Nanotube Photocatalyst Research Articles

Solar H2O2 production with carbon dots and nickel co-modified titania nanotube photocatalyst stabilized at water/benzyl alcohol interface

An interfacial reaction system with the advantage of in situ H2O2 production and separation has been developed, in which titania nanotube (TNT) photocatalyst modified by nickel species and carbon dots (CDs) can self-stabilize at interface of water/benzyl alcohol. Under visible light irradiation, the CDs/Ni-TNT yields H2O2 with an initial rate of 385.6 μmol/g/h. The improved activity could be attributed to multiple effects such as sufficient oxygen adsorption and mass transfer, separated reduction and oxidation sites at different phases, and rapid diffusion of H2O2 from the interfacial region into bulk aqueous solution.

Synthesis and photodegradation performance of a heterostructure ferromagnetic photocatalyst based on MWCNTs functionalized with (3-glycidyloxypropyl)trimethoxysilane and decorated with tungsten trioxide for metronidazole and acetaminophen degradation in aqueous environments.

The presence of metronidazole (MNZ) and acetaminophen (ACE) in aquatic environments has raised growing concerns regarding their potential impact on human health. Incorporating various patterns into a photocatalytic material is considered a critical approach to achieving enhanced photocatalytic efficiency in the photocatalysis process. In this study, WO3 nanoparticles, which were immobilized onto ferromagnetic multi-walled carbon nanotubes that were functionalized using (3-glycidyloxypropyl)trimethoxysilane (FMMWCNTs@GLYMO@WO3), exhibited remarkable efficiency in removing MNZ and ACE (93% and 97%) in only 15 min. In addition, the new visible-light FMMWCNTs@GLYMO@WO3 nanoparticles as a magnetically separable photocatalyst were characterized by Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction analysis (XRD), transmission electron microscopy (TEM), field emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectroscopy (EDS), EDS-mapping, vibrating sample magnetometry (VSM), thermogravimetric analysis (TGA), diffuse reflectance spectroscopy (DRS), high-performance liquid chromatography (HPLC), and total organic carbon (TOC) due to detailed studies (morphological, structural, magnetic and optical properties) of the photocatalyst. In-depth spectroscopic and microscopic characterization of the newly developed ferromagnetic FMMWCNTs@GLYMO@WO₃ (III) photocatalyst revealed a spherical morphology, with nanoparticle diameters averaging between 23 and 39 nm. Compared to conventional multiwall carbon nanotube and WO₃ photocatalysts, FMMWCNTs@GLYMO@WO₃ (III) demonstrated superior photocatalytic activity. Remarkably, it exhibited excellent reusability, maintaining its efficiency over a minimum of five cycles in the degradation of metronidazole (MNZ) and acetaminophen (ACE).

Tuning the potentials of aluminum phosphide nanotube photocatalyst for wastewater treatment through band gap engineering: a DFT study

The photocatalytic properties of semiconductor materials, which are controllable through the design of the bandgap structure, make them a promising catalyst for wastewater treatment. This work investigated the photocatalytic properties of single-walled aluminum phosphide nanotube (SWAlPNT) doped with different concentrations of boron (B) atoms for wastewater treatment. Analysis of the structural, electronic and optical properties of the SWAlPNT photocatalyst was performed using the density functional theory approach in terms of plane wave basis set and pseudopotential. SWAlPNT was found to be stable to B doping with 3.6% and 7.1% concentrations. The obtained formation energy values of 12.33 eV, 12.00 eV and 11.98 eV and also cohesive energies of −0.82, eV, −0.75 eV and 0.79 eV for pristine, 3.6% and 7.1% B-doped SWAlPNTs, revealed the systems’ well mechanical and thermodynamic stabilities. Results also revealed that cohesive energy decreases with an increase in concentration of B dopant, which significantly enhances efficient thermal stability. Electronic band gap calculations revealed that pristine SWAlPNT demonstrated a direct band gap value of 0.2 eV. Due to B doping, an indirect band gap value of 1.4 eV was obtained with 3.6% B-doped SWAlPNT, which agreed well with band gaps of other photocatalysts used for wastewater purification. Analysis using optical absorption spectra revealed that 3.6% B-doped system absorbs visible light while 7.1% doped system absorbs both visible and ultraviolet light. This study found both 3.6% and 7.1% B-doped SWAlPNT as suitable photocatalysts for wastewater treatment under solar irradiation, with the 3.6% B-doped system demonstrating relatively better performance for wastewater treatment.

