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112 result(s) for "H2 evolution"
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Recent Advances in Metal–Organic Frameworks Derived Nanocomposites for Photocatalytic Applications in Energy and Environment
Solar energy is a key sustainable energy resource, and materials with optimal properties are essential for efficient solar energy‐driven applications in photocatalysis. Metal–organic frameworks (MOFs) are excellent platforms to generate different nanocomposites comprising metals, oxides, chalcogenides, phosphides, or carbides embedded in porous carbon matrix. These MOF derived nanocomposites offer symbiosis of properties like high crystallinities, inherited morphologies, controllable dimensions, and tunable textural properties. Particularly, adjustable energy band positions achieved by in situ tailored self/external doping and controllable surface functionalities make these nanocomposites promising photocatalysts. Despite some progress in this field, fundamental questions remain to be addressed to further understand the relationship between the structures, properties, and photocatalytic performance of nanocomposites. In this review, different synthesis approaches including self‐template and external‐template methods to produce MOF derived nanocomposites with various dimensions (0D, 1D, 2D, or 3D), morphologies, chemical compositions, energy bandgaps, and surface functionalities are comprehensively summarized and analyzed. The state‐of‐the‐art progress in the applications of MOF derived nanocomposites in photocatalytic water splitting for H2 generation, photodegradation of organic pollutants, and photocatalytic CO2 reduction are systemically reviewed. The relationships between the nanocomposite properties and their photocatalytic performance are highlighted, and the perspectives of MOF derived nanocomposites for photocatalytic applications are also discussed. The state‐of‐the‐art progress in the production of metal–organic framework (MOF) derived nanocomposites with various dimensions (0D, 1D, 2D, or 3D), morphologies, chemical compositions, energy bandgaps, and surface functionalities are comprehensively summarized and analyzed. The photocatalytic applications of those MOF derived nanocomposites in photocatalytic water splitting for H2 generation, photodegradation of organic pollutants, and photocatalytic CO2 reduction are systemically reviewed.
Improved Plasmonic Hot-Electron Capture in Au Nanoparticle/Polymeric Carbon Nitride by Pt Single Atoms for Broad-Spectrum Photocatalytic H2 Evolution
HighlightsA hybrid co-catalysts system comprising Au nanoparticles (NPs) and PtSAs with different functions was constructed on the polymeric carbon nitride (PCN) surface by double-solvent method.For the dual co-catalysts, the Au NPs absorb relatively long-wavelength light to produce plasmonic hot-electrons, and the adjacent Pt single atoms (PtSAs) can trap the plasmonic hot-electrons effectively for H2 evolution.The PtSAs–Au2.5/PCN exhibits excellent broad-spectrum photocatalytic H2 evolution activity with the H2 evolution rate of 8.8 mmol g−1 h−1 at 420 nm and 264 μmol g−1 h−1 at 550 nm, respectively.Rationally designing broad-spectrum photocatalysts to harvest whole visible-light region photons and enhance solar energy conversion is a “holy grail” for researchers, but is still a challenging issue. Herein, based on the common polymeric carbon nitride (PCN), a hybrid co-catalysts system comprising plasmonic Au nanoparticles (NPs) and atomically dispersed Pt single atoms (PtSAs) with different functions was constructed to address this challenge. For the dual co-catalysts decorated PCN (PtSAs–Au2.5/PCN), the PCN is photoexcited to generate electrons under UV and short-wavelength visible light, and the synergetic Au NPs and PtSAs not only accelerate charge separation and transfer though Schottky junctions and metal-support bond but also act as the co-catalysts for H2 evolution. Furthermore, the Au NPs absorb long-wavelength visible light owing to its localized surface plasmon resonance, and the adjacent PtSAs trap the plasmonic hot-electrons for H2 evolution via direct electron transfer effect. Consequently, the PtSAs–Au2.5/PCN exhibits excellent broad-spectrum photocatalytic H2 evolution activity with the H2 evolution rate of 8.8 mmol g−1 h−1 at 420 nm and 264 μmol g−1 h−1 at 550 nm, much higher than that of Au2.5/PCN and PtSAs–PCN, respectively. This work provides a new strategy to design broad-spectrum photocatalysts for energy conversion reaction.
