Hierarchical CuS@ZnIn2S4 Hollow Double-Shelled p-n Heterojunction Octahedra Decorated with Fullerene C60 for Remarkable Selectivity and Activity of CO2 Photoreduction into CH4

D-band state control engineering over ZnIn2S4 for enhanced photoreduction of CO2 to CH4

Metal-based photocatalysts with d10 electronic configurations exhibit good photocatalytic performance due to strong band edge dispersion, however, the weak bonding between d10 metal sites and CO2 through 2p-3d orbital hybridization limits their activity and selectivity for CO2 to CH4 conversion. Herein, a strategy for modulating the d-band center is proposed to promote the formation of CH4 in the photocatalytic CO2 reduction process. In a model system taking ZnIn2S4 (ZIS) as photocatalysts, highly thermodynamically electronegative elements (such as Bi, Cu, and Co) are doped to upshift the d-band center of ZIS, enhance the selectivity and yield of CH4. In the absence of cocatalysts or photosensitizers, the CO2 photoreduction products of all doped ZIS samples shifts from pure CO to a mixture of CO and CH4, with CH4 being the predominant product. Among all samples, Bi-doped ZnIn2S4 (Bi-ZIS) demonstrates the highest performance, achieving a CH4 selectivity of 63.68 % and a high evolution rate of 21.07 µmol·g-1·h-1 during visible-light-driven CO2 reduction. Density functional theory (DFT) calculations indicate that doping highly electronegative elements can modulate the electron cloud distribution of ZIS, thereby raising its d-band center. This shift reduces the energy barrier for CO2 photoreduction to CH4, enhancing the binding energy between active sites and intermediates (such as *OCH2 and *OCH3), facilitating the formation of CH4. Consequently, this study not only validates the effectiveness of the d-band center modulation strategy but also offers a novel perspective for optimizing the activity and product selectivity of d10 metal-based photocatalysts in CO2RR.

Copper Sulfide based Photocatalysts, Electrocatalysts and Photoelectrocatalysts: Innovations in Structural Modulation and Application

Copper sulfides (CuxS, 1 ≤ x ≤ 2) are notable for their unique photoelectric properties and potential applications, particularly in photo/electrocatalysis. These materials are valued for their tunable band gap, near-infrared optical characteristics, and plasmonic resonance effects. However, challenges such as low catalytic activity and limited stability impede their practical applications. This review addresses these issues by exploring advanced strategies for electronic structure modulation, including atomic doping, shape alteration, heterojunction construction, and defect introduction to enhance catalytic efficiency. A detailed analysis of the optical and electrical properties of CuxS across various stoichiometric ratios and crystal structures is provided, offering a comprehensive overview of their applications in photocatalysis, electrocatalysis, and photo/electrocatalysis. Additionally, the review synthesizes current knowledge and highlights the potential of these strategies to optimize CuxS-based photo/electrocatalysts, proposing future research directions to bridge the gap between theoretical studies and practical applications. This work underscores the importance of CuxS in photo/electrocatalysis and aims to inspire further innovation and exploration in this field, emphasizing its significance in material science and engineering.

Photoelectrochemical immunosensor for chloramphenicol detection based on cation exchange reaction-mediacted photocurrent enhancement of ZnIn2S4/TiO2/Ti3C2 MXene coupled with controlled-release strategy

