Photocatalytic Dehydrogenation Research Articles

Ultrafast Charge Transfer in a Core-shell CdS@Cu-TCPP-Pt Heterojunction for Photocatalytic Hydrogen Production Coupled with Selective Benzylamine Oxidation.

Photocatalytic selective oxidation of organic substances coupled with hydrogen production is believed to be one of the most favorable pathways to make full use of photogenerated charge carriers. However, this catalytic reaction is often discouraged due to the rapid recombination of photogenerated carriers in practical applications. In this work, a core-shell CdS@Cu-TCPP-Pt nanorod heterojunction was dexterously designed for boosting the photocatalytic dehydrogenation performance of benzylamine. The transient absorption results revealed that the photogenerated electron-holes could be effectively separated by properly matching the energy levels in CdS@Cu-TCPP. Surprisingly, Pt embedded in Cu-TCPP not only provided abundant hydrogen production active sites but also facilitated ultrafast charge transfer, which endowed CdS@Cu-TCPP-Pt with remarkable photocatalytic performances for the coproductions of N-benzylidenebenzylamine (1 mL) with a conversion of 23.48% and H2 (20.75 mmol g-1 h-1) under visible irradiation, far surpassing those of CdS and Cu-TCPP. Obviously, the present work verifies that designing and fabricating a hybrid photocatalyst with high separation efficiency of electron-hole pairs is also a significant avenue for other high-performance cooperative dual-functional photocatalytic reactions.

Cooperative S-S coupling and H2 production from photocatalytic dehydrogenation of thiols over ReSe2/ZnIn2S4 heterostructure

Photocatalytic anaerobic dehydrogenation provides a new avenue to cooperatively produce clean fuels and fine chemicals, while minimizing waste discharge and reducing environmental impact. Here, we demonstrate an efficient co-production of disulfides and H2 via photocatalytic S-S dehydrogenation of thiols using a two-dimensional (2D) heterostructure of ultrathin ZnIn2S4 (ZIS) nanosheets decorated with dispersed (1T phase) ReSe2 nanoparticles. Experimental characterizations and DFT calculations reveal that integrating ReSe2 with ZIS leads to the formation of a robust internal electric field (IEF) within the ReSe2/ZIS heterostructure. The distorted 1T phase ReSe2 with abundant active Se sites and a high Fermi level induces downward band bending of ZIS at the interface, which promotes charge separation and expedites H2 evolution. Moreover, the introduction of ReSe2 provides more adsorptive sites, increasing the concentration of reactants on the catalyst surface. This enhancement fosters surface interactions between the catalyst and p-toluenethiol (PTT), ultimately accelerating the reaction rate. The optimal H2 and S-S coupling p-tolyl disulfide (PTD) production rates of the 5 wt% ReSe2/ZIS composite reach 2275 and 2303 µmol g−1h−1, respectively, approximately 5 times greater than those of blank ZIS. Importantly, the selectivity of PTD reaches 98.4 %. This visible-light-driven dehydrogenation process aligns with the principles and objectives of green chemistry, realizing high atom economy without generating byproducts. It is anticipated to open new possibilities for sustainable and environmentally friendly routes for synthesizing high-value chemicals and producing clean energy.

Ni-Pt nanoparticle decorated, C, N-doped titania microparticles with low band gap energy as an efficient catalyst for hydrogen generation from hydrous hydrazine

