Chemical Engineering Science
Volume 207,
2 November 2019
, Pages 1246-1255
Author links open overlay panel, , , ,
Abstract
The photocatalytic conversion of CO2 to renewable hydrocarbon fuels by solar energy is important in solving both energy and environmental problems. In this study, highly robust hybrid systems (H-Bi2WO6/MnP, F-Bi2WO6/MnP, and T-Bi2WO6/MnP) for visible-light reduction of CO2 to CO were developed. A Mn complex was anchored to Bi2WO6 particles via bisphosphonate functional groups. Photocatalytic CO2 reduction with this catalytic system under visible-light (λ > 400 nm) irradiation was investigated. CO was the only product, i.e., no other products were detected in the present system. The addition of water or triethylamine significantly enhanced the CO2 conversion activity of the hybrid photocatalytic system. The addition of 25% (v/v) water enhanced the photocatalytic CO2 reduction efficiency of H-Bi2WO6/MnP. A turnover number of 301 for 8 h was achieved, compared with 255 for F-Bi2WO6/MnP and 212 for T-Bi2WO6/MnP. The Mn complex played an important role in achieving highly selective conversion of CO2 to CO. A possible mechanism, namely a “Z-scheme”, for CO2 reduction is proposed. These results confirm that the H-Bi2WO6 semiconductor is an essential component in our heterogeneous hybrid system. It effectively acts as a photosensitizer, an electron reservoir, and an electron transport mediator.
Introduction
A rapid increase in the amount of CO2 in the atmosphere is causing global climate change, therefore methods for the conversion of CO2 to useful fuels for renewable energy sources have attracted considerable interest. Such conversions are important in the energy and environmental fields (Li et al., 2016, Choi et al., 2017, Gondal et al., 2017). A potential method for accomplishing such conversions is the use of photo-driven reduction of CO2 to fuels because solar energy, which is an inexhaustible source, can be used for the simultaneous reduction of CO2 emissions and production of commercially viable solar fuels (Dai et al., 2017, Jiang et al., 2017, Wang et al., 2017, Zhou et al., 2017).
Methods for the photocatalytic reduction of CO2 can be divided into two main categories: homogeneous photoreduction by a molecular catalyst and heterogeneous photoreduction by a semiconductor catalyst (Kumar et al., 2012). Homogeneous catalysis focuses on the use of transition-metal complexes. The metal complexes currently used are based on Re, Ru, and other precious metals (Wang et al., 2019). Recently, Won and co-workers developed a ternary hybrid system, which consists of a molecular Re catalyst (ReP) immobilized on dye-sensitized TiO2 nanoparticles, for the efficient photocatalysis of CO2 reduction (Won et al., 2017). This catalyst is expensive and its light response is weak. In recent years, Mn complexes have emerged as promising photocatalysts and electrocatalysts for CO2 reduction because of their high selectivity (Takeda et al., 2014, Rosser et al., 2016). These metal complexes are usually more stable than their organic counterparts and give good product selectivity. Inorganic nanomaterials can be incorporated into molecular catalysts as light absorbers (Lin et al., 2018, Liu et al., 2016a, Liu et al., 2016b). Use of a complex photosensitizer is necessary in the photocatalytic reduction of CO2 (Bian et al., 2008, Bian et al., 2009, Nakada et al., 2016).
