查看更多>>摘要：Photocatalytic hydrogen (H-2) production is a cascade reaction that involves multiple limiting steps, such as light-harvesting, charge separation and transfer, redox reaction rate, and so on. Thus, there is a need to optimize each reaction node to promote the photocatalytic H-2 production efficiency for the commercial application of sustainable energy. Herein, we report integrally designed CdS-Cu1.81S heteronanorods (HNRs) for photocatalytic H-2 production driven by near-infrared to ultraviolet irradiation. The intraparticle p-n junction and the well-constructed heterointerface result in highly efficient charge separation and transfer between the heterogeneous domains. Further adjusting the redox reaction sites on the surface of CdS-Cu1.81S HNRs leads to a high photocatalytic H-2 production rate of 2.714 mmol. h(-1).g(-1), representing 150-fold and 108-fold improvements compared with pristine Cu1.81S and CdS nanorods (NRs), respectively. Our work provides an alternative entry point for boosting the performance of noble-metal-free photocatalyst and highlights the importance of synergetic design.
查看更多>>摘要：Facile fabrication of visible light responsive multicomponent heterostructure photocatalysts with synergistic photoelectron migration is an effective approach with potential application in water remediation and renewable energy generation. In this study, a series of ternary multi-heterojunction CdS/Bi20TiO32/Bi4Ti3O12 (CdSxBTC) photocatalysts were prepared by hydrothermal deposition of CdS nanoparticles (15-25 nm) over one pot combustion synthesized Bi20TiO32/Bi4Ti3O12 (BTC) nanostructures. Comprehensive characterization of the ternary composites revealed enhanced optical absorption, high interfacial contact, fast electron channelization and a prolonged excited state life time. The CdSxBTC composite materials displayed enhanced photocatalytic activity for endosulfan degradation (k(app) value 6-12 times greater than pure semiconductors) and water splitting reaction (H-2 production rate 1890 mu molgb(-1) h(-1) and apparent conversion efficiency 19%). The cell viability -study disclosed non-cytotoxic nature of the treated endosulfan solution. A synergistic Type-I bridged coupled Z-scheme electron migration process accounted for robust radical generation ability (O-center dot(2)- and (OH)-O-center dot) and photocatalytic activity of the ternary composites.
查看更多>>摘要：Herein, we have synthesized fluorine-doped cobalt molybdate (F-CoMoO4) nanosheet arrays on graphite felt (GF) to efficiently promote the oxygen evolution reaction (OER) kinetics. Experimental results show that F-CoMoO4 has two significant effects: 1) inducing rich oxygen vacancies, and 2) optimizing the electronic configuration of CoMoO4, which is beneficial for exposure of active sites. The as-obtained F-CoMoO4-x-2@GF electrocatalyst exhibits lower OER overpotential of 256 mV at 10 mA cm(-2) with a small Tafel slope of 64.4 mV dec(-1) in alkaline solution, resulting in a nearly 100 mV of OER catalytic activity enhancement compared with that of pure CoMoO4. DFT results reveal that the change of Mo 4d state reduces the band-gap and increases the electrical conductivity of CoMoO4, thus optimizing its intrinsic activity. The synthesis strategy used in this work may provide some ideas for enhancing the electrical conductivity of other transition metal oxides (TMOs).
查看更多>>摘要：This manuscript proposed a synthesis strategy for simultaneously constructing defect structure and mixed valence coordinated unsaturated sites (CUS) in Cu-BTC (BTC=1,3,5-trihydroxybenzene) framework. Different defective linkers with increasing pKa value were used to regulate the defect concentration and Cu1+/Cu2+ CUS content. The pKa value of defective linkers was proved to be inversely proportional to the defect concentration and Cu1+/Cu2+ CUS content. Compared with pure Cu-BTC, the defective Cu-BTC samples have obviously improved specific surface area, light absorption, bandgap, and charge carrier separation rate. All of these advantages make defective variants become an excellent bifunctional overall water splitting catalyst with O2 and H2 generation rates of 3942 mu mol center dot g-1 center dot h-1 and 15107 mu mol center dot g-1 center dot h-1, respectively. Although the defective linkers with small pKa value can create more defects, excessive defects in framework will lead to the parent structure collapse, and can also serve as recombination centers to reduce the photocatalytic activity of materials.
查看更多>>摘要：Yolk-shell nanohybrids have garnered increasing interests in many applications, such as in catalysis, energy, and molecular sensing. However, their intrinsic architectural limitations have led to insufficient synergistic effects and instability which are unfavorable for nanocatalysis. Designing a unique yolk-in-shell nanostructure where the "yolk" is embedded in the "shell" can overcome this challenge to boost nanocatalysis. Herein, an unprecedented Au@TiO2 yolk-in-shell nanocatalyst has been developed to dramatically improve the visible light photocatalysis. The as-designed Au@TiO2 nanohybrid displays an efficient hydrogen-production (95.6 mmol h(-1) g(-1), Au: 0.04 wt%), 3- and 14-times better than conventional Au@TiO2 yolk-shell nanostructure and pure TiO2 hollow nanosphere, respectively. Our unique design also notably achieves high selectivity (similar to 100%) towards CO production (0.75 mmol h(-1) g(-1)) under visible light irradiation. This unique yolk-in-shell nanoarchitecture promises enormous opportunities for the design of next-generation hybrid nanocatalysts with enhanced catalytic performances.
