Suitable Band Positions Research Articles

General Synthesis of Single-Crystalline Ta2O5 Nanorods Towards Enhanced Photocatalytic H2 Production Activity.

As a potential candidate for photocatalytic H2 production from water splitting, Ta2O5 catalyst presents suitable conduction and valence band positions, but suffers from poor charge transfer ability, which seriously limits its photocatalytic performance enhancement. Here, a facile and eco-friendly hydrothermal method was developed for the fabrication of one-dimensional (1D) Ta2O5 nanorods using the freshly precipitated tantalic acids as the precursors. An oriented attachment mechanism was proposed for the growth of Ta2O5 nanorods. Moreover, the present synthetic approach was further extended to direct synthesis of nine kinds of alkaline tantalates and alkaline-earth tantalates nanostructures, suggesting its general applicability. A significant increase in activity in photocatalytic H2 production was revealed on 1D Ta2O5 nanorods. The improved photocatalytic H2 production activity of Ta2O5 nanorods was mainly attributed to its 1D nanorods structure with high crystallization and large specific surface areas as well as excellent charge transfer efficiency.

Near-Ideal Copper Oxide Heterostructure Design for Photoelectrochemical Water Splitting.

In recent years, photoelectrochemical (PEC) hydrogen generation through water splitting has gained significant attention as a carbon-free solar-to-energy conversion strategy. Among various materials, copper oxides, specifically cupric oxide (CuO) and cuprous oxide (Cu2O), have been extensively investigated for their suitable band positions and prominent performance, particularly in heterostructures. However, previously reported heterostructures, such as CuO layers on Cu2O, are not ideal configurations in terms of photoelectrical properties. In this study, we introduce the fabrication approach for an ideal heterostructure consisting of Cu2O nanowires on a CuO/Cu2O mixed-phase film, fabricated by a straightforward electrochemical/thermal method. The Cu2O nanowire with Cr layer (CNwC) shows potential for solar energy harvesting due to its suitable band positions and narrow bandgap, enabling enhanced photoabsorption across the entire visible spectrum. A thin chromium (Cr) layer underlying the nanostructure contributes to the formation of the ideal copper oxide heterostructure, acting as an adhesive and protective layer. The Cr layer is oxidized during the fabrication process of the CNwC and supports the hydrogen evolution reaction for water splitting. Moreover, the anodization time critically influences the phase composition, size, and density of the nanowires. Under optimal conditions, collective and slanted Cu2O nanowires can absorb incident light, maximizing both photon absorption and photon-to-energy conversion efficiency.

Z-Scheme LaFeO3/Cd0.7Zn0.3S heterojunction based on 3DOM LaFeO3 perovskite for enhanced photocatalytic hydrogen activity

The narrow band gap semiconductor LaFeO3 with ABO3 perovskite structure has been deeply studied in the field of photocatalysis due to its good thermal stability, chemical stability, photoelectric properties and suitable band position. The inverse opal structure gives the material a large specific surface area and increases the adsorption area and active site of the catalyst. In this work, it is reported for the first time that perovskite LaFeO3 inverse opal was applied to photocatalytic hydrogen production. The Cd0.7Zn0.3S QDs were deposited on the skeleton wall of LaFeO3 inverse opal to construct LaFeO3/Cd0.7Zn0.3S binary heterojunction catalyst. The LaFeO3 3DOM can effectively increase the contact area with Cd0.7Zn0.3S QDs with an increase in specific surface area, and the multiple scattering effect improves the efficiency of light utilization. The introduction of Zn2+ ions regulate the band gap position of Cd0.7Zn0.3S QDs and increases the thermodynamic reduction ability of photo generated electrons. The Z-type heterojunction effect formed by LaFeO3 inverse opal and Cd0.7Zn0.3S QDs facilitates the separation and transmission of photo generated charges. The LaFeO3/Cd0.7Zn0.3S heterojunction catalysts achieved a hydrogen production performance of 277.48 μmol/g/h due to the large specific surface area of 3DOM, good light capture ability, band gap regulation of element doping, and efficient charge separation synergistic effect of heterojunction. This work provides new insights into the design and manufacture of perovskite-type 3DOM heterojunction photocatalysts.