Semiconductor-based photocatalytic materials have great potential in environmental clean-up and renewable energy applications (Shindume et al., 2019, Le et al., 2019, Pan et al., 2019, Sun et al., 2019, Sheng et al., 2019, Tian et al., 2019, Shi et al., 2019b). The use of semiconductors such as TiO2 and SiC as heterogeneous catalysts for the photochemical conversion of CO2 to a variety of carbon products such as CO, methanol, and methane has been widely studied (Wang et al., 2016). These semiconductor materials have strong light responses but weak catalytic abilities. The visible-light responses of TiO2 and other semiconductor materials are relatively weak, which further limits their potential industrial applications (Bae et al., 2007, Asi et al., 2011, Nikokavoura and Trapalis, 2017, Liu et al., 2016a, Liu et al., 2016b, Zhao et al., 2019a). Bi2WO6 has been attracting increasing attention as a photocatalyst for CO2 reduction because of its strong response to visible light (Ahsaine et al., 2016, Alderman et al., 2017, Cheng et al., 2012, Shang et al., 2009). In 2011, ultrathin and uniform Bi2WO6 square nanoplates were used in the photocatalytic reduction of CO2 to renewable hydrocarbon fuels under visible light (Zhou et al., 2011). Anion-exchanged Bi2WO6 hollow microspheres can be used in the photocatalysis of CO2 to methanol (Cheng et al., 2012). However, because of the low catalytic efficiency of Bi2WO6, its large-scale use is difficult. Highly efficient and selective reduction of CO2 is therefore still a challenge. Recently, materials with heterostructures have attracted much attention for use as photocatalysts (Zhang et al., 2017a, Zhang et al., 2017b; Hou et al., 2019).
In this study, we developed a hybrid photocatalytic system, namely Bi2WO6/MnP, for highly efficient and selective visible-light-driven CO2 reduction. Inorganic–organic binary systems give low-cost and efficient reduction of CO2 under visible light. The composite catalysts prepared in this study are more promising for practical applications than TiO2, which has a weak visible-light response, and Ru, Re, and other precious-metal complexes, which are expensive. Three composites of Bi2WO6 and MnP, i.e., H-Bi2WO6/MnP, F-Bi2WO6/MnP, and T-Bi2WO6/MnP, were used to study the effects of the composite morphology. The H-Bi2WO6/MnP composite showed high selectivity for CO (TONco = 301; TON is the turnover number) in the photoreduction of CO2 under visible-light irradiation with triethylamine (TEOA) as a sacrificial donor.
Section snippets
Preparation of Bi2WO6/MnP
All starting materials were purchased from commercial sources and used without further purification.
Crystal structures and morphologies of Bi2WO6/MnP
The NMR spectrum of MnP is shown in Fig. S1. The 1H NMR signals (500 MHz, CD3OD), i.e., δ 6.5 (dd), 7.2 (dd), and 7.9 (d), are in accordance with published reference data (Zabri et al., 2004).
Fig. 2 shows that that the XRD patterns of the Bi2WO6 samples with three morphologies are the same as those of the corresponding standards. All the diffraction peaks of the spherical cavities correspond to Bi2WO6 (JCPDS Nos. 39-0256 and 73-1126). This indicates that the synthesized semiconductor material
Conclusions
Loading with a MnP complex greatly improves the catalytic performance of a Bi2WO6 semiconductor material. The catalytic effect of the composite catalyst is more than four times higher than that of the catalytic material before MnP loading. Bi2WO6 photocatalytic reduction of CO2 is efficient and produces only the target product, i.e., CO. The catalytic effect of H-Bi2WO6/MnP at 8 h is stronger than those of F-Bi2WO6/MnP and T-Bi2WO6/MnP: TONCO (H-Bi2WO6/MnP) = 301 > TONco (F-Bi2WO6
Declaration of Competing Interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Acknowledgements
This work was supported by the Fundamental Research Funds for the Central Universities (No. 2016ZCQ03); Beijing Forestry University Outstanding Young Talent Cultivation Project (No. 2019JQ03007); Beijing Natural Science Foundation (No. 8172035); and the National Natural Science Foundation of China (No. 21872009).
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Interfacial bonding of hydroxyl-modified g-C<inf>3</inf>N<inf>4</inf> and Bi<inf>2</inf>O<inf>2</inf>CO<inf>3</inf> toward boosted CO<inf>2</inf> photoreduction: Insights into the key role of OH groups
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Citation Excerpt :
The global climate change caused by the increase in carbon dioxide emissions from human industrial activities has aroused widespread concern [1], and the use of solar-driven methods to convert CO2 into useful products, such as CO, CH4, and CH3OH, has attracted great interest [2].