The recent studies demonstrated superior catalytic activity and higher selectivity of carbon doped defect-rich catalysts in hydrogen production via dehydrogenation of hydrazine hydrate (HH). The synthesis of a new defect-rich catalyst capable of providing high hydrogen evolution rate in either catalytic or photocatalytic dehydrogenation of HH was aimed. For this purpose, “polymerization-induced colloid aggregation” (PICA) was proposed for the synthesis of carbon and nitrogen doped-mesoporous, gravel-like TiO2 microparticles (m-CN/TiO2 MPs) with a reduced band-gap energy of 2.3 eV. The Ti(III) content and oxygen vacancy concentration of pristine m-CN/TiO2 MPs were 6.06 % and 22.57 %, respectively. A defect-rich catalyst with high Ti(III) content (40.25 %) and high oxygen vacancy concentration (39.14 %) was obtained by the decoration of m-CN/TiO2 MPs with nickel-platinum nanoparticles (Ni-Pt NPs) via NaBH4 reduction (Ni-Pt/m-CN/TiO2 MPs) for the first time. The charge unbalance stimulated by Ti(III) species supported the formation of oxygen vacancies on m-CN/TiO2 MPs. The unique approach based on the synthesis of a C, N doped-mesoporous TiO2 based support by PICA and the deposition of Ni-Pt NPs by NaBH4 reduction in the presence of m-CN/TiO2 MPs allowed to obtain a heterogeneous catalyst with a low band energy of 1.7 eV for hydrogen production. The turnover frequency (TOF) values up to 1140.7 h−1 were achieved with 100 % H2 selectivity using the catalyst containing an active metallic site composed of 78.3 % mol Ni and 21.7 % mol Pt on m-CN/TiO2 MPs in the catalytic dehydrogenations performed at 323 K. The TOF values up to 530 h−1 with 100 % H2 selectivity were obtained by using Ni-Pt/m-CN/TiO2 MPs as a photocatalyst in the visible light driven photocatalytic dehydrogenation of HH at room temperature.

Enhanced photocatalytic dehydrogenation of formic acid over ultrafine electron-deficient Pd nanoparticles immobilized on amine-functionalized mesoporous titanium dioxide

Formic acid (FA) has been increasingly favored by researchers as an ideal material for the chemical storage of hydrogen. However, the exploration of photocatalytic hydrogen evolution from FA is less extensive compared to conventional thermal catalytic FA decomposition. Therefore, constructing highly active photocatalysts for H2 release from FA presents a challenging issue. Herein, we employed a strategy that involves Pd nanoparticles (NPs) immobilized on amine-functionalized mesoporous titanium dioxide (TiO2–NH2) to promote hydrogen production from FA under full-spectrum light illumination. Impressively, the as-made 2 wt% Pd/TiO2–NH2 catalyst showed remarkable activity under full-spectrum light (Turnover frequency (TOF) of 1380.5 h−1 at 308 K, H2 selectivity: 100%). Characterization results indicated that the unique mesoporous structure of TiO2–NH2, the synergistic interaction of Pd NPs with –NH2, and the Mott-Schottky heterojunction are primarily responsible for the excellent photocatalytic performance of 2 wt% Pd/TiO2–NH2. This study modulates the metal-support interactions through surface engineering and proposes a novel and effective method for the construction of high-performance photocatalysts for H2 production from FA or other photoinduced reactions.

Ethylene production via photocatalytic dehydrogenation of ethane using LaMn1−xCuxO3

Ethylene production via photocatalytic dehydrogenation of ethane using LaMn1−xCuxO3

Significant augmentation of hydrogen and benzaldehyde production through mediator-free in-situ synthesis of CuNi/CN photocatalysts for benzyl alcohol splitting

Amidst growing concerns surrounding global warming and energy scarcity, there is an urgent demand for more efficient and environmentally friendly methods of hydrogen production. In response, we introduce a novel mediator-free in-situ approach for synthesizing CuNi/CN composite photocatalysts. This method entails the synthesis of copper and nickel complexes to fabricate bimetallic Cu and Ni nanoparticles on carbon nitride (CN). These catalysts are deployed for the photocatalytic dehydrogenation of benzyl alcohol, resulting in the generation of hydrogen and benzaldehyde. The CuNi bimetal-loaded CN structure provides ample active sites and demonstrates a low hydrogen reduction overpotential, thereby enhancing both charge separation and surface hydrogen reduction processes. In comparison to pure CN, the composite photocatalyst exhibits significantly improved photocatalytic activity. Notably, the composite 2 % Cu1Ni1/CN photocatalyst achieves a record-high hydrogen production rate of about 80 μmol g-1h−1, representing an impressive increase of approximately 533 times compared to pristine CN. Moreover, the catalyst offers cost-effectiveness, ease of preparation, and reusability, ensuring stable hydrogen production efficiency over multiple cycles. This precious metal-free composite photocatalyst not only facilitates the synthesis of valuable compounds but also promotes sustainable advancements in efficient hydrogen energy generation.

