Efficient Cocatalyst Research Articles

Engineering Single Ni Sites on 3D Cage-like Cucurbit[n]uril Ligands for Efficient and Selective CO2 Photocatalytic Reduction.

Solar-driven CO2 selective reduction with high conversion is a challenging task yet holds immense promise for both CO2 neutralization and green fuel production. Enhancing CO2 adsorption at the catalytic centre can trigger a highly efficient CO2 capture-to-conversion process. Herein, we introduce cucurbit[n]urils (CB[n]), a new family of molecular ligands, as a key component in the creation of a 3D cage-like metal (nickel, Ni)-complex molecular co-catalyst (CB[7]-Ni) for photocatalysis. It exhibits an unprecedented CO yield rate of 72.1 µmol· h-1 with a high selectivity of 97.9% under visible light irradiation. To verify the origin of the carbon source in the products, a straightforward isotopic tracing method is designed based on tandem reactions. The catalytic process commences with photoelectron transfer from Ru(bpy)32+ to the Ni2+ site, resulting in the reduction of Ni2+ to Ni+. The locally enriched CO2 molecules in the cage ligand CB[7] undergo selective reduction by the Ni+ nearby to form CO product. This work exemplifies the inspiring potential of ligand structure engineering in advancing the development of efficient unanchored molecular co-catalysts.

Novel Synthesis Route of Plasmonic CuS Quantum Dots as Efficient Co-Catalysts to TiO2/Ti for Light-Assisted Water Splitting.

Self-doped CuS nanoparticles (NPs) were successfully synthesized via microwave-assisted polyol process to act as co-catalysts to TiO2 nanofiber (NF)-based photoanodes to achieve higher photocurrents on visible light-assisted water electrolysis. The strategy adopted to perform the copper cation sulfidation in polyol allowed us to overcome the challenges associated with the copper cation reactivity and particle size control. The impregnation of the CuS NPs on TiO2 NFs synthesized via hydrothermal corrosion of a metallic Ti support resulted in composites with increased visible and near-infrared light absorption compared to the pristine support. This allows an improved overall efficiency of water oxidation (and consequently hydrogen generation at the Pt counter electrode) in passive electrolyte (pH = 7) even at 0 V bias. These low-cost and easy-to-achieve composite materials represent a promising alternative to those involving highly toxic co-catalysts.

Mixed Redox-Couple-Involved Bornite Phase Cu5FeS4 as Efficient and Robust Cocatalysts for Greatly Enhanced Visible-Light Photocatalytic Activities

Mixed Redox-Couple-Involved Bornite Phase Cu₅FeS₄ as Efficient and Robust Cocatalysts for Greatly Enhanced Visible-Light Photocatalytic Activities

Enhanced hydrogen production performance via noble-metal-free amorphous NiZnSx-CS co-catalyst with novel gradient coating structure

In photocatalytic water splitting for hydrogen production, co-catalyst is a key factor in enhancing the efficiency of photocatalyst. Various inexpensive co-catalysts besides noble metal co-catalysts have been developed; however, the illumination of the relationship between the structure and performance remains a challenge. Here, we present a bimetallic sulfide co-catalyst denoted as NiZnSx-CS with amorphous and gradient coating structures to achieve highly efficient hydrogen production activity. Upon coupling the co-catalyst with CdS, the hydrogen production rate of CdS loaded with NiZnSx-CS reaches 38.0 mmol/g/h, 11.0, 40.0 and 161.0 times higher than that loaded with bulk NiZnSx, 1.0 %Pt and naked CdS, respectively. The co-catalyst with an amorphous and gradient coating structure shows large capacitance and thus facilitates efficient storage, transfer, and separation of photo-excited electrons of semiconductors, effectively reducing the over-potential of hydrogen production. The co-catalyst also has a large specific surface area and excellent hydrophilicity attributed to the abundant active sites and intimate contact with the reactant. Additionally, the coordination structure and chemical environment of NiZnSx-CS elucidated using X-ray absorption spectroscopy (XAS). The intermediates and the role of lactic acid and water on the surface of NiZnSx-CS after irradiation are determined by in situ Fourier transform infrared spectroscopy (in situ FT-IR). This work proposes a strategy to develop a highly efficient special structure co-catalyst with suitable capacitance, specific surface area and hydrophilicity.