The development of heterogeneous photocatalysts with superior photogenerated charge separation and CO2 activation is a key challenge for artificial photosynthesis. Herein, novel hydroxyl-modified g-C3N4/flower-like Bi2O2CO3 composites (OH-CN/BOC) with covalently bonded heterointerfaces were fabricated through a direct mechanical mixing approach. The bonded samples exhibited remarkable CO2 photoreduction activity under visible light. The CO production rate of the optimized sample was 91.8, 18.2, 8.6, and 6.1 times greater than those of BOC, CN, OH-CN, and CN/BOC, respectively, reaching 26.69μmolg-1h−1; and it remained stable after four cycles. The experimental and DFT studies reveal that the introduction of OH groups on CN leads to the chemical bonding of CN and BOC, induces stable surface oxygen vacancies (OVs) on BOC, and enhances the interaction between the catalyst with CO2 and H2O molecules, hence greatly improving the CO2 photoreduction activity of OH-CN/BOC. This work provides new insights and potential strategies for constructing high-quality interfacial heterojunctions with strong chemical bonds to facilitate the photocatalytic performance.
Polyethyleneimine-reinforced Sn/Cu foam dendritic self-supporting catalytic cathode for CO<inf>2</inf> reduction to HCOOH
2022, Chemosphere
In this work, a novel catalytic cathode of polyethyleneimine (PEI)–Sn/Cu foam with dendritic structure was prepared by electrodeposition and impregnation. It was used in the electrocatalytic reduction of CO2 to HCOOH, and its performance in this process was evaluated. At −0.97V vs. RHE, the faradaic efficiency and current density reached 92.3% and 57.1mAcm−2, respectively, in a 0.5M KHCO3 electrolyte. The HCOOH production rate reached 890.4μmolh−1cm−2, which exceeds those for most reported Sn catalysts. Density functional theory calculations showed that use of Sn/Cu foam is more conducive to HCOOH formation than use of Cu or Sn alone, and *OCHO is the main intermediate in HCOOH formation. The results of OH− adsorption experiments confirmed that the introduction of PEI enhanced the catalytic capacity of the Sn/Cu foam, stabilized CO2·− intermediates, and promoted HCOOH generation. These results will provide an attractive strategy for developing efficient catalysts with excellent activities and stabilities for CO2 electroreduction.
Surface oxygen vacancy and graphene quantum dots co-modified Bi<inf>2</inf>WO<inf>6</inf> toward highly efficient photocatalytic reduction of CO<inf>2</inf>
2022, Applied Catalysis B: Environmental
Citation Excerpt :
Surface oxygen vacancy is a promising method to accelerate charge separation. The introduction of surface Vo can lead to some prominent advantages, such as tuning band structure and modifying surface chemical states [11,12]. Li et al. [13] fabricated three different TiO2 nanomaterials with the surface, surface/bulk, and bulk oxygen vacancies.
(Video) New Heterogeneous Photocatalysts Designed for Water Oxidation and CO2 ReductionWeak light-harvesting capability and low electron-hole separation efficiency remain significant problems unresolved in the design of high-efficient photocatalyst. This work designed and prepared a surface oxygen vacancy (Vo) and graphene quantum dots (GQDs) co-modified Bi2WO6 (GQDs/BWO6−x). It exhibited enhanced photocatalytic conversion of CO2 to CO with a yield of 43.9 μmol·g−1·h−1, which is 1.7-fold higher than Bi2WO6 (BWO). The photogenerated electrons over GQDs/BWO6−x had a longer average fluorescence lifetime (3.3ns) than BWO (2.7ns), implying a high electron-hole separation efficiency. The DFT calculation results revealed that the electrons in GQDs/BWO6−x flow from the Vo-remote atoms to the Vo-neighboring atoms instead of confining in the GQDs molecules. Easy transformation of *COOH to *CO, a rate-limiting step, was suggested by an energy barrier calculation result (0.16eV for GQDs/BWO6−x, 1.12eV for BWO).
