Membrane electrode assemblies (MEAs) represent the preeminent configuration for industrial-scale CO₂ electrolysis, yet their dynamic interfaces and degradation pathways remain inadequately resolved. This perspective highlights how advanced operando characterization techniques—synchrotron X-ray spectroscopy, spatially resolved X-ray fluorescence, vibrational spectroscopy, electrochemical diagnostics et al.—decipher atomic-scale catalyst evolution, transient ion/water fluxes, and extreme interfacial microenvironments under industrial current densities. These methodologies reveal critical degradation mechanisms, including catalyst restructuring, carbonate precipitation-driven flooding, and cation-induced pH gradients, which are inaccessible to conventional ex-situ or three-electrode analyses. Integrating multimodal characterization is paramount to correlate transient interfacial chemistry with system-level performance, guiding the rational design of durable, high-selectivity MEAs for scalable CO₂ conversion.

Porous molecular sieve catalysts, including aluminosilicate zeolites and silicoaluminophosphate (SAPO) molecular sieves, have found widespread use in heterogeneous catalysis and are expected to play a key role in advancing carbon neutrality and sustainable development. Given the ubiquitous presence of water during catalyst synthesis, storage, and application, the interactions between water and molecular sieves as well as their consequent effects on frameworks and catalytic reactions have attracted considerable attention. These effects are inherently complex and highly dependent on various factors such as temperature, water phase, and partial pressure. In this review, we provide a comprehensive overview of the current understanding of water-molecular sieve interactions and their roles in catalysis, based on both experimental and theoretical calculation results. Special attention is paid to water-induced reversible and irreversible structural changes in aluminosilicate and SAPO frameworks at the atomic level, underscoring the dynamic and labile nature of these frameworks in water environments. The influence of water on catalytic performance and reaction kinetics in molecular sieve-catalyzed reactions is discussed from two perspectives: (1) its participation in reaction through hydrogen bonding interactions, such as competitive adsorption at active sites, stabilization of ground and transition states, and proton transfer bridge; (2) its role as a direct reactant forming new species via reactions with other guest molecules. Recent advancements in this area provide valuable insights for the rational design and optimization of catalysts for water-involved reactions.

Metal-organic frameworks (MOFs) are porous materials formed by the coordination of organic and inorganic components through coordination bonds. MOF-derived materials preserve the large surface area and inherent porosity of their parent structures, while simultaneously offering enhanced electrical conductivity and more efficient charge transport. Studies have shown that integrating electrospinning with MOFs into continuous nanofiber networks can effectively address issues such as MOF structural collapse, low conductivity, and leaching of active sites. Moreover, the electrospinning technique enables fine-tuning of the product’s morphology, architecture, and chemical composition, thereby unlocking new possibilities for advancing high-performance ZABs. This review provides a systematic overview of recent advances in non-precious metal electrocatalysts derived from electrospun-MOF composites and examines the unique advantages of combining electrospinning with MOF precursors in the design of oxygen electrocatalysts. It also investigates the morphological regulation of various fiber structures, including porous, hollow, core-shell, and beaded structures, as well as their influence on the catalytic performance. Finally, the performance enhancement strategies of electrospun-MOF catalyst materials are examined, and the development prospects along with future research directions related to oxygen electrocatalysts based on electrospun nanofibers are emphasized. This thorough review aims to offer meaningful insights and practical guidance for advancing the understanding, design, and fabrication of next-generation devices for energy conversion and storage.

Electrocatalytic conversion of carbon dioxide (CO₂) offers an effective method of CO₂ fixation to mitigate global warming and the energy crisis. However, for supported Ni single-atom catalysts (SACs), which are among the most promising candidates for this application, the relationship between Ni coordination structure and catalytic properties is still under strong debate. Here, we fabricated a series of Ni SACs through precise-engineering of anchor sites on nitrogen-doped carbon (NC) followed by Ni atom anchoring using atomic layer deposition. Among them, a Ni₁/NC SAC, with a coordination number (CN) of four but less pyridinic nitrogen (N_pyri), achieved over 90% faradaic efficiency for CO at potentials from -0.7 to -1.0 V and a mass activity of 6.5 A/mg_Ni at -0.78 V along with high stability, outperforming other Ni SACs with lower CN and more N_pyri. Theoretical calculations of various three and four-coordinated Ni₁-N_xC_y structures revealed a linear correlation between the reaction Gibbs free energy for the potential-limiting step and the highest occupied molecular orbital (HOMO) position of Ni-3d orbitals, therein the four-coordinated Ni₁-N₁C₃ with the highest HOMO position is identified as the active site for the electrocatalytic CO₂-to-CO process, in line with the experimental results.

