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In-situ hydrothermal fabrication of CdS/g-C3N4 nanocomposites for enhanced photocatalytic water splitting
摘要： In this work, a series of CdS/g-C3N4 nanocomposites with varying wt% CdS were prepared via an in-situ hydrothermal synthesis method. 10 wt% CdS/g-C3N4 nanocomposites displayed the highest rate of hydrogen evolution via photocatalytic water splitting. The H2 evolution rate of 10 wt% CdS/g-C3N4 is 21 times greater than pure g-C3N4 and 4 times greater than that of pure CdS. Key factors responsible for the enhanced photocatalytic activity can be attributed to the improved charge separation and increased surface area of CdS/g-C3N4 nanocomposites. These findings may serve as a platform for the fabrication of other photocatalytic multi-material nanocomposites in the future.
关键词： Nanocomposite,Photocatalysis,Solar fuels,Electrical properties,Hydrogen production
更新于2025-09-23 15:22:29
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Thermochemical oxygen pumping for improved hydrogen production in solar redox cycles
摘要： Solar thermochemical cycles are promising processes for the efficient production of renewable hydrogen at large scale. One area for process optimization is the high temperature reduction step. The oxygen released during this step has to be removed from the reactor in order to increase the reduction extent of the redox material. If low partial pressures of oxygen are required, the removal of oxygen can result in a significant energy penalty for the process. Two options for oxygen removal are mainly considered so far: the use of sweep gas and vacuum pumping. Here, a third promising option is discussed - thermochemical oxygen pumping. This approach shows large energy saving potentials especially at low partial pressures of oxygen. In this study, the interaction between splitting material and pumping material is theoretically analyzed for the conditions of a demonstration campaign previously published. The presented model approach is able to capture the main mechanisms of the interaction between the two materials and the gas phase and provides predictions of the thermochemical oxygen pumping effect on the reduction extent of the splitting material. A parametric study shows the importance of the optimization of the relative material amounts. Furthermore, the influence of using different perovskite materials on the energy consumption of such a process is addressed in a more generic thermodynamic analysis. The results indicate, that by using perovskite-based redox materials, the lower limit of oxygen partial pressures for solar thermochemical cycles from an energy demand perspective might be pushed well below 10?1? bar. At low oxygen partial pressures, thermochemical pumps seem to be far more efficient than mechanical pumps, and their efficiency can be further improved by recovering the heat released during the oxidation of the pumping material.
关键词： Thermochemical pump,Perovskites,Thermochemical cycles,Oxygen pumping,Solar fuels
更新于2025-09-23 15:22:29
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Decoupling Effects of Surface Recombination and Barrier Height on p-Si(111) Photovoltage in Semiconductor|Liquid Junctions via Molecular Dipoles and Metal Oxides
摘要： This work provides insight into carrier dynamics in a model photoelectrochemical system comprised of a semiconductor, metal oxide, and metal. To isolate carrier dynamics from catalysis, a common catalytic metal (Pt) is used in concert with an outer-sphere redox couple. Silicon (111) substrates were surface-functionalized with electronegative aryl moieties (p-nitrophenyl and m-dinitrophenyl). A mixed monolayer using p-nitrophenyl/methyl exhibited high surface quality as determined by X-ray photoelectron spectroscopy (low surface SiOx content) and low surface recombination velocity. This substrate also exhibited the expected positive surface dipole, as evidenced by rectifying J?V behavior on p-type substrates, and by positive photovoltage measured by surface photovoltage spectroscopy. Its close molecular relative m-dinitrophenyl exhibited poor electronic surface quality as indicated by high SiOx coverage and high surface recombination velocities (S > 3000 cm s?1). Photoelectrochemical J?V measurements of p-type Si-functionalized surfaces in contact with a high concentration (50 mM) of methyl viologen (MV2+) in aqueous media revealed VOC values that are correlated with the measured barrier heights. In contrast, low-concentration (1.5 mM) MV2+ experiments revealed significant contributions from surface recombination. Next, the electronic and (photo)electrochemical properties were studied as a function of ALD metal oxide deposition (TiO2, Al2O3) and Pt deposition. For the m-dinitrophenyl substrate, ALD deposition of both TiO2 and Al2O3 (150 °C, amorphous) decreased the surface recombination velocity. Surprisingly, this TiO2 deposition resulted in negative shifts in VOC for all surfaces (possibly ALD-TiO2 defect band effects). However, Pt deposition recovered the efficiencies beyond those lost in TiO2 deposition, affording the most positive VOC values for each substrate. Overall, this work demonstrates that (1) when carrier collection is kinetically fast, p-Si(111)?R devices are limited by thermal emission of carriers over the barrier, rather than by surface recombination. And (2) although TiO2 |Pt improves the PEC performance of all substrates, the beneficial effects of the underlying (positive) surface dipole are still realized. Lastly (3) Pt deposition is demonstrated to provide beneficial charge separation effects beyond enhancing catalytic rates.