Efficient photocatalytic toluene selective oxidation over Cs<inf>3</inf>Bi<inf>1.8</inf>Sb<inf>0.2</inf>Br<inf>9</inf> Nanosheets: Enhanced charge carriers generation and C–H bond dissociation
2022, Chemical Engineering Science
Citation Excerpt :
To address this issue, replacing traditional thermocatalysis with photocatalysis might be a solution because the latter is always conducted under mild conditions (Li, et al., 2020; Yin, et al., 2018). By virtue of stability and ease of separation, several heterogeneous photocatalytic systems based on metal oxides and metal sulfides attracted extensive attention (Zhang et al., 2019a; Pan, et al., 2021). Nevertheless, hampered by poor conversion efficiency due to limited optical absorption windows, low charge separation efficiency and the limited capacity for C(sp3)–H bond dissociation, the performance of these photocatalysts are far from ideal (Li, et al., 2016; Chen, et al., 2019a; Wang, et al., 2020).
Inert C–H bonds activation at room temperature has been regarded as the control step in photocatalytic generation of valuable products from hydrocarbons. Herein, lead-free perovskite Cs3Bi1.8Sb0.2Br9 nanosheets with a proper amount of Sb in Cs3Bi2Br9 not only improves optical absorption due to anomalous band gap behavior, but also promotes the generation of holes (h+). The convergence of h+ on the surface of Cs3Bi1.8Sb0.2Br9 is crucial for the dissociation of toluene C(sp3)–H bond, which was proved by the density functional theory calculation and isotopic labelling results. The excellent activity in photocatalytic selective oxidation of toluene with a conversion rate of 5.83mmolg−1h−1 under visible light is the highest ever achieved. This work sheds light on the modification of halide perovskites through the regulation of B-site cations for photocatalytic applications.
Visible-light-driven CO<inf>2</inf> reduction with g-C<inf>3</inf>N<inf>4</inf>-based composite: Enhancing the activity of manganese catalysts
2021, Chemical Engineering Science
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The main reason for the improved photocatalytic activity of Mn complexes is that the synergistic effect between g-C3N4 and an Mn complex promotes effective separation of photogenerated electrons and holes (Yang et al., 2020; Vesali-Kermani et al., 2020). Some studies have shown that addition of a Mn complex effectively prevents recombination of charge carriers and improves the catalytic ability (Ma et al., 2020; Zhang et al., 2019; Zhang et al., 2019; Vesali-Kermani et al., 2020). g-C3N4 is converted to the excited state by light excitation.
A heterogeneous photocatalytic system that consists of a manganese complex and g-C3N4, which mainly act as the catalytic and light-harvesting units, respectively, was developed for the reduction of CO2 to CO. The anchoring group (carboxyl) and the structure of g-C3N4 promote electron transfer from g-C3N4 to the manganese unit and strengthen electronic interactions between the two units. The photocatalytic properties and stability of a tricarbonyl Mn bipyridyl complex were significantly enhanced by anchoring on a g-C3N4 support. The turnover number for CO formation reached 75.7 under the optimal reaction conditions. This photocatalytic system is environmentally friendly and sustainable, and will stimulate the development of potential photocatalytic CO2 transformation methods that use solar energy.
Hybrid photocatalytic systems comprising a manganese complex anchored on g-C<inf>3</inf>N<inf>4</inf> for efficient visible-light photoreduction of CO<inf>2</inf>
2020, Inorganic Chemistry Communications
Citation Excerpt :
Fig. 9 shows a possible mechanism for the visible-light catalytic reduction of CO2 by the as-synthesized g-C3N4/MnP composite catalyst. Under light irradiation, the electron transfer pathway of g-C3N4/MnP can follow a “Z-scheme” to achieve efficient CO2 reduction [23,24]. When the g-C3N4 surface is irradiated with light, the energy of the absorbed light is higher than the band gap energy.