Synergistic photodegradation of moxifloxacin with BiFeO3@ZIF-67 heterojunction co-catalyst

The increasing frequency of pharmaceutical pollutants in water sources poses significant environmental and health challenges worldwide. Among these, moxifloxacin antibiotic persists in aquatic environments, exerting adverse effects on ecosystems and human health. In this study, we synthesized BiFeO3@ZIF-67 nanocomposites through the "bottle around ship" method and investigated their efficacy as co-catalysts for the photodegradation of moxifloxacin. Characterization techniques including X-ray diffraction (XRD) and scanning electron microscopy (SEM) confirmed the successful encapsulation of BiFeO3 nanoparticles within the ZIF-67 framework. Photocatalytic experiments demonstrated a significant enhancement in moxifloxacin degradation efficiency using BiFeO3@ZIF-67 nanocomposites compared to pristine BiFeO3 and ZIF-67 nanoparticles. The optimized nanocomposite exhibited a removal efficiency of up to 87 % under solar irradiation within 90 min. The synergistic effects between BiFeO3 nanoparticles and ZIF-67 matrix contribute to improved light absorption and generation of reactive oxygen species, facilitating the degradation of moxifloxacin. Our findings highlight the potential of BiFeO3@ZIF-67 nanocomposites as sustainable and efficient co-catalysts for the remediation of antibiotic-contaminated water sources, addressing critical environmental and public health concerns.

Enhanced tetracycline hydrochloride degradation at near neutral conditions with FeOx modified Bi4TaO8Cl catalyst: Coupling the photocatalytic and Fenton oxidation

The efficient regeneration of Fe2+ active sites in heterogeneous catalysts is of great significance for the photo-Fenton progress. Herein, amorphous FeOx as one efficient cocatalyst was anchored on the Bi4TaO8Cl nanosheets to boost the activation of H2O2 and the separation of photogenerated carriers. The surface-exposed FeOx can produce Fe2+ active sites by extracting the photogenerated electrons from Bi4TaO8Cl. As a result, the redox cycle of Fe3+/Fe2+ was built and the carriers were separated to boost the continuous photo-Fenton degradation. As a result, H2O2 are continuously activated through the cycle of Fe3+/Fe2+. The coupling of photocatalysis and the Fenton reaction enhances the TC-H degradation performance and suppress the loss-activation of iron sites. The optimized FeOx/Bi4TaO8Cl sample exhibited the highest degradation ratio of about 83.5 % in 20 min, which was nearly 4 times that of the pure Bi4TaO8Cl. In addition, the better performance of FeOx/Bi4TaO8Cl catalyst under near-neutral conditions also sheds new insights about the design of efficient photo-Fenton catalysts that can work under mild conditions.

NiMoP2 co-catalyst modified Cu doped ZnS for enhanced photocatalytic hydrogen evolution

The design of a low-cost, efficient and durable co-catalyst for hydrogen evolution is of great significance for improving photocatalytic activity. In this work, a NiMoP2/Cu-ZnS composite photocatalyst was prepared by in-situ growth of NiMoP2 on the surface of copper-doped zinc sulfide (Cu-ZnS). The test results showed that the hydrogen production rate of the optimized NiMoP2/Cu-ZnS under visible light irradiation was significantly improved. Among them, NiMoP2/Cu-ZnS-1 exhibited the highest photocatalytic activity (5.13 mmol·g−1·h−1), which was 2.47 times that of Cu-ZnS and maintained good stability during the reaction. The improvement of hydrogen production performance of the photocatalyst was mainly attributed to the synergistic effect of Cu-ZnS and co-catalyst NiMoP2. The ohmic contact formed between Cu-ZnS and NiMoP2 could improve the separation efficiency of photogenerated carriers and reduce the overpotential of H2 evolution. Besides, NiMoP2 was found to provide the active site for the reduction reaction, and accelerate the transfer efficiency of photogenerated electrons. This strategy opens up a new way for the construction of co-catalyst modified semiconductor materials to improve the photocatalytic hydrogen production rate.