Selective Photocatalytic Dehydrogenation of Formic Acid on Graphite Carbon Nitride with Dual-Sited Cobalt and Platinum Cocatalysts

Selective Photocatalytic Dehydrogenation of Formic Acid on Graphite Carbon Nitride with Dual-Sited Cobalt and Platinum Cocatalysts

Improved photocatalytic activity of graphene oxide modified Ag-TiO2 for degradation of piroxicam-20 and dehydrogenation of methanol under light irradiation

BackgroundGraphene oxide (GO), an atomic sheet structure made of sp2-bonded carbon atoms with superior optoelectronic, and catalytic properties, has attracted much interest. Incorporating a carbon-rich material, onto metal-loaded TiO2 is reported to increase the photocatalytic properties of resultant composites. MethodsThis research aimed at the deposition of different amounts (1–5 wt.%) of GO using the ultrasonication method on bare TiO2 and Ag (3 wt.%)-TiO2 (AT3) and studied their influence on piroxicam-20 degradation under visible light and methanol dehydrogenation under UV light. The prepared composites' structural, optical, and morphological properties were characterized using XRD, DRS, HR-TEM, FE-SEM, and XPS. Significant findingsHRTEM analysis confirmed the existence of GO layers and spherical-shaped Ag nanoparticles deposited over the TiO2 surface. GO(5 wt.%)@Ag(3 wt.%)-TiO2 (G5@AT3) displayed better photodegradation efficiency (78 %) (k = 0.0082 min−1) under 120 min, and GO(1 wt.%)@Ag(3 wt.%)-TiO2 (G1@AT3) composite produced higher amount (427 mmol) of H2 from photocatalytic dehydrogenation of CH3OH under 5 h relative to TiO2 (2 mmol), AT3 (166 mmol) and GO(5 wt.%)@TiO2 composite (GT5) (11 mmol). HRMS analysis was performed to identify the piroxicam-20 degradation intermediates. Thus, this research provides a proactive strategy highlighting the cooperative effect of Ag and GO loading to improve the photocatalytic efficiency of TiO2 photocatalyst using both UV–visible light irradiation.

Efficient photocatalytic dehydrogenation and synergistic selective oxidation of benzyl alcohol to benzaldehyde for Zn0.5Cd0.5S co-modified with MoS2 nanoflowers and g-C3N4 nanosheets

Zn0.5Cd0.5S solid solution co-modified by MoS2 nanoflowers and g-C3N4 nanosheets (C3N4/MoS2/Zn0.5Cd0.5S) was synthesized with highly efficient photocatalytic dehydrogenation and synergistic selective oxidation of benzyl alcohol (BA) to benzaldehyde (BAD). The photocatalytic dehydrogenation rate and BAD yield are 1.7 mmol·g−1·h−1 and 35.8% for C3N4/MoS2/Zn0.5Cd0.5S, and selective oxidation to BAD is almost 100%. Reaction selectivity was explored by detecting all the substances of the solution after reaction for Zn0.5Cd0.5S and C3N4/Zn0.5Cd0.5S using gas chromatography-mass spectrometry (GCMS), and analysis results indicated that BA was converted to other substances because of the insufficient hole oxidation capacity of the samples. The mechanism for highly efficient photocatalytic dehydrogenation and synergistic selective oxidation of BA to BAD was systematically investigated by electron paramagnetic resonance (EPR) and first-principle density-functional theory calculations. The EPR spectra of the phenyl-N-tert-butyl-nitrone (PBN)-carbon centered radical indicated that ·C induced by photo-generated holes are the key intermediate of the photocatalytic dehydrogenation of BA. The loading of flower-like MoS2 accelerates charge transport and enhances the hole oxidation ability of Zn0.5Cd0.5S, and the introduction of g-C3N4 has a negative valence band potential that can collect photogenerated holes of Zn0.5Cd0.5S, thereby inhibiting photocorrosion. Therefore, the photocatalytic dehydrogenation and synergistic selection of BA to BAD for the C3N4/MoS2/Zn0.5Cd0.5S ternary heterostructure were greatly improved. The research work would provide a feasible, sustainable, economical, and potential technique for the highly efficient dehydrogenation and synergistic selective oxidation of BA based on photocatalysis that excludes the usage of noble metals and sacrificial reagents.

Visible-Light-Driven Photocatalytic Dehydrogenation of Alcohols on TiO2 via Ligand-to-Metal Charge Transfer for Coproduction of H2 and Aldehydes.