A photocurrent enhancing photoelectrochemical (PEC) immunosensor was developed for chloramphenicol (CAP) detection based on cation exchange reaction. The efficient split-type PEC immunosensor combined with controlled-release strategy was established using the ZnIn2S4/TiO2/Ti3C2 MXene (ZIS/T/M) composite as the photoactive material and CuO as the signal response probe. In the presence of target CAP, CuO-labeled CAP antibody (CuO-mAb) was introduced onto the microplate via a competitive-type immunoassay. Under acidic conditions, a large amount of Cu2+ released from CuO-mAb, which triggered a cation exchange reaction with the Zn2+ in ZIS/T/M-modified photoelectrode to generate CuxS, resulting in enhancing the photocurrent. As a result, the quantitative detection of CAP was achieved by detecting the photocurrent change. Under optimized conditions, the linear range of the sensor was 1 pg/mL to 50 ng/mL, and the detection limit was 0.24 pg/mL. The excellent PEC behavior of ZIS/T/M composite could be attributed to the fact that heterojunction formation improved the migration and separation of the photocarrier. Additionally, by virtue of the photocurrent-enhancing strategy via cation exchange reaction and the controlled releasing signal amplification method of ion, the PEC immunosensor has high sensitivity and satisfactory accuracy, offering great potential applications in the determination of CAP.

Photoelectrochemical detection of Cu2+ based on ZnIn2S4/WO3 Z-scheme heterojunction

A one-step hydrothermal technique was utilized to generate WO3 nanosheets on fluorine-doped tin oxide (FTO) (WO3/FTO), which were subsequently modified with ZnIn2S4 microspheres to create a Z-scheme heterojunction ZnIn2S4/WO3/FTO electrode for Cu2+ detection. The heterojunction exhibited excellent photoelectric conversion efficiency, which was nearly 2.5-fold and 5.1-fold greater than that of WO3 and ZnIn2S4. The reduced photoelectrochemical response signal was caused by the formation of CuxS and enabled Cu2+ assessment in water samples. After optimizing the experimental conditions, the anodic photocurrent at 0 V vs SCE in 0.100 M phosphate buffer (pH 7.0) containing 0.100 M L-ascorbic acid was linear with the common logarithm of Cu2+ concentration from 5.00 nM to 100 μM, with a limit of detection of 1.2 nM (S/N = 3). Satisfactory recovery results were obtained in the analyses of Xiangjiang River water samples.

Efficient Photoelectrocatalytic Reduction of CO2 to Selectively Produce Ethanol Using FeS2/TiO2 p-n Heterojunction Photoelectrodes

Herein, the FeS2/TiO2 p-n heterojunction was first utilized as a photoelectrode for the PEC reduction of CO2 to selectively produce ethanol. The FeS2/TiO2 photoelectrode was fabricated through electrochemical anodization, electrodeposition, and vulcanization methods. The impact of the FeS2 loading amount and applied bias on the PEC performance was investigated. The behavior of photocurrent polarity reverse is observed depending on the FeS2 loading amount, which is related to the energy band structure of the semiconductor/electrolyte interface. The active sites for ethanol production were identified on TiO2 nanotubes rather than on the FeS2 surface. Incorporation of FeS2 not only broadened the visible light absorption range but also formed a p-n heterojunction with TiO2. FeS2/TiO2 with an electrodeposition time of 15 min exhibits the highest ethanol yield of 1170 μmol L-1 cm-2 for 3.5 h of reaction under ultraviolet-visible (UV-Vis) illumination at an applied bias of -0.7 V. Compared to TiO2, FeS2/TiO2 showed significantly higher ethanol yield due to its appropriate loading amount of FeS2 and the synergistic effect of strong UV-Vis light absorption and efficient separation and transfer of charge carriers at the p-n junction.

Reasonable Design and Deep Insight of Efficient Integrated Photorechargeable Li-Ion Batteries by Using a Cu/CuO/Cu2S Electrode

Herein, Cu-foam-supported CuO nanowire arrays covered with Cu2S nanosheet substrates (Cu/CuO/Cu2S) are adopted as efficient photoelectrodes for photorechargeable lithium-ion batteries (PR-LIBs). The assembled PR-LIB exhibits remarkable solar energy conversion efficiency alongside superior lithium storage capabilities. Without an electrical power supply, the photocharged PR-LIB sustained a discharge process for 63.0 h under a constant current density of 0.05 mA cm-2. The corresponding solar-to-electrical energy conversion efficiency is 4.50%, which is an impressive achievement among recently reported contemporary technologies. Mechanism investigation shows that the Cu/CuO/Cu2S photogenerated carriers augment the extraction and insertion of Li+ according to different oxidation and reduction reactions in the charging and discharging reactions. This research delineates a refined model system and proposes innovative directions for developing efficient heterojunction photoelectrodes, significantly propelling the development of PR-LIB technology.