Inorganic–organic composites are triggering an increasing interest in the photocatalytic reduction of CO2 due to its stability and high efficiency. In this study, the reflux condensation method was used to synthesize 2,2-bipyridine-4,4-bisphosphonic acid tricarbonyl manganese bromide complex (MnP), which was then anchored onto g-C3N4 via a facile self-assembly method. The resulting g-C3N4/MnP composites catalysts exhibited efficient photocatalytic reduction of CO2 under visible light irradiation. Moreover, the yield of CO of g-C3N4/MnP catalyst was 5 times more compared with pure g-C3N4 catalyst. Additionally, the only product of catalytic reduction of CO2 was CO. These results were attributed to that the Mn complex played important role in the photocatalytic reduction of CO2 to CO by the composite catalyst. An integrated “Z-scheme” mechanism was proposed for CO2 reduction using the g-C3N4/MnP system. This hybrid photocatalyst system has good application prospects in the field of photocatalysis owing to its environmental friendliness and strong visible- light absorption.
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FAQs
Which photocatalyst is best for CO2 reduction? ›
| photocatalyst | light source | reaction medium |
|---|---|---|
| TiO2 (anatase:brukite) | solar | CO2 and H2O |
| P25 (anatase–rutile) | solar | CO2 and H2O |
| CuO–TiO2–xNx | solar | CO2 and H2O |
| α-Fe2O3/Cu2O | visible | CO2 and H2O |
During the process of CO2 photoreduction with H2O, photo-illumination of the catalyst surface induces the generation of electron-hole (e– –h+)pairs in TiO2. The excited electrons in the conduction band (CB) of TiO2 could migrate to the surface and reduce CO2 to solar fuels (e.g., CO, CH4, CH3OH, HCOOH).
How efficient could photocatalytic CO2 reduction with H2O into solar fuels be? ›Efficiency limit of photocatalytic reduction of CO2 with H2O into CH3OH is 46.7%.
What materials are photocatalytic CO2 reduction? ›- Adsorption.
- Carbon Monoxide.
- Graphene.
- Methanol.
- Perovskite.
- CO2 Conversion.
- Carbon Dioxide Reduction.
- Nanosheet.
Although photocatalysis is an advanced and effective technology, there are some problems related to the photocatalyst materials, such as: Most of the semiconductor materials are not visible light active or show poor activity. High band gap energy. Fast electron-hole (e−/h+) pair recombination rate.
What is the most efficient CO2 capture? ›Oxyfuel combustion capture is the most efficient carbon capture technology, with the ability to capture 100% of carbon emissions.
Which material can be used for photocatalytic reaction? ›Several materials like titanium dioxide (TiO2), zinc oxide (ZnO), tin oxide (SnO2), tungsten oxide (WO3), cadmium sulfide (CdS), ZnS, CdSe, WS2, MoS2, and so on. are used as photocatalysts (Duan et al., 2012; Yue et al., 2017).
What are the advantages of photocatalytic process? ›Photocatalysis has many advantages and applications. It is cost-effective and easy to use for producing energy, removing environmental pollution, and reducing CO2. A photocatalytic reaction is prompted by absorption of light on a solid material.
What are the steps of photocatalysis? ›(I) light absorption to generate electron-hole pairs; (II) separation of excited charges; (III) transfer of electrons and holes to the surface of photocatalysts; (III′) recombination of electrons and holes; (IV) utilization of charges on the surface for redox reactions.
How much CO2 does a solar panel reduce per kwh? ›There have been many studies on the carbon footprint of solar panels with varying results. The Intergovernmental Panel on Climate Change (IPCC) found the median value among peer-reviewed studies for life-cycle emissions for rooftop solar is 41 grams of CO2 equivalent per kilowatt hour of electricity produced.