In this paper we report the preparation of nano-dendritic Cu₂O/Cu heterojunctions doped with varying concentrations of cobalt through a convenient, energy-consumption-free, and environmentally friendly chemical replacement method. The analysis results reveal that the incorporation of cobalt in its atomic form enhances the adsorption of nitrate species onto the catalyst surface, whereas doping with metallic cobalt promotes the production of active hydrogen (*H). By adjusting the doping concentration of cobalt, we effectively control its doping form (atomic and metallic states) on the surface of dendritic copper, thereby enabling controllable modulation of the active hydrogen concentration on the catalyst surface. By ensuring sufficient consumption of *H during the NITRR process while avoiding excessively high concentrations that could trigger detrimental hydrogen evolution reaction side reactions, this approach remarkably enhances the selectivity of ammonia synthesis in NITRR. This study offers an effective approach to regulate the *H concentration on the surface of the catalyst through adjusting the metal doping form, thereby improving the performance of ammonia synthesis from NITRR.

The hydrogen evolution reaction (HER) in alkaline water electrolysis faces significant kinetic and thermodynamic challenges that hinder its efficiency and scalability for sustainable hydrogen production. Herein, we employed an in-situ synthesis strategy to incorporate H atoms into the PdRu alloy lattice to form H_Inc-PdRu electrocatalyst, thereby modulating its electronic structure and enhancing its alkaline HER performance. We demonstrate that the incorporation of H atoms significantly improves electrocatalytic activity, achieving a remarkably low overpotential of 25 mV at 10 mA cm^‒2 compared with the Pd, Ru and PdRu catalysts while maintaining robust catalyst stability. Operando spectroscopic analysis indicates that H insertion into the H_Inc-PdRu electrocatalyst enhances the availability of H₂O* at the surface, promoting water dissociation at the active sites. Theoretical calculations proposed that the co-incorporating H and Ru atoms induces s-d orbital coupling within the Pd lattices, effectively weakening hydrogen adsorption strength and optimizing the alkaline HER energetics. This work presents a facile approach for the rational design of bimetallic electrocatalysts for efficient and stable alkaline water electrolysis for renewable hydrogen production.

Designing exceptional-performance and long-lasting oxygen reduction reaction (ORR) catalysts is a critical challenge for the development of rechargeable Zn-air batteries (ZABs). In this study, we introduce a metal-free ORR catalyst composed of F-N co-doped hollow carbon (FNC), specifically engineered to address the limitations of conventional catalysts. The FNC catalysts were synthesized using a template-assisted pyrolysis method, resulting in a hollow, porous architecture with a high specific surface area and numerous active sites. Concurrently, F doping optimized the electronic configuration of pyridinic nitrogen. The introduction of C-F bonds reduced the reaction energy barrier, and the resulting N-C-F configuration enhanced the stability of the nitrogen center. The catalyst exhibits outstanding ORR activity in alkaline media, exhibiting a half-wave potential (E_1/2) of 0.87 V, surpassing that of commercial Pt/C (E_1/2 = 0.85 V). When applied to both aqueous and flexible ZAB configurations, the FNC catalyst achieved peak power densities of 172 and 85 mW cm^-2, respectively, along with exceptional cycling stabilities exceeding 5300 and 302 h, respectively. This study establishes a novel approach for designing metal-free ORR catalysts and next-generation ZABs, particularly for use in flexible and wearable microelectronic devices.