Insights into the effect of Ni doping on In2S3 for enhanced activity and selectivity of photocatalytic CO2 reduction

The limited photocatalytic CO2 reduction performance mainly lies in the low utilization of photogenerated electrons during the reaction. In this work, we developed the defect level within the Ni-doped In2S3 nanotube photocatalysts via a simple solvothermal method to increase the available amount of photogenerated electrons for enhanced photocatalytic CO2 reduction performance than the pristine In2S3. The introduction of Ni element into the lattice of In2S3 could significantly improve the photocatalytic activity and selectivity without destruction of the nanotube structure of In2S3. The yield of CO reaches 243.2 μmol/g/h under visible light, which is the highest reported value among In2S3 photocatalysts, and is 8.2 times more than the pure In2S3. Moreover, by modulating the doping amount of Ni element, the selectivity of CO varied from 27.7% to 51.0%. Further characterizations suggest that the doping of Ni element altered the electronic bandgap arrangement of In2S3, where the position of the conduction band is conducive to the activation of CO2 molecules. Moreover, the defect level resulting from Ni-doping not only facilitates the separation of photoexcited electron-hole pairs but also suppresses the recombination of electrons and holes. This study provides an available and reliable strategy for enhancing the photocatalytic CO2 reduction performance of related sulfide photocatalytic materials in future studies.

Effect of Photocatalytic Pretreatment on the Membrane Performance in Nanofiltration of Textile Wastewater

Traditional methods like biological treatment, flocculation-coagulation, adsorption, and advanced oxidation are commonly employed for textile wastewater treatment, but their sustainability is hindered by issues such as the adverse impact of textile wastewater on microorganisms and the requirement for substantial chemical usage. In response to increasingly stringent legal discharge standards, membrane technologies are emerging as prominent alternatives for effective textile wastewater treatment. The application of photocatalysis as a pretreatment to improve effluent quality and treatment performance has shown effective results in the treatment of textile wastewater by nanofiltration (NF). However, innovative solutions are needed to improve the efficiency of UV photocatalytic reactors. Here, the TiO2/halloysite nanotube (HNT) photocatalyst was shown to completely remove dyes under UV illumination. Two wastewater samples from photocatalytic (PC) pretreatment were treated using innovative NF membranes with different contents. The study examined the impact of PC pretreatment on the flux of wastewater from a textile factory heat recovery tank, which increased from 18.32 to 27.63 L/m2.h. The membranes achieved > 98% removal in COD, while bare membrane achieved 95% removal in conductivity. The addition of s-DADPS as monomer and HNT as nanoparticles to the membranes with different compositions affected the cross-linking in the TFC layer. During the tests conducted on the water extracted from the dyeing tank, the color was completely eliminated without any loss of flux. Additionally, improvements in COD removal were observed.

Photocatalytic Activity and Antibacterial Properties of ZnO/CNTs Composites

Photocatalytic technology is one of the promising technologies for wastewater treatment. Herein, zinc oxide/multi-walled carbon nanotubes (ZnO/CNTs) photocatalyst was successfully prepared by hydrothermal method with combining in-situ synthesis technology. The micro-morphology, crystalline structure, surface chemical elements, and optical properties were characterized by SEM, TEM, XRD, FTIR, UV-Vis, and DRS technologies. The ZnO/CNTs photo-catalyst exhibited enhancement photo activity for degradation of organic pollutants under simulated light irradiation. Specifically, the photo-catalytic activity of the ZnO/CNTs catalysts improved with the rise of CNTs content in the composites. Investigation on the photo-degradation mechanism verified that the presence of CNTs in the catalyst not only optimized the band structure of ZnO semiconductor but also contributed to the transfer of photo-generated electrons and reducing the recombination of electron-hole pairs due to its excellent conductivity. Moreover, the active radical groups such as superoxide radical (O-2), hole (h+), and hydroxyl radical (·OH) played the dominated role for the pollutants degradation under the simulated sunlight irradiation. In addition, ZCT20 catalysts and light irradiation had synergistic effects on antibacterial activity, whose antibacterial rates against E. coli and S. aureus were up to 99.96% and 99.94%, respectively. Investigation on antibacterial mechanisms revealed that the existence of ROS and the continuous release of Zn2+ played an important role for improving the antibacterial activity of the ZCT20 catalyst under the simulated sunlight irradiation.

