Strong Interfacial Interaction Research Articles

Electronegativity-Induced Valence State Augmentation of Ni and Co through Electronic Redistribution between Co-Ni3N/CeF3 Interfaces for Oxygen Evolution Reaction

The development of high-performance and inexpensive electrocatalysts for the oxygen evolution reaction is one of the most desired objectives in energy conversion reactions. Due to sluggish reaction kinetics, the commercialization of such processes could not be achieved yet. Choosing an appropriate coupling interface to boost the catalyst performance is essential for the creation of high-efficiency electrocatalysts. Herein, metal-nitride and metal-fluoride heterostructures are reported with an extremely low overpotential of 180 mV at a current density of 10 mA cm–2 for OER application. The Co–Ni3N/CeF3 catalyst shows strong interfacial interaction, causing significant electronic redistribution between Co–Ni3N and CeF3 phases. X-ray photoelectron spectroscopy studies reveal the charge transfer from the Co–Ni3N to the CeF3 phase, resulting in the augmentation in the valence states of Co and Ni and making them highly active sites for the adsorption of intermediates (O*, OH*, and HOO*). This phenomenon is possibly driven by the high polarity of CeF3 due to the presence of highly electronegative F atoms. The stability study of the catalyst was performed for 120 h at large current densities of 100 and 200 mA cm–2. The detailed analysis of the surface reconstruction of Co–Ni3N/CeF3 is also carried out after a long-term stability test. This work offers a fresh look at the possibilities of the design and fabrication of an efficient and low-cost catalyst.

Electrochemical Performance Evaluation of Bimetallic Sulfide Nanocomposite with Fullerene (CeNdS/C60) for Efficient Oxygen Evolution Reaction (OER)

In recent decades, developing cost-stable electrocatalysts for oxygen evolution reactions at low overpotential has still been challenging for chemical energy conversion devices. In the present work, we have reported the facile development of the CeNdS/C60 nanocomposite via the solution method. The covered C60 over CeNdS is confirmed by TEM and STEM, providing strong interfacial interaction between CeNdS and C60. In a medium consisting of 1.00 M KOH, CeNdS/C60 electrode displayed a very small overpotential of 346 mV and a small Tafel slope of 68 mV dec–1 at a benchmark current density. Chronoamperometric and continuous CV sweeps confirmed the good stability of this catalyst at a scan rate of 5 mV s–1 (5000 cycles). The turnover frequency of CeNdS/C60 was 1.7 s–1, and the corresponding electrochemically active surface area was 3057.5 cm2. Brunauer–Emmett–Teller (BET) surface area results also confirmed the attachment of C60 particles with CeNdS by developing a high surface area with porous channels that further facilitate electrolyte penetration and the charge transfer rate, thus improving the OER property of CeNdS/C60. All performed techniques showed that the presence of Nd and C60 ions in the CeNdS/C60 catalyst is responsible for growing the superb intrinsic OER catalytic activity. Furthermore, these findings have revealed an excellent potential for CeS-based electrocatalysts for more electrochemical energy-conversion applications.

Fully bio-based ternary polymer blends: structural characterization and mechanical behavior

In this work, ternary immiscible blends based on poly (lactic acid) (PLA) as major phase and polybutylene succinate (PBS) and poly (3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBHH) as minor phases were prepared through melt blending, aiming at obtaining fully biobased materials with enhanced ductility and toughness as compared to the inherently brittle matrix. Thermodynamic considerations based on the calculation of the interfacial tensions predicted the achievement of a partial encapsulation between the domains of the two minor components embedded in the PLA matrix. The rheological characterization revealed higher melt viscosity and elasticity for all the ternary blends as compared to the PLA matrix and a growing level of interfacial interactions between the different phases when increasing amounts of PBS are incorporated. This last was confirmed through morphological observations, which allowed demonstrating the achievement of an improved homogeneous microstructure for the blends containing 30 and 40 wt% of PBS, notwithstanding the relatively good interfacial adhesion obtained in all the explored materials. The combined effect of the strong established interfacial interactions and of the uniform morphology resulted in the obtainment of dramatic increments of ductility, tensile toughness and impact strength for all formulated ternary blends as compared to the PLA matrix, and especially for those containing 30 or 40 wt% of PBS, while maintaining satisfactory levels of stiffness and tensile strength.