Vanadium phosphorus oxide (VPO) catalyst is a promising candidate for the condensation reaction of formaldehyde (FA) and acetic acid (HAc) to produce acrylic acid (AA). However, the complexity of the active phases and their dynamic interconversion under redox conditions has led to controversies regarding the actual active phase in this reaction. To address this, this study systematically investigates the phase transition and underlying mechanism of VPO catalysts under reaction conditions. X-ray diffraction (XRD) patterns, Raman spectra, transmission electron microscopy images and X-ray photoelectron spectroscopy collectively demonstrated that the V⁴⁺ phase (VO)₂P₂O₇ retained the bulk phase structure throughout the reaction, with only minor surface phase transition observed. In contrast, the V⁵⁺ phase underwent reduction to other phases in both bulk and surface regions. Specifically, the δ-VOPO₄ phase rapidly transformed into the α_II-VOPO₄ phase, which could reversibly convert into the R1-VOHPO₄ phase (V⁴⁺). Controlled variable experiments, H₂-temperature programmed reduction and in-situ XRD experiments in a hydrogen atmosphere further demonstrated that these phase transitions were primarily attributed to the loss of lattice oxygen. The presence of V⁴⁺ phase in VPO catalysts enhanced the selectivity of acrylic acid, while the existence of V⁵⁺ phase promoted the activation of acetic acid. This work elucidates the redox-driven phase evolution of VPO catalysts and offers valuable insights for designing efficient catalysts for FA-HAc cross-condensation by balancing phase stability and activity.

The direct oxidation of cyclohexane to adipic acid (AA) without the use of HNO₃ is important but still challenging. Herein, hierarchical manganese-containing TS-1 zeolite (HMTS) was prepared using an improved direct synthesis method, in which titanium and manganese coexist within the zeolite matrix, as characterized by X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy, ultraviolet, extended X-ray absorption fine structure etc. The introduction of matrix Mn species (Mn³⁺, Mn⁴⁺) not only increased the surface oxygen vacancies, but also generated medium-strong acid sites, which endowed HMTS catalysts with the ability to efficiently activate oxygen and facilitate substrate coordination. On HMTS-3, one-pot oxidation of cyclohexane at 140 °C and 2 MPa O₂ gave 81.6% conversion and 71.5% AA selectivity, the highest value obtained at present. Control experiments with single-component samples confirmed that matrix Ti⁴⁺ catalyzed the conversion of cyclohexane to a mixture of cyclohexanone and cyclohexanol (KA oil), and matrix Mn favored the conversion of KA oil to AA. The synergy between matrix Ti and Mn inside the hierarchical structure were the key factor for the superior activity. Specifically, the matrix Ti⁴⁺ might activate oxygen to form Ti-O₂^2- which facilitated the activation of the C-H bond of cyclohexane. The activation of O₂ on matrix Mn³⁺ formed Mn⁴⁺-O₂^- favoring the breaking of the C-C bond of cyclohexanone. The hierarchical structure not only exposed more active sites and promoted mass transfer, but also provided a better microenvironment for the matrix Mn to synergize with the matrix Ti, which facilitated the overall reaction. This work demonstrated the practical application potential of HMTS and provided useful insights into the direct oxidation of cyclohexane to AA.

Since conventional photocatalytic technology fails to achieve complete elimination of chlorophenol contaminants from aqueous environments, this study presents a synergistic photocatalysis-capacitive deionization (PC-CDI) system as an advanced solution for industrial chlorophenol wastewater remediation. The PC-CDI system, employing boron nitride/carbon nitride (BN/CN) heterojunction electrodes, demonstrates exceptional degradation performance toward chlorophenols. The high-surface-area porous BN/CN heterojunction facilitates electro-adsorption and charge carrier separation, thereby synergistically optimizing both photocatalytic (PC) and capacitive deionization (CDI) functionalities. Remarkably, the integrated system achieves a 2,4-DCP degradation efficiency of 97.15% and a 2,4,6-TCP degradation efficiency of 100% in 2 h. The CDI component enables spatial separation through the electro-adsorption of Cl^- ions at the anode, effectively mitigating their interference and suppressing chlorinated byproduct formation. Concurrently, the electro-adsorption of positively charged chlorophenol pollutants accelerates their diffusion to catalytic sites, promoting the reactive oxygen species (ROS)-driven degradation of chlorophenol pollutants. The PC-CDI system exhibits robust stability (> 95% efficiency retention over five cycles) and broad applicability across various chlorophenol derivatives. By circumventing Cl^--induced side reactions and inhibiting chlorine radical generation during photocatalysis, this strategy minimizes the environmental risks associated with chlorinated byproducts during chlorophenol wastewater treatment. These findings establish the PC-CDI system as a sustainable and eco-friendly technology for industrial wastewater treatment.