Aqueous electrolyte additives for zinc-ion batteries
Because of their high safety, low cost, and high volumetric specific capacity, zinc-ion batteries (ZIBs) are considered promising next-generation energy storage devices, especially given their high potential for large-scale energy storage. Despite these advantages, many problems remain for ZIBs—such as Zn dendrite growth, hydrogen evolution, and Zn anode corrosion—which significantly reduce the coulomb efficiency and reversibility of the battery and limit its cycle lifespan, resulting in much uncertainty in terms of its practical applications. Numerous electrolyte additives have been proposed in recent years to solve the aforementioned problems. This review focuses on electrolyte additives and discusses the different substances employed as additives to overcome the problems by altering the Zn 2+ solvation structure, creating a protective layer at the anode–electrolyte interface, and modulating the Zn 2+ distribution to be even and Zn deposition to be uniform. On the basis of the review, the possible research strategies, future directions of electrolyte additive development, and the existing problems to be solved are also described. The review summarizes different types of additives for aqueous zinc ion batteries, including dipole organic additives, ionic liquid additives, SEI/quasi-SEI formation additives, metal ions additives, polymer type additives, and adsorption type additives. The review illustrates the mechanism of different types of additives such as adsorption, texture effect, and cathode dissolution effect. The review proposes some possible directions for the development of additives for aqueous zinc ion batteries.
2D/2D Heterojunction of R-scheme Ti3C2 MXene/MoS2 Nanosheets for Enhanced Photocatalytic Performance
Combination of two-dimensional (2D) materials and semiconductors is considered to be an effective way for fabricating photocatalysts for solving the environmental pollution and energy crisis. In this work, novel 2D/2D heterojunction of R-scheme Ti3C2 MXene/MoS2 nanosheets is successfully synthesized by hydrothermal reaction. The photocatalytic activity of the Ti3C2 MXene/MoS2 composites is evaluated by photocatalytic degradation and hydrogen evolution reaction. Especially, 0.5 wt% Ti3C2 MXene/MoS2 sample exhibits optimum methyl orange (MO) degradation and H2 evolution rate of 97.4% and H2 evolution rate of 380.2 μmol h−1 g−1, respectively, which is attributed to the enhanced optical absorption ability and increased specific surface area. Additionally, Ti3C2 MXene coupled with MoS2 nanosheets is favorable for improving the photocurrent response and reducing the electrochemical impedance, leading to the enhanced electron transfer of excited semiconductor and inhibition of charge recombination. This work demonstrates that Ti3C2 MXene could be a promising carrier to construct 2D/2D heterojunction in photocatalytic degradation and hydrogen evolution reaction.
Rational Photodeposition of Cobalt Phosphate on Flower-like ZnIn2S4 for Efficient Photocatalytic Hydrogen Evolution
The high electrons and holes recombination rate of ZnIn2S4 significantly limits its photocatalytic performance. Herein, a simple in situ photodeposition strategy is adopted to introduce the cocatalyst cobalt phosphate (Co-Pi) on ZnIn2S4, aiming at facilitating the separation of electron–hole by promoting the transfer of photogenerated holes of ZnIn2S4. The study reveals that the composite catalyst has superior photocatalytic performance than blank ZnIn2S4. In particular, ZnIn2S4 loaded with 5% Co-Pi (ZnIn2S4/5%Co-Pi) has the best photocatalytic activity, and the H2 production rate reaches 3593 μmol·g−1·h−1, approximately double that of ZnIn2S4 alone. Subsequent characterization data demonstrate that the introduction of the cocatalyst Co-Pi facilitates the transfer of ZnIn2S4 holes, thus improving the efficiency of photogenerated carrier separation. This investigation focuses on the rational utilization of high-content and rich cocatalysts on earth to design low-cost and efficient composite catalysts to achieve sustainable photocatalytic hydrogen evolution.