关键词： solar fuels,interfacial dipole,atomic layer deposition (ALD),surface functionalization,band-edge modulation,photoelectrochemistry
更新于2025-09-23 15:22:29
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All-in-one photosynthetic assemblies for solar fuels
摘要： Converting solar energy into chemical fuel using an all-in-one photosynthetic assembly requires novel concept and cutting-edge technologies. Up to now, a series of new concepts have been suggested for designing of the assembly. It is thus important to examine present physics and research status of the assembly to glean the design guidelines for future devices. Here we introduce the concept of all-in-one photosynthetic assembly, which including photoelectrochemical diodes, all-in-one membranes and monolithic photovoltaic-photoelectrolysis cells. Key physical aspects are examined to identify the state-of-the-art in device design. We then discuss the device configurations, requirements and practical implications. Key features of the assemblies are also highlighted with their photosynthetic performance. Finally, a potential design that can be scalable to large area is projected for a more complete picture of the field. These concepts and their successful realization will be an important contribution towards realization of artificial photosynthesis.
关键词： Photochemical cells,All-in-one,Device,Artificial photosynthesis,Solar fuels
更新于2025-09-23 15:21:01
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Solar–gliding arc plasma reactor for carbon dioxide decomposition: Design and characterization
摘要： The conversion of low-value feedstock such as carbon dioxide (CO2) into higher-value products using renewable energy, particularly solar, can help fulfill the increasing need for fuels and chemicals while mitigating environmental emissions. A direct solar receiver-reactor fitted with a gliding arc (glidarc) electrical discharge for potentially greater efficiency and continuous operation solar thermochemical synthesis is presented. The nonequilibrium plasma inside the reactor chamber leads to increased solar energy absorption by the gas-phase feedstock, potentially enhancing chemical conversion. Moreover, the reliance on electrical energy to sustain the plasma allows compensating for fluctuations in the solar radiation input. Two solar-glidarc reactor configurations are investigated and evaluated for the decomposition of CO2 at atmospheric pressure conditions, namely: axi-radial (AXR) and reverse-vortex (RVX) flow. The former provides greater control of residence time but presents limited solar-plasma interaction; whereas the latter allows for greater interaction, but requires higher flow rates to confine the plasma, lowering the residence time. Flow paths and residence times are evaluated via Computational Fluid Dynamics (CFD) models used to guide reactor design and operation. Evaluation of the plasma volume at different reactor orientations, aimed to mimic in-field operation, show that the AXR configuration leads to a larger plasma volume compared to that by the RVX design. Net-absorption tests, aimed to assess the extent of solar-plasma interaction, showed up to 18% net-absorption of solar radiation for the RVX configuration and 7% for the AXR one, compared to 0% in the absence of plasma. The AXR configuration, despite its lower absorption of solar energy, leads to greater CO2 homogeneous gas-phase decomposition (i.e. in the absence of any catalyst), of up to 4.5%, mainly due to its flexibility in operating with lower residence times. The results indicate solar-plasma direct-receiver reactors provide a compelling approach to solar thermochemical synthesis processes.