What is the problem with photocatalytic water splitting? ›
thermodynamics, sluggish kinetics, dissolved oxygen, backward reaction, and side reaction make photocatalytic overall water splitting enormously difficult. These obstacles must be overcome to achieve efficiency in photocatalytic overall water splitting.
How efficient is photocatalytic water splitting? ›Including light from the UV to the visible (to 600 nm) results in a maximum theoretical STH efficiency of 17.8%, while up to 800 nm results in >35% (using a single semiconductor).
What is the best material for CO2 reduction? ›CU BCT is the most well known catalyst for CO2 Reduction.
Why titanium dioxide is used for photocatalytic? ›Currently, titanium dioxide (TiO2) has gained great attention as a promising photocatalyst due to its beneficial properties among the other photocatalysts, such as excellent optical and electronic properties, high chemical stability, low cost, non-toxicity, and eco-friendliness.
What are the new materials for CO2 capture? ›This issue highlights some promising new materials for CO2 capture, such as ionic liquids, DAC sorbents, membranes, and solid borohydrides, as well as new approaches for accelerated design of such materials based on machine learning.
What is the difference between photocatalytic and photocatalysis? ›The term photocatalyst is a combination of two words: photo related to photon and catalyst, which is a substance altering the reaction rate in its presence. Therefore, photocatalysts are materials that change the rate of a chemical reaction on exposure to light. This phenomenon is known as photocatalysis.
What is the lifetime of photocatalyst? ›To characterize the lifetime of the photocatalyst, we applied g MO/g TiO2. Approximately 1.12 g of MO was destroyed in the presence of 2.16 g of photocatalyst before complete catalyst deactivation. The lifetime of the photocatalyst was 0.52 g MO/g TiO2.
Does photocatalysis produce ozone? ›Does Photocatalytic Oxidation Create Ozone? PCO does not emit harmful substances that might harm the ozone layer nor does it produce ozone. The photocatalytic oxidation technology uses nanoparticle science to destroy pathogens causing respiratory diseases.
What is the latest technology for CO2 capture? ›1. Direct air capture with balloons: High Hopes. Direct air capture (DAC) is a process that removes CO2 that's already present in the atmosphere. It's an energy-intensive process that includes capturing, heating, and compressing carbon and, as a result, is expensive to operate.
Who is the No 1 emitter of CO2? ›China was the biggest emitter of carbon dioxide (CO₂) emissions in 2021, accounting for nearly 31 percent of the global emissions.
What is the cheapest method of carbon capture? ›
The PNNL system is cheaper than other carbon capture systems because its it operates with 2 percent water, as opposed to as much as 70 percent water, which is the upper boundary for previous and similar carbon capture technologies.
Which solvent is best for photocatalysis? ›Thus, an organic solvent such as acetonitrile is often used in photocatalytic oxidation reactions.
What is the most common catalyst used in the field of photocatalysis? ›So, the correct answer is 'Titanium oxide'.
How do you make a photocatalyst? ›The different methods for photocatalyst preparation include sol-gel, coprecipitation, hydrothermal, solvothermal, sonochemical, chemical vapour deposition, etc. Sol-gel is one of the most commonly used methods for the preparation of photocatalyst by solidifaction from their precursor solution.
What is the difference between photocatalytic and photovoltaic? ›That means Photovoltaic is the conversion of light in electricity, produced by chemical action in a battery. Whist, Photocatalyst stands for usage of the light to accelerate a chemical reaction. Semiconductors are the materials, which possess conductivity higher than the insulator but lower than the conductor.
What is the difference between photocatalytic and Photodegradation? ›But, there are not much differences: Photocatalysis: is the science that involves use of both catalysts and light. Photo-catalytic degradation: Is a specific application of photocatalysis. Specifically in the case of degradation of contaminants or pollutants (generally in the liquid phase).
