RESUMO
Current chemical recycling of bulk synthetic plastic, polyethylene (PE), operates at high temperature/pressure and yields a complex mixture of products. PE conversion under mild conditions and with good selectivity toward value-added chemicals remains a practical challenge. Here, we demonstrate an atomic engineering strategy to modify a TiO2 photocatalyst with reversible Pd species for the selective conversion of PE to ethylene (C2H4) and propionic acid via dicarboxylic acid intermediates under moderate conditions. TiO2-supported atomically dispersed Pd species exhibits C2H4 evolution of 531.2 µmol gcat-1 hour-1, 408 times that of pristine TiO2. The liquid product is a valuable chemical propanoic acid with 98.8% selectivity. Plastic conversion with a C2 hydrocarbon yield of 0.9% and a propionic acid yield of 6.3% was achieved in oxidation coupled with 3 hours of photoreaction. In situ spectroscopic studies confirm a dual role of atomic Pd species: an electron acceptor to boost charge separation/transfer for efficient photoredox, and a mediator to stabilize reaction intermediates for selective decarboxylation.
RESUMO
High-performance and low-cost photocatalysts play the key role in achieving the large-scale solar hydrogen production. In this work, we report a liquid-exfoliation approach to prepare NiPS3 ultrathin nanosheets as a versatile platform to greatly improve the light-induced hydrogen production on various photocatalysts, including TiO2, CdS, In2ZnS4 and C3N4. The superb visible-light-induced hydrogen production rate (13,600 µmol h-1 g-1) is achieved on NiPS3/CdS hetero-junction with the highest improvement factor (~1,667%) compared with that of pure CdS. This significantly better performance is attributed to the strongly correlated NiPS3/CdS interface assuring efficient electron-hole dissociation/transport, as well as abundant atomic-level edge P/S sites and activated basal S sites on NiPS3 ultrathin nanosheets advancing hydrogen evolution. These findings are revealed by the state-of-art characterizations and theoretical computations. Our work for the first time demonstrates the great potential of metal phosphorous chalcogenide as a general platform to tremendously raise the performance of different photocatalysts.
RESUMO
Single-atom photocatalysts have demonstrated an enormous potential in producing value-added chemicals and/or fuels using sustainable and clean solar light to replace fossil fuels causing global energy and environmental issues. These photocatalysts not only exhibit outstanding activities, selectivity, and stabilities due to their distinct electronic structures and unsaturated coordination centers but also tremendously reduce the consumption of catalytic metals owing to the atomic dispersion of catalytic species. Besides, the single-atom active sites facilitate the elucidation of reaction mechanisms and understanding of the structure-performance relationships. Presently, apart from the well-known reactions (H2 production, N2 fixation, and CO2 conversion), various novel reactions are successfully catalyzed by single-atom photocatalysts possessing high efficiency, selectivity, and stability. In this contribution, we summarize and discuss the design and fabrication of single-atom photocatalysts for three different kinds of emerging reactions (i.e., reduction reactions, oxidation reactions, as well as redox reactions) to generate desirable chemicals and/or fuels. The relationships between the composition/structure of single-atom photocatalysts and their activity/selectivity/stability are explained in detail. Additionally, the insightful reaction mechanisms of single-atom photocatalysts are also introduced. Finally, we propose the possible opportunities in this area for the design and fabrication of brand-new high-performance single-atom photocatalysts.
RESUMO
As photocatalysis technology could transform renewable and clean solar energy into green hydrogen (H2 ) energy through solar water splitting, it is regarded as the "Holy Grail" in chemistry field in the 21st century. Unfortunately, the bottleneck of this technique still lies in the exploration of highly active, cost-effective, and robust photocatalysts. This work reports the design and synthesis of a novel zeolitic imidazole framework (ZIF) coupled Zn0.8 Cd0.2 S hetero-structured photocatalyst for high-performance visible-light-induced H2 production. State-of-the-art characterizations and theoretical computations disclose that the interfacial electronic interaction between ZIF and Zn0.8 Cd0.2 S, the high distribution of Zn0.8 Cd0.2 S on ZIF, and the atomically dispersed coordinately unsaturated Co sites in ZIF synergistically arouse the significantly improved visible-light photocatalytic H2 production performance.
RESUMO
The rapid consumption of non-renewable fossil fuels and the relevant critical environmental issues have significantly boosted the demand for clean, renewable and carbon-free energy sources. The conversion of solar energy into green hydrogen (H2) via photocatalytic water splitting stands out as a promising, cost-effective and environmentally friendly technology. However, the realization of large-scale solar-driven photocatalytic H2 production relies on the development of inexpensive, efficient and stable photocatalysts. Here, for the first time, we report the fabrication of Zn0.8Cd0.2S (ZCS) nanoparticles (NPs) dispersed Co-based metal-organic layers (CMLs) using an easy self-assembly approach. The as-synthesized ZCS/CML composite shows a remarkable visible-light-induced H2-production activity of 18 102 µmol h-1 g-1, 492% higher than that of pure ZCS. A series of advanced characterization studies, e.g., synchrotron-based X-ray absorption near edge structure and time-resolved photoluminescence spectroscopy, disclose that the strong electronic interaction between ZCS and CML and the abundant reactive sites on the CML lead to the significantly improved photocatalytic H2-production activity. Our contribution not only demonstrates the application of CML as an earth-abundant support and promoter to tremendously boost photocatalytic H2 production without noble-metal co-catalysts, but also sheds light on the tailored design and synthesis of metal-organic-layer based materials for energy conversion and storage.