Pt-Chitosan-TiO2 for Efficient Photocatalytic Hydrogen Evolution via Ligand-to-Metal Charge Transfer Mechanism under Visible Light
The Pt-chitosan-TiO2 charge transfer (CT) complex was synthesized via the sol-gel and impregnation method. The synthesized photocatalysts were thoroughly characterized, and their photocatalytic activity were evaluated toward H2 production through water reduction under visible-light irradiation. The effect of the preparation conditions of the photocatalysts (the degree of deacetylation of chitosan, addition amount of chitosan, and calcination temperature) on the photocatalytic activity was discussed. The optimal Pt-10%DD75-T200 showed a H2 generation rate of 280.4 μmol within 3 h. The remarkable visible-light photocatalytic activity of Pt-chitosan-TiO2 was due to the CT complex formation between chitosan and TiO2, which extended the visible-light absorption and induced the ligand-to-metal charge transfer (LMCT). The photocatalytic mechanism of Pt-chitosan-TiO2 was also investigated. This paper outlines a new and facile pathway for designing novel visible-light-driven photocatalysts that are based on TiO2 modified by polysaccharide biomass wastes that are widely found in nature.
Electrostatic Self-Assembly of CdS Quantum Dots with Co9S8 Hollow Nanotubes for Enhanced Visible Light Photocatalytic H2 Production
CdS quantum dots (CdS QDs) are regarded as a promising photocatalyst due to their remarkable response to visible light and suitable placement of conduction bands and valence bands. However, the problem of photocorrosion severely restricts their application. Herein, the CdS QDs-Co9S8 hollow nanotube composite photocatalyst has been successfully prepared by loading Co9S8 nanotubes onto CdS QDs through an electrostatic self-assembly method. The experimental results show that the introduction of Co9S8 cocatalyst can form a stable structure with CdS QDs, and can effectively avoid the photocorrosion of CdS QDs. Compared with blank CdS QDs, the CdS QDs-Co9S8 composite exhibits obviously better photocatalytic hydrogen evolution performance. In particular, CdS QDs loaded with 30% Co9S8 (CdS QDs-30%Co9S8) demonstrate the best photocatalytic performance, and the H2 production rate reaches 9642.7 μmol·g−1·h−1, which is 60.3 times that of the blank CdS QDs. A series of characterizations confirm that the growth of CdS QDs on Co9S8 nanotubes effectively facilitates the separation and migration of photogenerated carriers, thereby improving the photocatalytic hydrogen production properties of the composite. We expect that this work will facilitate the rational design of CdS-based photocatalysts, thereby enabling the development of more low-cost, high-efficiency and high-stability composites for photocatalysis.
Electroshock synthesis of a bifunctional nonprecious multi‐element alloy for alkaline hydrogen oxidation and evolution
The design and production of active, durable, and nonprecious electrocatalysts toward alkaline hydrogen oxidation and evolution reactions (HOR/HER) are extremely appealing for the implementation of hydrogen economy, but remain challenging. Here, we report a facile electric shock synthesis of an efficient, stable, and inexpensive NiCoCuMoW multi‐element alloy on Ni foam (NiCoCuMoW) as a bifunctional electrocatalyst for both HOR and HER. For the HOR, the current density of NiCoCuMoW could reach ∼11.2 mA cm–2 when the overpotential is 100 mV, higher than that for commercial Pt/C (∼7.2 mA cm–2) and control alloy samples with less elements, along with superior CO tolerance. Moreover, for the HER, the overpotential at 10 mA cm−2 for NiCoCuMoW is only 21 mV, along with a Tafel slope of low to 63.7 mV dec−1, rivaling the commercial Pt/C as well (35 mV and 109.7 mV dec−1). Density functional theory calculations indicate that alloying Ni, Co, Cu, Mo, and W can tune the electronic structure of individual metals and provide multiple active sites to optimize the hydrogen and hydroxyl intermediates adsorption, collaboratively resulting in enhanced electrocatalytic activity. A facile electric shock method is used to synthesize an efficient, stable, and inexpensive NiCoCuMoW bifunctional alloy electrocatalyst for both hydrogen oxidation reaction (HOR) and hydrogen evolution reaction (HER). Combined experiments and theory calculations reveal that the multi‐component synergy of different elements and plentiful active sites render the NiCoCuMoW superior HOR/HER performance, rivaling the Pt/C benchmark and most reported nonprecious catalysts.