Visible-light driven H2 evolution over a precious metal-free hybrid photocatalyst constructed from CuO and NiFe layered double hydroxide

The strong interfacial interaction between the two components of the composites of cupric oxide and NiFe layered double hydroxide enabled efficient charge transport in the photocatalyst and subsequent H2 evolution catalysis.

Self-assembled A-D-A type indacenodithiophene-based small conjugated molecule/TiO2 for enhancing the photocatalytic activity.

Herein, A-D-A type indacenodithiophene-based small conjugated molecule IDT-COOH and IDT-COOH/TiO2 photocatalysts with stable non-covalent bonding have been successfully synthesized via in situ electrostatic assembly. The self-assembled three-dimensional π-conjugation structure IDT-COOH with high crystallinity not only broadens the visible absorption to produce more photogenerated carriers but also provides directional charge-transfer channels to accelerate the charge mobility. Thus, 7 log inactivation of S. aureus in 2 h and 92.5% decomposition of TC in 4 h under visible light exposure are achieved for optimized 30% IDT-COOH/TiO2. The dynamic constants (k) of S. aureus disinfection and TC degradation for 30% IDT-COOH/TiO2 are 3.69 and 2.45 times compared to those of self-assembled IDT-COOH, respectively. The notable inactivation performance is among the best reported for conjugated semiconductor/TiO2 photocatalysts for photocatalytic sterilization. ˙O2-, e- and ˙OH are the primary reactive species in the photocatalytic process. The strong interfacial interaction between TiO2 and IDT-COOH is in favour of rapid charge transfer, which leads to enhanced photocatalytic performance. This work offers a feasible method to fabricate TiO2-based photocatalytic agents with a wide visible light response and improved exciton dissociation.

Methanol upgrading coupled with hydrogen product at large current density promoted by strong interfacial interactions

The ultrafast solution combustion synthesis of heterogeneous interface is developed to boost anodic organic upgrading reaction, which exhibits remarkable current density and faradaic efficiency benefiting from the strong electronic interaction.

A NiCoSex/CG heterostructure with strong interfacial interaction showing rapid diffusion kinetics as a flexible anode for high-rate sodium storage.

Flexible sodium-ion batteries (SIBs) have aroused great interest in energy storage devices. However, the choice of suitable anode materials is a key step in the application of SIBs. Here, a simple vacuum filtration method is reported to obtain a bimetallic heterojunction structure. The heterojunction exhibits better performance than any single-phase material in sodium storage. The results show that the electron rich Se site and the internal electric field generated by the electron transfer in the heterojunction structure can provide rich electrochemically active areas and effectively promote the electron transport during sodiation/desodiation. More attractively, the strong interfacial interaction in the interface on the one hand maintains the stability of the structure and on the other hand promotes the diffusion of electrons. The NiCoSex/CG heterojunction with a strong oxygen bridge exhibits a high reversible capacity of 338 mA h g-1 at 0.1 A g-1, and an ignorable capacity attenuation at 2 A g-1 for 2000 cycles. The flexible full battery still shows good reversibility and output stability under bending and crimping. This idea of obtaining high-performance anodes by designing a heterojunction structure and constructing an oxygen bridge can provide a new vision for the design of other materials.

Combined digestion and bleaching of New Zealand flax /harakeke fibre and its effects on the mechanical, thermal, and dynamic mechanical properties of poly(lactic) acid matrix composites

In this study, New Zealand flax (harakeke) fibre was initially modified through digestion in an alkali solution followed by bleaching with hydrogen peroxide and sodium silicate with the aim of improving thermal and mechanical performance of its composites, through increased interfacial bonding. X-ray diffraction analysis (XRD), Fourier transform infrared spectroscopy and lignin analysis showed that the combination of bleaching and alkali treatment resulted in a higher cellulose content than digestion alone. Fibre inclusion was found to increase the crystallinity of PLA, likely due to heterogeneous nucleation on the treated fibres, which in turn helped to improve the composite strength. The highest tensile strength, tensile modulus and thermal stability were achieved with the bleached fibre which is believed to be due to better fibre distribution and stronger interfacial interaction. This was supported by the adhesion factor and effectiveness coefficient calculated using the data obtained from dynamic mechanical analysis.

Plasma synthesis of oxygen vacancy-rich CuO/Cu2(OH)3NO3 heterostructure nanosheets for boosting degradation performance.

