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Few-Layered 1T-MoS2-Modified ZnCoS Solid-Solution Hollow Dodecahedra for Enhanced Photocatalytic Hydrogen Evolution
摘要： Enhancing solar hydrogen production efficiency essentially relies on the modification of low-cost and highly stable photocatalysts with enhanced light-harvesting ability and promoted charge transfer kinetics. Herein, we report a facile synthetic route to modify the performance of a low-cost metal sulfide semiconductor, consisting of the bimetallic metal-organic frameworks (MOFs)-templating and the simultaneous sulfidation of the photocatalyst and loading of MoS2 co-catalyst. The mutual sulfur atom shared by all the transition metal sulfides allowed the formation of ZnCoS solid-solution structure and the stabilization of the metallic 1T-MoS2 phase, contributing to the photocatalytic activity enhancement from several aspects: i) extending the light absorption region from UV to visible and near-infrared light by the incorporation of another transition metal sulfide species, i.e., CoS; ii) achieving abundant catalytically active sites, and high electronic conductivity between the intimately contacted ZnCoS and MoS2 by loading few-layered 1T-MoS2; and iii) further increasing its capability of utilizing the single-photon with relatively higher energy in the UV-visible region by the involvement of a metal-free photosensitizer–Eosin Y (EY). As a consequence, the novel few-layered 1T MoS2-modified hollow Zn0.5Co0.5S rhombic dodecahedra exhibited a high photocatalytic H2 production activity of 15.47 mmol h-1 g-1 with an apparent quantum efficiency of 30.3% at 420 nm and stability with 90% H2 evolution retention even after seven consecutive runs for total 35 h irradiation. This novel approach to prepare advanced materials could be further extended to the phase-controllable preparation of MoS2 and the discovery of other transition metal chalcogenides with high activity and stability in various applications.
关键词： ZnCoS solid-solution,hollow dodecahedra,dye-sensitization,1T-MoS2,photocatalytic hydrogen evolution,MOF-templating
更新于2025-11-21 10:59:37
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Challenges in semiconductor single entity photoelectrochemistry
摘要： It is challenging to study the single semiconductor (SC) nanocrystal electrochemistry and photoelectrochemistry. The photocatalytic process that results from the electron-hole pair formed within a nanoparticle (NP) like the oxidation of methanol and iodide allow the detection of discrete current transient events assigned to single entities. Photocatalytic current amplification allows detection of collisions between the semiconductor NPs and the ultramicroelectrode (UME) that produce current transient. Staircase responses and blips in the i vs. t response indicate that irreversible and reversible NP/electrode interactions result depending on the experimental conditions. Dye sensitization increases the photocurrent magnitude of ZnO and TiO2 with respect to bare TiO2 NPs. The microelectrodes used are Pt, TiO2/Pt, TiO2/Au and F-doped SnO2 (FTO).
关键词： semiconductor,photoelectrochemistry,ultramicroelectrode,nanoparticle,dye sensitization,single entity
更新于2025-09-23 15:23:52
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Carbon Nanotube-Supported Cu <sub/>3</sub> P as High-Efficiency and Low-Cost Cocatalysts for Exceptional Semiconductor-Free Photocatalytic H <sub/>2</sub> Evolution
摘要： Developing an inexpensive and high-efficiency hydrogen-production cocatalyst to replace the noble metal Pt remains a big challenge in the fields of sustainable photocatalytic hydrogen evolution. Herein, we report the exploration of a high-efficient binary noble metal free Cu3P-CNT H2-evolution cocatalyst by direct high-temperature phosphatizing of Cu(OH)2-CNT. Impressively, combining the advantages of noble metal free Cu3P and carbon nanotube (CNT), the binary Cu3P-CNT cocatalysts show high-efficient photocatalytic H2 evolution in Eosin Y(EY)-contained semiconductor-free photocatalytic systems. The maximum visible-light H2-generation rate for promising EY-Cu3P-CNT systems was 17.22 mmolg-1h-1. The highest apparent quantum efficiency (AQE) could reach 10.23% at 500 nm. More importantly, we found that the separation of photogenerated electrons and holes in the Eosin Y, the efficiency of electron transfer from EY to the active edge sites of Cu3P, and the electrocatalytic H2-evolution activity of Cu3P, could be simultaneously boosted via readily adding the conductive CNT, thus achieving the significantly improved photocatalytic H2 evolution. This work provides a simple and facile strategy to design highly efficient semiconductor-free photocatalytic proton-reduction systems using high-activity transition metal phosphides (TMPs) and inexpensive carbon nanomaterials.
关键词： Photocatalytic Hydrogen Evolution,noble metal-free Cu3P Co-catalysts,Solar Fuel,Carbon nanotube (CNT),Dye sensitization
更新于2025-09-23 15:23:52
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Photoregeneration of Biomimetic Nicotinamide Adenine Dinucleotide Analogues via a Dye-Sensitized Approach
摘要： Two-step photochemical reduction of an acridinium-based cation 2O+ to the corresponding anion 2O? was investigated using a dye-sensitized approach involving 2O+?COOH attached to the surface of a wide-bandgap semiconductor, p-NiO. The cation 2O+ and corresponding one-electron reduced radical form, 2O? were synthesized and characterized using steady-state UV/vis and electron paramagnectic resonance spectroscopy. The thermodynamics for the photoinduced hole injection from 2O+ and 2O? were evaluated and found to be favorable. Subsequent femtosecond transient absorption spectroscopy was utilized to evaluate the photoinduced hole injection into NiO, starting from 2O+?COOH/NiO and 2O??COOH/NiO samples. The excitation of 2O+?COOH at 620 nm initiated fast (2.8 ps) hole injection into NiO. However, 90% of the charge-separated population recombined within ～40 ps, while ～10% of the charge-separated population exhibited lifetimes longer than the time scale of our instrument (1.6 ns). In the case of 2O??COOH/NiO, the light absorption occurs predominantly by NiO (2O??COOH absorbs at 310 nm) and is associated with the electron transfer from the conduction band of NiO to the radical. The charge-separated state in this case appears to be long-lived, based on the slow (ns) growth of the trapped carriers formed on the NiO surface. The results of this work indicate that the photochemical reduction of 2O+ to the corresponding hydride form (2OH) can be achieved, opening the possibility of using such a dye-sensitized approach for regeneration of nicotinamide adenine dinucleotide analogues in enzymatic and chemical catalysis.
