As the most abundant renewable aromatic biopolymer resource on the Earth, lignin has become a cutting-edge research hotspot in clean photocatalysis, thanks to the distinct highest occupied molecular-orbital and lowest unoccupied molecular-orbital energy levels driven by the major β-O-4 linked bonds. However, the complex spatial architecture of functional groups, represented by benzene rings in the 3D intertwined macromolecular chains of lignin, and the challenge of enhancing carrier separation efficiency remain persistent obstacles hindering the development of lignin-based photocatalysts. Herein, a strategy of constructing lignin nanosphere-graphene oxide heterointerfaces (EL-GO) is proposed to comprehensively enhance the efficacy of functional groups and facilitate photoelectron migration modes. The recombination time of light-excited photoelectrons is effectively prolonged by the π-π interactions between the “Donor site” and “Acceptor site” functional regions, along with the directional migration of photoelectrons between EL and GO. The photocatalytic efficiency of H₂O₂ production using EL-GO is significantly enhanced under the protective mechanism of GO. To assess its potential, a prospect estimation of EL-GO in a lake containing various pollutants and metal ions was conducted, simulating real water conditions. This pioneering engineering effort aims to curb excessive consumption of fossil fuels and explore the green applications of lignin, thereby constructing a “carbon-neutral” feedstock system.

Developing low-cost and high-performance nanofiber-based polyelectrolyte membranes for fuel cell applications is a promising solution to energy depletion. Due to the high specific surface area and one-dimensional long-range continuous structure of the nanofiber, ion-charged groups can be induced to form long-range continuous ion transfer channels in the nanofiber composite membrane, significantly increasing the ion conductivity of the membrane. This review stands apart from previous endeavors by offering a comprehensive overview of the strategies employed over the past decade in utilizing both electrospun and natural nanofibers as key components of proton exchange membranes and anion exchange membranes for fuel cells. Electrospun nanofibers are categorized based on their material properties into two primary groups: (1) ionomer nanofibers, inherently endowed with the ability to conduct H⁺ (such as perfluorosulfonic acid or sulfonated poly (ether ether ketone)) or OH⁻ (e.g., FAA-3), and (2) nonionic polymer nanofibers, comprising inert polymers like polyvinylidene difluoride, polytetrafluoroethylene, and polyacrylonitrile. Notably, the latter often necessitates surface modifications to impart ion transport channels, given their inherent proton inertness. Furthermore, this review delves into the recent progress made with three natural nanofibers derived from biodegradable cellulose—cellulose nanocrystals, cellulose nanofibers, and bacterial nanofibers—as crucial elements in polyelectrolyte membranes. The effect of the physical structure of such nanofibers on polyelectrolyte membrane properties is also briefly discussed. Lastly, the review emphasizes the challenges and outlines potential solutions for future research in the field of nanofiber-based polyelectrolyte membranes, aiming to propel the development of high-performance polymer electrolyte fuel cells.

The architectural design of redox-active organic molecules and the modulation of their electronic properties significantly influence their application in energy storage systems within aqueous environments. However, these organic molecules often exhibit sluggish reaction kinetics and unsatisfactory utilization of active sites, presenting significant challenges for their practical deployment as electrode materials in aqueous batteries. In this study, we have synthesized a novel organic compound (PTPZ), comprised of a centrally symmetric and fully ladder-type structure, tailored for aqueous proton storage. This unique configuration imparts the PTPZ molecule with high electron delocalization and enhanced structural stability. As an electrode material, PTPZ demonstrates a substantial proton-storage capacity of 311.9 mAh g⁻¹, with an active group utilization efficiency of up to 89% facilitated by an 8-electron transfer process, while maintaining a capacity retention of 92.89% after 8000 charging-discharging cycles. Furthermore, in-situ monitoring technologies and various theoretical analyses have pinpointed the associated electrochemical processes of the PTPZ electrode, revealing exceptional redox activity, rapid proton diffusion, and efficient charge transfer. These attributes confer a significant competitive advantage to PTPZ as an anode material for high-performance proton storage devices. Consequently, this work contributes to the rational design of organic electrode materials for the advancement of rechargeable aqueous batteries.