The significant role of Z-scheme band alignment at the heterojunction for the enhanced photocatalytic H2 production in TiO2/BiNbO4/rGO nanocomposite

An efficient ternary TiO2/BiNbO4/rGO nanocomposite was prepared by a simple wet impregnation process. PXRD confirmed the tetragonal and orthorhombic crystalline natures of titanium dioxide (TiO2) and bismuth niobate (BiNbO4) respectively. The loading of BiNbO4 and reduced graphene oxide (rGO) shifted the light absorption of TiO2 to a longer wavelength from 400 to 430 nm. The suitable conduction band position of BiNbO4 facilitated a favourable band alignment to suppress the electron/hole (e−/h+) recombination in TiO2 via the Z scheme mechanism at the heterojunction. The excited electrons at the CB of TiO2 were easily transported via the fast electron accepting and conducting rGO matrix for the surface redox reactions with the improved charge transfer efficiency, which was confirmed by EIS and PL studies respectively. BiNbO4 and rGO synergistically improved the specific surface area and solar light absorption. EPR analysis confirmed the presence of increased oxygen vacancies at the heterojunction. Hence, the ternary TiO2/BiNbO4/rGO nanocomposite demonstrated an enhanced hydrogen evolution (8910 μ mol h−1 gcat−1) than bare TiO2 (4820 μ mol h−1 gcat−1), bare BiNbO4 (950 μ mol h−1 gcat−1) and TiO2/BiNbO4 (6730 μ mol h−1 gcat−1) under direct solar light. The optimum of 1 wt % BiNbO4 and rGO loaded TiO2 nanocomposite produced twice the H2 production than the bare TiO2. This also further confirms that rGO played a major role during the photocatalytic process by highlighting the potential of metal oxides combined with carbon material as an efficient photocatalyst which prominently enhances the H2 evolution.

In-situ construction of the novel In2S3/BiOIO3 heterojunction with boosted visible-light photodegradation performance for diverse persistent organic pollutants

Designing rational heterojunctions to achieve efficient separation and transmission of photoinduced charge carriers is one of the effective strategies to improve the activity of semiconductor photocatalysts. In this study, the novel In2S3/BiOIO3 binary heterojunctions were facilely synthesized at room temperature using a simple in-situ growth method. The physicochemical properties of the fabricated In2S3/BiOIO3 heterojunction catalyst were investigated using various techniques including XRD, FT-IR, BET, XPS, TEM, UV–vis DRS, PL, EIS, and PC analysis. The In2S3/BiOIO3 composite catalyst possesses suitable band position and bandgap energy and therefore is capable of degrading organic contaminants under visible light irradiation. The optimized composite catalyst with In2S3/BiOIO3 molar ratio of 0.5 (In2S3/BiOIO3-5) exhibited superior photocatalytic activity, achieving 98.6 % degradation rate for Rhodamine B (RhB), far surpassing the performance of the individual components. In addition, In2S3/BiOIO3-5 showed broad-spectrum photocatalytic activity in the decomposition of various organic pollutants including methyl orange (MO), methylene blue (MB), tetracycline (TC) and bisphenol A (BPA). The improved photocatalytic activity of the prepared composite catalysts can be ascribed to the formation of type-II heterojunction, which facilitates the separation and migration of e–/h+ pairs. The excellent photocatalytic properties and favorable structural stability make In2S3/BiOIO3-5 a viable material for degrading various persistent organic pollutants.

Elucidation of the optical, electronic, and photoelectrochemical properties of p-type CuFe2O4 photocathodes

High-quality thin films of p-type CuFe2O4 photocathode were prepared for the first time on FTO-coated glass substrates by a novel nonaqueous solution using spray pyrolysis method. The films' critical physical and photophysical properties, including morphology, optical properties, carrier transport properties, band position, and photoelectrochemical (PEC) characteristics, were analyzed and estimated. The feasibility of PEC water splitting was systematically evaluated. The prepared reddish-brown CuFe2O4 film exhibits a compact and uniform morphology. Its optical bandgap is approximately 1.42 eV, and it possesses a suitable conduction band position, indicating its capability to facilitate solar-driven water splitting and absorb visible light. Under AM 1.5 simulated solar illumination, the photocurrent density of 12 μA/cm2 was attained in a 1 mol NaOH solution. However, the prepared CuFe2O4 films demonstrate instability under constant light in the electrolyte owing to the copper reduction reaction. These research results offer a fresh insight into the potential application of CuFe2O4 as a photocathode semiconductor in PEC water splitting.