关键词： Chemical synthesis,Radiation absorption,Solar fuels,Atmospheric pressure nonequilibrium plasma,Solar receiver-reactor
更新于2025-09-19 17:15:36
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When Does Organic Photoredox Catalysis Meet Artificial Photosynthesis?
摘要： The basics of photocatalysis are under investigation for more than a century. Contemporary science maintains an emphasis on fundamental studies, but application-oriented research in solar energy conversion, environmental remediation, light-promoted chemical synthesis and medicinal phototherapy is growing rapidly. These prospects have triggered a renaissance of the field and breath-taking progress has been made in the last decade by chemists from all major branches. Artificial photosynthesis aims to produce a renewable fuel using sunlight. This 'solar fuel' is thereby synthesized from the reduction of water or carbon dioxide, coupled to the oxidation of a substrate; typically, water to O2. The underlying endothermic multi-electron/multi-proton chemistry is relatively well understood, but the assembly of a commercially viable device remains elusive due to the 'low' market-value of chemical fuels. Photoreforming can decompose organics such as waste biomass (lignocellulose), plastics or pollutants to produce a fuel using solar irradiation. This process has overall a much-reduced thermodynamic barrier compared to overall water splitting, but suffers from a kinetically challenging reaction, insufficient solubility of polymeric substrate or low concentration of pollutants. Organic photoredox catalysis uses light to accelerate chemical reactions by well-controlled single-electron redox events. This radical chemistry approach has not only allowed for improved synthetic procedures, but also new transformations to proceed. The value-added organic products are synthesized in controlled laboratory environments, usually using LED lamps. Although photocatalysis is of growing interest to the chemical and pharmaceutical industry, large-scale processes have rarely been implemented. Medicinal chemistry develops light sensitive medication for the destruction of abnormal cells. In photodynamic therapy, the photosensitizer drug is irradiated using a defined wavelength and reacts with O2 to produce reactive oxygen species to exert phototoxicity. Achieving high quantum yields and the development of red (or near IR) light absorbers (for improved skin penetration) are common objectives with artificial photosynthesis (for optimal solar light harvesting). Although the same basics of photochemistry unite these applications, they are being developed in surprising isolation as inorganic and physical chemists focus on artificial photosynthesis, chemical engineers on photoreformation, organic chemists on photoredox catalysis, and medicinal chemists on photodynamic therapy. This divide is cemented by separating the scientists often in different institutes, teaching structures and firmly placing them in separate academic communities. This editorial is intended as a call to join forces and embrace progress in all of these areas to enable accelerated development of a more holistic science in photocatalysis. There is plenty we can learn from each other as we share mutual interests and common goals. The quickly developing pool of environmentally benign, robust, non-toxic, scalable and efficient photocatalysts for solar fuel synthesis provides vast opportunities for improved and new organic catalysis. For example, heterogeneous photocatalysts such as semiconductor powders and photoelectrochemical architectures are rarely employed in organic chemistry. Time-resolved spectroscopy can provide in-depth understanding of electron transfer dynamics and insights into organic mechanisms. Proton-coupled multi-electron and endothermic photochemistry may pave the way to currently inaccessible organic chemistry. Coupling of solar fuel synthesis to value added oxidation chemistry for bulk or even fine chemical synthesis is a largely untapped territory (Figure 1). The simultaneous production of a chemical fuel and value-added organic improves