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A direct one-step synthesis of ultrathin g-C3N4 nanosheets from thiourea for boosting solar photocatalytic H2 evolution
摘要： Two-dimensional (2D) graphitic carbon nitride (g-C3N4) nanosheets, as the promising photocatalyst with fascinating properties, have become a 'rising star' in the field of photocatalysis. Although g-C3N4 nanosheets exfoliated from the bulk g-C3N4 powders are extensively emerged, developing a simple synthetic approach is still full of challenge. To this end, here we report a direct polymerization strategy to fabricate the ultrathin g-C3N4 nanosheets, that is only heating treatment of thiourea in air without addition of any template. The photocatalytic activities of as-prepared samples were evaluated by photoreduction of water to hydrogen (H2) using triethanolamine as sacrificial agent and Pt as co-catalyst under visible-light irradiation (λ > 420 nm). As a result, our few-layered g-C3N4 nanosheets with an average thickness of 3.5 nm exhibit a superior visible-light photocatalytic H2 evolution rate (HER) of 1391 μmol g?1 h?1 and a remarkable apparent quantum efficiency of 6.6% at 420 nm. Eventually, the HER of as-fabricated ultrathin g-C3N4 nanosheets is not only much higher than the dicyandiamide-derived g-C3N4 or melamine-derived g-C3N4, but also greater than the thermal-oxidation etched g-C3N4 nanosheets under the same condition.
关键词： g-C3N4 nanosheets,Template-free polymerization,Solar energy conversion,2D materials,Photocatalysis,One-step synthesis
更新于2025-11-14 17:03:37
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Unravelling the effect of charge dynamics at the plasmonic metal/semiconductor interface for CO2 photoreduction
摘要： Sunlight plays a critical role in the development of emerging sustainable energy conversion and storage technologies. Light-induced CO2 reduction by artificial photosynthesis is one of the cornerstones to produce renewable fuels and environmentally friendly chemicals. Interface interactions between plasmonic metal nanoparticles and semiconductors exhibit improved photoactivities under a wide range of the solar spectrum. However, the photo-induced charge transfer processes and their influence on photocatalysis with these materials are still under debate, mainly due to the complexity of the involved routes occurring at different timescales. Here, we use a combination of advanced in situ and time-resolved spectroscopies covering different timescales, combined with theoretical calculations, to unravel the overall mechanism of photocatalytic CO2 reduction by Ag/TiO2 catalysts. Our findings provide evidence of the key factors determining the enhancement of photoactivity under ultraviolet and visible irradiation, which have important implications for the design of solar energy conversion materials.
关键词： Ag/TiO2 catalysts,photocatalysis,plasmonic metal nanoparticles,sustainable energy,solar energy conversion,artificial photosynthesis
更新于2025-10-22 19:40:53
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Edge/Defect-rich, Metallic, and Oxygen-heteroatom-doped WS2 Superstructure with Superior Electrocatalytic Performance for Green Solar Energy Conversion
摘要： Two-dimensional tungsten sulfide is widely applied in electrocatalysis field. However, WS2 possesses catalytic active sites located at the layer edge and an inert surface for catalysis. Therefore, increasing the exposure of active sites at the edge and effectively activating the inert sites on the surface is important challenges. Here, we synthesize edge/defect-rich and oxygen-heteroatom-doped WS2 (ED-O-WS2) superstructure. The power-conversion efficiency (PCE) of dye-sensitized solar cells (DSCs) based on ED-O-WS2 counter electrode reach 10.36% (under 1 Sun, AM 1.5, 100 mW cm?2) and 11.19% (under 40 mW cm?2). These values are, to our knowledge, the highest reported efficiency for DSCs based on Pt-free counter electrodes in I3-/I- electrolytes. Analysis of micro-nano structure and electrocatalytic mechanism indicate that ED-O-WS2 exhibit metallic properties in the electrolyte, and that rich edge/defect and oxygen doping in ED-O-WS2 play an important role in improving the catalytic activity of WS2. Moreover, ED-O-WS2 displays better catalytic reversibility for I3-/I- electrolytes than that of noble metal Pt.