Defect regulation and the construction of a heterojunction structure are effective strategies to improve the catalytic activity of catalysts. In this work, the rapid conversion of CuO to Cu2(OH)3NO3 was achieved by fixing nitrogen in air as NO3- using dielectric barrier discharge (DBD) plasma. This innovative approach resulted in the successful synthesis of a CuO/Cu2(OH)3NO3 nanosheet heterostructure. Notably, the samples prepared using plasma exhibit thinner thickness and larger specific surface area. Importantly, oxygen vacancies are introduced, simultaneously forming heterojunction interfaces within the CuO/Cu2(OH)3NO3 structure. CuO/Cu2(OH)3NO3 using plasma effectively degraded 96% of methyl orange within 8 min in the dark. The degradation rate is 81 and 23 times that of CuO and Cu2(OH)3NO3 using hydrothermal methods, respectively. The high catalytic activity is attributed to the large specific surface area, the abundance of active sites, and the synergy between oxygen vacancies and the strong heterojunction interfacial interactions, which accelerate the transfer of electrons and the production of reactive oxygen species (˙O2- and ˙OH). The mechanism of plasma preparation was proposed on account of microstructure characterization and online mass spectroscopy, which indicated that gas etching, gas expansion, and the repulsive force of electrons play key roles in plasma exfoliation.

Mechanistic understanding of the interfacial properties of metal-PtSe2 contacts.

With the advantages of a moderate band gap, high carrier mobility and good environmental stability, two-dimensional (2D) semiconductors show promising applications in next-generation electronics. However, the accustomed metal-2D semiconductor contact may lead to a strong Fermi level pinning (FLP) effect, which severely limits the practical performance of 2D electronics. Herein, the interfacial properties of the contacts between a promising 2D semiconductor, PtSe2, and a sequence of metal electrodes are systematically investigated. The strong interfacial interactions formed in all metal-PtSe2 contacts lead to chemical bonds and a significant interfacial dipole, resulting in a vertical Schottky barrier for Ag, Au, Pd and Pt-based systems and a lateral Schottky barrier for Al, Cu, Sc and Ti-based systems, with a strong FLP effect. Remarkably, the tunneling probability for most metal-PtSe2 is significantly high and the tunneling-specific resistivity is two orders of magnitude lower than that of the state-of-the-art contacts, demonstrating the high efficiency for electron injection from metals to PtSe2. Moreover, the introduction of h-BN as a buffer layer leads to a weakened FLP effect (S = 0.50) and the transformation into p-type Schottky contact for Pt-PtSe2 contacts. These results reveal the underlying mechanism of the interfacial properties of metal-PtSe2 contacts, which is useful for designing advanced 2D semiconductor-based electronics.

Silane functionalization of WS2 nanotubes for interaction with poly(lactic acid).

Functionalisation of nanofillers is required for the promotion of strong interfacial interactions with polymers and is essential as a route for the preparation of (nano)composites with superior mechanical properties. Tungsten disulphide nanotubes (WS2 NTs) were functionalized using (3-aminopropyl) triethoxysilane (APTES) for preparation of composites with poly(lactic acid) (PLA). The WS2NTs : APTES ratios used were 1 : 1, 1 : 2 and 1 : 4 WS2 NTs : APTES. The APTES formed siloxane networks bound to the NTs via surface oxygen and carbon moieties adsorbed on the WS2 NTs surface, detected by X-ray photoelectron spectroscopy (XPS) studies and chemical mapping using energy dispersive X-ray spectroscopy in the scanning transmission electron microscope (STEM-EDS). The successful silane modification of the WS2 NTs was clearly evident with both significant peak shifting by as much as 60 cm-1 for Si-O-Si vibrations (FTIR) and peak broadening of the A1g band in the Raman spectra of the WS2 NTs. The evolution of new bands was also observed and are associated with Si-CH2-CH2 and, symmetric and assymetric -NH3+ deformation modes (FTIR). Further evidence for functionalization was obtained from zeta potential measurements as there was a change in surface charge from negative for pure WS2 NTs to positive for APTES modified WS2 NTs. Additionally, the thermal stability of APTES was shifted to much higher temperatures as it was bound to the WS2 NTs. The APTES modified WS2 NTs were organophilic and readily dispersed in PLA, while presence of the pendant amine and hydroxyl groups resulted in strong interfacial interactions with the polymer matrix. The inclusion of as little as 0.5 wt% WS2 NTs modified with 2.0 wt% APTES resulted in an increase of 600% in both the elongation at break (a measure of ductility) and the tensile toughness relative to neat PLA, without impacting the stiffness or strength of the polymer.

