Thin In-Plane In2 O3 /ZnIn2 S4 Heterostructure Formed by Topological-Atom-Extraction: Optimal Distance and Charge Transfer for Effective CO2 Photoreduction

Synthesis of in-plane Mo2C/MoO3 heterostructures by a novel spatial-confined partial oxidation approach for enhanced TEA sensing

In-plane heterostructures exhibit extraordinary chemical and electron transfer properties, which have received remarkable research attention. However, the synthesis of an in-plane Mo2C/MoO3 heterostructure has been rarely reported, and the deep investigation of the effect of its fine structure on reactivity is of great significance. Notably, the in-plane heterostructures endow the material with abundant grain boundaries, which facilitate the formation of surface acid sites and active oxygen species, thus contributing to the sensing performance. Our work provides a promising platform to design in-plane heterostructures for various advanced applications.

Two-Dimensional BiOCl Nanosheet-Encapsulated Cu2O Octahedra: p-n Junction Photocatalysts for Efficient Visible Light Driven CO2-To-CH4 Conversion

Cu2O has attracted significant attention as a potential photocatalyst for CO2 reduction. However, its practical use is limited by rapid charge recombination, insufficient catalytic sites, and poor stability. In this study, we report a facile synthesis of Cu2O@BiOCl core-shell hybrids with a well-defined shape of Cu2O and a two-dimensional nanosheet structure of BiOCl. The strategic selection of BiOCl nanosheet promotes charge separation efficiency via the formation of interfacial p-n junction and provides the active site for the CO2 reduction leading to enhanced photocatalytic CO2-to-CH4 conversion efficiency. In addition, the core-shell hybrids also showed improved stability against photocorrosion of Cu2O. These findings highlight the potential of Cu2O@BiOCl core-shell hybrids as robust and efficient photocatalysts for sustainable fuel production.

Engineering of in-plane SnS2-SnO2 nanosheets heterostructures for enhanced H2S sensing

In-plane heterostructures has attracted considerable interest due to exceptional electron transport properties, high specific surface area, and abundant active sites. However, synthesis of in-plane SnS2-SnO2 heterostructures are rarely reported, and the deep investigation of the fine structure on reactivity is of great significance. Here, we propose partial in-situ oxidation strategy to construct the in-plane SnS2-SnO2 heterostructures and the surface properties, the ratio of two components can be finely tuned by precisely adjusting the treatment temperature. In particular, the SnS2-SnO2 heterostructures formed after annealing of SnS2 nanosheets at 350 °C exhibits a unique electronic structure and surface properties due to rich grain boundaries, which exhibits excellent gas sensing performance to H2S (Ra/Rg = 169.81 for 5 ppm H2S at 160 °C, fast response and recovery dynamic (41/101 s), excellent reliability (σ = 0.01) and sensing stability (φ = 0.11 %)). Notably, the in-plane heterostructures endow the material with abundant grain boundaries and effectively regulates the electronic structure of the Sn p-orbital, which facilitate the formation of active oxygen species (O-(ad)), thus contributing to the sensing performance. Our work provides a promising platform to design in-plane heterostructures for various advanced applications.

Sensitive detection of Hg(II) on MoS2/NiS2 based on interfacial engineering to accelerate the Ni2+/Ni3+ cycle: Identification the role of atomic-level heterojunction-induced electron transfer in electroanalysis

The valence change of transition metal ions in nanomaterials can highly enhance the electrochemical detection performance toward heavy metal ions (HMIs), and how to further promote the valence change calls enormous concerns in electroanalysis. In this work, an interfacial engineering that combing the MoS2 and NiS2 together to form the MoS2/NiS2 complex is proposed. The density functional theory (DFT) results reveals that the novel atomic-level heterojunction between MoS2 and NiS2 will build an internal electric field (IEF), which leads to an enhanced conductivity and valence change behavior of Ni atoms in MoS2/NiS2 complex, resulting in a superior detection performance. In detail, the formation of atomic-level heterojunctions in the MoS2/NiS2 complex accelerates electron transfer due to the valence changes associated with Ni2+/Ni3+ cycling. The active Mo4+ species on MoS2 act as electron donors, facilitating the reduction of Ni3+ to Ni2+ on NiS2, thereby promoting Ni2+/Ni3+ cycling. As anticipated, the MoS2/NiS2 complex exhibits exceptional detection performance for Hg(II), with a sensitivity of 459.13 μA μM-1 cm-2, surpassing even that of other composite materials. In general, these findings are expected to significantly advance the application of electron transfer acceleration in electroanalysis based on the construction of heterojunction.