What is the effect of light intensity on photocatalytic degradation? ›At low light intensities (0–20 mW/cm 2 ), the rate of photocatalytic degradation is proportional directly with light intensity (first order). b. At high light intensities (25 mW/cm 2 ), the rate of photocatalytic degradation is proportional directly with the square root of the light intensity (half order).
Which light source is visible for photocatalysis? ›Photocatalysis light sources summary
– Sirius-300P-F focus on simulated sunlight of visible light, – Sirius-300P-UV has strong continuous output within 200-400 and focus on applications of high UV requirements.
Ultraviolet LED (UVLEDs) are mainly employed for the photocatalytic degradation of organic pollutants present in air and water. Recent findings have shown that visible LEDs, like blue, red, green, and white, can also be used for photocatalytic applications.
How much CO2 does it take to produce 1 kWh? ›We calculate emissions from electricity generation with the EPA's eGRID emission factors based on 2020 data published in 2022, using the US average electricity source emissions of 0.818 lbs CO2e per kWh (0.371 kgs CO2e per kWh).
How do you convert kWh to CO2 emissions? ›
For electricity, the calculation will be 15,000kWh x 0.21233kgCO2e ÷ 1,000 = 3.2tCO2e. For natural gas, the calculation will be 20,000kWh x 0.18316kgCO2e ÷ 1,000 = 3.7tCO2e. For the supply of water, the calculation will be 500m3 x 0.149kgCO2e ÷ 1,000 = 0.1tCO2e.
How much CO2 does it take to make a kWh? ›| Electricity generation | ||
|---|---|---|
| million kWh | pounds per kWh | |
| Coal | 897,885 | 2.26 |
| Natural gas | 1,579,361 | 0.97 |
| Petroleum | 19,176 | 2.44 |
The application of photocatalysts such as TiO2 and ZnO is limited by the fact that ultraviolet (UV) activation is needed (the bandgap energy is about 3.2 eV, and this means that less than 5% of the solar spectrum has sufficient energy to activate the photocatalyst) and by the fast recombination rate of the electron– ...
What is the best photocatalyst for water splitting? ›Rutile and anatase TiO2 are the most used polymorphs for photocatalytic water splitting; nevertheless, some attempts with amorphous TiO2 (aTiO2) have been made as shown in Figure 2.
What are the challenges of photocatalysis? ›Several factors, including charge-carrier recombination, interfacial charge transfer inhibition, degradation efficiency, and charge separation, reduce the effectiveness of photocatalysis process when exposed to the visible spectrum [138] . One of the prominent challenges emphasized is low hydrogen storage [83]. ...
What is the most efficient water splitting? ›Photoelectrochemical water splitting
Using electricity produced by photovoltaic systems potentially offers the cleanest way to produce hydrogen, other than nuclear, wind, geothermal, and hydroelectric.
In this regard, graphene, modified graphene, tin based metal chalcogenides and MXene are used as co-catalysts (which are electron acceptors or mediators) to separate the photo-excited charges efficiently in photocatalytic water splitting and CO2 reduction owing to their 2D layered structure and low electrical ...
Which catalyst is used in photocatalytic water splitting? ›Water Oxidation Catalysts
Titanium dioxide (TiO2) is the earliest developed semiconductor photocatalyst for photo(electro)catalytic water splitting. TiO2 has three common polymorphs, including anatase, rutile and brookite, each of which contains TiO6 octahedra.
On a weight basis, as shown in Figure 1, acetone exhibits the greatest ability to absorb CO2 due to its low molar mass (58.08 g·mol−1) and inclusion of a CO2-philic carbonyl group.
What absorbs CO2 fastest? ›The key to dissolving carbon dioxide is temperature. Cold water is better at dissolving and absorbing gasses like CO2 compared to warmer water, which is why a large amount of it gets dissolved in the ocean's chilliest waters, according to the report.
