing the efficiency of ion transfer to the surface Ni(OH)₂ layer. Third, Ni(OH)₂ and NiOOH, which have similar crystal structures but different b-axis lattice parameters, are formed during electrochromic cycling, and large volume changes in the unit cell reduce the structural stability of the thin film. Finally, we clarified the mechanism of electrochromic performance degradation of NiO films in alkaline aqueous electrolytes and provide a route to activation of NiO films, which will promote the development of electrochromic technology.

In recent years, paper-based functional materials have received extensive attention in the field of energy storage due to their advantages of rich and adjustable porous network structure and good flexibility. As an important energy storage device, paper-based supercapacitors have important application prospects in many fields and have also received extensive attention from researchers in recent years. At present, researchers have modified and regulated paper-based materials by different means such as structural design and material composition to enhance their electrochemical storage capacity. The development of paper-based supercapacitors provides an important direction for the development of green and sustainable energy. Therefore, it is of great significance to summarize the relevant work of paper-based supercapacitors for their rapid development and application. In this review, the recent research progress of paper-based supercapacitors based on cellulose was summarized in terms of various cellulose-based composites, preparation skills, and electrochemical performance. Finally, some opinions on the problems in the development of this field and the future development trend were proposed. It is hoped that this review can provide valuable references and ideas for the rapid development of paper-based energy storage devices.

Because poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS) is water processable, thermally stable, and highly conductive, PEDOT:PSS and its composites have been considered to be one of the most promising flexible thermoelectric materials. However, the PEDOT:PSS film prepared from its commercial aqueous dispersion usually has very low conductivity, thus cannot be directly utilized for TE applications. Here, a simple environmental friendly strategy via femtosecond laser irradiation without any chemical dopants and treatments was demonstrated. Under optimal conditions, the electrical conductivity of the treated film is increased to 803.1 S cm⁻¹ from 1.2 S cm⁻¹ around three order of magnitude higher, and the power factor is improved to 19.0 μW m⁻¹ K⁻², which is enhanced more than 200 times. The mechanism for such remarkable enhancement was attributed to the transition of the PEDOT chains from a coil to a linear or expanded coil conformation, reduction of the interplanar stacking distance, and the removal of insulating PSS with increasing the oxidation level of PEDOT, facilitating the charge transportation. This work presents an effective route for fabricating high-performance flexible conductive polymer films and wearable thermoelectric devices.

In this work, a modified polyurethane adhesive (PUA) was prepared to realize a convenient encapsulation strategy for lead sedimentation and attachable perovskite solar cells (A-PSCs). The modified PUA can completely self-heal within 45 min at room temperature with an efficient lead ion-blocking rate of 99.3%. The PUA film can be coated on a metal electrode with slight efficiency improvement from 23.96% to 24.15%. The thermal stability at 65 ℃ and the humidity stability at 55% relative humidity (RH) are superior to the devices encapsulated with polyisobutylene. The PUA film has strong adhesion to the flexible substrate and the initial efficiency of the flexible perovskite module (17.2%) encapsulated by PUA remains 92.6% within 1825 h. These results suggest that PUA encapsulation is universal for rigid and flexible PSCs with enhanced stability and low lead hazards. Moreover, it was found that flexible PSCs can be well attached to various substrates with PUA, providing a facile route for the A-PSCs in various scenarios without additional encapsulation and installation.

High Li⁺ transference number electrolytes have long been understood to provide attractive candidates for realizing uniform deposition of Li⁺. However, such electrolytes with immobilized anions would result in incomplete solid electrolyte interphase (SEI) formation on the Li anode because it suffers from the absence of appropriate inorganic components entirely derived from anions decomposition. Herein, a boron-rich hexagonal polymer structured all-solid-state polymer electrolyte (BSPE+10% LiBOB) with regulated intermolecular interaction is proposed to trade off a high Li⁺ transference number against stable SEI properties. The Li⁺ transference number of the as-prepared electrolyte is increased from 0.23 to 0.83 owing to the boron-rich cross-linker (BC) addition. More intriguingly, for the first time, the experiments combined with theoretical calculation results reveal that BOB⁻ anions have stronger interaction with B atoms in polymer chain than TFSI⁻, which significantly induce the TFSI⁻ decomposition and consequently increase the amount of LiF and Li₃N in the SEI layer. Eventually, a LiFePO₄|BSPE+10% LiBOB|Li cell retains 96.7% after 400 cycles while the cell without BC-resisted electrolyte only retains 40.8%. BSPE+10% LiBOB also facilitates stable electrochemical cycling of solid-state Li-S cells. This study blazes a new trail in controlling the Li⁺ transport ability and SEI properties, synergistically.