Developing visible-light-driven photocatalysts for the catalytic dehydrogenation of organics is of great significance for sustainable solar energy utilization. Here, we first report that aromatic alcohols could be efficiently split into H2 and aldehydes over TiO2 under visible-light irradiation through a ligand-to-metal charge transfer (LMCT) mechanism. A series of TiO2 catalysts with different surface contents of the hydroxyl group (-OH) have been synthesized by controlling the hydrothermal and calcination synthesis methods. An optimal H2 production rate of 18.6 μmol h-1 is obtained on TiO2 synthesized from the hydrothermal method with a high content of surface -OH. Experimental characterizations and comparison studies reveal that the surface -OH markedly influences the formation of LMCT complexes and thus changes the visible-light-driven photocatalytic performance. This work is anticipated to inspire further research endeavors in the design and fabrication of visible-light-driven photocatalyst systems based on the LMCT mechanism to realize the simultaneous synthesis of clean fuel and fine chemicals.

In-situ construction of FAPbBr3-wrapped MoS2 heterostructure for photocatalytic H2 evolution from dehydrogenation of aromatic alcohols

Photocatalytic H2 evolution from organics dehydrogenation has sparked tremendous research attention. Metal halide perovskites (MHPs) with unique photoelectrical properties are deemed as a promising new-generation photocatalysts. Here, FAPbBr3-wrapped MoS2 heterostructure photocatalysts are in-situ constructed by an anti-solvent method for photocatalytic dehydrogenation of aromatic alcohols, which realizes a co-production of clean H2 fuel and value-added aldehydes. Experimental characterizations and theoretical calculations disclose that the introduction of MoS2 decreases the size of the FAPbBr3, and forms a built-in electric field in the composite, which synergistically inhibit the electron-hole pairs recombination and enhance the charge separation. Meanwhile, the MoS2 with low hydrogen binding energy provides abundant reduction sites to accelerate the kinetic of H2 evolution. As a consequence, the optimal FAPbBr3/MoS2-7 composite exhibits a H2 evolution rate of 1150 μmol g−1 h−1 and a benzyl aldehyde (BAD) generation rate of 1040 μmol g−1 h−1 under visible light irradiation, which is about 6 times of blank FAPbBr3. The activity is comparable to the reported value of H2 production from photocatalytic haloid acid splitting using MHPs-based catalysts. Electron paramagnetic resonance (EPR) measurement reveals that carbon-centered radical of •CH(OH)Ph is the primary intermediate for the photocatalytic dehydrogenation of aromatic alcohols.

Boosting photocatalytic dehydrogenation and simultaneous selective oxidation of benzyl alcohol to benzaldehyde over flower-like MoS2 modified Zn0.5Cd0.5S solid solution

A series of MoS2/Zn0.5Cd0.5S with varying concentrations of flower-like MoS2 is prepared based on a simple and practical method with highly efficient photocatalytic dehydrogenation and simultaneous selective oxidation of benzyl alcohol (BA) to benzaldehyde (BAD). A comparative study between the composites and their two components (pristine MoS2 and Zn0.5Cd0.5S) is carried out for various structural, optical, electrical, and photocatalytic characterization. The studies reveal that the size of Zn0.5Cd0.5S nanoparticles is in the order of 3∼5 nm and is distributed uniformly over the surface of the flower-like 350 nm sized MoS2. The optical research conducted using UV–vis diffuse reflectance spectroscopy reflecting an excellent photoresponse by the MoS2/Zn0.5Cd0.5S. The photoelectrochemical tests showed that the adding of proper ratio of flower-like MoS2 (6%) results in an efficient separation and migration of photogenerated carriers for pristine Zn0.5Cd0.5S nanoparticles. The photocatalytic dehydrogenation rate of BA for the 6%-MoS2/Zn0.5Cd0.5S is the highest at 3.03 mmol g−1 h−1, meanwhile the yield of BAD and the selective conversion of BA to BAD are 49.3% and 100%, respectively. The essential stages of the photocatalytic dehydrogenation of BA are ·C caused by the photo-generated holes, according to the EPR spectra of the PBN-carbon centered radical (PBN–C). Besides, the mechanism for improved photocatalytic dehydrogenation and synergistic selective oxidation of BA to BAD with flower-like MoS2 modified Zn0.5Cd0.5S nanoparticles was systematically studied through gas chromatography-mass spectrometry analysis and first principle density functional theory calculations. The highly efficient dehydrogenation and synergistic selective oxidation of BA to BAD for MoS2/Zn0.5Cd0.5S are mainly attributed to the introduction of MoS2 nanoflowers that can provide abundant active sites, and formed MoS2/Zn0.5Cd0.5S heterostructures could further promote the separation of photogenerated electron-hole pairs. Moreover, the valance band position of the 6%-MoS2/Zn0.5Cd0.5S is more positive, so the hole at the VB position has the stronger ability to oxidize BA. This study provides a feasible method for efficiently photocatalytic dehydrogenation synergism selective oxidation of organic substrates into valuable products.