Pre-intercalation is the mainstream approach to inhibit the unpredicted structural degradation and the sluggish kinetics of Zn-ions migrating in vanadium oxide cathode of aqueous zinc-ion batteries (AZIBs), which has been extensively explored over the past 5 years. The functional principles behind the improvement are widely discussed but have been limited to the enlargement of interspace between VO layers. As the different types of ions could change the properties of vanadium oxides in various ways, the review starts with a comprehensive overview of pre-intercalated vanadium oxide cathode with different types of molecules and ions, such as metal ions, water molecules, and non-metallic cations, along with their functional principles and resulting performance. Furthermore, the pre-intercalated vanadium cathodes reported so far are summarized, comparing their interlayer space, capacity, cycling rate, and capacity retention after long cycling. A discussion of the relationship between the interspace and the performance is provided. The widest interspaces could result in the decay of the cycling stability. Based on the data, the optimal interspace is likely to be around 12 Å, indicating that precise control of the interspace is a useful method. However, more consideration is required regarding the other impacts of pre-intercalated ions on vanadium oxide. It is hoped that this review can inspire further understanding of pre-intercalated vanadium oxide cathodes, paving a new pathway to the development of advanced vanadium oxide cathodes with better cycling stability and larger energy density.

The key to obtaining high intrinsic catalytic activity of Me-N_x-C electrocatalysts for Zn-air batteries is to form high-density bifunctional Me-N_x active sites during the pyrolysis of the precursor while maintaining structural stability. In this study, a host–guest spatial confinement strategy was utilized to synthesize a composite catalyst consisting of Co₃Fe₇ nanoparticles confined in an N-doped carbon network. The coupling between the host (MIL-88B) and guest (cobalt porphyrin, CoPP) produces high-density bimetallic atomic active sites. By controlling the mass of guest molecules, it is possible to construct precursors with the highest activity potential. The Co₃Fe₇/NC material with a certain amount of the guest displays a better electrocatalytic performance for both oxygen reduction reaction and oxygen evolution reaction with a half-wave potential (E_1/2) of 0.85 V and an overpotential of 1.59 V at 10 mA cm⁻², respectively. The specific structure of bimetallic active centers is verified to be FeN₂-CoN₄ using experimental characterizations, and the oxygen reaction mechanism is explored by in-situ characterization techniques and first-principles calculations. The Zn-air battery assembled with Co₃Fe₇/NC cathode exhibits a remarkable open-circuit voltage of 1.52 V, an exceptional peak power density of 248.1 mW cm⁻², and stable cycling stability over 1000 h. Particularly, the corresponding flexible Zn-air battery affords prominent cycling performance under different bending angles. This study supplies the idea and method of designing catalysts with specific structures at the atomic and electronic scales for breaking through the large-scale application of electrocatalysts based on oxygen reactions in fuel cells/metal-air batteries.

The reduction of CO₂ toward CO and CH₄ over Ni-loaded MoS₂-like layered nanomaterials is investigated. The mild hydrothermal synthesis induced the formation of a molybdenum oxysulfide (MoO_xS_y) phase, enriched with sulfur defects and multiple Mo oxidation states that favor the insertion of Ni²⁺ cations via photo-assisted precipitation. The photocatalytic tests under LED irradiation at different wavelengths from 365 to 940 nm at 250°C rendered 1% CO₂ conversion and continuous CO production up to 0.6 mmol/(g_cat h). The incorporation of Ni into the MoO_xS_y structure boosted the continuous production of CO up to 5.1 mmol/(g_cat h) with a CO₂ conversion of 3.5%. In situ spectroscopic techniques and DFT simulations showed the O-incorporated MoS₂ structure, in addition to Ni clusters as a supported metal catalyst. The mechanistic study of the CO₂ reduction reaction over the catalysts revealed that the reverse water–gas shift reaction is favored due to the preferential formation of carboxylic species.