In-situ construction of In2O3/In2S3-CdIn2S4 Z-scheme heterojunction nanotubes for enhanced photocatalytic hydrogen production

Semiconductor photocatalysis was considered as an ideal solution to energy shortages. Herein, a novel ternary In2O3/In2S3-CdIn2S4 (IOSC) nanotube (NTs) photocatalyst was successfully constructed via in situ growth of In2S3 and CdIn2S4 nanosheets onto In2O3 skeleton. It was used for the efficient and stable photo-production of hydrogen from water splitting. The rationally designed IOSC NTs displayed significantly enhanced photocatalytic H2 production under visible light irradiation (≥420 nm), with the highest H2 yield determined to be 2892 μmol·g−1, which is much higher than that of pristine In2S3 and In2O3/In2S3 (IOS) NTs. Cyclic testing has shown that the IOSC2 product remains stable after four cycles of repeated use. The enhanced photocatalytic activity was contributed by its tightly bound tube-nanosheets heterogeneous structure and superior light absorption. Photoelectrons transfer in IOSC2 follows a Z-scheme mechanism, which greatly facilitates its utilization of photogenerated electrons and prevents CdIn2S4 from undergoing photo-corrosion affecting material stability. This work demonstrates the key role of in situ growth in the interface design of ternary heterostructures.

Fabrication of Ag3PO4/N-doped TiO2 nanotubes heterojunction photocatalysts for visible-light-driven photocatalysis

As an environmentally friendly and energy-efficient technology, photocatalysis holds considerable potential for eliminating organic pollutants. In this study, novel visible-light-driven Ag3PO4-decorated nitrogen-doped TiO2 nanotubes (Ag3PO4/N-TNTs) photocatalysts with advanced properties of heterostructures were successfully synthesized and used to degrade methylene blue (MB) dye. The fabrication of Ag3PO4/N-TNTs photocatalysts involved a two-step electrochemical anodization to obtain TiO2 nanotubes (TNTs) and the wet impregnation of the amorphous tubular structure in NH3 solution, followed by calcination in air to obtain crystallized nitrogen-doped TiO2 nanotubes (N-TNTs). Finally, the decoration of the N-TNTs with Ag3PO4 nanoparticles was conducted to enhance visible-light reactivity. Various heterojunction photocatalysts were obtained by changing the concentration of NH3 (0.5–2.5 M) and the dosage of Ag3PO4 (0.25–1.5 wt%) in the composites. Results of ultraviolet–visible (UV–Vis) absorption, photocurrent transient, and electrochemical impedance spectroscopy measurement revealed that Ag3PO4/N-TNTs possessed a significant response in the visible-light range and good photoelectronic properties. The superior photocatalytic activity of the Ag3PO4/N-TNTs catalyst was achieved under the optimal conditions of N-doping using 2-M NH3 and Ag3PO4 deposition at a dosage of 0.75 wt%. Based on the degradation efficiency (DE) of MB, the optimal Ag3PO4/N-TNTs exhibited rate constants of 4.5 and 2 times higher than those of the pristine TNTs and N-TNTs, respectively. The high stability of Ag3PO4/N-TNTs was confirmed through four cycles of reutilization, with a small decay of only 5.3% in the DE of MB dye for each run of photocatalysis. The scavenger tests of generated reactive oxygen species revealed that ·OH and ·O2− were the primary contributors to photocatalytic performance. The synthesized Ag3PO4/N-TNTs heterostructure photocatalysts were proven to possess efficient separation of photogenerated charge carriers, high reactivity, and stability in the visible-light region.