Near‐Infrared‐Plasmonic Energy Upconversion in a Nonmetallic Heterostructure for Efficient H2 Evolution from Ammonia Borane
Plasmonic metal nanostructures have been widely used to enhance the upconversion efficiency of the near‐infrared (NIR) photons into the visible region via the localized surface plasmon resonance (LSPR) effect. However, the direct utilization of low‐cost nonmetallic semiconductors to both concentrate and transfer the NIR‐plasmonic energy in the upconversion system remains a significant challenge. Here, a fascinating process of NIR‐plasmonic energy upconversion in Yb3+/Er3+‐doped NaYF4 nanoparticles (NaYF4:Yb‐Er NPs)/W18O49 nanowires (NWs) heterostructures, which can selectively enhance the upconversion luminescence by two orders of magnitude, is demonstrated. Combined with theoretical calculations, it is proposed that the NIR‐excited LSPR of W18O49 NWs is the primary reason for the enhanced upconversion luminescence of NaYF4:Yb‐Er NPs. Meanwhile, this plasmon‐enhanced upconversion luminescence can be partly absorbed by the W18O49 NWs to re‐excite its higher energy LSPR, thus leading to the selective enhancement of upconversion luminescence for the NaYF4:Yb‐Er/W18O49 heterostructures. More importantly, based on this process of plasmonic energy transfer, an NIR‐driven catalyst of NaYF4:Yb‐Er NPs@W18O49 NWs quasi‐core/shell heterostructure, which exhibits a ≈35‐fold increase in the catalytic H2 evolution from ammonia borane (BH3NH3) is designed and synthesized. This work provides insight on the development of nonmetallic plasmon‐sensitized optical materials that can potentially be applied in photocatalysis, optoelectronic, and photovoltaic devices. Nonmetallic plasmon‐induced selective enhancement of upconversion luminescence is observed in a layer‐structured NaYF4:Yb‐Er/W18O49 film due to the near‐infrared‐plasmonic energy upconversion. Based on this photonics process, an infrared‐driven plasmonic catalyst of NaYF4:Yb‐Er@W18O49 heterostructures is designed and synthesized, which exhibits a ≈35‐fold increase in catalytic H2 evolution upon IR excitation.
Fabrication of ZnO/Red Phosphorus Heterostructure for Effective Photocatalytic H2 Evolution from Water Splitting
Photocatalysis is a green technique that can convert solar energy to chemical energy, especially in H2 production from water splitting. In this study, ZnO and red phosphorus (ZnO/RP) heterostructures were fabricated through a facile calcination method for the first time, which showed the considerable photocatalytic activity of H2 evolution. The photocatalytic activities of heterostructures with different ratios of RP have been investigated in detail. Compared to bare ZnO, ZnO/RP heterostructures exhibit a 20.8-fold enhancement for H2 production and furthermore overcome the photocorrosion issue of ZnO. The improved photocatalytic activities highly depend on the synergistic effect of the high migration efficiency of photo-induced electron–hole pairs with the inhibited charge carrier recombination on the surface. The presented strategy can also be applied to other semiconductors for various optoelectronics applications.