Hydrogen is a highly promising energy carrier because of its renewable and clean qualities. Among the different methods for H₂ production, photoelectrocatalysis (PEC) water splitting has garnered significant interest, thanks to the abundant and perennial solar energy. Single-atom catalysts (SACs), which feature well-distributed atoms anchored on supports, have gained great attention in PEC water splitting for their unique advantages in overcoming the limitations of conventional PEC reactions. Herein, we comprehensively review SAC-incorporated photoelectrocatalysts for efficient PEC water splitting. We begin by highlighting the benefits of SACs in improving charge transfer, catalytic selectivity, and catalytic activity, which address the limitations of conventional PEC reactions. Next, we provide a comprehensive overview of established synthetic techniques for optimizing the properties of SACs, along with modern characterization methods to confirm their unique structures. Finally, we discuss the challenges and future directions in basic research and advancements, providing insights and guidance for this developing field.

Substituting the sluggish oxygen evolution reaction with a more thermodynamically favorable ethanol oxidation reaction (EOR) offers an opportunity to circumvent the efficiency loss in water splitting and metal-air batteries. However, the effect of the dynamic surface evolution of the catalyst in operating conditions on the activity of EOR lacks comprehensive understanding. Herein, we demonstrate a tunable operational catalyst activity through the modulated redox property of nickel oxalate (NCO) by establishing a relation between the oxidation behavior of Ni, surface reconstruction, and catalyst activity. We propose a repeated chemical–electrochemical reaction mechanism of EOR on NCO, which is rigorously investigated through a combination of operando Raman and nuclear magnetic resonance. The modulation of the oxidation trend of Ni by doping heteroatoms stimulates the electrochemical oxidation of the catalyst surface to NiOOH, which alters the catalyst activity for EOR. Assembled ethanol-assisted water electrolysis cell exhibits a reduced operating voltage for hydrogen production by 200 mV with a ~100% Faradaic efficiency, and zinc–ethanol–air battery showed a 287 mV decreased charge–discharge voltage window and enhanced stability for over 500 h.

3D-printed Ti₃C₂T_x MXene-based interdigital micro-supercapacitors (MSCs) have great potential as energy supply devices in the field of microelectronics due to their short ion diffusion path, high conductivity, excellent pseudocapacitance, and fast charging capabilities. However, searching for eco-friendly aqueous Ti₃C₂T_x MXene-based inks without additives and preventing severe restack of MXene nanosheets in high-concentration inks are significantly challenging. This study develops an additive-free, highly printable, viscosity adjustable, and environmentally friendly MXene/carbon nanotube (CNT) hybrid aqueous inks, in which the CNT can not only adjust the viscosity of Ti₃C₂T_x MXene inks but also widen the interlayer spacing of adjacent Ti₃C₂T_x MXene nanosheets effectively. The optimized MXene/CNT composite inks are successfully adopted to construct various configurations of MSCs with remarkable shape fidelity and geometric accuracy, together with enhanced surface area accessibility for electrons and ions diffusion. As a result, the constructed interdigital symmetrical MSCs demonstrate outstanding areal capacitance (1249.3 mF cm⁻²), superior energy density (111 μWh cm⁻² at 0.4 mW cm⁻²), and high power density (8 mW cm⁻² at 47.1 μWh cm⁻²). Furthermore, a self-powered modular system of solar cells integrated with MXene/CNT-MSCs and pressure sensors is successfully tailored, simultaneously achieving efficient solar energy collection and real-time human activities monitoring. This work offers insight into the understanding of the role of CNTs in MXene/CNT ink. Moreover, it provides a new approach for preparing environmentally friendly MXene-based inks for the 3D printing of high-performance MSCs, contributing to the development of miniaturized, flexible, and self-powered printable electronic microsystems.