Dielectric Barrier Discharge Plasma Processing and Sr-Doped ZnO/CNT Photocatalyst Decoration of Cotton Fabrics for Self-Cleaning Application.

Nonthermal plasma processing is a chemical-free and environmentally friendly technique to enhance the self-cleaning activity of nanoparticle-coated cotton fabrics. In this research, Sr-doped ZnO/carbon nanotube (CNT) photocatalysts, namely, S10ZC2, S15ZC2, and S20ZC2 with different Sr doping concentrations, were synthesized using the sol-gel method and coated on plasma-functionalized fabric to perform the self-cleaning tests. The fabrics were treated with dielectric barrier discharge plasma in an open environment for 3 min to achieve a stable coating of nanoparticles. The energy band gap of the photocatalyst decreased with an increase in the level of Sr doping. The band gap of S10ZC2, S15ZC2, and S20ZC2 photocatalysts was estimated to be 2.85, 2.78, and 2.5 eV, respectively. The hexagonal wurtzite structure of ZnO was observed on the fabric surface composited with CNTs and Sr. The S20ZC2 photocatalyst showed better homogeneity and photocatalytic response on the fabric when compared with S10ZC2- and S15ZC2-coated fabrics. The S20ZC2 photocatalyst showed 89% dye degradation efficiency after 4 h of light exposure in methylene blue solution, followed by S15ZC2 (84%) and S10ZC2 (80%) photocatalysts.

Enhanced microalgal hydrogen production subsisting on visible light TiO2 nanotubes photocatalyst pre-treated palm kernel expeller

The present study investigated the application of photocatalytic process using TiO2 nanotubes (NTs) photocatalyst as an effective pre-treatment method for palm kernel expeller (PKE) in increasing its biodegradability to enhance the microalgal hydrogen production via dark fermentation. A series of TiO2 NTs photocatalysts were synthesized via employing electrochemical anodization of Ti foil at various voltages each in different types of electrolytes (choline chloride-ethylene glycol (ChCl-EG), choline chloride-urea (ChCl-U), choline chloride-glycerol (ChCl-Gly)). Increasing trend of average NTs diameters at 26.14 ± 1.30, 73.01 ± 1.94 and 122.00 ± 13.32 nm was observed for 25, 30 and 35 V in synthesizing TiO2 NTs using suitable ChCl-EG electrolyte, respectively. The high 35 V had resulted in noticeable pore ruptures within this TiO2 NTs photocatalyst. The PKE pre-treated by TiO2 NTs photocatalyst anodized at optimum 30 V in ChCl-EG electrolyte had demonstrated the highest releases of biochemical oxygen demand (BOD5) and soluble chemical oxygen demand (SCOD) concentrations at 594 and 607 mg/L, respectively. Moreover, the microalgal efficiency of BOD5 conversion and hydrogen yield were also consistently maintained from third cycle of TiO2 NTs photocatalyst's reutilizations, signifying the stability of TiO2 NTs photocatalyst.

Structural, mechanical, electronic and optical properties of Si decorated zinc oxide nanotube photocatalyst for hydrogen evolution via overall water splitting: A DFT study

This work investigated an Si-doped single-walled zinc oxide nanotube (SWZnONT) as photocatalyst for hydrogen energy production. Photocatalytic properties of the Si-doped SWZnONT were determined based on analysis of structural, electronic and optical absorption spectra using density functional theory. The obtained data for structural and mechanical properties of the systems revealed that Si-doped SWZnONT was stable under 2.7 % and 5.5 % of Si concentrations. Furthermore, the studied SWZnONT doped with 2.7 % Si demonstrated an indirect band gap of 2.6 eV which is desirable to be an ideal photocatalyst. Results from optical spectra analysis revealed that Photo-generated holes on the Si-doped SWZnONT surface promote water splitting.