关键词： WS2,green solar energy conversion,dye-sensitized solar cells,counter electrode
更新于2025-09-23 15:23:52
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Surface-Immobilized Conjugated Polymers Incorporating Rhenium Bipyridine Motifs for Electrocatalytic and Photocatalytic CO <sub/>2</sub> Reduction
摘要： The solar-driven conversion of CO2 to value-added products provides a promising route for solar energy storage and atmospheric CO2 remediation. In this report, a variety of supporting electrode materials were successfully modified with a [2,2′-bipyridine]-5,5′-bis(diazonium) rhenium complex through a surface-localized electropolymerization method. Physical characterization of the resulting multilayer films confirms that the coordination environments of the rhenium bipyridine tricarbonyl sites are preserved upon immobilization and that the polymerized catalyst moieties exhibit long-range structural order with uniform film growth. UV?vis studies reveal additional absorption bands in the visible region for the polymeric films that are not present in the analogous rhenium bipyridine complexes. Electrochemical studies with modified graphite rod electrodes show that the electrocatalytic activity of these films increases with catalyst loading up to an optimal value, beyond which electron and mass transport through the material become rate-limiting. Electrocatalytic studies performed at ?2.25 V vs Fc/Fc+ for 2 h reveal CO production with faradaic efficiencies and turnover numbers up to 99% and 3606, respectively. Photocatalytic studies of the modified TiO2 devices demonstrate enhanced activity at low catalyst loadings, with turnover numbers up to 70 during 5 h of irradiation.
关键词： metallopolymers,surface modification,photocatalysis,rhenium bipyridine,solar energy conversion,electrocatalysis
更新于2025-09-23 15:23:52
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Transparent Ta3N5 Photoanodes for Efficient Oxygen Evolution toward the Development of Tandem Cells
摘要： Photoelectrochemical water splitting is regarded as a promising approach to the production of hydrogen, and the development of efficient photoelectrodes is one aspect of realizing practical systems. In this work, transparent Ta3N5 photoanodes were fabricated on n-type GaN/sapphire substrates to promote O2 evolution in tandem with a photocathode, to realize overall water splitting. Following the incorporation of an underlying GaN layer, a photocurrent of 6.3 mA cm-2 was achieved at 1.23 V vs. a reversible hydrogen electrode. The transparency of Ta3N5 to wavelengths longer than 600 nm allowed incoming solar light to be transmitted to a CuInSe2 (CIS), which absorbs up to 1100 nm. A stand-alone tandem cell with a serially-connected dual-CIS unit terminated with a Pt/Ni electrode was thus constructed for H2 evolution. This tandem cell exhibited a solar-to-hydrogen energy conversion efficiency greater than 7% at the initial stage of the reaction.
关键词： solar energy conversion,photoelectrochemistry,water splitting,photoelectrochemical tandem cell,(oxy)nitrides
更新于2025-09-23 15:22:29
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Influence of the energy dependence of the absorption coefficient on the solar energy conversion efficiency
摘要： In most cases, when the ef?ciencies of a single or multi-gap (with intermediate bands) solar cell are evaluated, the energy dependence of the absorption coef?cients is ignored. In this work we will evaluate the range of optical thickness and average absorption coef?cients in which this dependence should be considered. For this study we use different absorption coef?cients generated randomly as a function of the energy. In many practical cases, the ef?ciencies are lower than those expected.
关键词： optical thickness,energy dependence,intermediate-band solar cells,solar energy conversion efficiency,absorption coefficient
更新于2025-09-23 15:21:21
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Unified theory of plasmon-induced resonance energy transfer and hot electron injection processes for enhanced photocurrent efficiency
摘要： Plasmons in metal nanoparticles (MNPs) promise to enhance solar energy conversion in semiconductors. Two essential mechanisms of enhancement in the near-field regime are hot electron injection (HEI) and plasmon-induced resonance energy transfer (PIRET). Individual studies of both mechanisms indicate that the PIRET efficiency is limited by the short lifetime of the plasmon, whereas the hot electrons result from the plasmon decay. The development of a unified theory of the coupled HEI and PIRET processes is fundamentally interesting and necessary for making reliable predictions but is complicated by the multiple interactions between various components that participate in the enhancement process. In this paper, we use the model-Hamiltonian approach to develop a combined theoretical framework including both PIRET and HEI. The coupled dynamics as well as the time evolution of hot electron energy distribution are studied. The theory further predicts an interference-induced asymmetry in the spectral dependence of PIRET, which can be used to distinguish it from HEI. As the relative contributions of PIRET and HEI strongly depend on the size of the MNPs, this presents itself as a simple route to control the strength of their contributions. The results presented here can further guide future applications of plasmonic solar energy harvesting.