A new Ni-based cocatalyst nickel thiocarbonate enhancing graphitic carbon nitride photocatalytic hydrogen production by constructing a built-in electric field

Despite the excellent photocatalytic activity under visible light, graphitic carbon nitride (g-C3N4) exhibits a high overpotential for hydrogen evolution. To address this issue, cocatalysts have been utilized to modify g-C3N4. However, the use of high-performance cocatalysts typically involves noble metals such as platinum and palladium, which are cost-prohibitive for practical applications. Therefore, the development of efficient and cost-effective cocatalysts is crucial for advancing photocatalysis. In this study, we synthesized a new Ni-based cocatalyst, nickel thiocarbonate (NiCS3), to enhance the photocatalytic hydrogen evolution reaction (HER) on g-C3N4. The NiCS3/g-C3N4 composite demonstrated a significantly increased hydrogen evolution rate of 951 μmol·h−1·g−1 under visible light, representing more than a 105-fold improvement compared to pure g-C3N4. Theoretical calculations suggested that the enhanced performance in photocatalytic hydrogen production can be attributed to the generation of a built-in electric field within the composite, facilitating efficient charge carrier separation and migration. Additionally, the C site in NiCS3 provides a favorable Gibbs free energy of adsorbed H* (ΔGH∗). This work underscores the potential of NiCS3 as a viable alternative to precious metals in photocatalytic hydrogen production using g-C3N4.

LaCoO3 supported Pt for efficient photo-thermal catalytic reverse water-gas shift via the Mott-Schottky effect

The conversion of CO2 into valuable chemicals like CO through the reverse water–gas shift (RWGS) process is a significant strategy for both mitigating and utilizing atmospheric CO2. It is crucial to enhance catalytic performance for RWGS at low-temperatures by designing efficient photo-thermal co-catalysts with strong photo-response and photo-thermal effects. Herein, Pt nanoparticles (NPs) supported on LaCoO3 with Mott-Schottky heterojunctions were synthesized to improve the performance of RWGS at low-temperatures. The results show that the narrow bandgap of LaCoO3 has excellent light-absorbing properties, generating abundant photo-carriers under light irradiation. The presence of ultra-small Pt NPs effectively reduces carrier recombination, enhancing carrier separation efficiency. 1.0 Pt/LaCoO3 (1.0 wt% Pt loading) at 350 °C under photo-thermal conditions showed a CO2 conversion of 32.9 % and CO production rate of 58.6 mmol gcat−1 h−1. The excellent photo-thermal co-catalytic performance of Pt/LaCoO3 was attributed to the remarkable Mott-Schottky heterojunctions of Pt with high electron density and the narrow bandgap of the support with abundant surface defects. This study provides valuable insights into the development of Mott-Schottky heterojunction catalysts for efficient photo-thermal co-catalytic RWGS at low-temperatures.

Harnessing the Power of Light: The Synergistic Effects of Crystalline Carbon Nitride and Ti3C2Tx MXene in Photocatalytic Hydrogen Production.

Photocatalytic hydrogen evolution is an environmentally friendly means of energy generation. Although g-C3N4 possesses fascinating features, its inherent shortcomings limit its photocatalytic applications. Therefore, modifying the intrinsic properties of g-C3N4 and introducing cocatalysts are essential to ameliorate the photocatalytic efficiency. To achieve this, metal-like Ti3C2Tx is integrated with crystalline g-C3N4 via a combined salt-assisted and freeze-drying approach to form crystalline g-C3N4/Ti3C2Tx (CCN/TCT) hybrids with different Ti3C2Tx loading amounts (0, 0.2, 0.3, 0.4, 0.5, 1, 5, 10 wt.%). Benefiting from the crystallization of CN, as evidenced by the XRD graph, and the marvelous conductivity of Ti3C2Tx supported by EIS plots, CCN/TCT/Pt loaded with 0.5 wt.% Ti3C2Tx displays an elevated H2 (2) should be subscripted evolution rate of 2651.93µmol g-1 h-1 and a high apparent quantum efficiency of 7.26% (420nm), outperforming CN/Pt, CCN/Pt, and other CCN/TCT/Pt hybrids. The enhanced performance is attributed to the synergistic effect of the highly crystalline structure of CCN that enables fleet charge transport and the efficient dual cocatalysts, Ti3C2Tx and Pt, that foster charge separation and provide plentiful active sites. This work demonstrates the potential of CCN/TCT as a promising material for hydrogen production, suggesting a significant advancement in the design of CCN heterostructures for effective photocatalytic systems.