Resorcinol‐Phthalaldehyde Resins for Photosynthesis of Hydrogen Peroxide: Modulation of Electronic Structure and Integration of Dual Channel Pathway

AbstractModulating of electronic structure of photocatalyst and integration of dual channel pathway are promising strategy for efficient photosynthesis of hydrogen peroxide (H2O2) from pure water without sacrificial agent and oxygen exposure. In this work, nontoxic aromatic dialdehyde is used to replace the commonly used toxic formaldehyde to form resorcinol‐phthalaldehyde resins through a hydrothermal method. The introducing of aromatic ring as π spacer increases the separation distance of electrons and holes to avoid their recombination. H2O2 can be produced via integrated oxygen reduction reaction (ORR) and water oxidation reaction (WOR) due to the suitable energy band positions and spatially separated reaction sites. Resorcinol‐p‐phthalaldehyde (RP) resin exhibits a promising H2O2 yield of 3351 µmol g−1 h−1 with high apparent quantum yield (AQY) of 14.9% at 420 nm and solar‐to‐chemical conversion (SCC) efficiency of 1.54%. This work provides a simple strategy to modulate the charge separation efficiency and redox reaction pathway on photocatalyst at molecular level design.

Fabricating waxberry-shaped N–C–TiO2 composite with excellent visible light catalytic activity

Herein, a nitrogen, carbon co-doped anatase and rutile double-phase waxberry-shaped [Formula: see text] composite photocatalyst is prepared with the one-step simple hydrothermal synthesis process, in which P25 was used as the precursor, and urea as the source of nitrogen and carbon. A suitable valence band position (2.52 eV) is provided by [Formula: see text], with more active species (e.g. [Formula: see text], [Formula: see text], •[Formula: see text] and •[Formula: see text]) being formed on the active catalysis surface, which is helpful to the redox reaction. Further comparison of experimental results ([Formula: see text] = 3.01 eV) proved that the novel [Formula: see text] has preferable photocatalytic activity. In this study, an ingenious nitrogen- carbon co-doping structure was designed for the improvement of [Formula: see text] photocatalytic performance, which is much for reference of this method to other photocatalyst designs.

Photoredox-promoted co-production of 3,4-dihydroisoquinoline and H2 over Pd-doped leaf-like CdS catalyst

Integrating selective organic transformation and hydrogen (H2) evolution in one photoredox reaction system is one of the most sustainable and promising approaches to efficiently produce solar fuels and chemicals by simultaneously utilizing photogenerated electrons and holes. Herein, through the cation-exchange engineering method, the nanoleaf-like Pd/CdS composites are gingerly fabricated for visible-light-driven receptor-free dehydrogenation of 1,2,3,4-tetrahydroisoquinoline (THIQ) to 3,4-dihydroisoquinoline (DHIQ) and H2 under ambient conditions. The optimized electronic structure endows Pd/CdS with a narrow band gap and suitable energy band positions, thus facilitating the light harvesting as well as the separation and transfer of photoexcited charge carriers. Consequently, the Pd/CdS exhibits significantly improved photoredox activity compared to bare CdS. In-situ Fourier-transform infrared spectroscopy and electron paramagnetic resonance spectroscopy track the progression of reaction intermediates during such a dual-functional photoredox-catalyzed system, revealing that the carbon-centered radical is the key reaction intermediate in this reaction process. It is anticipated that this work would guide the rational utilization of CdS-based materials to enable simultaneous photochemical coupling of organic transformation and H2 evolution.