Solar vapor generation (SVG) represents a promising technique for seawater desalination to alleviate the global water crisis and energy shortage. One of its main bottleneck problems is that the evaporation efficiency and stability are limited by salt crystallization under high-salinity brines. Herein, we demonstrate that the 3D porous melamine-foam (MF) wrapped by a type of self-assembling composite materials based on reduced polyoxometalates (i.e. heteropoly blue, HPB), oleic acid (OA), and polypyrrole (PPy) (labeled with MF@HPB-PPy_n-OA) can serve as efficient and stable SVG material at high salinity. Structural characterizations of MF@HPB-PPy_n-OA indicate that both hydrophilic region of HPBs and hydrophobic region of OA co-exist on the surface of composite materials, optimizing the hydrophilic and hydrophobic interfaces of the SVG materials, and fully exerting its functionality for ultrahigh water-evaporation and anti-salt fouling. The optimal MF@HPB-PPy₁₀-OA operates continuously and stably for over 100 h in 10 wt% brine. Furthermore, MF@HPB-PPy₁₀-OA accomplishes complete salt-water separation of 10 wt% brine with 3.3 kg m⁻² h⁻¹ under 1-sun irradiation, yielding salt harvesting efficiency of 96.5%, which belongs to the record high of high-salinity systems reported so far and is close to achieving zero liquid discharge. Moreover, the low cost of MF@HPB-PPy₁₀-OA (2.56 $ m⁻²) suggests its potential application in the practical SVG technique.

The ever-increasing complexity of environmental pollutants urgently warrants the development of new detection technologies. Sensors based on the optical properties of hydrogels enabling fast and easy in situ detection are attracting increasing attention. In this paper, the data from 138 papers about different optical hydrogels (OHs) are extracted for statistical analysis. The detection performance and potential of various types of OHs in different environmental pollutant detection scenarios were evaluated and compared to those obtained using the standard detection method. Based on this analysis, the target recognition and sensing mechanisms of two main types of OHs are reviewed and discussed: photonic crystal hydrogels (PCHs) and fluorescent hydrogels (FHs). For PCHs, the environmental stimulus response, target receptors, inverse opal structures, and molecular imprinting techniques related to PCHs are reviewed and summarized. Furthermore, the different types of fluorophores (i.e., compound probes, biomacromolecules, quantum dots, and luminescent microbes) of FHs are discussed. Finally, the potential academic research directions to address the challenges of applying and developing OHs in environmental sensing are proposed, including the fusion of various OHs, introduction of the latest technologies in various fields to the construction of OHs, and development of multifunctional sensor arrays.

Manganese-based material is a prospective cathode material for aqueous zinc ion batteries (ZIBs) by virtue of its high theoretical capacity, high operating voltage, and low price. However, the manganese dissolution during the electrochemical reaction causes its electrochemical cycling stability to be undesirable. In this work, heterointerface engineering-induced oxygen defects are introduced into heterostructure MnO₂ (δa-MnO₂) by in situ electrochemical activation to inhibit manganese dissolution for aqueous zinc ion batteries. Meanwhile, the heterointerface between the disordered amorphous and the crystalline MnO₂ of δa-MnO₂ is decisive for the formation of oxygen defects. And the experimental results indicate that the manganese dissolution of δa-MnO₂ is considerably inhibited during the charge/discharge cycle. Theoretical analysis indicates that the oxygen defect regulates the electronic and band structure and the Mn-O bonding state of the electrode material, thereby promoting electron transport kinetics as well as inhibiting Mn dissolution. Consequently, the capacity of δa-MnO₂ does not degrade after 100 cycles at a current density of 0.5 A g⁻¹ and also 91% capacity retention after 500 cycles at 1 A g⁻¹. This study provides a promising insight into the development of high-performance manganese-based cathode materials through a facile and low-cost strategy.