Heterointerface of Monodispersed Ultrathin-MnO2@Amorphous Carbon to Attain Durable Lattice Oxygen Redox Chemistry through Creation of Dual Lattice Oxygens

Lattice oxygen (OL) redox chemistry is a key to alleviating the energy and environmental crisis, but it faces challenges in activating the OL while ensuring structural stability. We disclosed herein that engineering a heterogeneous interface between ultrathin oxide and amorphous carbon can attain the durable OL redox chemistry without introducing catalytically impure sites. To this end, we proposed a green strategy to grow ∼3.9 nm-thickness wrinkled δ-MnO2 nanosheets that are rich in defects and are vertically aligned on amorphous carbon spheres. Experiments and calculations reveal that the electrons can easily migrate from the amorphous carbon to MnO2 at the δ-MnO2@C heterointerface. The heterogeneous interfaces can not only regulate the Mn-O bond and create oxygen defects in δ-MnO2 but also introduce lattice oxygen with varying reactivities. Specifically, the δ-MnO2@C structure carries more activated lattice oxygen that contributes to the enhanced activity on catalytic oxidation of bioderived 5-hydroxymethylfurfural (HMF) to 2,5-furandicarboxylic acid (FDCA), with a high FDCA formation rate of 1759 μmol gcat-1 h-1 and a high selectivity of 95%. The heterogeneous interface of MnO2@C also brings inert lattice oxygen, so that it manifests high structural stability during the oxidation reactions. This work deepens the fundamental understandings in the engineering of lattice oxygen for durable lattice oxygen redox chemistry and showcases an effective interface technique in creating advanced catalysts for clean sustainable energy.

General and Scalable Synthesis of Mesoporous 2D MZrO2 (M = Co, Mn, Ni, Cu, Fe) Nanocatalysts by Amorphous-to-Crystalline Transformation

In modern heterogeneous catalysis, it remains highly challenging to create stable, low-cost, mesoporous 2D photo-/electro-catalysts that carry atomically dispersed active sites. In this work, a general shape-preserving amorphous-to-crystalline transformation (ACT) strategy is developed to dope various transition metal (TM) heteroatoms in ZrO2, which enabled the scalable synthesis of TMs/oxide with a mesoporous 2D structure and rich defects. During the ACT process, the amorphous MZrO2 nanoparticles (M = Fe, Ni, Cu, Co, Mn) are deposited within a confined space created by the NaCl template, and they transform to crystalline 2D ACT-MZrO2 nanosheets in a shape-preserving manner. The interconnected crystalline ACT-MZrO2 nanoparticles thus inherit the same structure as the original MZrO2 precursor. Owing to its rich active sites on the surface and abundant oxygen vacancies (OVs), ACT-CoZrO2 gives superior performance in catalyzing the CO2-to-syngas conversion as demonstrated by experiments and theoretical calculations. The ACT chemistry opens a general route for the scalable synthesis of advanced catalysts with precise microstructure by reconciliating the control of crystalline morphologies and the dispersion of heteroatoms.

In Situ Etching-Hydrolysis Strategy To Construct an In-Plane ZnIn2S4/In(OH)3 Heterojunction with Enhanced CO2 Photoreduction Performance

The in-plane heterojunctions with atomic-level thickness and chemical-bond-connected tight interfaces possess high carrier separation efficiency and fully exposed surface active sites, thus exhibiting exceptional photocatalytic performance. However, the construction of in-plane heterojunctions remains a significant challenge. Herein, we prepared an in-plane ZnIn2S4/In(OH)3 heterojunction (ZISOH) by partial conversion of ZnIn2S4 to In(OH)3 through the addition of H2O2. This in situ oxidation etching-hydrolysis approach enables the ZISOH heterojunction to not only preserve the original nanosheet morphology of ZnIn2S4 but also form an intimate interface. Moreover, generated In(OH)3 serves as an electron-accepting platform and also promotes the adsorption of CO2. As a result, the heterojunction exhibits a remarkably enhanced performance for photocatalytic CO2 reduction. The production rate and selectivity of CO reach 1760 μmol g-1 h-1 and 78%, respectively, significantly higher than those of ZnIn2S4 (842 μmol g-1 h-1 and 65%). This work puts forward a feasible and facile approach to construct in-plane heterojunctions to enhance the photocatalytic performance of two-dimensional metal sulfides.