the economics in artificial photosynthesis and may accelerate market penetration for solar fuels. Understanding organic transformations and industrial processes allows the selection of meaningful alternatives to water oxidation. Clean organic oxidations with high selectivity and conversion yield are key criteria to distinguish them from the use of undesirable sacrificial electron donors. It may be true that we cannot produce enough fuel to power the planet by coupling fuel synthesis to organic chemistry, but it is nevertheless an attractive entry point for commercialisation as well as a rich intellectual playground for academic research. Photoreforming can be exploited for simultaneous fuel production and chemical synthesis from an organic waste substrate, thereby addressing the issues of renewable energy generation and sustainable chemical synthesis with environmental remediation. Agricultural and plastic waste are a valuable resource that should not go to landfills. It contains stored energy and useful chemical building blocks for chemical transformations. Photoreformation of lignocellulose and plastics has been demonstrated to provide access to clean H2 fuel as well as organic chemicals. A final question concerns the use of sunlight versus electrical (LED) irradiation and this will ultimately depend on the application. The common view is that the synthesis of organics will be performed in the laboratory using LEDs, whereas fuel production requires large land-areas and therefore sunlight. But there are plenty of alternative possibilities and scenarios to challenge this traditional view. Could the drop in renewable (solar) electricity production may ultimately make fuel synthesis with efficient LEDs possible? Why not consider swimming-pool sized flow-reactors powered by the sun for bulk chemical production or solar-concentrators for greener organic synthesis? Solar-driven chemistry can also give access to off-grid synthesis of fertilisers, medicine, and commodities in remote areas and sun-rich developing countries. Some of these suggestions may indeed appear naive, but cross-fertilisation and an open mind will ultimately provide the basis for new developments in photocatalysis.
关键词： photocatalysis,photosynthesis,organocatalysis,solar fuels,redox chemistry
更新于2025-09-19 17:15:36
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Plasmonic photocatalysis applied to solar fuels
摘要： The induction of chemical processes by plasmonic systems is a rapidly growing field with potentially many strategic applications. One of them is the transformation of solar energy into chemical fuel by the association of plasmonic metal nanoparticles (M NPs) and a semi-conductor (SC). When the localized surface plasmon resonance (LSPR) and the SC absorption do not match, one limitation of these systems is the efficiency of hot electron transfer from M NPs to SC through the Schottky barrier formed at the M NPs/SC interfaces. Here we show that high surface area 1wt.%Au/TiO2-UV100, prepared by adsorption of a NaBH4-protected 3 nm gold sol, readily catalyzes the photoreduction of carbon dioxide with water into methane under both solar and visible-only irradiations with a CH4 vs. H2 selectivity of 63%. Tuning Au NPs size and titania surface area, in particular via thermal treatments, highlights the key role of the metal dispersion and of the accessible Au-TiO2 perimeter interface on the direct SC-based solar process. The impact of Au NPs density in turn evidences the dual role of gold as co-catalyst and recombination sites for charge carriers. It is shown that the plasmon-induced process contributes up to 20% of the solar activity. The plasmon-based contribution is enhanced by a large Au NP size and a high degree of crystallinity of the SC support. By minimizing surface hydroxylation while retaining a relatively high surface area of 120 m2 g-1, pre-calcining TiO2-UV100 at 450°C leads to an optimum monometallic system in terms of activity and selectivity under both solar and visible irradiation. A state-of-the-art methane selectivity of 100% is achieved in the hot electron process.