Construction of Dual-Active Sites by Interfacing with Polyhydroxy Fullerene on Nickel Hydroxide Surfaces to Promote CO2 Deep Photoreduction to CH4

Due to the complex series of elementary steps involved, achieving deep photoreduction of CO2 to multielectron products such as CH4 remains a challenging task. Therefore, it is crucial to strategically design catalysts that facilitate the controlled formation of the crucial intermediates and provide precise control over the reaction pathway. Herein, we present a pioneering approach by employing polyhydroxy fullerene (PHF) molecules to modify the surface of Ni(OH)2, creating stable and effective synergistic sites to enhance the formation of CH4 from CO2 under light irradiation. As a result, the optimized PHF-modified Ni(OH)2 cocatalyst achieves a CH4 production rate of 455 μmol g-1 h-1, with an electron-based selectivity of approximately 60%. The combination of in situ characterizations and theoretical calculations reveals that the hydroxyl species on the surface of PHF can participate in stabilizing crucial intermediates and facilitating water activation, thereby altering the reaction pathway to form CH4 instead of CO. This study provides a novel approach to regulating the selectivity of photocatalytic CO2 reduction by exploring molecular surface modification through interfacing with functionalized carbon clusters.

ZnIn2S4 Heterojunctions Constructed with In-MOF Precursor for Photocatalytic Hydrogen Evolution without Cocatalysts

Znln2S4 has great prospects for photocatalytic water splitting to hydrogen by visible light. Herein, a novel Znln2S4-In-MOF (ZnInMS4) photocatalyst is elaborately synthesized by in situ method with In-MOF as the template and In3+ as the source. ZnInMS4 overcomes the fast interface charge recombination and a sluggish charge lifetime via the formed heterojunctions. Photoelectrochemical measurements reveal that the charge-transfer kinetics is enhanced since In-MOF is introduced to act as a reliable charge-transport channel. ZnInMS4 exhibits outstanding cocatalyst-free H2 evolution rate of 70 μmol h-1 under irradiation (λ > 420 nm), which is 3.2-fold higher than that of Znln2S4. In addition, the ZnInMS4 photocatalyst shows good stability in the 16 h continuous reaction. This work illustrates the feasibility of the MOF precursor instead of inorganic salts to directly synthesize photocatalysts with high performance.

Multisite Cocatalysis: Single atomic Pt2+/Pt0 active sites synergistically improve the simulated sunlight driven H2O-to-H2 conversion performance of Sb2S3 nanorods

Single atomic metal (SAM) cocatalysis is a potential strategy to improve the performance of photocatalytic materials. However, the cocatalytic mechanism of SAM sites in different valence states is rarely reported. Herein, single atomic Pt2+/Pt0 active sites were anchored on Sb2S3 nanorods to synergistically improve the photoactivity for hydrogen production under simulated sunlight. Experimental results and density functional theory calculations indicated that the coexistence of single atomic Pt2+/Pt0 sites synergistically improves the broadband light harvesting and promotes the Sb2S3-to-Pt electron transfer following inhibited photoexciton recombination kinetics and enhanced H proton adsorption capacity, resulting higher and more durable photoactivity for hydrogen production. Therefore, the optimal Sb2S3-Pt0.9‰ composite catalyst achieved remarkably enhanced hydrogen evolution rate of 1.37 mmol∙g-1∙h-1 (about 105-fold greater of that of Sb2S3 NRs) under faintly alkaline condition, and about 5.41 % of apparent quantum yield (AQY700 nm) was achieved, which shows obvious superiority in hydrogen production by contrasting with the reported Sb2S3-based photocatalysts and conventional semiconductor photocatalytic materials modified with noble metals. This study elucidate a well-defined mechanism of multisite cocatalysis for photoactivity improvement.