Which compound absorbs CO2 the most? ›
Potassium hydroxide absorbs carbon dioxide from the atmosphere.
Why not to use titanium dioxide? ›Health Concerns
The International Agency for Research on Cancer designates titanium dioxide (TiO2) as a carcinogen, largely due to studies that have found increased lung cancers due to inhalation exposure in animals.
Semiconductor nanoparticles are best suitable photo-catalyst for photocatalytic application due to wide band and remarkable catalytic application, especially their band gap in visible region make them suitable for photocatalytic application (Liqiang et al., 2006, Marschall, 2014) Polymeric nanoparticles another ...
What is the difference between TiO2 and TiO2 nanoparticles? ›Unlike larger TiO 2 particles, TiO 2 nanoparticles are transparent rather than white. Ultraviolet absorption characteristics are dependent from the crystal size of titanium dioxide and ultrafine particles has strong absorption against both ultraviolet-A (320-400 nm) and ultraviolet-B (280-320 nm) radiation.
What is a simple cheap material for carbon capture? ›The material is made from aluminum hydroxide and formic acid, two commodity chemicals that are inexpensive, widely available, and relatively easy to work with. The Science Advances study found that aluminum formate is especially effective at capturing CO2 molecules.
What are three main carbon capture technologies? ›They fall into three categories: post-combustion carbon capture (the primary method used in existing power plants), pre-combustion carbon capture (largely used in industrial processes), and oxy-fuel combustion systems.
What absorbs CO2 the best? ›A carbon sink absorbs carbon dioxide from the atmosphere. The ocean, soil and forests are the world's largest carbon sinks.
What is the best solution to reduce CO2? ›- Consume local and seasonal products (forget strawberries in winter)
- Limit meat consumption, especially beef.
- Select fish from sustainable fishing.
- Bring reusable shopping bags and avoid products with excessive plastic packaging.
- Make sure to buy only what you need, to avoid waste.
CFCMS is the best carbon-based adsorbent material for CO2 adsorption, exhibiting a high affinity for CO2 relative to conventional carbon-based adsorbents (Burchell et al.
Is nano ZrO2 a better photocatalyst than nano TiO2 for degradation of plastics? ›In both treatment conditions, it was found that there is a significant difference in the degradation of plastics and ZrO2 nanoparticle suspension treated polyethylene and polypropylene showed higher degradation than the TiO2 nanoparticle suspension treated samples at 95% confidence levels.
What mineral absorbs CO2? ›
Olivine (n.): a magnesium-iron silicate that absorbs carbon dioxide from the air. Humans have been trying to save beaches for decades.
Do air purifiers remove CO2? ›No. They do not remove carbon dioxide (CO2). Almost all air purifiers are designed to capture some combination of particles and toxic gasses, but CO2 can't be captured by the same filters that capture other gaseous air pollution. Only ventilation removes CO2.
What are the disadvantages of adsorption for CO2 capture? ›CO2 CAPTURE BY ADSORPTION
Because aqueous amine absorption processes exhibit some disadvantages such as low contact area between gas and liquid, low CO2 loading, and severe absorbent corrosion, solid adsorption process may be an alternative to achieve the CO2 capture purpose.
Carbon dioxide is an acid gas, which is easier to adsorb on the basic sites of metal oxides. Therefore, metal oxide adsorbents have high adsorption capacity, good selectivity, vast sources, and low cost.
What material can capture CO2? ›Alkaline sorbents such as lithium hydroxide (LiOH) have been used for the removal of CO2 at low concentration from air (<1%), in spacecraft. Zeolites, silica gels, activated carbons, amine-supported sorbents, and MOFs are some of the sorbents currently used in carbon capture applications.
What is the most widely used photocatalyst? ›Currently, titanium dioxide (TiO2) has gained great attention as a promising photocatalyst due to its beneficial properties among the other photocatalysts, such as excellent optical and electronic properties, high chemical stability, low cost, non-toxicity, and eco-friendliness.