Electrocatalytic hydrogen evolution and sulfion (S²⁻) recycling are promising strategies for boosting H₂ production and removing environmental pollutants. Here, a nano-Ni-functionalized molybdenum disulfide (MoS₂) nanosheet was assembled on steel mesh (Ni-MoS₂/SM) for use in sulfide oxidation reaction-assisted, energy-saving H₂ production. Experimental and theoretical calculation results revealed that anchoring nano-Ni on high-surface-area slack MoS₂ nanosheets not only optimized catalyst adsorption of polysulfides but also played an important role in promoting hydrogen evolution reaction kinetics by absorbing OH_ad, thereby greatly enhancing the catalytic performance toward sulfide oxidation reaction and hydrogen evolution reaction. Meanwhile, the Ni/MoS₂-based hydrogen evolution reaction + sulfide oxidation reaction system achieved nearly 100% hydrogen production efficiency and only consumed 61% less power per kWh than the oxygen evolution reaction + hydrogen evolution reaction system, which suggested our proposed Ni-MoS₂ and novel hydrogen production system are promising for sustainable energy production.

Exploring high efficiency S-scheme heterojunction photocatalysts with strong redox ability for removing volatile organic compounds from the air is of great interest and importance. However, how to predict and regulate the transport of photogenerated carriers in heterojunctions is a great challenge. Here, density functional theory calculations were first used to successfully predict the formation of a CdS quantum dots/InVO₄ atomic-layer (110)/(110) facet S-scheme heterojunction. Subsequently, a CdS quantum dots/InVO₄ atomic-layer was synthesized by in-situ loading of CdS quantum dots with (110) facets onto the (110) facets of InVO₄ atomic-layer. As a result of the deliberately constructed built-in electric field between the adjoining facets, we obtain a remarkably enhanced photocatalytic degradation rate for ethylene. This rate is 13.8 times that of pure CdS and 13.2 times that of pure InVO₄. In-situ irradiated X-ray photoelectron spectroscopy, photoluminescence and time-resolved photoluminescence measurements were carried out. These experiments validate that the built-in electric field enhanced the dissociation of photoexcited excitons and the separation of free charge carriers, and results in the formation of S-scheme charge transfer pathways. The reaction mechanism of the photocatalytic C₂H₄ oxidation is investigated by in-situ electron paramagnetic resonance. This work provides a mechanistic insight into the construction and optimization of semiconductor heterojunction photocatalysts for application to environmental remediation.

Anode-free Li-metal batteries are of significant interest to energy storage industries due to their intrinsically high energy. However, the accumulative Li dendrites and dead Li continuously consume active Li during cycling. That results in a short lifetime and low Coulombic efficiency of anode-free Li-metal batteries. Introducing effective electrolyte additives can improve the Li deposition homogeneity and solid electrolyte interphase (SEI) stability for anode-free Li-metal batteries. Herein, we reveal that introducing dual additives, composed of LiAsF₆ and fluoroethylene carbonate, into a low-cost commercial carbonate electrolyte will boost the cycle life and average Coulombic efficiency of NMC||Cu anode-free Li-metal batteries. The NMC||Cu anode-free Li-metal batteries with the dual additives exhibit a capacity retention of about 75% after 50 cycles, much higher than those with bare electrolytes (35%). The average Coulombic efficiency of the NMC||Cu anode-free Li-metal batteries with additives can maintain 98.3% over 100 cycles. In contrast, the average Coulombic efficiency without additives rapidly decline to 97% after only 50 cycles. In situ Raman measurements reveal that the prepared dual additives facilitate denser and smoother Li morphology during Li deposition. The dual additives significantly suppress the Li dendrite growth, enabling stable SEI formation on anode and cathode surfaces. Our results provide a broad view of developing low-cost and high-effective functional electrolytes for high-energy and long-life anode-free Li-metal batteries.