Solar-driven water splitting has emerged as a promising route for sustainable hydrogen generation, however, developing broad-spectrum responsive photocatalysts remains a challenge for achieving efficient solar-to-hydrogen conversion. Here, we demonstrate a g-C₃N₄ -based (UCN) catalyst with dispersed Ag single atoms (Ag SAs) and Ag nanoparticles (Ag NPs) for synergistically broad-spectrum photocatalytic hydrogen evolution. Experimental and theoretical results reveal that both Ag SAs and Ag NPs serve as active sites, with the Schottky junction between Ag NPs and g-C₃N₄ effectively promoting charge separation, while Ag NPs induce localized surface plasmon resonance, extending the light response range from visible to near-infrared regions. The optimized catalyst Ag-UCN-3 exhibits a hydrogen evolution rate as high as 22.11 mmol/g/h and an apparent quantum efficiency (AQE) of 10.16% under 420 nm light illumination. Notably, it still had a high hydrogen evolution rate of 633.57 μmol/g/h under 700 nm irradiation. This work unveils dual active sites engineering strategy that couples Ag SAs and Ag NPs with plasma and hot electrons, offering a new strategy for designing high-performance solar-driven energy systems.

The construction of crystalline/amorphous g-C₃N₄ homojunctions presents a versatile strategy to obtain all-organic homojunction photocatalysts with better interface matching and lower interface charge carrier movement resistance for optimized photocatalytic activity. However, the process entails a complex multi-step workup, which compromises its feasibility. To overcome this challenge, this work provided an innovative Na₂CO₃-induced crystallinity modulation strategy to construct a Na-doped crystalline/amorphous g-C₃N₄ S-scheme homojunction photocatalyst in a single step. The approach involves the initial pre-assembling of melamine and cyanuric acid molecules, and subsequent introduction of Na₂CO₃ before the calcination. Na₂CO₃ plays key roles to induce in-situ crystallinity modulation during the calcination and as a source for Na-doping. The prepared g-C₃N₄ S-scheme homojunction photocatalyst demonstrated a prominent H₂O₂-production rate of 444.6 μmol·L^-1·h^-1, which is 6.1-fold higher than that of bulk g-C₃N₄. The enhanced activity was attributed to the synergistic effect of charge carrier separation induced by the S-scheme homojunction system, and the optimized interfacial H₂O₂ generation kinetics. The latter was fostered by the Na-doping. This study provides an innovative approach for the one-step construction of g-C₃N₄ S-scheme homojunction and its integration in photocatalytic applications.

The regulation of peroxymonosulfate (PMS) activation by constructing oxygen vacancy and heterogeneous interface catalytic is crucial towards the oxidation of refractory pollutants still remains a major hurdle. This work demonstrates a strategy to constructed ethylene glycol (EG) well-coupled S-scheme heterojunction of NiFe₂O_4‒x/NiS with oxygen vacancy (V_O)-modified to efficiently achieve pollutant removal by activating PMS through photoexcitation, a 99% PMS decomposition efficiency is achieved. Photoassisted Kelvin probe force microscopy and in-situ electron spin resonance verify the establishment of a charge-transfer pathway consistent in NiFe₂O_4-x/NiS with an S-scheme heterojunction, which dramatically provides abundant active sites and distinct charge transport pathway for organic pollutant oxidation. The S-scheme NiFe₂O_4-x/NiS heterojunction in the photo-Fenton-like system exhibited significantly enhanced degradation rate (0.15 min^-1) at a low PMS dosage of 0.1 g/L, which is 19 times greater than that of the pristine NiS (0.0077 min^-1). Density functional theory calculations confirmed that V_O in NiFe₂O_4-x/NiS efficiently promoted PMS adsorption and lowered the energy barrier for electron transfer. Moreover, in-situ experiments and experimental evidence offer mechanistic insights into the PMS activation through photoexcitation, unraveling a dual-pathway activation mechanism involving reduction and oxidation processes over NiFe₂O_4-x/NiS during the reaction. This work emphasizes the potential of vacancy engineering synergistic S-scheme heterojunction in developing efficient catalysts for regulating PMS activation, providing a promising solution the cost-effective and efficient treatment of organic wastewater.

