CO2 Production Rate Research Articles

Synergetic effect of oxygen vacancies coupled with in-situ Bi clusters in Bi2WO6 for enhancing photocatalytic CO2 reduction

In order to improve photocatalytic performance, Bi2WO6 (BWO) with oxygen vacancies (Vo) and in-situ loaded Bi clusters was prepared by using mild aluminothermic reduction. From morphological and structural characterization, it can be seen that Bi clusters gradually precipitates from the surface of BWO owing to oxygen vacancies as annealing temperature increases. The photocatalyst annealed at 450 ℃ (Bi-Vo-BWO-450) demonstrates the best photocatalytic CO2 reduction performance with CO and CH4 production rate reaching 5.94 and 1.18 µmol·g−1·h−1, respectively. From experimental analyses and first principles calculation, in-situ Bi clusters exhibit the unique surface plasma resonance (SPR) effect and induce the formation of internal electric field by Schottky barrier between Bi and BWO, which enhance the light absorption of photocatalyst and improve charge separation and transfer efficiency. Meanwhile, Bi clusters act as the surface active sites to activate CO2 adsorption for reducing the rate-limiting potential barrier in photocatalytic CO2 reduction, and improve the activity of oxygen vacancies by preventing the oxygen-containing groups from being adsorbed at the oxygen defect site. This work has a clear understanding of the synergetic effect between Bi clusters and oxygen vacancies, and provides a new enlightenment into high-efficiency catalyst.

Synergism of Ultrasmall Pt Clusters and Basic La2O2CO3 Supports Boosts the Reverse Water Gas Reaction Efficiency

AbstractThe reverse water‐gas shift reaction (RWGS) has been regarded as a promising approach for fighting climate change caused by the excessive emission of the greenhouse gas CO2, but it still suffers from relatively poor low‐temperature reactivity. Herein, a high‐performance RWGS catalyst composed of ultrasmall Pt clusters (1.38 nm on average) anchored by La2O2CO3 support (PtNC/LOC), which possesses a record CO production rate of 2678 molCO molPt−1 h−1 with nearly 100% CO selectivity at 300 °C, is reported. The specific activity is nearly 1.5 and 7.9 fold higher than that of Pt single atoms and nanoparticles on La2O2CO3, respectively. More importantly, over 87.7% of the initial activity of PtNC/LOC remains after 80 h constant operation at 380 °C, firmly verifying the structural robustness. LOC support is essential, because of not only the moderate basicity that can boost the reaction efficiency but also the strong interaction with Pt species that can stabilize the ultrasmall particle size. Further investigations also point out the key role of the Pt clusters. The two key steps, CO2 adsorption, and CO desorption, individually prefer electron‐rich and electron‐deficient Pt species. Ultrasmall Pt clusters successfully integrate the unique surface states of single atoms and nanoparticles, thus achieving excellent low‐temperature RWGS performance.

Selective CO2 electrolysis to CO using isolated antimony alloyed copper

Renewable electricity-powered CO evolution from CO2 emissions is a promising first step in the sustainable production of commodity chemicals, but performing electrochemical CO2 reduction economically at scale is challenging since only noble metals, for example, gold and silver, have shown high performance for CO2-to-CO. Cu is a potential catalyst to achieve CO2 reduction to CO at the industrial scale, but the C-C coupling process on Cu significantly depletes CO* intermediates, thus limiting the CO evolution rate and producing many hydrocarbon and oxygenate mixtures. Herein, we tune the CO selectivity of Cu by alloying a second metal Sb into Cu, and report an antimony-copper single-atom alloy catalyst (Sb1Cu) of isolated Sb-Cu interfaces that catalyzes the efficient conversion of CO2-to-CO with a Faradaic efficiency over 95%. The partial current density reaches 452 mA cm−2 with approximately 91% CO Faradaic efficiency, and negligible C2+ products are observed. In situ spectroscopic measurements and theoretical simulations reason that the atomic Sb-Cu interface in Cu promotes CO2 adsorption/activation and weakens the binding strength of CO*, which ends up with enhanced CO selectivity and production rates.