2D MoB MBene: An Efficient Co-Catalyst for Photocatalytic Hydrogen Production under Visible Light.

Highly active and low-cost co-catalysts have a positive effect on the enhancement of solar H2 production. Here, we employ two-dimensional (2D) MBene as a noble-metal-free co-catalyst to boost semiconductor for photocatalytic H2 production. MoB MBene is a 2D nanoboride, which is directly made from MoAlB by a facile hydrothermal etching and manual scraping off process. The as-synthesized MoB MBene with purity >95 wt % is treated by ultrasonic cell pulverization to obtain ultrathin 2D MoB MBene nanosheets (∼0.61 nm) and integrated with CdS via an electrostatic interaction strategy. The CdS/MoB composites exhibit an ultrahigh photocatalytic H2 production activity of 16,892 μmol g-1 h-1 under visible light, surpassing that of pure CdS by an exciting factor of ≈1135%. Theoretical calculations and various measurements account for the high performance in terms of Gibbs free energy, work functions, and photoelectrochemical properties. This work discovers the huge potential of these promising 2D MBene family materials as high-efficiency and low-cost co-catalysts for photocatalytic H2 production.

Facile synthesis of WSe2/PEG nanostructures as a highly efficient with superior photocatalytic performance

Recent research has concentrated on developing efficient and cost-effective co-catalysts to enhance photocatalytic applications, which are prominent among the various emerging techniques for harnessing easily accessible energy sources. The present work focuses on the hydrothermal approach to fabricate and thoroughly characterize tungsten selenium (WSe2) nanoparticles using polyethylene glycol (PEG-4000) as their surfactant. The samples underwent advanced characterizations such as SEM and HRTEM to examine morphology, X-ray diffraction (XRD) to validate phase and crystal structure, photoluminescence (PL) and Raman studies for defect density determination, Fourier transform infrared (FTIR) spectroscopy for analyzing functional groups and bonds, and XPS for insights into elemental composition and chemical state of the hybrid nanostructures. A comparative analysis was conducted, utilizing both bare WSe2 and WSe2/PEG nanostructures, to observe their enhanced photocatalytic degradation efficiency and degradation kinetics on RhB. The superior photocatalytic performances were attributed to enhanced pore size and reduced defect density in the WSe2/PEG nanostructures.

Bridging the gap between metallic MoO2 and ZnIn2S4 for enhanced photocatalytic H2 production

Noble metal-free cocatalysts have shown unprecedented potential in enhancing photocatalytic H2 evolution. However, it remains challenging to accelerate the carrier transfer rate by circuiting the substantial Schottky barrier between the metallic cocatalyst and the semiconductor. Herein, an in-situ carbonization strategy is used to accurately anchor MoO2 nanoparticles onto the surface of conductive carbon rods (MoO2/C), which serves as an efficient and stable metallic cocatalyst for ZnIn2S4 towards photocatalytic H2 evolution. The in-site derived carbon skeleton not only prevents the agglomeration of MoO2 nanoparticles thus enriching the active sites for H2 evolution, but also acts as conductor of photogenerated electrons to accelerate electron transfer. In addition, the formed Mo-S bonds at the interface provide additional electron transport channels for hierarchical core–shell MoO2/C@ZnIn2S4 (MO/C@ZIS) heterojunction. It is worth noting that the H2 evolution activity of the optimized MO/C@ZIS sample (2357 μmol·h−1·g−1) is 8.7 times higher than pure ZnIn2S4 (271 μmol·h−1·g−1), and also surpasses the activity of optimized Pt-modified ZnIn2S4 (2123 μmol·h−1·g−1). This work casts a new paradigm for the rational engineering of heterointerface between metallic cocatalysts and semiconductors towards fast electron transport and enhanced photocatalytic performance.