Hollow Nanoreactors for Controlled Photocatalytic Behaviors: Fundamental Theory, Structure-Performance Relationship, and Catalytic Advantages

Hollow nanoreactors (HoNRs) have regarded as an attractive catalytic material for photocatalysis due to their exceptional capabilities in enhancing light harvesting, facilitating charge separation and transfer, and optimizing surface reactions. Developing novel HoNRs offers new options to realize controllable catalytic behavior. However, the catalytic mechanism of photocatalysis occurring in HoNRs has not yet been fully revealed. Against this backdrop, this review elaborates on three aspects: 1) the fundamental theoretical insights of HoNRs-driven photocatalytic kinetics; 2) structure-performance relationship of HoNRs to photocatalysis; 3) catalytic advantages of HoNRs in photocatalytic applications. Specifically, the review focuses on the fundamental theories of HoNRs for photocatalysis and their structural advantages for strengthening light scattering, promoting charge separation and transfer, and facilitating surface reaction kinetics, and the relationship between key structural parameters of HoNRs and their photocatalytic performance is in-depth discussed. Also, future prospects and challenges are proposed. It is anticipated that this review paper will pave the way for forthcoming investigations in the realm of HoNRs for photocatalysis.

Hollow Plasmonic P-Metal-N S-Scheme Heterojunction Photoreactor with Spatially Separated Dual Cocatalysts toward Artificial Photosynthesis

Semiconductor-based step-scheme (S-scheme) heterojunctions possess many merits toward mimicking natural photosynthesis. However, their applications for solar-to-chemical energy conversion are hindered by inefficient charge utilization and unsatisfactory surface reactivity. Herein, two synergistic protocols are demonstrated to overcome these limitations based on the construction of a hollow plasmonic p-metal-n S-scheme heterojunction photoreactor with spatially separated dual noble-metal-free cocatalysts. On one side, plasmonic Au, inserted into the heterointerfaces of CuS@ZnIn2 S4 core-shell nanoboxes, not only accelerates the transfer and recombination of useless charges, enabling a more thorough separation of useful ones for CO2 reduction and H2 O oxidation but also generates hot electrons and holes, respectively injects them into ZnIn2 S4 and CuS, further increasing the number of active carriers participating in redox reactions. On the other side, Fe(OH)x and Ti3 C2 cocatalysts, separately located on the CuS and ZnIn2 S4 surface, enrich the redox sites, adjust the reduction potential and pathway for selective CO2 -to-CH4 transformation, and balance the transfer and consumption of photocarriers. As expected, significantly enhanced activity and selectivity in CH4 production are achieved by the smart design along with nearly stoichiometric ratios of reduction and oxidation products. This study paves the way for optimizing artificial photosynthetic systems via rational interfacial channel introduction and surface cocatalyst modification.

Fabricated ZnO@ZnIn2S4 S-scheme heterojunction photocatalyst for enhanced electron-transfer and CO2 reduction

Step-scheme (S-scheme) heterojunctions can efficiently promote the separation of photogenerated carriers while maintaining the strong oxidation/reduction ability of photocatalysts; thus, research attention on S-scheme heterojunctions is increasing year by year. In this study, the S-scheme ZnO@ZnIn2S4 (ZnO@ZIS) heterojunction was prepared successfully. Then, electron spin resonance (ESR) characterization was applied to prove the successful construction of the S-scheme heterojunction. Photoluminescence (PL), time-resolved photoluminescence (TRPL), and photoelectrochemical experiments have demonstrated efficient interfacial charge transport in ZnO@ZIS. Finally, the mechanism of CO2 activation and electron transport was investigated by in situ Fourier transform infrared spectroscopy (FT-IR) and discrete Fourier transform (DFT) calculation analysis. The 40-ZnO@ZIS composite showed the best activity under light, and its CO and CH4 yields reached 39.76 and 3.92 μmol∙g-1∙h-1, respectively. This study provides a solution for optimizing the photocatalytic reduction activity of semiconductor photocatalysts by constructing S-scheme heterojunction materials to improve the CO2 reduction capacity.