Spatial Heterogeneity and Strong Coupling of FeII /FeIII in an Individual Metal-Organic Framework Nanoparticle for Efficient CO2 Photoreduction

The synthesis and characterization of an FeII /FeIII metal-organic framework (MOF) nanocrystal with spatial heterogeneity that arises from the non-uniform distribution of different valence states is disclosed. The FeII /FeIII -Ni Prussian blue analog (PBA) delivers superior photocatalytic performance in the selective CO2 reduction reaction thanks to the strong FeII /FeIII coupling, with CO yield up to 12.27 mmol g-1 h-1 and 90.6% selectivity under visible-light irradiation. Density functional theory calculation and experimental studies prove that the spatial heterogeneity of FeII /FeIII in the individual MOF nanocrystal not only directs and expedites the charge transfer within a catalyst particle but also creates the heterogeneity of catalytically-active Ni sites for efficient CO2 photoreduction. The current findings add to a growing literature of materials with compositional heterogeneity and provide a reference for future research.

Designing Z-scheme In2O3 @ZnIn2S4 core-shell heterojunctions for enhanced photocatalytic multi-pollutant removal

In water bodies, the coexistence of and interaction between multiple pollutants complicate remediation. In this study, the In2O3 @ZnIn2S4 Z-scheme heterojunction with a stratified core-shell structure was constructed and used to remove multiple pollutants (tetracycline hydrochloride and Cr(VI)). The large number of active sites and the mechanism of photogenerated charge separation ensured the substantially enhanced catalytic activity of this photocatalyst, making it superior to In2O3 nanospheres and pure ZnIn2S4. The optimised In2O3 @ZnIn2S4 nano-flowers (In2O3 @ZnIn2S4 NFs) realised 99.8% removal of tetracycline hydrochloride and 100% removal of Cr(VI) within 60 min under visible-light. The material's high stability was demonstrated by five experiment cycles. Effects of organics, inorganics, and pH about the photocatalytic performance of the optimised In2O3 @ZnIn2S4 NFs when tetracycline hydrochloride and Cr(VI) coexist were also explored. Finally, the intermediates and degradation pathways were analysed, and the possible photocatalytic mechanism was also investigated by performing density functional theory calculations.

Localized Phase Transformation Triggering Lattice Matching of Metal Oxide and Carbonate Hydroxide for Efficient CO2 Photoreduction

Orderly heterostructured catalysts, which integrate nanomaterials of complementary structures and dimensions into single-entity structures, have hold great promise for sustainability applications. In this work, it is showcased that air as green reagent can trigger in situ localized phase transformation and transform the metal carbonate hydroxide nanowires into ordered heterostructured catalyst. In single-crystal nanowire heterostructure, the in situ generated and nanosized Co3 O4 will be anchored in single-crystal Co6 (CO3 )2 (OH)8 nanowires spontaneously, triggered by the lattice matching between the (220) plane of Co3 O4 and the (001) plane of Co6 (CO3 )2 (OH)8 . The lattice matching allows intimate contact at heterointerface with well-defined orientation and strong interfacial coupling, and thus significantly expedites the transfer of photogenerated electrons from tiny Co3 O4 to catalytically active Co6 (CO3 )2 (OH)8 in single-crystal nanowire, which elevates the catalytic efficiency of metal carbonate catalyst in the CO2 reduction reaction (VCO = 19.46 mmol g-1 h-1 and VH2 = 11.53 mmol g-1 h-1 ). The present findings add to the growing body of knowledge on exploiting Earth-abundant metal-carbonate catalysts, and demonstrate the utility of localized phase transformation in constructing advanced catalysts for energy and environmental sustainability applications.