G-C3N4 nanosheets coupled with CoSe2 as co-catalyst for efficient photooxidation of xylose to xylonic acid

Photocatalysis has emerged as an effective approach to sustainably convert biomass into value-added products. CoSe2 is a promising non-precious, efficient cocatalyst for photooxidation, which can facilitate the separation of photogenerated electron–holes, increase the reaction rates, and enhance photocatalytic efficiency. In this work, we synthesized a stable and efficient photocatalysis system of CoSe2/g-C3N4 through attaching CoSe2 on g-C3N4 sheets, with a yield of 50.12% for the selective photooxidation of xylose to xylonic acid. Under light illumination, the photogenerated electrons were prone to migrating from g-C3N4 to CoSe2 due to the higher work function of CoSe2, resulting in the accelerated separation of photogenerated electron–holes and the promoted photooxidation. Herein, this study reveals the unique function of CoSe2, which can significantly promote oxygen adsorption, work as an electron sink and accelerate the generation of ·O2−, thereby improving the selectivity toward xylonic acid over other by-products. This work provides useful insights into the design of selective photocatalysts by engineering g-C3N4 for biomass high-value utilization.

Syngas production by photoreforming of formic acid with 2D VxW1−xN1.5 solid solution as an efficient cocatalyst

Syngas production by photoreforming of formic acid with 2D VxW1−xN1.5 solid solution as an efficient cocatalyst

Defect-decorated Cu2MoS4 as a new efficient hydrogen evolution cocatalyst: Rich active sites, rapid charge transfer and optimized hydrogen adsorption

Herein, a new defect-decorated Cu2MoS4 cocatalyst was successfully synthesized using a sacrificial-template method. Detailed characterizations confirmed the presence of multivalent metal ions (Cu2+/Cu+, Mo6+/Mo4+) and abundant sulfur vacancies. To assess its cocatalytic performance, Cu2MoS4/Cd0.5Zn0.5S Schottky heterojunction was constructed and achieved a hydrogen production rate of 11.83 mmol∙g−1∙h−1, which is 6.33 and 2.03 times higher than pristine Cd0.5Zn0.5S and MoS2/Cd0.5Zn0.5S, respectively. The superior photocatalytic activity is attributed to multiple factors. Sulfur vacancies regulate the charge density of neighboring atoms and induce production of more coordination-unsaturated atoms as active sites to accelerate hydrogen generation. Meanwhile, the high conductivity of Cu2MoS4, Schottky heterojunction, and redox couples could synergistically boost charge transfer and separation efficiency. Theoretical calculations further illustrated the key role of sulfur vacancies in optimizing H2-evolution kinetics, which reduced the hydrogen adsorption free energy of in-plane S atoms. This work demonstrates that Cu2MoS4 has significant potential as an efficient cocatalyst material, enhancing the photocatalytic performance of metal sulfides.

Understanding the unique Ohmic-junction for enhancing the photocatalytic activity of CoS2/MgIn2S4 towards hydrogen production

MgIn2S4 is a photocatalyst with a suitable band gap for renewable energy production, but its effectiveness is hindered by pronounced photocorrosion, insufficient surface active sites and rapid charge recombination. Herein, we report the synthesis of CoS2/MgIn2S4 Ohmic junction with a robust internal electric field. The optimized CoS2/MgIn2S4 photocatalyst with a CoS2 loading of 20.5 wt%, depicts a maximum H2 evolution rate of 290 μmol g−1 h−1, which is 3.1 times higher than the value of MgIn2S4. The improved photocatalytic activity of CoS2/MgIn2S4 can be attributed to the intimate Ohmic junction at the CoS2/MgIn2S4 interface, which promotes effective photoelectron transfer from MgIn2S4 to CoS2. Simultaneously, CoS2 can act as an efficient surface cocatalyst, with an optimal hydrogen-adsorption Gibbs free energy, enabling highly efficient proton reduction at the catalyst/H2O interface. The present work introduces a novel approach to modulate interfaces, creating transition metal sulfide cocatalysts for photocatalysts, resulting in high photocatalytic performance.

MoxC Heterostructures as Efficient Cocatalysts in Robust MoxC/g-C3N4 Nanocomposites for Photocatalytic H2 Production from Ethanol.