Controlled photocatalytic conversion of CO₂ into premium fuel such as methane (CH₄) offers a sustainable pathway towards a carbon energy cycle. However, the photocatalytic efficiency and selectivity are still unsatisfactory due to the limited availability of active sites on the current photocatalysts. To resolve this issue, the design of oxygen vacancies (OVs) in metal–oxide semiconductors is an effective option. Herein, in situ deposition of TiO₂ onto SiO₂ nanospheres to construct a SiO₂@TiO₂ core–shell structure was performed to modulate the oxygen vacancy concentrations. Meanwhile, charge redistribution led to the formation of abundant OV-regulated Ti–Ti (Ti–OV–Ti) dual sites. It is revealed that Ti–OV–Ti dual sites served as the key active site for capturing the photogenerated electrons during light-driven CO₂ reduction reaction (CO₂RR). Such electron-rich active sites enabled efficient CO₂ adsorption and activation, thus lowering the energy barrier associated with the rate-determining step. More importantly, the formation of a highly stable *CHO intermediate at Ti–OV–Ti dual sites energetically favored the reaction pathway towards the production of CH₄ rather than CO, thereby facilitating the selective product of CH₄. As a result, SiO₂@TiO₂-50 with an optimized oxygen vacancy concentration of 9.0% showed a remarkable selectivity (90.32%) for CH₄ production with a rate of 13.21 μmol g⁻¹ h⁻¹, which is 17.38-fold higher than that of pristine TiO₂. This study provides a new avenue for engineering superior photocatalysts through a rational methodology towards selective reduction of CO₂.

Aqueous zinc-ion batteries (ZIBs) are promising candidates for next-generation energy storage, but the problems related to Zn dendrites and side reactions severely hinder their practical applications. Herein, a self-recognition separator based on a Bi-based metal–organic framework (GF@CAU-17) is developed for ion management to achieve highly reversible Zn anodes. The GF@CAU-17 has self-recognition behavior to customize selective Zn²⁺ channels, effectively repelling SO₄^2– and H₂O, but facilitating Zn²⁺ conduction. The inherent properties of CAU-17 result in the repulsion of SO₄^2– ions while disrupting the hydrogen bond network among free H₂O molecules, restraining side reactions and by-products. Simultaneously, the zincophilic characteristic of CAU-17 expedites the desolvation of [Zn(H₂O)₆]²⁺, leading to a self-expedited Zn²⁺ ion pumping effect that dynamically produces a steady and homogeneous Zn²⁺ ion flux, and thereby alleviates concentration polarization. Consequently, a symmetric cell based on the GF@CAU-17 separator can achieve a long lifespan of 4450 h. Moreover, the constructed Zn//GF@CAU-17//MnO₂ cell delivers a high specific capacity of 221.8 mAh g⁻¹ and 88.0% capacity retention after 2000 cycles.

Surface passivation with organic ammoniums improves perovskite solar cell performance by forming 2D/quasi-2D structures or adsorbing onto surfaces. However, complexity from mixed phases can trigger phase transitions, compromising stability. The control of surface dimensionality after organic ammonium passivation presents significant importance to device stability. In this study, we developed a poly-fluorination strategy for surface treatment in perovskite solar cells, which enabled a high and durable interfacial phase purity after surface passivation. The locked surface dimensionality of perovskite was achieved through robust interaction between the poly-fluorinated ammoniums and the perovskite surface, along with the steric hindrance imparted by fluorine atoms, reducing its reactivity and penetration capabilities. The high hydrophobicity of the poly-fluorinated surface also aids in moisture resistance of the perovskite layer. The champion device achieved a power conversion efficiency (PCE) of 25.2% with certified 24.6%, with 90% of its initial PCE retained after approximately 1200 h under continuous 1-sun illumination, and over 14,400 h storage stability and superior stability under high-temperature operation.