查看更多>>摘要：The effect of H2O on acetaldehyde oxidation was studied and alpha-, gamma-, delta-MnO2 can be affected by the H2O vapor, while beta-MnO2 is hardly affected by the H2O vapor during acetaldehyde oxidation. The H2O vapor can facilitate the catalytic oxidation of acetaldehyde at moderate temperatures (ca. 70 similar to 100 degrees C), with a negative effect observed at high temperatures (>100 degrees C). The stretching mode of the Mn-O-Mn chains in alpha-, gamma-, delta-MnO2 allows the associatively adsorbed water to absorb on the surface prior to acetaldehyde. Afterwards, acetaldehyde can form hydrogen bonds with the associatively adsorbed water molecules, thus, producing the intermediate carboxylic acid species, which are easily degraded to CO2. The negative effect of H2O on the acetaldehyde oxidation at high temperatures is attributed to the difficulty in adsorbing acetaldehyde on MnO2 via hydrogen bonding with the adsorbed H2O. These findings reveal the role of water in the catalytic oxidation of acetaldehyde.
查看更多>>摘要：Photocatalysis is a promising technology for energy and environment applications. Herein, a dual-defect heterojunction system of TiO2 hierarchical microspheres with oxygen vacancies modified with ultrathin MoS2-x nanosheets (MoS2-x @TiO2-OV) is designed for simultaneously degrading pollutants and evolving hydrogen. MoS2- x @TiO2-OV exhibits a dramatically enhanced photocatalytic activity with a H2 evolution rate of 2985.16 mu mol g- 1h- 1. In treating the simulated pharmaceutical wastewater, MoS2- x @TiO2-OV is capable of purifying various refractory contaminants, with the highest H2 evolution rate of 41.59 mu mol g- 1h- 1 during enrofloxacin degradation. While treating the simulated coking wastewater, the catalyst achieves a H2 evolution rate of 102.72 mu mol g- 1h- 1 and a mineralization rate of 50%. Computational studies suggest that the dual-defect is superior for the adsorption of H* and producing.OH ('dual-defect boosted dual-function'). Also, the dual-defect sites significantly boosted the charge-carrier separation and transfer efficiencies. This work highlights the crucial role of defect engineering to develop the energy-recovering wastewater treatment approaches.
查看更多>>摘要：A micropore-rich mesoporous carbon (MMC) derived from ordered mesoporous carbon (OMC) is fabricated as support to prepare a highly active nano Cu2O catalyst for methanol oxidation carbonylation. The well-dispersed -3.3 nm Cu nanoparticles with ca. 90% purity of Cu2O are obtained. The space-time yield and turnover frequency of DMC are significantly enhanced to 34.2 g g-Cu1 h-1 and 89.1 h-1, both of which are greater than that over the mesoporous-only Cu/OMC catalyst. It is found that plentiful under-coordinated carbon atoms are formed in the introduced micropores, which serve as binding sites to immobilize Cu precursors to form the welldispersed Cu nanoparticles. A large number of these atoms are favorable to accelerate auto-reduction of CuO to Cu2O in kinetics and further promote to form high-purity Cu2O. Besides, the electrons of Cu2O are forced to transfer to the micropore surrounding, forming an electron-deficient Cu+ site in favor of intrinsic activity enhancement.
查看更多>>摘要：Transition metal phosphides are promising candidates for alkaline hydrogen evolution reaction (HER), but the activation of H2O molecule is deficient. We adopt an interface engineering strategy to synthesize a hierarchical FeNiP/MoOx integrated electrode with multi-interface grown on monocrystalline NiMoO4 nanorods. Such catalyst exhibits remarkable alkaline HER performance with a low overpotential of 97 mV at the current density of 100 mA cm(-2) and sustainable durability over 20 h. Experimental and theoretical results reveal that interfaces among Fe2P, Ni5P4, and MoOx can efficiently activate H2O molecules and facilitate H desorption. Moreover, employing FeNiP/MoOx/NiMoO4/NF as a cathode, the cell voltage as low as 1.62 V to achieve a current density of 100 mA cm(-2), with admirable durability over 20 h for alkaline water splitting (1.0 M NaOH + 0.5 M NaCl). This work offers a new avenue to rationally design a 3D robust, cost-effective catalyst with multi-interface for large-scale practical hydrogen production.
Pawar, Amol U.Pal, UmapadaZheng, Jin YouKim, Chang Woo...
11页
查看更多>>摘要：Transforming greenhouse gases such as CO2 to energy rich carbon-based chemicals is considered as one of the most efficient technologies for environmental and energy sustainability. However, CO2 is highly stable molecule and difficult to reduce due to its linear structure. The rate of reduction and the nature of fuel product depend on the kinetics and thermodynamics of involved reactions. While the overall reaction kinetics depends on the energy of activated CO2 molecule and its subsequent transition states along with reduction dynamics. Here we demonstrate that by activation of thermodynamically stable CO2 molecule through complexation or coordination with suitable activator such as N-heterocyclic polymers (e.g., poly(4-vinyl)pyridine, PVP), both the kinetics and thermodynamics of photoelectrochemical CO2 reduction reaction can be controlled by proper choice of electrode materials and bias potential. We present a solar light driven photoelectrochemical process for producing formaldehyde and acetaldehyde selectively on multi-layered Cu/rGO/PVP/Nafion hybrid cathode.
NSTL
Elsevier