Microstructure regulation of Zn0.5Cd0.5S for enhancing the photocatalytic H2 production

As an excellent photocatalytic material, ZnxCd1-xS is widely used in photocatalytic H2 production due to its good visible light response and suitable band position. Based on our previous studies, this paper systematically studies the relationship of Zn0.5Cd0.5S (ZCS) material between microstructure and photocatalytic activity. By controlling the synthesized temperature, S sources and solvents, a series of ZCS nanomaterials with different morphology and crystalline phase have been prepared by hydrothermal, solvothermal and ion-exchange methods. When several sacrificial agents are added in photocatalytic H2 production, ZCS performs the highest activity synthesized by solvothermal method, about 12.15 mmol g−1 under 4 h’s visible light illumination. To explore the difference of ZCS samples in photocatalytic performance, many factors are considered, such as crystal size, crystallinity, separation of photogenerated charge carriers (PCCs), specific surface area and defect sites, which play important roles in the improving photocatalytic activity. This work provides a new direction for the design of photocatalyst from the microstructural regulation to achieve highly efficient activity.

Morphology-Controlled ZnO@ZnWO4 Hetero-Nanostructures for Efficient Photooxidation of Water in Near-Neutral pH.

One-dimensional ZnO nanorods (NRs) have been extensively studied as photoanodes because of their unique optical properties, high electron mobility, and suitable band positions for water oxidation. However, their practical efficiency is often compromised by chemical instability during water oxidation and high carrier recombination rates. To overcome this issue, precise morphological control of ZnO@ZnWO4 core-shell structured photoanodes, featuring a ZnO core and a ZnWO4 shell was used. This was accomplished by depositing WO3 onto hydrothermally grown ZnO NRs using the thermal chemical vapor deposition process. The photoelectrochemical performance of ZnO@ZnWO4 with an optimized morphology outperforms that of pristine ZnO NRs. Systematic optical and electrochemical analyses of ZnO@ZnWO4 demonstrated that the enhancement is attributed to the enhanced charge transfer efficiency facilitated by the optimized ZnWO4 shells.

Construct 2D/1D BiOX (X = Cl, Br)@Bi5O7I heterojunctions with rich interfaces and wide visible light response range for pollutant removal in water under LED light

At present, the development of photocatalysts with high visible light sensitivity and efficient catalytic activity for environmental pollution control is the focus of research in the field of photocatalysis. In this work, 2D/1D BiOX (X = Cl, Br)@Bi5O7I heterojunction with abundant interfaces was prepared by a low-temperature liquid-phase method using Bi5O7I nanorods as substrate and BiOX nanoflakes as shell. The rich interfaces can be used as transport bridge for photogenerated electrons between Bi5O7I and BiOX. Under the optimum condition of BiOX content of 60%, the surface charge transfer efficiency increased from 20.79% (Bi5O7I) to 55.44% (BOI-BC-60) and 67.36% (BOI-BC-60) according to the photoelectrochemical measurement results. In the application of photocatalytic degradation of levofloxacin, the prepared BiOX (X = Cl, Br)@Bi5O7I heterojunctions exhibited enhanced adsorption capacity in darkness and improved photocatalytic activity under visible light. The reaction rate and pollutant removal efficiency of BOI-BC-60 and BOI-BB-60 were 6.87, 2.07 and 12.17, 3.28 times higher than that of Bi5O7I, respectively. It is proved that the suitable valence band and conduction band positions of BiOX and Bi5O7I components in BiOX@Bi5O7I heterojunction provide thermodynamic conditions for the migration of photogenerated electrons and holes.

Dual activation and C-C coupling on single atom catalyst for CO2 photoreduction

An excellent single-atomic photocatalyst, Ti@C4N3, is theoretically found to effectively convert CO2 to C2H6 by density functional theory (DFT) calculations and non-adiabatic molecular dynamics (NAMD) simulations. The Ti@C4N3 photocatalyst has remarkable stability both thermally, chemically, and mechanically. Electronically, it has strong absorption properties (λ = 327.77 and 529.61 nm), suitable band positions, and a long photogenerated electron lifetime (τe = 38.21 ps), allowing photogenerated electrons to migrate to the surface. Notably, the high-valence active site effectively activates two CO2 through dual activation: Under light irradiation, the weakly adsorbed CO2 undergoes photo-induced activation by the photoelectron of conduction band minimum (CBM); without light, the high Lewis acidity of the Ti site induces CO2 activation through back-donating π-bond. Contrast simulation results uncovered that dual activation of CO2 is attributed to the thermal and photonic synergy. Furthermore, two activated CO2 species under light easily couple to form oxalate with the barrier of 0.19 eV, and further reduced to C2H6 with a low activation energy of 1.09 eV.