Photocatalytic reduction of CO2 by two-dimensional Zn-MOF-NH2/Cu heterojunctions

The two-dimensional (2D) Zn-MOF-NH2/Cu heterojunctions were prepared via in situ photodeposition of Cu NPs on the surface of 2D Zn-MOF-NH2. The 2D Zn-MOF-NH2/Cu (1 wt%) heterojunction exhibited the excellent photocatalytic activity with a CO production rate of 0.76 μmol/h under irradiation of full spectrum light only using H2O as a hole sacrificial agent, which is 16.2 and 2.7 times that of bulk Zn-MOF-NH2 and 2D Zn-MOF-NH2 nanosheets, respectively. This work provides an insight into design of a highly efficient 2D MOFs-based photocatalysts in catalytic CO2 reduction.

Rational Construction of Metal Organic Framework Hybrid Assemblies for Visible Light-Driven CO2 Conversion

Photocatalytic reduction of CO2 to value-added chemicals is known to be a promising approach for CO2 conversion. The design and preparation of ideal photocatalysts for CO2 conversion are of pivotal significance for the sustainable development of the whole society. In this work, we integrated two functional organic linkers to prepare a novel metal organic framework (MOF) photocatalyst {[Co(9,10-bis(4-pyridyl)anthracene)0.5(bpda)]·4DMF} (Co-MOF). The existence of anthryl and amino groups leads to a wide range of visible light absorption and efficient separation of photogenerated electrons. To extend the lifetime of photogenerated electrons in the photocatalytic system, we modified Co-MOF particles onto g-C3N4. As expected, Co-MOF/g-C3N4 composites exhibited an ultrahigh selectivity (more than 97%) in the photocatalytic process, and the highest CO production rate (1824 μmol/g/h) was 7.1 and 27.2 times of Co-MOFs and g-C3N4, respectively. What's more, we also discussed the reaction mechanism of the Co-MOF/g-C3N4 photocatalytic CO2 reduction, and this work paves the pathway for designing photocatalysts with ideal CO2 reduction performance.

Temperature Response of Metabolic Activity of an Antarctic Nematode.

Because of climate change, the McMurdo Dry Valleys of Antarctica (MCM) have experienced an increase in the frequency and magnitude of summer pulse warming and surface ice and snow melting events. In response to these environmental changes, some nematode species in the MCM have experienced steady population declines over the last three decades, but Plectus murrayi, a mesophilic nematode species, has responded with a steady increase in range and abundance. To determine how P. murrayi responds to increasing temperatures, we measured metabolic heat and CO2 production rates and calculated O2 consumption rates as a function of temperature at 5 °C intervals from 5 to 50 °C. Heat, CO2 production, and O2 consumption rates increase approximately exponentially up to 40 °C, a temperature never experienced in their polar habitat. Metabolic rates decline rapidly above 40 °C and are irreversibly lost at 50 °C due to thermal stress and mortality. Caenorhabditis elegans, a much more widespread nematode that is found in more temperate environments reaches peak metabolic heat rate at just 27 °C, above which it experiences high mortality due to thermal stress. At temperatures from 10 to 40 °C, P. murrayi produces about 6 times more CO2 than the O2 it consumes, a respiratory quotient indicative of either acetogenesis or de novo lipogenesis. No potential acetogenic microbes were identified in the P. murrayi microbiome, suggesting that P. murrayi is producing increased CO2 as a byproduct of de novo lipogenesis. This phenomenon, in conjunction with increased summer temperatures in their polar habitat, will likely lead to increased demand for carbon and subsequent increases in CO2 production, population abundance, and range expansion. If such changes are not concomitant with increased carbon inputs, we predict the MCM soil ecosystems will experience dramatic declines in functional and taxonomic diversity.

Impact of hematopoietic stem cell transplantation in glycogen storage disease type Ib: A single-subject research design using 13C-glucose breath test