Interfacial Water Tuning by Intermolecular Spacing for Stable CO2 Electroreduction to C2+ Products

Electroreduction of CO2 to multi-carbon (C2+ ) products is a promising approach for utilization of renewable energy, in which the interfacial water quantity is critical for both the C2+ product selectivity and the stability of Cu-based electrocatalytic sites. Functionalization of long-chain alkyl molecules on a catalyst surface can help to increase its stability, while it also tends to block the transport of water, thus inhibiting the C2+ product formation. Herein, we demonstrate the fine tuning of interfacial water by surface assembly of toluene on Cu nanosheets, allowing for sustained and enriched CO2 supply but retarded water transfer to catalytic surface. Compared to bare Cu with fast cathodic corrosion and long-chain alkyl-modified Cu with main CO product, the toluene assembly on Cu nanosheet surface enabled a high Faradaic efficiency of 78 % for C2+ and a partial current density of 1.81 A cm-2 . The toluene-modified Cu catalyst further exhibited highly stable CO2 -to-C2 H4 conversion of 400 h in a membrane-electrode-assembly electrolyzer, suggesting the attractive feature for both efficient C2+ selectivity and excellent stability.

Strain-Engineering of Mesoporous Cs3 Bi2 Br9 /BiVO4 S-Scheme Heterojunction for Efficient CO2 Photoreduction

Slow charge kinetics and unfavorable CO₂ adsorption/activation strongly inhibit CO₂ photoreduction. In this study, a strain-engineered Cs₃ Bi₂ Br₉ /hierarchically porous BiVO₄ (s-CBB/HP-BVO) heterojunction with improved charge separation and tailored CO₂ adsorption/activation capability is developed. Density functional theory calculations suggest that the presence of tensile strain in Cs₃ Bi₂ Br₉ can significantly downshift the p-band center of the active Bi atoms, which enhances the adsorption/activation of inert CO₂ . Meanwhile, in situ irradiation X-ray photoelectron spectroscopy and electron spin resonance confirm that efficient charge transfer occurs in s-CBB/HP-BVO following an S-scheme with built-in electric field acceleration. Therefore, the well-designed s-CBB/HP-BVO heterojunction exhibits a boosted photocatalytic activity, with a total electron consumption rate of 70.63 µmol g^-1 h^-1 , and 79.66% selectivity of CO production. Additionally, in situ diffuse reflectance infrared Fourier transform spectroscopy reveals that CO₂ photoreduction undergoes a formaldehyde-mediated reaction process. This work provides insight into strain engineering to improve the photocatalytic performance of halide perovskite.

Efficiency and mechanism on photocatalytic degradation of fluoranthene in soil by Z-scheme g-C3N4/α-Fe2O3 photocatalyst under simulated sunlight

Polycyclic aromatic hydrocarbons (PAHs) in soil have potential harm on human health. However, remediation of PAH-contaminated soils through photocatalytic technology remains a challenge. Therefore, the photocatalyst g-C₃N₄/α-Fe₂O₃ was synthesized and applied to photocatalytic degradation of fluoranthene in soil. The physicochemical properties of g-C₃N₄/α-Fe₂O₃ and various degradation parameters, such as catalyst dosage, the ratio of water/soil, and initial pH, were investigated in detail. In soil slurry reaction system (water/soil=10:1, w/w), the optimal degradation efficiency on fluoranthene was 88.7% after simulated sunlight irradiation for 12 h (contaminated soil=2 g, initial fluoranthene concentration=36 mg/kg, catalyst dosage=5%, and pH=6.8), and the photocatalytic degradation followed pseudo-first-order kinetics. The degradation efficiency of g-C₃N₄/α-Fe₂O₃ was higher compared with P25. Degradation mechanism analysis showed that •O₂^- and h⁺ are the main active species in photocatalytic degradation process of fluoranthene by g-C₃N₄/α-Fe₂O₃. Coupling g-C₃N₄ and α-Fe₂O₃ enhances the interfacial charge transport capacity via Z-scheme charge transfer route and inhibits the recombination of photogenerated electrons and holes of g-C₃N₄ and α-Fe₂O₃, then significantly improves the production of active species and photocatalytic activity. Results showed that photocatalytic treatment of soil by g-C₃N₄/α-Fe₂O₃ is an effective strategy for remediation of soils contaminated by PAHs.