Photodegradation of Methyl violet using Ag modified TiO2 nanotubes by UV and UV/ H2O2

Titanium dioxide (TiO2) is a semiconductor material that is frequently utilized in photodegradation applications. Its application in photodegradation is constrained by its broad band gap of 3.2 eV and increased rate of photoelectron recombination. However, by doping TiO2 with metallic nanoparticles, the band gap can be modified and photodegradation can be improved. The present study explores the fabrication of Ag-modified TiO2 nanotube photocatalysts by electrochemical anodization followed by hydrothermal method. The structural, morphological, compositional, optical, and thermal properties of prepared photocatalysts were characterized by X-ray analysis, Field emission scanning electron microscopy, N2 adsorption desorption analysis, X-ray photoelectron spectroscopy, Energy dispersive X-ray spectroscopy, UV–Vis diffuse reflectance analysis and Thermogravimetric-differential thermal analysis. The prepared photocatalyst was utilized to investigate the degradation of methyl violet in the presence of UVA and UVC radiation. The effects of UVA and UVC illumination on the degradation process, the effect of Ag loading in the TiO2 nanotube arrays and the role of H2O2 in the degradation of pollutant were studied. The degradation efficiency of methyl violet in the presence of UVC light was three times that of UVA light. For pristine TiO2 photocatalyst, the maximum degradation of 70% was obtained under UVC illumination in 8 h. When H2O2 was added, complete degradation was observed within 3 h. Reusability studies have shown that photocatalysts are stable and can be used for the degradation of methyl violet.

Structural, mechanical, electronic and optical properties of N-decorated single-walled silicon carbide nanotube photocatalyst for hydrogen evolution via water splitting: a DFT study

ABSTRACT This work investigates the fundamental photocatalytic properties of nitrogen-doped single-walled silicon carbide nanotubes (N-doped SWSiCNTs) for hydrogen evolution for the first time. Investigations of the structural, mechanical, electronic, and optical properties of the studied systems were carried out using popular density functional theory implemented in quantum ESPRESSO and Yambo codes. Analysis of the structural properties revealed high mechanical stability with the 3.6% and 7.4% N-doped SWSiCNT. The calculated band gap of the N-doped SWSiCNT with 3.6% demonstrated a value of 2.56 eV which is within the photocatalytic range of 2.3 eV−2.8 eV. The hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) potentials of the 3.6% N-doped SWSiCNT also showed good agreement with previous theoretical data. The studied material showed the best photocatalytic performance in both parallel and perpendicular directions by absorbing photons in the visible region. Therefore, the observed structural, mechanical, electronic and optical behaviors demonstrated by the 3.6% N-doped SWSiCNT exposed it as a better photocatalyst for hydrogen production under visible light.

Selective reduction of NO3− to N2 using a highly stable Cu0/Cu2O-PANI-CNTs as a photocatalyst at neutral pH

The selective photoreduction of nitrate (NO3−) to nitrogen (N2) has emerged as an energy-efficient and environmentally friendly NO3− removal route under mild conditions. However, NO3− photoreduction often suffers low NO3− removal efficiency in the absence of hole scavengers at neutral pH, the generation of undesired side products (nitrite (NO2−), ammonium (NH4+), nitrogen oxides (NOx), etc.) and poor photocatalyst stability. In this study, a novel copper/copper(I) oxide-polyaniline-carbon nanotubes (Cu0/Cu2O-PANI-CNTs) photocatalyst was prepared through a combination of in situ polymerization and liquid phase reduction processes and used to reduce NO3− to N2. In the Cu0/Cu2O-PANI-CNTs/hv system, NO3− was reduced to NO2− by photogenerated electrons (ecb−) on the surface of Cu0/Cu2O, and the generated NO2− was further reduced to N2 by PANI, resulting in high N2 selectivity. –NH– in PANI acted as photogenerated hole (hvb+) capture centres, leading to NO3− photoreduction without additional hole scavengers. Given the interaction between Cu0, ecb− and PANI, Cu0/Cu2O-PANI-CNTs show excellent repeatability. A 100% NO3− removal efficiency and 100 % N2 selectivity could be achieved by the Cu0/Cu2O-PANI-CNTs/hv system at neutral pH. With river water, secondary effluent and the fourth reuse of the catalyst, the NO3− removal efficiencies were as high as 93.0%, 91.2% and 84.4%, respectively, with 100 % N2 selectivity.