In this work, we studied new materials free of noble metals that are active in photocatalytic H2 generation from ethanol aqueous solutions (EtOHaq), which can be obtained from biomass. MoxC/g-C3N4 photocatalysts containing hexagonal (hcp) Mo2C and/or cubic (fcc) MoC nanoparticles on g-C3N4 nanosheets were prepared, characterized, and evaluated for photocatalytic hydrogen production from EtOHaq (25% v/v). Tailored MoxC/g-C3N4 nanocomposites with MoxC crystallite sizes in the 4-37 nm range were prepared by treatment with ultrasound of dispersions containing MoxC and g-C3N4 nanosheets, formerly synthesized. The characterization of the resulting nanocomposites, MoxC/g-C3N4, by different techniques, including photoelectrochemical measurements, allowed us to relate the photocatalytic performance of materials with the characteristics of the MoxC phase integrated onto g-C3N4. The samples containing smaller hcp Mo2C crystallites showed better photocatalytic performance. The most performant nanocomposite contained nanoparticles of both hcp Mo2C and fcc MoC and produced 27.9 mmol H2 g-1 Mo; this sample showed the lowest recombination of photogenerated charges, the highest photocurrent response, and the lowest electron transfer resistance, which can be related to the presence of MoC-Mo2C heterojunctions. Moreover, this material allows for easy reusability. This work provides new insights for future research on noble-metal-free g-C3N4-based photocatalysts.

Molybdenum nitride(γ-Mo2N) as a novel co-catalyst to enhance Fe(III)/Fe(II) cycle for homogeneous and heterogeneous peroxymonosulfate activation: Performance and mechanism

In this work, molybdenum nitride (γ-Mo2N) was investigated for the first time as a co-catalyst to accelerate the activation of PMS by enhancing iron cycling for the treatment of acid orange 7. γ-Mo2N/PMS/Fe3+ system showed excellent performance: 95% of acid orange 7 were highly degraded within 9 mins, and the γ-Mo2N proved to be stable and reusable after a 4-cycles experiment. The homogeneous Fe2+-activated PMS process was determined by testing the change in the concentration of iron species during the experiments. In addition, the heterogeneous activation of PMS by the iron retained on the catalyst surface was further determined by ICP-OES and the degradation effect of the *γ-Mo2N (used γ-Mo2N)/PMS system. In addition, the main active species for the homogeneous and heterogeneous activation of the PMS process were identified as hydroxyl radicals(⋅OH), sulfate radicals (SO4·-) and singlet oxygen (1O2) by EPR tests. Based on XPS, TEM and FT-IR analyses, a possible mechanism was proposed: Mo(III) and Mo(IV) play the role in the reduction of Fe3+, and γ-Mo2N forms Mo-N-O-Fe as well as Mo-N-Fe electron-transfer processes with iron in the reaction, which correspond to heterogeneous and homogeneous activation for PMS to achieve efficient degradation of the target. In summary, this work clarifies that γ-Mo2N can act as an efficient co-catalyst in the γ-Mo2N/PMS/Fe3+ system to accelerate the Fe(III)/Fe(II) cycle and thus promote homogeneous and heterogeneous PMS activation, which provides a promising γ-Mo2N co-catalyzed AOPs for rapid and efficient abatement of organic contaminants.

Site-selective arene C–H functionalization by cooperative metal catalysis

Abstract Efforts made over the past 3 decades have led to the development of various organic transformations that directly convert unfunctionalized C–H bonds into functional groups by metal catalysis. However, many of these transformations are restricted to specific reaction sites controlled by directing groups, which bring the metal centers into proximity with the C–H bonds being functionalized. These directing groups are typically tailored for specific C–H functionalization reactions, necessitating additional steps for their installation and removal, thereby limiting overall utility and efficiency. There is a strong desire to achieve site-selectivity control using catalysts with compounds bearing common functional groups. We have investigated catalytic Lewis-pair formations to electronically activate substrates and control the site selectivity of metal-catalyzed arene C–H functionalization. In this account, we present C–C and C–B bond-forming reactions through cooperative transition metal/Lewis acid (LA) catalysis. Common LA catalysts derived from Zn, B, and Al have been demonstrated as highly efficient co-catalysts for Ni- and Ir-catalyzed arene C–H functionalization. Steric repulsion between the LA and Ni or Ir catalysts facilitates para-selective C–H functionalization, while ligands bearing LA moieties effectively control meta-selectivity.