Dual Z‐scheme ternary heterojunction photocatalyst with enhanced visible‐light photocatalytic degradation of organic pollutants

AbstractPhotocatalysis technology driven by solar energy is considered to be promising for solving energy crisis and environmental problems. Graphitic carbon nitride has been widely researched in the photocatalysis field due to its suitable band positions, non‐toxicity, easy synthesis, high stability, and low cost. However, the slow separation and rapid recombination of photogenerated carriers, the poor visible light response and the low specific surface area seriously limit the photocatalytic activity of g‐C3N4. Here, firstly, g‐C3N4 nanosheets with a large specific surface area of 152.2 m2 g−1 which provide more surface‐active sites for photocatalysis were prepared by secondary calcination method. Next, MoS2 and metal–organic framework (MIL‐101(Cr)) were tightly bonded on g‐C3N4 nanosheets to form ternary g‐C3N4/MoS2/MIL‐101(Cr) heterojunction photocatalyst. In which, a ternary dual Z‐scheme heterojunction photocatalyst composed of g‐C3N4, MoS2, and MIL‐101(Cr) was constructed to facilitate the separation and the migration of photogenerated charges. At the same time, MoS2 enhanced the visible light response of the ternary photocatalyst. The optimal ternary photocatalyst displayed the highest activity for methyl orange degradation (degradation efficiency of 98% in 60 min) under visible light irradiation. Finally, a photocatalytic mechanism of a dual Z‐scheme electron transfer channel and h+‐·O2− double oxidation sites were proposed and discussed.

Construction of novel g-C3N4/β-FeOOH Z-Scheme heterostructure photocatalyst modified with carbon quantum dots for efficient degradation of RhB

The degradation of organic pollutants using semiconductor photocatalysts is a new ecological approach, but the currently available photocatalysts are not very efficient. Herein, in order to obtain efficient visible-light photocatalysts, g-C3N4/β-FeOOH-modified carbon quantum dots (CDs) composite photocatalysts with Z-Scheme charge transfer mechanism were successfully synthesized. The phase composition and morphology of the composite were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectrophotometry (FT-IR), and X-ray photoelectron spectroscopy (XPS) techniques. Due to the upconversion effect of the CDs, the optical response range of the composite was effectively widened, and the optical utilization rate was improved. The Z-Scheme heterostructure not only improves the light trapping ability, significantly inhibits charge-carrier complexation, and realizes the spatial separation of redox sites, but also ensures that the photocatalyst maintains a suitable valence-conductivity band position and maintains the strong redox reactivity. In addition, CDs have the unique characteristics of electronic storage and transfer, which effectively enhance the quantum separation efficiency of the composite. The photocatalytic efficiency was measured by degrading rhodamine B (RhB) under visible light. The degradation performance was the best when the weight ratio of CDs was 6%, and the RhB solution degradation rate reached 100 % in 60 min. The unique structure and reliable mechanism provide a way for the development of advanced photocatalyst.

(Digital Presentation) 2D Molybdenum Disulfide Nanosheets As Cocatalyst and Passivation Layer over CuInS2 Based Photocathode for Solar Hydrogen Evolution