All-organic intermolecular S-scheme heterojunction photocatalysts are promising for efficient and fast carrier separation, yet attaining strong reducing capacity and tracking directional charge transfer remain critical challenges. Herein, we unveiled an intermolecular S-scheme heterojunction through in-situ growth of conjugated poly(1,4-diethynylbenzene) (pDEB, reduction photocatalyst) on graphitic carbon nitride (g-C₃N₄, oxidation photocatalyst), forming the nanofiber-decorated nanosheet-like pDEB/CN architecture via π-conjugated polymer templating. By leveraging the electron-donating effect and the expanded π-electron delocalization range of electron-rich conjugated acetylenic polymers, pDEB with high energy band positions was introduced into the intermolecular S-scheme heterojunction with enhanced reducibility. The directional S-scheme charge migration is mechanistically demonstrated by deploying dual metal oxide cocatalysts as spatially resolved electron donor-acceptor probes, with light-modulated in-situ X-ray photoelectron spectroscopy capturing real-time interfacial charge migration. Femtosecond transient absorption spectroscopy further elucidates accelerated ultrafast electron transfer kinetics mediated by the S-scheme interfacial electric field. The S-scheme heterojunction attained an apparent quantum efficiency of 5.18% at 420 nm during the photocatalytic H₂O₂ production. Notably, pDEB/CN has demonstrated an excellent H₂O₂ yield for the first time in a continuous flow photocatalytic system, reaching 394.27 μmol g^-1 h^-1 within 24 h, which illustrates the stable interfacial charge transfer brought about by the rigid structure. The work demonstrated the transformative potential of architecting directional charge superhighways through band level engineering, while advancing S-scheme heterojunctions design with molecular precision.

Developing efficient photocatalysts for CO₂ conversion under full-spectrum irradiation remains a key challenge for solar-to-chemical energy conversion. In this study, a novel S-scheme heterojunction composed of reduction Cs_0.32WO₃ (CWO) nanosheets with hexagonal structure and oxidation WO₃·2H₂O (WO) nanorods with monoclinic structure photocatalyst was successfully constructed via an ultrasound strategy. Under full-spectrum irradiation for 4 h, the optimized 2D/1D of heterostructure CWO/WO-0.8 exhibited superior photocatalytic performance, achieving CO and CH₃OH yields of 29.74 and 63.71 μmol·g^-1, respectively. The enhanced activity is primarily ascribed to the formation of an S-scheme charge transfer pathway, which facilitates efficient separation and directional migration of photogenerated charge carriers through the internal electric field at the CWO/WO interface. This process facilitates the electron enrichment on the CWO surface and significantly enhances its CO₂ reduction ability. Besides, the results of various characterizations show that CWO/WO-0.8 possesses enhanced optical response capability. The results of density functional theory calculations and CO₂-temperature programmed desorption analysis confirmed that the CWO/WO heterojunction exhibits stronger CO₂ adsorption and activation abilities compared to the pristine CWO and WO. The reaction pathway for CH₃OH production was elucidated by in-situ diffused reflectance Fourier transformed infrared tests. This work provides new insights into the rational design of S-scheme photocatalysts for efficient and selective CO₂ conversion.

Constructing S-scheme heterojunctions preserves the intrinsic redox capabilities of both semiconductors while promoting the separation of photogenerated electrons and holes, making it a promising approach for enhancing the properties of semiconductors. In this study, an S-scheme Cd_0.8Zn_0.2S-CeO₂ (CZS-CeO₂) heterojunction was successfully fabricated via the in-situ growth of CZS nanowires on CeO₂ nanocubes. The S-scheme charge-transfer mechanism of the CZS-CeO₂ composites during photocatalytic reactions was confirmed through in-situ X-ray photoelectron spectroscopy and density functional theory calculations. These results demonstrate that the interfacial electric field (IEF) significantly facilitates charge separation and transport within the heterojunction. Consequently, the CZS-CeO₂ composites exhibited excellent photocatalytic hydrogen production performance under simulated sunlight irradiation, surpassing that of blank CZS. Particularly, the optimal photocatalytic hydrogen generation rate for CZS-15%CeO₂ reached 58 mmol·g^-1·h^-1, approximately 8.8 times higher than that of blank CZS. After five consecutive cycles of testing, CZS-15%CeO₂ retained a relatively high level of activity. This enhanced stability can be attributed to the fabrication of S-scheme heterojunctions, which effectively suppressed hole-induced photocorrosion of CZS. This investigation provides a beneficial reference for the rational design of S-scheme heterojunction photocatalysts for efficient and stable photocatalytic hydrogen production.