Scalable Synthesis of Holey Deficient 2D Co/NiO Single-Crystal Nanomeshes via Topological Transformation for Efficient Photocatalytic CO2 Reduction

Preparation of holey, single-crystal, 2D nanomaterials containing in-plane nanosized pores is very appealing for the environment and energy-related applications. Herein, an in situ topological transformation is showcased of 2D layered double hydroxides (LDHs) allows scalable synthesis of holey, single-crystal 2D transition metal oxides (TMOs) nanomesh of ultrathin thickness. As-synthesized 2D Co/NiO-2 nanomesh delivers superior photocatalytic CO₂ -syngas conversion efficiency (i.e., V_CO of 32460 µmol h^-1 g^-1 CO and V H 2 ${V_{{{\rm{H}}_2}}}$ of 17840 µmol h^-1 g^-1 H₂ ), with V_CO about 7.08 and 2.53 times that of NiO and 2D Co/NiO-1 nanomesh containing larger pore size, respectively. As revealed in high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM), the high performance of Co/NiO-2 nanomesh primarily originates from the edge sites of nanopores, which carry more defect structures (e.g., atomic steps or vacancies) than basal plane for CO₂ adsorption, and from its single-crystal structure adept at charge transport. Theoretical calculation shows the topological transformation from 2D hydroxide to holey 2D oxide can be achieved, probably since the trace Co dopant induces a lattice distortion and thus a sharp decrease of the dehydration energy of hydroxide precursor. The findings can advance the design of intriguing holey 2D materials with well-defined geometric and electronic properties.

One-step hydrothermal synthesis of rhombohedral ZnIn2S4 with high visible photocatalytic activity for aqueous pollutants removal

The phase composition of photocatalyst has a substantial effect on its photocatalytic activity. In this work, the rhombohedral phase ZnIn₂S₄ was synthesized by a one-step hydrothermal method by using inexpensive Na₂S as a sulfur source with the assistance of NaCl. The Na₂S as the S source can promote the generation of rhombohedral ZnIn₂S₄, and the addition of NaCl enhances the crystallinity of the as-prepared rhombohedral ZnIn₂S₄. The rhombohedral ZnIn₂S₄ nanosheets had a narrower energy gap, more negative conductive band potential, and higher separation efficiency of photogenerated carriers relative to the hexagonal ZnIn₂S₄. The as-synthesized rhombohedral ZnIn₂S₄ exhibited high visible photocatalytic activity with removal efficiencies of 96.7% in 80 min for the methyl orange, 86.3% in 120 min for ciprofloxacin hydrochloride and nearly 100% in 40 min for Cr(VI).

Trade-Off of Metal Sites in Fe-Ni Bimetal Metal-Organic Frameworks for Efficient CO2 Photoreduction with Nearly 100% CO Selectivity

This work disclosed the trade-off effect of two metal sites, which display distinct, key functionalities in naturally occurring and artificial catalysts for developing an advanced CO₂ reduction system. To exploit the metal-organic frameworks (MOFs) as advanced catalysts, we prepared a series of Prussian blue analogues (FeNi_x PBAs) of tunable Ni/Fe molar ratio without changing the oxidation state of Fe and Ni for use as a photocatalyst in the CO₂ reduction reaction (CRR). The FeNi_0.66 PBA gives a superior CO yield rate (14.28 mmol·g^-1·h^-1) with nearly 100% CO selectivity, but the PBA would be basically CRR-inactive without either Ni or Fe. Experimental and calculation studies demonstrate that Fe and Ni display distinct functionalities. Specifically, Fe is an efficient mediator that boosts the electron transfer both from the photosensitizer to FeNi_x PBA and from FeNi_x PBA to CO₂, and Ni serves as the active site for CO₂ adsorption and reduction. Intriguingly, when there is already sufficient Ni in the catalyst, further increase of the Ni content gives marginal gains in the CO₂ adsorption affinity that cannot offset the weakened electron transfer due to the Ni excess. The findings can help advance the design of bimetallic MOF catalysts that mimic naturally occurring bimetallic catalysts.