关键词： Methane production,Gold nanoparticles,Titania,Selectivity,CO2 reduction,Hot electrons,Plasmonic photocatalysis,Solar fuels
更新于2025-09-19 17:15:36
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CO2 adsorption and photocatalytic reduction over Mg(OH)2/CuO/Cu2O under UV-Visible light to solar fuels
摘要： Powders of Mg(OH)2, CuO, and Cu2O were effectively coupled by microwave-hydrothermal method, in order to proposed bifunctional materials for both capture and photocatalytic conversion of CO2 under UV-visible light irradiation. This was done to take advantage of the high CO2 adsorption capacity of Mg(OH)2 and the good photocatalytic performance of CuO/Cu2O for CO2 reduction to solar fuels in liquid (CH3OH and HCOH) and gas phase (CH4 and CO). In order to establish correlations between the physical properties and the photocatalytic activity, the composites were characterized by XRD, XPS, UV-Vis DRS, SEM, HRTEM, N2 physisorption and photoelectrochemical techniques. According to the characterization, the synthesis method employed allowed the adequate interaction between Mg(OH)2 with CuO and Cu2O, which not inhibited the ability of Mg(OH)2 for gas adsorption. The best yield to obtain liquid fuels such as CH3OH (6 μmol g-1 h-1) and HCOH (9 μmol g-1 h-1) was obtained using 10% of CuO in the composite. The improved photocatalytic activity in liquid phase was assigned to a high CO2 adsorption and a more negative potential of conduction band. It was found that the presence of Cu2O favored the selectivity towards CH3OH production; as higher Cu+ concentration better selectivity. A reaction mechanism is discussed on the basis of combined CO2 adsorption and photocatalytic activity of the materials involved. Furthermore, it was study the photocatalytic activity in gas phase, and it was determined the presence of CO and CH4 in low concentrations (< 0.4 μmol g-1 h-1).
关键词： CuO,Solar fuels,CO2 utilization,CO2 capture,Cu2O,Copper oxides,Mg(OH)2
更新于2025-09-19 17:15:36
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Multifunctional Photocatalytic Materials for Energy || Energy band engineering of metal oxide for enhanced visible light absorption
摘要： Since the 1970s, when it was discovered that TiO2 could split water and reduce CO2 [1,2], the pursuit has continued to produce solar fuels via renewable sunlight, by mimicking photosynthesis. However, doing so remains one of the major scientific challenges. This process requires both efficient light absorption and effective charge carrier transfer for chemical reactions. For commercial applications, long-term stability is also a prerequisite. Many catalysts have been reported for this exciting process [3–6]. In practice, metal oxide semiconductors are the most abundant ones in nature, and they are more stable in a variety of harsh conditions when used as photocatalysts [7–12]. Regarding the energetic criteria, only wide band gap semiconductors (e.g., TiO2 and SrTiO3) are thermodynamically able to drive water splitting without applied external bias. However, the wide band gap of such oxides limits their light absorption within the ultraviolet region. Some oxides, such as Fe2O3 (Eg = 2.0 eV), have advantages for absorbing visible light, but suffer from high electron affinities and poor charge carrier mobility and diffusion [13–15].
关键词： Energy band engineering,photocatalysis,visible light absorption,metal oxide,solar fuels
更新于2025-09-10 09:29:36
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Photocatalytic Reduction of Bicarbonate to Formic Acid using Hierarchical ZnO Nanostructures
摘要： Zinc oxide (ZnO) is an earth abundant, non-toxic, and low-cost material that has been used widely for photocatalytic water splitting, gas sensing, and dye degradation. In this study, several ZnO structures were tested for the photochemical reduction of bicarbonate to formic acid, an intermediate to methanol, a high-octane-number fuel with higher energy density than compressed hydrogen. The different ZnO morphologies studied included micron- and nano-particulate ZnO, rods, wires, belts, and flowers. ZnO was also synthesized from the direct calcination of zinc acetate, which provided a cheap and large-scale synthesis method to produce ZnO. The photocatalytic efficiency of the synthesized ZnO was compared to commercial micron- and nano-particulate ZnO, and was proven to be just as efficient. ZnO flowers, possessing the largest surface area of 12.9 m2/g, were found to be the most efficient reaching an apparent quantum efficiency (AQE) of 10.04±0.09%, with a superior performance over commercial TiO2 (P25), a benchmark photocatalyst. This is the first study to compare different shapes and sizes of ZnO for bicarbonate reduction in an aqueous system with excellent photocatalytic performance.
关键词： solar fuels,ZnO nanostructures,zincite,bicarbonate photoreduction
更新于2025-09-10 09:29:36