An excellent strategy to improve photoelectrochemical (PEC) water splitting is to develop cost-effective co-catalysts that do not use noble metals such as Platinum (Pt), Iridium (Ir), Ruthenium (Ru). Transition metal cocatalysts have shown excellent catalytic property towards hydrogen evolution (HER) and oxygen evolution reaction (OER). The surface active sites and lower free energy of H* adsorption (GH adsorption) on the surface are the factors ameliorating and boosting their catalytic activity. Molybdenum Disulfide (MoS2), one the transition metal dichalcogenide with 2D-sheet like structure with high surface area, active sites, and excellent property to catalyze HER comparable to Pt. The property of higher stability towards the photocorrosion as compared to other cocatalysts provides MoS2 with an additional feature of passivation layer. The sheet-like structure also enhances the light absorption minimizing the effect of parasitic light absorption.Copper based oxides and chalcogenides are well known p-type semiconductors being investigated for photocathode materials to be used in unassisted PEC water splitting cell. CuInS2, a ternary copper chalcogenide material with tunable bandgap (Eg = 1.5-1.8 eV), high absorption coefficient (> 104), suitable band positions for hydrogen evolution reaction. Despite all the necessary features and properties, it suffers with the problem of high rate of recombination between photogenerated charge carriers, lower diffusional lengths and poor photostability. Several approaches have been developed to improve the PEC performance of CuInS2 that include decoration of metal NPs, heterojunction fabrication, deposition of electron (ETLs) and hole transporting layers (HTLs). CdS forms a proper heterojunction with CuInS2 owing to its conduction (CB) and valence (VB) offsets.The integration of CuInS2 with CdS could form a facile heterojunction for the effective charge separation and reduce the rate of recombination and decoration of MoS2 over the CuInS2/CdS can be beneficial in terms of improved reaction kinetics at the surface and photostability by avoiding direct contact of CuInS2 and CdS with electrolyte. A CuInS2 nanosheet array-based photocathode that is modified with CdS and the co-catalyst MoS2. This green approach enhances water splitting under solar irradiation. By introducing CdS and MoS2, we significantly improved the visible light absorption of the modified hybrid photocathode (CIS/CdS/MoS2). Photoluminescence, impedance spectroscopy, and Mott–Schottky analysis confirmed that excited electron-hole pairs were better separated, the resistance of charge transfer was minimized, and the excited-state charge carrier concentration increased, leading to increased photocurrent.Typical results demonstrated that CIS/CdS/MoS2 photocathode delivered higher photocurrent (-1.75 mA/cm2 at 0 VRHE) and HC-STH conversion efficiency (0.42% at 0.49 VRHE) than those of CIS and CIS/CdS photoelectrodes. We attribute this improved PEC performance to the synergetic impact of CdS in charge generation and transfer and MoS2 as a cocatalyst with active surface sites for proton reduction. The hydrogen evolution experiment showed CIS/CdS/MoS2 (56.9 μmol/h) showed high activity and rate of hydrogen evolution compared to CIS (22.6 μmol/h). This study not only demonstrates the promising nature of CuInS2-based light absorber photocathodes for solar energy utilization but also recommends the use of MoS2 as a cocatalyst for the proton reduction reactions for widespread applications in solar-to-hydrogen conversion. Reference (1) Kumar, M.; Meena, B.; Subramanyam, P.; Ummethala, G.; Malladi, S. R. K.; Dutta-Gupta, S.; Subrahmanyam, C. CuInS 2 Nanosheet Arrays with a MoS 2 Heterojunction as a Photocathode for PEC Water Splitting. Energy & Fuels 2023, 37 (3), 2340–2349. https://doi.org/10.1021/acs.energyfuels.2c03502. Figure 1

New insight into the enhanced photocatalytic activity of Al-, C- and Al-C co doped rutile TiO2 photocatalysts

TiO2 has been proven to be the most suitable photocatalytic materials for wide environmental and energy applications because of its suitable valence band and conduction band positions, long-term stability, non-toxicity, cost-effectiveness and strong oxidizing power. Based on the first-principles density functional theory calculations in the framework of density functional theory, the crystal structure, electronic properties, optical properties and photocatalytic activity of photocarriers in Al- doped, C- doped and Al-C co-doped rutile TiO2 systems were investigated. The results show that doping changes the local density and electronic property of rutile TiO2 around the Fermi level. Doping can improve the optical absorption capacity of TiO2 and enlarge its response range to visible light. In addition, the larger of the relative effective mass of photogenerated hole electrons indicates the smaller recombination probability of photogenerated carriers and the higher light catalytic activity. This work will provide some new ideas for understanding the differences in photocatalytic activity between Al- doped, C- doped and Al-C co-doped rutile TiO2, and also provide a new direction for the study of metal and non-metal doped rutile TiO2.