Photocatalytic Dehydrogenation of N-Heterocycles Promoted by Radicals from Graphene Oxide

Abstract Visible light-induced photocatalytic dehydrogenation of N-heterocycles was achieved by graphene oxide (GO). Unlike previously reported thermally induced GO-promoted reactions, this system generates radicals and molecular hydrogen, which are confirmed by electron spin resonance and gas chromatography. A metal-free, oxidant-free, and recyclable photocatalytic reaction were achieved by a carbon-based system for the first time.

Acetylene functionalized covalent triazine frameworks with AuPd nanoparticles as photocatalysts for hydrogen evolution from formic acid

Photocatalytic dehydrogenation of formic acid (FA) at room temperature is a promising way to meet the increasing demand for hydrogen energy. In this work, we loaded nanoparticles of plasmonic AuPd alloys on the acetylene functionalized covalent triazine frameworks (CTFs) for the design of Mott-Schottky catalysts (AuPd/CTFs) with further application to photocatalytic hydrogen production from FA. Experimental data showed that the introduction of acetylene (-C≡C-) unit and AuPd alloy into the CTF could significantly enhance the performance of hydrogen evolution. The results of photoelectrochemical tests showed that the introduction of carbon-carbon triple bonds and AuPd alloy could adjust the electronic structure of CTF and inhibit charge recombination. Thus, benefiting from these positive effects, the FA photocatalytic decomposition by the obtained AuPd-CTF-EDDBN photocatalyst yielded H2 at a good rate of 10600 μmol·gcat −1·h−1.

Map of 20 reactions that take place during vapor–solid phase photocatalytic dehydrogenation of ethanol on metal‐loaded TiO2

AbstractWe report the map of 20 reactions that take place during vapor‐phase photochemical dehydrogenation of ethanol on four metal‐doped TiO2 (Mn/TiO2, Mn = nanoparticles of Pd, Pt, Au, and Cu) under solar simulated light. The reactions are sensitively affected by the moisture amount and the nature of the carrier gas. To construct the above map, we also used CH3CHO, CH3CO2H, (C2H5O)2CHCH3, and CH3CO2C2H5, respectively, as an independent starting reagent. Amazingly, Mn/TiO2 not only serves as photocatalysts but also as thermocatalysts for various reactions that appear in the above map. The reaction is proposed to proceed by a radical mechanism in which photoinduced electron transfer from the valence band to the conduction band of TiO2 is the initial step and the subsequent electron injection from organic reactants to the hole in the TiO2 valence band. This report also features highly valuable unprecedented reactions, which bear great potential to be commercialized.

Metal-free and water-compatible nanocatalysts for green photocatalytic dehydrogenation in aqueous medium

Two types of poly-porphyrin-based heterogeneous photocatalysts including insoluble polymer and water-soluble nanoparticles exhibited excellent photocatalytic activity in visible-light-induced dehydrogenation in water. The extremely low catalyst loading (0.01 ​mol%) of water-soluble nanoparticles provided so far the highest turnover frequency (TOF) value (333 h-1) for such transformation among reported records.

Synthesis of AgBr/Ti3C2@TiO2 ternary composite for photocatalytic dehydrogenation of 1,4-dihydropyridine and photocatalytic degradation of tetracycline hydrochloride.