BackgroundGlycogen storage disease type Ib (GSD Ib) is an autosomal recessively inherited deficiency of the glucose-6-phosphate translocase (G6PT). Clinical features include a combination of a metabolic phenotype (fasting hypoglycemia, lactic acidosis, hepatomegaly) and a hematologic phenotype with neutropenia and neutrophil dysfunction. Dietary treatment involves provision of starches such as uncooked cornstarch (UCCS) and Glycosade® to provide prolonged enteral supply of glucose. Granulocyte colony-stimulating factor (G-CSF) is the treatment of choice for neutropenia. Because long-term stimulation of hematopoiesis with G-CSF causes serious complications such as splenomegaly, hypersplenism, and osteopenia; hematopoietic stem cell transplantation (HSCT) has been considered in some patients with GSD Ib to correct neutropenia and avoid G-CSF related adverse effects. Whether HSCT also has an effect on the metabolic phenotype and utilization of carbohydrate sources has not been determined. ObjectiveOur objective was to measure the utilization of starch in a patient with GSD Ib before and after HSCT using the minimally invasive 13C-glucose breath test (13C-GBT). DesignA case of GSD Ib (18y; female) underwent 13C-GBT four times: UCCS (pre-HSCT), UCCS (3, 5 months post-HSCT) and Glycosade® (6 months post-HSCT) with a dose of 80 g administered via nasogastric tube after a 4 h fast according to our patient's fasting tolerance. Breath samples were collected at baseline and every 30 min for 240 min. Rate of CO2 production was measured at 120 min using indirect calorimetry. Finger-prick blood glucose was measured using a glucometer hourly to test hypoglycemia (glucose <4 mmol/L). Biochemical and clinical data were obtained from the medical records as a post-hoc chart review. ResultsUCCS utilization was significantly higher in GSD Ib pre-HSCT, which reduced and stabilized 5 months post-HSCT. UCCS and Glycosade® utilizations were low and not different at 5 and 6 months post-HSCT. Blood glucose concentrations were not significantly different at any time point. ConclusionsFindings show that HSCT stabilized UCCS utilization, as reflected by lower and stable glucose oxidation. The results also illustrate the application of 13C-GBT to examine glucose metabolism in response to various carbohydrate sources after other treatment modalities like HSCT in GSD Ib.

Guest Editorial: Solar Energy Utilization

Guest Editorial: Solar Energy Utilization

Seasonal Change in CO2 Production Rate along Depth in a Grassland Field

Seasonal Change in CO2 Production Rate along Depth in a Grassland Field

One-step photodeposition of spatially separated CuOx and MnOx dual cocatalysts on g-C3N4 for enhanced CO2 photoreduction.

The rapid recombination of photogenerated carriers of photocatalysts greatly limits their actual application in CO2 conversion into valuable chemicals. Herein, dual CuOx and MnOx cocatalysts are decorated on g-C3N4 nanosheets via a one-step photodeposition strategy. Benefiting from the repulsion between Cu2+ and Mn2+ cations, a novel g-C3N4-based heterostructure loaded with spatially separated CuOx and MnOx nanoparticle dual cocatalysts has been successfully fabricated. Cu favors the trapping of electrons, while MnOx tends to collect holes. Moreover, the Cu2O/g-C3N4 p-n heterojunction also accelerates the charge separation. As a result, the photogenerated holes and electrons flow into and out of the photocatalyst, respectively, resulting in enhanced charge separation for achieving efficient CO2 photoreduction over CuOx/g-C3N4/MnOx. Accordingly, the optimized CuOx/g-C3N4/MnOx exhibits an improved CO production rate of 5.49 μmol g-1 h-1, which is 27.5 times higher than that of bare g-C3N4.

Investigating the interfacial properties of halide perovskite/TiOx heterostructures for versatile photocatalytic reactions under sunlight.

Heterostructures of metal halide perovskites and TiOx are efficient photocatalytic materials owing to the combination of the advantages of each compound, specifically the high absorption coefficients and long charge-carrier lifetimes of perovskites, and efficient photocatalytic activity of TiOx. However, chemical reduction of CO2 using PNC/TiOx heterostructures without organic solvents has not been reported yet. Here, we report the first solvent-free reduction of CO2 using amorphous TiOx with embedded colloidal perovskite nanocrystals (PNCs). The combination was obtained by carrying out hydrolysis of titanium butoxide (TBOT) on the PNC surface without high-temperature calcination. We proposed a mechanism involving photoexcited electrons being transferred from PNCs to TBOT, enabling photocatalytic reactions using TiOx under visible-light excitation. We demonstrated efficient visible-light-driven photocatalytic reactions at PNC/TiOx interfaces, specifically with a CO production rate of 30.43 μmol g-1 h-1 and accelerated degradation of organic pollutants under natural sunlight. Our work has provided a simple path toward both efficient CO2 reduction and photocatalytic degradation of organic dyes.

A Cu medium designed Z-scheme ZnO-Cu-CdS heterojunction photocatalyst for stable and excellent H2 evolution, methylene blue degradation, and CO2 reduction.