关键词： multiple charge accumulation,stable radical,NADH,photochemistry,NiO,dye sensitization
更新于2025-09-23 15:21:21
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Role of phosphate in ruthenium-complex-sensitized TiO2 system for hydrogen production: mechanism and kinetics
摘要： Most Ru(II) complex-sensitized TiO2 systems for hydrogen (H2) production suffer from instability of the photosensitized system because the anchoring groups of Ru(II) dyes, which are required for their adsorption on TiO2, are intrinsically vulnerable to chemical and photochemical cleavage. In this study, a new method that enables the use of a Ru(II) dye without any anchoring groups (Ru(bpy)3 2+) was developed and investigated. The stable photocatalytic efficiency in repeated H2 production cycles under visible-light irradiation indicates that the Ru(II) dye without anchoring groups is highly stable during dye-sensitized H2 production. The dye-sensitized H2 production in the Ru(bpy)3 2+-sensitized TiO2 system comprising Ru(bpy)3 2+ as a photosensitizer, platinized TiO2 (Pt-TiO2) as a cocatalyst-electron mediator, and ethylenediaminetetraacetic acid as an electron donor was negligible. However, the addition of phosphate (PO4 3–) to the Ru(bpy)3 2+-sensitized TiO2 system enabled the production of H2 via dye sensitization in the absence of any anchoring groups on the dye. The adsorption of PO4 3– changed the surface charge of Pt-TiO2 from positive to negative under acidic conditions, thereby inducing adsorption of cationic Ru(bpy)3 2+ on the surface of Pt-TiO2 and facilitating electron transfer from excited Ru(bpy)3 2+ to the conduction band of TiO2. The PO4 3– adsorption-induced change in the surface charge and the subsequent adsorption of Ru(bpy)3 2+ on the surface of PO4 3–-adsorbed Pt-TiO2 were confirmed by zeta potential measurements and Fourier transform infrared spectroscopy, respectively. In contrast with H2 production, the presence of PO4 3– had little effect on the kinetics of anionic chromate (CrO4 2–) reduction in the Ru(bpy)3 2+-sensitized TiO2 system. This result indicates that electron transfer from Pt to the electron acceptor on PO4 3–-adsorbed Pt-TiO2 is highly dependent on the charge character of the electron acceptor (i.e., electron transfer to the cationic electron acceptor is more favored). The negative charge on the surface of Pt-TiO2 induced by the adsorption of PO4 3– attracts the positively charged protons to the surface, which kinetically enhanced electron transfer from Pt to the protons. The (photo)electrochemical data demonstrate that PO4 3– adsorbed on Pt-TiO2 facilitates the interfacial electron transfer processes by enhancing the adsorption of Ru(bpy)3 2+ and attracting protons to the surface. The positive effect of PO4 3– on H2 production increased with increasing PO4 3– concentration and decreasing pH, where the conditions are more favorable for PO4 3– and proton adsorption on the surface of Pt-TiO2. Among the five anions evaluated in this study (PO4 3–, AsO4 3–, F–, NO3 –, and SO4 2–), PO4 3– was most efficient and facilitated stable H2 production.
关键词： Phosphate,Dye sensitization,Hydrogen production,Photocatalysis,Ruthenium-complex
更新于2025-09-10 09:29:36
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Donor-π-acceptor dye-sensitized photoelectrochemical and photocatalytic hydrogen evolution by using Cu2WS4 co-catalyst
摘要： Photoelectrochemical and photocatalytic hydrogen evolution reaction (HER) have been investigated by using metal free donor-acceptor (D-A) and donor-p-acceptor (D-p-A) dyes, which are abbreviated as MC-32 and MC-048, respectively, sensitized TiO2 as a photocatalyst with or without Cu2WS4 co-catalyst. This co-catalyst is synthesized by a low-cost and simple hot injection method, under visible light illumination. The photoactivities of these dyes have been clarified according to their structural, optical and electrochemical properties. Photocatalytic activities have been slightly increased when added the Cu2WS4 co-catalyst (dye/TiO2/Cu2WS4). This catalytic activity is also compared to that of noble metal Pt (dye/TiO2/Pt). It has been found that 121 mmolg-1h-1, 179 mmolg-1h-1, 348 mmolg-1h-1, 212 mmolg-1h-1, 422 mmolg-1h-1 and 1139 mmolg-1h-1 hydrogen have been evolved by using MC-32/TiO2, MC-32/TiO2/Cu2WS4, MC-32/TiO2/Pt, MC-048/TiO2, MC-048/TiO2/Cu2WS4 and MC-048/TiO2/Pt, respectively.
关键词： Dye sensitization,Donor-p-acceptor dyes,Hydrogen evolution
更新于2025-09-04 15:30:14