In this work, AgBr/Ti3C2@TiO2 ternary composite photocatalyst was prepared by a solvothermal and precipitation method with the aims of introducing Ti3C2 as a cocatalyst and TiO2 as a compositing semiconductor. The crystal structure, morphology, elemental state, functional groups and photoelectrochemical properties were studied by XRD, SEM, TEM, XPS, FI-IR and EIS. The photocatalytic performances of the composites were investigated by the photodehydrogenation of diethyl 1,4-dihydro-2,6-dimethyl-3,5-pyridinedicarboxylate (1,4-DHP) and the photodegradation of tetracycline hydrochloride (TCH) under visible light irradiation (λ > 400 nm). The AgBr/Ti3C2@TiO2 composite photocatalyst showed enhanced photocatalytic performance in both photocatalytic reactions. The photocatalytic activity of the composite photocatalyst is dependent on the proportional content of Ti3C2@TiO2. With optimized Ti3C2@TiO2 proportion, the photocatalytic ability of the AgBr/Ti3C2@TiO2 composite was 24.5 times as high as that of Ti3C2@TiO2 for photodehydrogenation of 1,4-DHP and 1.9 times as high as that of pure AgBr for photodegradation of TCH. The enhanced photocatalytic performance of the AgBr/Ti3C2@TiO2 composite should be due to the formation of a p-n heterojunction structure between AgBr and Ti3C2@TiO2 and the excellent electronic properties of Ti3C2, which enhanced the visible light absorption capacity, lowered the internal resistance, speeded up the charge transfer and reduced the recombination efficiency of photo-generated carriers. Mechanism studies showed that superoxide free radical (˙O2-) was the main active species. In addition, the composite photocatalyst also displayed good stability, indicating its reutilization in practical application.

Photocatalytic dehydrogenation of ammonia borane over Ti3C2/MOF-supported Pd-doped Co nanoparticles

Pd-Doped Co nanoparticles were incorporated into Ti3C2/UiO-66-NH2 composite. The heterogeneous catalyst exhibited outstanding catalytic activity for the dehydrogenation of ammonia borane under light irradiation at 298 K.

Efficient acceptorless dehydrogenation of 5-Hydroxymethylfurfural (HMF) to 2,5-Diformylfuran (DFF) over Pt/CdS under visible light

The selective transformation of 5-hydroxymethylfurfural (HMF) to 2,5-diformylfuran (DFF) with coproduction of hydrogen under visible light is appealing yet still challenging. In this manuscript, Pt/CdS nanocomposites obtained via photoreduction of [PtCl6]2- over CdS were found to be an efficient and chemoselective photocatalyst for dehydrogenation of HMF to produce DFF under visible light, with simultaneously generation of stoichiometric hydrogen. An optimum performance was observed over 1.0 wt% Pt/CdS nanocomposite, with a complete conversion of HMF to DFF and stoichiometric hydrogen generated in 14 h. By comparison with the performance over MoS2/CdS, it is revealed that the superior performance for photocatalytic dehydrogenation of HMF over Pt/CdS should be ascribed to the strong interaction between the furan ring in HMF with Pt nanoparticles (NPs), which enables the protons released from HMF to fast transfer to Pt NPs in close vicinity for further reduction to generate hydrogen. This study provides an efficient and green strategy for the simultaneous transformation of biomass-derived HMF to DFF and the production of clean energy hydrogen. This work also highlights the great potential of photocatalysis in biomass valorization.

Mini AuAg Wavy Nanorods Displaying Plasmon‐Induced Photothermal and Photocatalytic Properties

Alloyed AuAg wavy nanorods (wNRs) of ≈24.0 nm length and 3.5 nm width are formed by the mild decomposition of the organometallic complex [Au2Ag2(C6F5)4(OEt2)2]n in tetrahydrofuran (THF) in the presence of oleic acid. Ligand exchange with l‐glutathione (GSH) or poly(ethylene glycol) methyl ether thiol (PEG‐SH) leads to water‐soluble nanostructures. These AuAg wNRs display tunable size‐dependent longitudinal localized surface plasmon resonance (l‐LSPR) broad absorptions beyond 750 nm in the near‐infrared (NIR) I and II regions. These intense plasmonic absorptions lead to interesting photothermal, catalytic, and photocatalytic properties, including the catalytic reduction of 4‐nitrophenol, the photocatalytic reduction of 4‐nitrostyrene, or the photocatalytic dehydrogenation of ammonia borane for H2 release.