S-scheme Bi2O3/CdMoO4 hybrid with highly efficient charge separation for photocatalytic N2 fixation and tetracycline Degradation: Fabrication, catalytic Optimization, physicochemical studies

This study employed a deposition-oxidation method to design and synthesize a novel composite photocatalyst of Bi2O3/CdMoO4. A comprehensive investigation was conducted on the morphology, specific surface area, structure, optical properties, and photoelectric chemical properties of the Bi2O3/CdMoO4 composite. The results indicate the dispersion of Bi2O3 nanoparticles on the surface of CdMoO4 polymers, which increases the light absorption and facilitates the photocatalytic reaction. Furthermore, a tight contact between CdMoO4 and Bi2O3 was observed, resulting in the formation of a heterojunction structure at their contact region due to their suitable band positions. Density functional theory calculations and MS analysis revealed the higher work function of CdMoO4 compared to Bi2O3, causing electron drift from Bi2O3 to CdMoO4 and the subsequent formation of a built-in electric field. The presence of this electric field promotes the separation efficiency of electron-hole pairs through an S-scheme mechanism, thereby enhancing the performance of the Bi2O3/CdMoO4 composite in photocatalytic N2 fixation (PNF) reactions. Under simulated sunlight irradiation, the optimal Bi2O3/CdMoO4 catalyst displayed a PNF rate of 323 μmol/L g-1h−1, which was 3.6 and 11.8 times higher than that of pure CdMoO4 and Bi2O3, respectively. The Bi2O3/CdMoO4 composite also exhibited good performance in tetracycline degradation. Electron spin-resonance experiments indicate that hole and superoxide radicals serve as the primary reactive species. These findings offer practical knowledge about the design and synthesis of new S-scheme photocatalysts for PNF and antibiotics removal.

Increasing the Photocatalytic Hydrogen Generation Activity of CdS Nanorods by Introducing Interfacial and Polarization Electric Fields.

Cadmium sulfide (CdS) is a photocatalyst widely used for efficient H2 production under visible light irradiation, due to its narrow bandgap and suitable conduction band position. However, the fast recombination of carriers results in their low utilization. In order to improve photocatalytic hydrogen production, it reports the successful introduction of metallic Cd and S vacancies on CdS nanorods (CdS NRs) by a facile in situ chemical reduction method, using a thermal treatment process. This procedure generates interfacial and polarization electric fields, that significantly improve the photocatalytic hydrogen production performance of CdS NRs in sodium sulfide and sodium sulfite aqueous solutions, under visible light irradiation (λ>420nm). The introduction of these electric fields is believed to improve charge separation and facilitate faster interfacial charge migration, resulting in a significantly optimized catalyst, with a photocatalytic hydrogen evolution rate of up to 10.6mmol-1 g-1 h-1 with apparent quantum efficiency (AQE) of 12.1% (420nm), which is 8.5 times higher than that of CdS. This work provides a useful method to introduce metallic and S vacancies on metal sulfide photocatalysts to build local polarization and interfacial electric fields for high-performance photocatalytic H2 production.

Synergy effect of the Niδ+-Nδ− atom pair for photocatalytic conversion of CO to ethanol: A computation study

By constructing a unique Niδ+–Nδ− atom pair, we designed a promising catalyst for the photocatalytic reduction of CO (pCOR), namely, anchoring a single Ni atom on a defective hexagonal boron nitride monolayer with a B-N divacancy (Ni/d-BN). The density functional theory (DFT) computations revealed that the synergy effect between the anchored Ni atom and its adjacent N atoms can capture multiple CO molecules, followed by their effective C–C coupling with a low kinetic barrier. Interestingly, these coupled CO species can be favorably reduced to ethanol (C2H5OH) product with a less negative limiting potential (–0.27 V), as compared with methane (CH4, –0.63 V), propanol (C3H7OH, –0.46 V), and the competitive hydrogen evolution reaction (HER, –0.84 V), suggesting the superior catalytic activity and the excellent selectivity of Ni/d-BN catalyst towards pCOR. Specially, this Ni/d-BN catalyst can significantly improve the visible light absorption with a suitable band position, enabling it ideal for solar-driven conversion of CO into C2H5OH. In particular, Ni/d-BN holds great potential for experimental synthesis due to its extremely high stability. Our findings not only open a new avenue to solve the problems of the high energy-consumption in FTS, but also offer a tandem strategy for CO2 conversion to multi-carbon products.