A synergistic interfacial and topological strategy for reinforcing aramid nanofiber films.

While nanomaterials possess impressive mechanical properties at the microscale level, their macroscopic assemblies usually exhibit inferior properties due to ineffective stress transfer among individual nanomaterials. This issue is addressed in this work by achieving strong interfacial interactions between aramid nanofibers and graphene oxide nanosheets through a neutralization reaction in a dipolar solvent and regulating the topological properties using polymer micelles to form a compact structure, leading to the formation of a super-strong and super-tough nanofiber film. The film was prepared through a sol-gel-film transition process and possesses a nacre-like microstructure that deflects microcracks and prevents them from propagating straight through the film. Remarkably, it demonstrates a tensile strength of 599.0 MPa and a toughness of 37.7 MJ m-3, which are 491.0% and 1094.5% that of a pristine aramid nanofiber film, respectively. In addition, it exhibits excellent tolerance to extreme temperatures (-196 to 300 °C) and fatigue resistance to folding 10 000 times. Overall, this study presents a synergistic interfacial and topological enhancement strategy for constructing nanomaterial-based composites with inherited properties from the nanoscale building blocks to the macroscale structural material.

Nanomechanical study of aqueous-processed h-BN reinforced PVA composites

Hexagonal boron nitride (h-BN) as a filler has significantly improved the mechanical properties of various polymers composites. Among them, polyvinyl alcohol (PVA) is particularly important for its wide range of industrial applications and biocompatibility nature. However, preparing a homogenous composite of h-BN and PVA in water is troublesome as the aqueous processing of h-BN without any additives is challenging. In this context, a pre-processing technique is used to produce an additive-free aqueous dispersion of h-BN. The uniformly dispersed composites are then prepared with different concentrations of h-BN. Free-standing thin films are fabricated using the doctor blade technique, and nanoindentation is employed to understand their deformation behaviour at smaller length scale for better understanding of micro-mechanism involved. Reduced elastic modulus and hardness of 10 wt% h-BN/PVA composite film are enhanced by ∼93% and ∼159%, respectively, compared to pristine PVA. Frequency sweep dynamic mechanical analysis is performed between 1 and 50 Hz, and the elastic properties of composite materials are found to improve significantly upon addition of h-BN nanosheets. Besides, the impact of h-BN incorporation in stress relaxation behaviour and hardness depth profiling are also investigated. The observed improvement in mechanical properties of the composites may be attributed to the uniform distribution of the nanosheets and the strong interfacial interaction between h-BN and PVA, which ensures efficient mechanical stress transfer at the interface.

Pull-Out of Pristine and Functionalized Carbon Nanotubes from Cement: A Molecular Modelling Study

Carbon nanotubes (CNTs) are widely used as reinforcements in cement-based composites. The improvement in the mechanical properties of the resulting materials depends on the characteristics of the interface formed between CNTs and the cement matrix. The experimental characterization of the interfacial properties of these composites is still limited and hard to achieve with currently available technologies. In this work, molecular dynamics and molecular mechanics pull-out simulations of pristine and functionalized CNTs, taken from a tobermorite crystal, were carried out to study interfacial shear strength (ISS) from an atomic perspective. ISS was calculated from the potential energy of the systems. The effects of the CNT diameter and the degree of functionalization on the pull-out process were analyzed according to the ISS and non-bonded energy results. The influence of H-bonding and electrostatic interactions between the CNT and the matrix were also studied. The results show that ISS decreases with increasing CNT radius for pristine CNTs and depends upon the number of H-bonds for functionalized CNTs. ISS values are positively correlated to Enon-bonded energy, which is related to the number of carboxyl groups on the CNT surface. A high degree of functionalization increases both the number of H-bonds and the number of Ca2+-O interactions between the CNT and the tobermorite surface. This results in a stronger interfacial interaction and, therefore, an elevated ISS value.

