| Environmental pollution and energy crisis has become the two critical issues for the sustainable development of human beings.Clean energy and renewable energy are considered key routes to solve the energy crisis,as well as solutions to alleviate the pressures of environmental protection.Solar energy is a clean renewable energy source and has attracted extensive study concerning its utilization.Hydrogen(H2)is a clean energy source with high energy density.Since the frst successful photocatalytic water splitting by TiO2 under ultraviolet(UV)light,photocatalysis based on semiconductors represents another approach to convert light energy into chemical energy.The full process of photocatalytic water splitting into H2 and O2 is believed to be promising for generating renewable and green energy,and the process includes the photoreduction and photooxidation of water,respectively.From the semiconductor band theory and photocatalytic principle,it is known that only the photon energy is larger than the band gap width of the semiconductor can stimulate the semiconductor to carry on the effective photocatalytic reaction.The conventional semiconductor photocatalytic hydrogen evolution system mostly utilizes high-frequency ultraviolet light in the solar spectrum.However,visible and Near-infrared light comprises the largest part of the solar energy spectrum.Therefore,good utilization of the visible and Near-infrared light for the application in solar water splitting can solve many of the issues involved in the environmental and energy crisis.Based on above background and our conditions,we designed serval semiconductor heterojunction photocatalysts for the application in solar water splitting.Details are as follows:1.Firstly,we designed the reduced carbon dots(r-CDs)as both photon harvesters and photoelectron donors in combination with the platinum(Pt)clusters and fabricated the function-integrated r-CD/Pt photocatalyst through a photochemical route to control the anchoring of Pt clusters on r-CDs' surface for solar-driven hydrogen generation.In the obtained r-CD/Pt composite,the r-CDs absorb solar photons and transform them into energetic electrons,which transfer to the Pt clusters with favorable charge separation for H2 evolution reaction(HER).As a result,the effcient coupling of respective natures from r-CDs in photon harvesting and Pt in proton reduction is achieved through well-steered photoelectron transfer in the r-CD/Pt system to cultivate a remarkable and stable photocatalytic H2 evolution activity with an average rate of 681?mol g-1 h-1.This work integrates two functional components into an effective HER photocatalyst and gains deep insights into the regulation of the function coupling in composite photosynthetic systems.2.Next,the surface plasmon resonance(SPR)of Cu nanoparticles(NPs)anchored on WS2 nanosheets(NSs)was designed to expand light response over NIR region for broadband-solar-activated photoreduction of water to H2.We first prepared ultra-thin WS2 nanoflakes,and then prepared WS2@Cu composites through simple in-situ photoreduction.Due to the interfacial interaction between WS2 and Cu,an effective charge transfer took place to obtain the higher H2 precipitation rate than pure Cu nanoparticles and pure WS2 nanoflakes.Under the simulated 1 sun irradiation(100 mWcm-2),the optimized WS2@Cu nanohybrid exhibits a stable and remarkable H2-evolution rate of 65 mmol g-1h-1.WS2 acts as an electron reservoir to trap electrons generated from Cu NPs and hinder the recombination of electron-hole pairs,while the loading of Cu nanoparticles expands the active sites within the WS2 nanoflakes.Due to the surface plasmon resonance(SPR)effect of Cu nanoparticles,the composite sample also achieves favourable photocatalytic activity under>750 nm light irradiation.This work can open a new avenue of plasmon-mediated NIR utilization for artificial photosynthesis and solar energy conversion. |
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