DFT Studies on the Effects of C Vacancy on the CO2 Capture Mechanism of Silicon Carbide Nanotubes Photocatalyst (Si12C12-X; X = 1; 2)

DFT Studies on the Effects of C Vacancy on the CO2 Capture Mechanism of Silicon Carbide Nanotubes Photocatalyst (Si12C12-X; X = 1; 2)

Photocatalytic degradation of diclofenac using a novel double Z-scheme catalyst (O-g-C3N4/ZnO/TiO2@halloysite nanotubes): Degradation mechanism, identification of by-products and environmental implementation

It is challenging and expensive to synthesize multivariate composites with high photocatalytic efficiency and recyclability. Herein, a novel direct double Z-scheme O-g-C3N4/ZnO/TiO2@halloysite nanotubes (HNTs) photocatalyst was synthesized using a simple and low-cost method to degrade and mineralize diclofenac (DCF). During 50 min, O-g-C3N4/ZnO/TiO2@HNTs degraded DCF completely at pH 6.83, 10 mg/L DCF concentration, and 1.0 g/L catalyst, which was 1.66 and 2.4 times higher than ternary O-g-C3N4/ZnO/TiO2 and O-g-C3N4/HNTs/TiO2. Under the same conditions, 35.12 % of DCF was removed from urban wastewater. A negative effect of anions on the process was observed as follows: CO32− > HPO42− > Cl− > NO3−. Under the same conditions, 39.23 % of total organic carbon (TOC) was removed. Moreover, Mott-Schottky analysis and active species trapping experiments were performed to investigate the photodegradation mechanism systematically. It was observed that O2− played a minor part in the photodegradation process, while hole and OH were the more critical reactive species. Several intermediate compounds formed during the photocatalytic reaction were identified by LC-MS analysis. The results showed that a simple design and synthesis of multi-component complex catalysts presented a new insight into removing emerging pollutants from the aquatic environment and apprehending the enhanced photocatalytic mechanism.

Synergistic synthesis of Carrisa edulis fruit extract capped heterogeneous CuO-ZnO-HNT composite for photocatalytic removal of organic pollutants

Photocatalysis is a promising strategy for treating harmful pollutants in the ecosystem. Recently, the use of semiconductor photocatalysts to remove organic dyes and pharmaceutical drugs from polluted water has gained a lot of interest. In this work, initially, CuO-ZnO composite was synthesized using microwave method utilizing Carrisa edulis fruit extract as capping/stabilizing agent. Secondly, heterogeneous CuO-ZnO-Halloysite nanotube (HNT) photocatalyst have been synthesized via ultrasonication method. The synthesized composite was confirmed by various characterization techniques such as X-ray diffraction (XRD), UV–vis-DRS Spectroscopy (UV–vis-DRS), Fourier-Transform Infrared Spectroscopy (FT-IR), Field Emission Scanning Electron Microscope (FE-SEM), Energy Dispersive X-ray Analysis (EDAX), Brunauer Emmette Teller analysis (BET), X-ray Photoelectron Spectroscopy (XPS), Thermogravimetric analysis (TGA) and Zeta Potential. The resultant CuO-ZnO-HNT composite possesses narrow band gap, large surface area with microsphere morphology. Under visible light irradiation, the synthesized composite was evaluated for photocatalytic activity against Congo Red (CR) and Tetracycline (TC). It is observed that within 70 min of irradiation, the 20CZ-HNT composite showed 86 % and 90 % degradation of CR and TC respectively. The reusability test showed that the catalyst was stable even after five cycles. As a result, the CuO-ZnO-HNT composite exhibits great promise for photocatalytic removal of environmental pollutants utilizing visible light.