Mussel-inspired interfacial reinforcement of thermoplastic polyurethane based energetic composites

The interfacial interaction and the microstructure evolution play a vital role in the mechanical properties of thermoplastic polyurethane (TPU) based energetic composites. In this work, inspired by the strong adhesion of mussels, 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane (CL-20) energetic crystals were coated with polydopamine (PDA) via in-situ polymerization of dopamine and then dispersed in TPU matrix. The core-shell structure of CL-20@PDA was confirmed by in-depth structural characterizations. The uniform and compact PDA shell gave rise to a high thermal stability with phase transition temperature of CL-20 crystals increased by 11.5 °C. Moreover, the PDA modification endowed the TPU based composites with excellent mechanical properties. A striking increase in mechanical properties and creep resistance was achieved with 6 h polymerization time of PDA. Compared with the PBX-Raw with untreated CL-20 crystals, the compressive and tensile strength after PDA coating increased by 115% and 57%, and the compressive and tensile fracture energy increased by 148% and 68%. The storage modulus at 25 °C was 40% higher than PBX-Raw. The enhancement effectivity could be ascribed to both interfacial interaction and the microstructure evolution of TPU binder. The theoretical simulations by molecular dynamics demonstrated the strong interfacial interaction mechanism between CL-20 and PDA. Moreover, the abundant hydrogen bonds between the hard segments of TPU and functional groups of PDA facilitated the formation of more hard microdomains which acted as physical crosslinking points to promote the phase separation. This work provides a potential method for the mechanical and thermal enhancement for TPU based energetic materials based on dopamine chemistry.

MgAl Layered Double Oxide/Reduced Graphene Oxide Composites with Reduced Interfacial Thermal Resistance for Thermal Conductivity and Electrical Insulation Applications

Research and development of polymer composites with high thermal conductivity and excellent electrical insulation are one of the research hotspots in thermal management. Although the thermal conductivity issue has been improved effectively with many methods, it remains challenging due to the interface thermal resistance issues and how to hold the electrical insulation performance at high thermal conductivity. Herein, MgAl layered double oxide/reduced graphene oxide (MgAl-LDO/rGO-s) with a hierarchical structure was innovatively used in the CNF thermal conductivity field. The lamellar structure and strong interfacial interactions between MgAl-LDO and rGO construct the continuous thermal conduction path for phonons transport, and the interface thermal resistance is effectively reduced. Meanwhile, the insulated MgAl-LDO forms a hierarchical structure on the surface of rGO by its positive charge characteristics and keeps excellent electrical insulation properties. Therefore, the CNF/MgAl-LDO/rGO-s composite films exhibit high in-plane thermal conductivity (8.7 W·m–1·K–1), electrical insulation (ρv > 1013 Ω·m), and excellent thermal stability. This work provides an interface engineering strategy for heat conduction and electrical insulation and broadens the upper limit application of thermally conductive polymer composites (TCPC) in thermal management.

Design of XS2 (X=W or Mo)-Decorated VS2 Hybrid Nano-Architectures with Abundant Active Edge Sites for High-Rate Asymmetric Supercapacitors and Hydrogen Evolution Reactions.

Two-dimensional layered transition metal dichalcogenides have emerged as promising materials for supercapacitors and hydrogen evolution reaction (HER) applications. Herein, the molybdenum sulfide (MoS2 )@vanadium sulfide (VS2 ) and tungsten sulfide (WS2 )@VS2 hybrid nano-architectures prepared via a facile one-step hydrothermal approach is reported.Hierarchical hybrids lead to rich exposed active edge sites, tuned porous nanopetals-decorated morphologies, and high intrinsic activity owing to the strong interfacial interaction between the two materials. Fabricated supercapacitors using MoS2 @VS2 and WS2 @VS2 electrodes exhibit high specific capacitances of 513and 615F g- 1 , respectively, at an applied current of 2.5A g- 1 by the three-electrode configuration. The asymmetric device fabricated using WS2 @VS2 electrode exhibits a high specific capacitance of 222F g- 1 at an applied current of 2.5A g- 1 with the specific energy of 52Wh kg- 1 at a specific power of 1kW kg- 1 . For HER, the WS2 @VS2 catalyst shows noble characteristics with an overpotential of 56mV to yield 10mA cm- 2 , a Tafel slope of 39mV dec-1 , and an exchange current density of 1.73mA cm- 2 . In addition, density functional theory calculations are used to evaluate the durable heterostructure formation and adsorption of hydrogen atom on the various accessible sites of MoS2 @VS2 and WS2 @VS2 heterostructures.