Safe operation of electrochemical capacitors (supercapacitors) is hindered by the flammability of commercial organic electrolytes. Non-flammable Water-in-Salt (WIS) electrolytes are promising alternatives; however, they are plagued by the limited operation voltage window (typically ≤2.3 V) and inherent corrosion of current collectors. Herein, a novel deep eutectic solvent (DES)-based electrolyte which uses formamide (FMD) as hydrogen-bond donor and sodium nitrate (NaNO₃) as hydrogen-bond acceptor is demonstrated. The electrolyte exhibits the wide electrochemical stability window (3.14 V), high electrical conductivity (14.01 mS cm⁻¹), good flame-retardance, anticorrosive property, and ultralow cost (7% of the commercial electrolyte and 2% of WIS). Raman spectroscopy and Density Functional Theory calculations reveal that the hydrogen bonds between the FMD molecules and NO₃^- ions are primarily responsible for the superior stability and conductivity. The developed NaNO₃/FMD-based coin cell supercapacitor is among the best-performing state-of-art DES and WIS devices, evidenced by the high voltage window (2.6 V), outstanding energy and power densities (22.77 Wh kg⁻¹ at 630 W kg⁻¹ and 17.37 kW kg⁻¹ at 12.55 Wh kg⁻¹), ultralong cyclic stability (86% after 30 000 cycles), and negligible current collector corrosion. The NaNO₃/FMD industry adoption potential is demonstrated by fabricating 100 F pouch cell supercapacitors using commercial aluminum current collectors.

The layered δ-MnO₂ (dMO) is an excellent cathode material for rechargeable aqueous zinc-ion batteries owing to its large interlayer distance (~0.7 nm), high capacity, and low cost; however, such cathodes suffer from structural degradation during the long-term cycling process, leading to capacity fading. In this study, a Co-doped dMO composite with reduced graphene oxide (GC-dMO) is developed using a simple cost-effective hydrothermal method. The degree of disorderness increases owing to the hetero-atom doping and graphene oxide composites. It is demonstrated that layered dMO and GC-dMO undergo a structural transition from K-birnessite to the Zn-buserite phase upon the first discharge, which enhances the intercalation of Zn²⁺ ions, H₂O molecules in the layered structure. The GC-dMO cathode exhibits an excellent capacity of 302 mAh g⁻¹ at a current density of 100 mA g⁻¹ after 100 cycles as compared with the dMO cathode (159 mAh g⁻¹). The excellent electrochemical performance of the GC-dMO cathode owing to Co-doping and graphene oxide sheets enhances the interlayer gap and disorderness, and maintains structural stability, which facilitates the easy reverse intercalation and de-intercalation of Zn²⁺ ions and H₂O molecules. Therefore, GC-dMO is a promising cathode material for large-scale aqueous ZIBs.

Tunable bandgaps make halide perovskites promising candidates for developing tandem solar cells (TSCs), a strategy to break the radiative limit of 33.7% for single-junction solar cells. Combining perovskites with market-dominant crystalline silicon (c-Si) is particularly attractive; simple estimates based on the bandgap matching indicate that the efficiency limit in such tandem device is as high as 46%. However, state-of-the-art perovskite/c-Si TSCs only achieve an efficiency of ~32.5%, implying significant challenges and also rich opportunities. In this review, we start with the operating mechanism and efficiency limit of TSCs, followed by systematical discussions on wide-bandgap perovskite front cells, interface selective contacts, and electrical interconnection layer, as well as photon management for highly efficient perovskite/c-Si TSCs. We highlight the challenges in this field and provide our understanding of future research directions toward highly efficient and stable large-scale wide-bandgap perovskite front cells for the commercialization of perovskite/c-Si TSCs.

The chemoselective hydrodeoxygenation of natural lignocellulosic materials plays a crucial role in converting biomass into value-added chemicals. Yet their complex molecular structures often require multiple active sites synergy for effective activation and achieving high chemoselectivity. Herein, it is reported that a high-entropy alloy (HEA) on high-entropy oxide (HEO) hetero-structured catalyst for highly active, chemoselective, and robust vanillin hydrodeoxygenation. The heterogenous HEA/HEO catalysts were prepared by thermal reduction of senary HEOs (NiZnCuFeAlZrO_x), where exsolvable metals (e.g., Ni, Zn, Cu) in situ emerged and formed randomly dispersed HEA nanoparticles anchoring on the HEO matrix. This catalyst exhibits excellent catalytic performance: 100% conversion of vanillin and 95% selectivity toward high-value 2-methyl-4 methoxy phenol at low temperature of 120 ℃, which were attributed to the synergistic effect among HEO matrix (with abundant oxygen vacancies), anchored HEA nanoparticles (having excellent hydrogenolysis capability), and their intimate hetero-interfaces (showing strong electron transferring effect). Therefore, our work reported the successful construction of HEA/HEO heterogeneous catalysts and their superior multifunctionality in biomass conversion, which could shed light on catalyst design for many important reactions that are complex and require multifunctional active sites.