Engineering Single Cu Sites into Covalent Organic Framework for Selective Photocatalytic CO2 Reduction

Photocatalytic CO₂ conversion into value-added chemicals is a promising route but remains challenging due to poor product selectivity. Covalent organic frameworks (COFs) as an emerging class of porous materials are considered as promising candidates for photocatalysis. Incorporating metallic sites into COF is a successful strategy to realize high photocatalytic activities. Herein, 2,2'-bipyridine-based COF bearing non-noble single Cu sites is fabricated by chelating coordination of dipyridyl units for photocatalytic CO₂ reduction. The coordinated single Cu sites not only significantly enhance light harvesting and accelerate electron-hole separation but also provide adsorption and activation sites for CO₂ molecules. As a proof of concept, the Cu-Bpy-COF as a representative catalyst exhibits superior photocatalytic activity for reducing CO₂ to CO and CH₄ without photosensitizer, and impressively, the product selectivity of CO and CH₄ can be readily modulated only by changing reaction media. Experimental and theoretical results reveal the crucial role of single Cu sites in promoting photoinduced charge separation and solvent effect in regulating product selectivity, which provides an important sight onto the design of COF photocatalysts for selective CO₂ photoreduction.

Integration of CuS/ZnIn2S4 flower-like heterojunctions and (MnCo)Fe2O4 nanozyme for signal amplification and their application to ultrasensitive PEC aptasensing of cancer biomarker

Vascular endothelial growth factor 165 (VEGF₁₆₅) is a crucial regulator of angiogenesis and works as a major protein biomarker of cancer metastasis. Therefore, its quantitative detection is pivotal in clinic. In this work, CuS/ZnIn₂S₄ flower-like heterojunctions had strong and stable photocurrents, which behaved as photoactive material to construct a photoelectrochemical (PEC) aptasensor for detecting VEGF₁₆₅, combined by home-prepared (MnCo)Fe₂O₄ nanozyme-mediated signal amplification. The interfacial photo-induced electron transfer mechanism was chiefly discussed by UV-vis diffuse reflectance spectroscopy in details. Specifically, the (MnCo)Fe₂O₄ modified VEGF₁₆₅ aptamer was released from the PEC aptasensing platform for its highly specific affinity to target VEGF₁₆₅, which terminated the color precipitation reaction, ultimately recovering the PEC signals. The developed sensor displayed a wider linear range from 1 × 10^-2 to 1 × 10⁴ pg mL^-1 with a smaller limit of detection (LOD) of 0.1 fg mL^-1. This study provides some valuable insights for building other ultrasensitive aptasensors for clinical assays of cancer biomarkers in practice.

Recent Advances and Perspectives of Core-Shell Nanostructured Materials for Photocatalytic CO2 Reduction

Photocatalytic CO₂ conversion into solar fuels is a promising technology to alleviate CO₂ emissions and energy crises. The development of core-shell structured photocatalysts brings many benefits to the photocatalytic CO₂ reduction process, such as high conversion efficiency, sufficient product selectivity, and endurable catalyst stability. Core-shell nanostructured materials with excellent physicochemical features take an irreplaceable position in the field of photocatalytic CO₂ reduction. In this review, the recent development of core-shell materials applied for photocatalytic reduction of CO_{2 is introduced} . First, the basic principle of photocatalytic CO₂ reduction is introduced. In detail, the classification and synthesis techniques of core-shell catalysts are discussed. Furthermore, it is also emphasized that the excellent properties of the core-shell structure can greatly improve the activity, selectivity, and stability in the process of photocatalytic CO₂ reduction. Hopefully, this paper can provide a favorable reference for the preparation of efficient photocatalysts for CO₂ reduction.