Elucidation of inter/intra molecular H-bonding mediated charge transportation mechanism in water swelled, hydrophilic organic PVA-Co3O4 nanocomposite films

In this article, we have explored the water molecules mediated charge transportation kinetics in Polyvinyl alcohol (PVA)-Cobalt Oxide (Co3O4) flexible nanocomposite films that rely heavily on the comprehension of surface and interface chemistry. Understanding the chemical interactions at the aqueous hydrophilic PVA-Co3O4 interface is essential in recognising the H-bonding revolution for complex nanocomposite films. The amount of water intake with time evolution has been monitored by the contact angle and wettability measurements. The chemical interactions and the revolution of the weak dangling bonds have been studied by Fourier transform infrared spectroscopy (FTIR), Raman and photoluminance (PL) spectra of the water-swollen hydrophilic PVA-Co3O4 nanocomposite films. The dissociation of water molecules following the fragmentation of inter/intra-molecular dangling bonds is correlated with the water diffusion kinetics and saturation in the sorption capacity of water-swollen PVA-Co3O4 nanocomposite films. The trap-states development due to the interfacial charge accumulation, after absorption of water molecules, are favourable for the trap-assisted space charge limited current conduction (TA-SCLC) mechanism and increase current density ∼ 102 times as compared to the dehydrated nanocomposite films. Meticulous tuning of the strong interfacial interactions and the manifestations of fragmented H+ ions have been identified as the primary craftsman for enhancing the dielectric constant up to eight times in the presence of 30 μL deionized water. Due to the disintegration of the free water molecules at the measurement voltage, the ac conductivity (charge transport) changes from the Jonscher's power law type variation to the jump relaxation model (JRM). The origin and accumulation of H+ ions at the grain boundary interfaces have been analyzed with impedance spectroscopic (IS) studies. An electrical equivalent circuit model is proposed for the water-mediated charge transport mechanism in swelled, hydrophilic, organic nanocomposite films.

Hydroxyl and Amino Bifunctionalized Boron Nitride Nanosheets for High-Strength and Thermoconductive Composite Films

Boron nitride nanosheets (BNNSs) have attracted more and more attention in the field of thermal management due to their excellent thermal and electrical properties. However, the low dispersity and low production yield are still a great baffle for its application. Herein, high-performance hydroxyl and amino bifunctionalized BNNSs (HA-BNNSs) were successfully prepared by the citric acid-assisted ball milling one-step method. Based on the additional friction provided by citric acid during ball milling, the aspect ratio of HA-BNNSs was up to 499 and the production yield was as high as 89.7%. Simultaneously, arising from the high functionalization rate, the HA-BNNSs show excellent dispersity in a variety of polar solvents, particularly in 50% aqueous ethanol solution. The dispersibility of HA-BNNSs was much improved to 39.8 mg/mL. Based on the good dispersibility of HA-BNNSs and strong interface interactions between HA-BNNSs and the matrix, HA-BNNSs have been introduced to aramid nanofibers (ANFs) to fabricate layered HA-BNNSs/ANF composite films for thermal management applications. In comparison with the pure BNNSs/ANF, the HA-BNNSS/ANF composite exhibits improved mechanical strength (85.6–175.6 MPa) and better thermal conductivity (8–39.5 W/m·K) at a relatively low filler content (≤50%). In summary, benefiting from the bifunctional group, improved dispersibility, and high aspect ratio, the HA-BNNSs have great application potential in the fields of composite reinforcement, drug delivery, and photocatalysis.

Interface Engineering in 2D/2D Heterogeneous Photocatalysts

Assembling different 2D nanomaterials into heterostructures with strong interfacial interactions presents a promising approach for novel artificial photocatalytic materials. Chemically implementing the 2D nanomaterials' construction/stacking modes to regulate different interfaces can extend their functionalities and achieve good performance. Herein, based on different fundamental principles and photochemical processes, multiple construction modes (e.g., face-to-face, edge-to-face, interface-to-face, edge-to-edge) are overviewed systematically with emphasis on the relationships between their interfacial characteristics (e.g., point, linear, planar), synthetic strategies (e.g., in situ growth, ex situ assembly), and enhanced applications to achieve precise regulation. Meanwhile, recent efforts for enhancing photocatalytic performances of 2D/2D heterostructures are summarized from the critical factors of enhancing visible light absorption, accelerating charge transfer/separation, and introducing novel active sites. Notably, the crucial roles of surface defects, cocatalysts, and surface modification for photocatalytic performance optimization of 2D/2D heterostructures are also discussed based on the synergistic effect of optimization engineering and heterogeneous interfaces. Finally, perspectives and challenges are proposed to emphasize future opportunities for expanding 2D/2D heterostructures for photocatalysis.