关键词： plasmon,metal nanoparticles,hot electron injection,solar energy conversion,plasmon-induced resonance energy transfer
更新于2025-09-23 15:21:01
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Highly Efficient Inorganic-Organic Heterojunction Solar Cells Based on Polymer and CdX (X=Se, Te) Quantum Dots: An Insight from a Theoretical Study
摘要： By using the density functional method, we explore the potentiality of recently synthesized CdX (X=Se, Te)QD/P3HT composites in solar energy conversion devices. Our study reveals that inorganic/organic hybrid CdXQD/P3HT nanocomposites with larger size of CdX QDs exhibit type-II band alignment, suggesting efficient charge separation upon photoexcitation. But for smaller size of QDs, the composites show type-I band alignment which are devoid of charge separation and thus are not suitable for solar cell applications. To remove this obstacle, we focus on chemical modification to polymer P3HT. The substitution of hydrogen at the beta position of each thiophene ring of polymer by electron withdrawing group (CN) results type-II band alignment and yield spatial charge separation even for smaller size of QDs. Finally, we calculated the powerconversion efficiency (PCE) of CdXQD and CN functionalized P3HT nanocomposites. The maximum calculated PCE value of 10.82% is achieved, which makes them immensely competitive with other reported heterojunction solar cells.
关键词： CdX (X=Se, Te)QD/P3HT composites,powerconversion efficiency,solar energy conversion,charge separation,type-II band alignment
更新于2025-09-23 15:21:01
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Magnetically separable nanocomposites based on ZnO and their applications in photocatalytic processes: A review
摘要： Among the most challenging problems that human beings appear to face are depleting energy sources and increasing environmental pollutions. Heterogeneous photocatalytic processes are the most rewarding technology to generate renewable energy and degrade environmental pollutants. In these processes, semiconductors are used as photocatalysts. ZnO is a widely used photocatalyst, because of its strong oxidation ability, cost effectiveness, non-toxicity, versatility in synthesis, abundance in nature, and ease of crystallization. However, pure ZnO has some drawbacks, due to its wide band gap, poor solar-light utilization, and rapid recombination of the photoinduced charge carriers. Modification of ZnO using different strategies including coupling with narrow band gap semiconductors, noble metal deposition, surface sensitization by organic dyes, and elemental doping can easily address these shortcomings. In addition, separation of photocatalysts from the treated systems limits their broad applications. Incorporation of photocatalysts in magnetic materials will help their recycling using external magnetic field. This combination leads to a new generation of photocatalysts, known as magnetically separable photocatalysts. The present review provides helpful insights into preparation of magnetically separable photocatalysts based on ZnO and their applications for degradations of different pollutants.
关键词： water pollutants,Magnetic photocatalysts,solar-energy conversion,ZnO-based nanocomposites
更新于2025-09-23 15:21:01
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Plum Puddinga??Like Electrocatalyst of Na??Doped SnO <sub/><i>x</i> </sub> @Sn Loaded on Carbon Matrix to Construct Photovoltaic CO <sub/>2</sub> Reduction System with Solara??toa??Fuel Efficiency of 11.3%
摘要： A plum pudding-like Sn-based electrocatalyst is synthesized by calcinating precursor of SnC2O4 on carbon black with polymeric carbon nitride. This material exhibits a structure of Sn metallic ball coated by nitrogen-doped SnOx native layer (N-doped SnOx@Sn) embedding on carbon matrix. The electrochemical activity of the CN-Sn catalyst. The introduction of nitrogen that occupies interstitial space of surface SnOx layer further enhances electron transport; furthermore, it provides an electron-rich environment for oxygen because of its lower electronegativity, which is the fundamental cause of selectivity in electrochemical reduction of CO2 to CO. The maximum CO faradaic efficiency over the optimal catalyst reaches 57.5% with a high CO partial current density of 6.09 mA cm-2 at -0.7 V vs. RHE. This catalyst is further applied to construct a photovoltaic-electrocatalytic CO2 reduction/oxygen evolution reaction device to stably convert CO2 to chemicals for 6 hs at a high solar-to-fuel efficiency of 11.3%. This work explores a strategy of rational modulation on surface electronic structure to obtain high-performance electrocatalysts, inspiring the selectivity tuning in electrochemical CO2 reduction via electronegativity difference of various elements.
关键词： Sn,Doping,Electrocatalysis,Solar Energy Conversion,CO2 Reduction
更新于2025-09-23 15:19:57