Pyrite (FeS2)‐decorated 1D TiO2 nanotubes in a bilayer as a sustainable photoanode for photoelectrochemical water splitting activity

AbstractHerein, FeS2@TiO2 nanotubes photocatalyst was prepared by electrochemical anodization method followed by successive ionic layer adsorption and reaction method, and then finally annealed in a tube furnace for homogenous crystallization. The surface morphology, elemental composition, optical properties, and crystalline structure of the prepared FeS2@TiO2 nanocomposite were found out by performing scanning electron microscopy, energy dispersive X‐ray spectroscopy, X‐ray diffraction, UV–Vis diffuse reflectance spectroscopy, and fluorescence spectroscopy, respectively, while bonds vibrations and various functional groups' presence were analyzed using Raman and Fourier transform infrared spectroscopy. A higher photocurrent density of 1.59 mA/cm2 at 0.3 V versus reference electrode of Ag/AgCl (1.23 V versus reversible hydrogen electrode) using 100 mW/cm2 intensive light source was shown by 15‐FeS2@TiO2 nanotubes (uniformly loaded photoanode) while donor density (ND) of 3.68 × 10−13 cm−3 as compared to pure TiO2 NTs (0.09 mA/cm2), 05‐FeS2@TiO2 NTs (0.19 mA/cm2), 10‐FeS2@TiO2 NTs (0.53 mA/cm2) and 20‐FeS2@TiO2 NTs (0.61 mA/cm2), respectively. The exceptional photoelectrochemical activity results were attributed to the homogenous integration of FeS2 that not only increase the charge separation but also, intensively interacted with the substrate (TiO2 nanotubes), which results in an excellent photoelectrochemical activity.

Construction atomic-level N-P charge transfer channel for boosted CO2 photoreduction

Efficient conversion of CO2 to high value-added chemical products is a promising strategy for achieving carbon neutrality. Although the photocatalyst technique has been made widespread researched, highly efficient photoreduction CO2 with metal-free photocatalysts remains a challenge. Herein, we report a zero-dimensional black phosphorus quantum dots (BPQDs)-decorated one-dimensional carbon nitride nanotubes (CNNT) photocatalyst that reduces CO2 to CO with a rate of 44.6 μmol g–1 h–1, which is better than the similar photocatalysts and pristine carbon nitride nanotubes. Synchrotron radiation XAFS measurements substantiate the construction of N-P electron transfer channels within BPQDs and CNNT. Time-resolved PL spectrum demonstrates the faster separated electron hole pairs. In situ irradiated X-ray photoelectron spectroscopy confirms the photogenerated-electron flow trend and the active site of photocatalytic reaction. Moreover, the main intermediate *COOH is verified by in situ FT-IR characterization which is corresponding to the previous research. The construction of atomic-level N-P charge transfer channel efficiently facilitates the charge transfer and accelerates the catalytic rate. This work provides a novel insight into the design of BPQDs-anchoring heterostructures for photocatalytic CO2 reduction.

Hierarchical S-scheme titanium dioxide@cobalt-nickel based metal-organic framework nanotube photocatalyst for selective carbon dioxide photoreduction to methane.

Efficient photocatalysts are of great importance for the photochemical conversion of CO2 into fuels. Herein, S-scheme titanium dioxide@cobalt-nickel based metal-organic framework (TiO2@CoNi-MOF) heterojunction photocatalysts with high surface area and porosity are designed and fabricated by a multi-step controllable strategy. The photocatalytic activity of the composites can be optimized by adjusting the loading content of CoNi-MOF in TiO2@CoNi-MOF and molar ratios of Co2+ and Ni2+ in CoNi-MOF. The optimized hybrid photocatalyst showed a much higher CO2 photoreduction activity than the control single-component samples (TiO2 and CoNi-MOF) with a high CH4 yield (41.65μmolg-1h-1) and selectivity (93.2%). The accelerated charge carrier separation induced by the S-scheme heterojunction significantly promoted the photocatalytic performance of TiO2@CoNi-MOF NTs. Meanwhile, the introduction of bimetallic CoNi-MOF nanosheets significantly resulted in the increase of active sites, CO2 adsorbability, visible-light utilization, and CH4 selectivity. Moreover, the S-scheme photoinduced charge transfer model of the TiO2@CoNi-MOF NTs photocatalyst was confirmed by photoluminescence spectroscopy, free radical trapping tests, and work function calculated from Kelvin probe. The work aims to design and fabricate heterojunction photocatalysts with high efficiency for solar fuel production.