Solar photocatalysis has emerged as a pollution-free and inexhaustible technique that has been extensively researched in the domains of environmental remediation and energy production. Herein, we have integrated ZnO and CdS nanoparticles through Cu as a solid-state electron mediator to design a ZnO-Cu-CdS Z-scheme heterosystem via a sol-gel route and further tested this as a photocatalyst for dye degradation, H2 evolution, and CO2 reduction. Within 60 min of visible light exposure, about 97% of methylene blue (MB) is degraded with a degradation rate constant of 0.042 min-1 for the ZnO0.45Cu0.1CdS0.45 catalyst. The MB degradation with this catalyst is 84, 21, 4.8, and 2 times as high as those of ZnO, CdS, ZnO0.5CdS0.5, and Cu0.1ZnO0.9 catalysts. The ZnO-Cu-CdS catalyst manifests an H2 evolution efficiency of 5579 μmol h-1 g-1, which is 169, 41, 3.9, and 3.5 times as high as those of ZnO, CdS, ZnO0.5CdS0.5, and Cu0.1ZnO0.9 catalysts. Using H2 as a reducing agent, the CO production rate over the ZnO0.45Cu0.1CdS0.45 catalyst reaches 770 μmol h-1 g-1, which is 3 and 1.8 times higher than those of ZnO0.5CdS0.5 and Cu0.1ZnO0.9 catalysts. Besides, the optimal CH4 production rate over ZnO0.45Cu0.1CdS0.45 reaches 890 μmol h-1 g-1. The improved photocatalytic response of the ZnO-Cu-CdS catalyst is assigned to the delayed recombination of photoexcited charge carriers through a Z-scheme charge transport mode, maintaining the photocarriers with strong redox potentials and the dual role of Cu to serve as a conductive bridge to accelerate the charge transfer rate and enhance the light absorption due to its SPR phenomenon. This research offers a promising strategy for developing binary/ternary Z-scheme heterojunction photocatalytic systems for different photocatalytic applications.

Boosting photocatalytic conversion of formic acid to CO over P-doped CdS.

In this work, NaH2PO2, Na2S2O3 and CdCl2 were used to synthesize P-doped CdS samples for the photocatalytic decomposition of formic acid to CO reaction. The CO production rates and selectivity of P-doped CdS are as high as 24.5 mmol g-1 h-1 and 92.4%, in which the rate is 7 times higher than that of the pure CdS. Multiple characterizations show that the P-doping increases the specific surface area, widens the band gap and shifts the energy band position of CdS, resulting in enhanced photocatalytic activity.

Mo2TiC2 MXene-Supported Ru Clusters for Efficient Photothermal Reverse Water-Gas Shift.

Driving metal-cluster-catalyzed high-temperature chemical reactions by sunlight holds promise for the development of negative-carbon-footprint industrial catalysis, which has yet often been hindered by the poor ability of metal clusters to harvest and utilize the full spectrum of solar energy. Here, we report the preparation of Mo2TiC2 MXene-supported Ru clusters (Ru/Mo2TiC2) with pronounced broadband sunlight absorption ability and high sintering resistance. Under illumination of focused sunlight, Ru/Mo2TiC2 can catalyze the reverse water-gas shift (RWGS) reaction to produce carbon monoxide from the greenhouse gas carbon dioxide and renewable hydrogen with enhanced activity, selectivity, and stability compared to their nanoparticle counterparts. Notably, the CO production rate of MXene-supported Ru clusters reached 4.0 mol·gRu-1·h-1, which is among the best reported so far for photothermal RWGS catalysts. Detailed studies suggest that the production of methane is kinetically inhibited by the rapid desorption of CO from the surface of the Ru clusters.

Simultaneously improving the hydrophobic property and flame retardancy of aluminum hypophosphite using rare earth based coupling agent for epoxy composites

AbstractA novel hydrophobic rare earth‐based aluminum hypophosphite (AHP) was prepared using rare earth aluminate coupling agent (REA) in a ball mill with a one‐step mechanochemistry method, and used as flame retardant for epoxy resin. It has been found that RaAHP‐4 (AHP was modified by 4 wt% REA) exhibited excellent hydrophobic properties with the water contact angle of 94.58°. The effect of RaAHP‐2 (AHP was modified by 2 wt% REA) and RaAHP‐4 on the flame retardancy, thermal stability, and hydrophobic properties of EP/6RaAHP‐2 and EP/6RaAHP‐4 composites were investigated. It has been found RaAHP‐2 and RaAHP‐4 can significantly improve the flame retardant performance of EP/6RaAHP‐2 and EP/6RaAHP‐4 composites. And the peak heat release rate (PHRR) and total heat release (THR) values of EP/6RaAHP‐4 were reduced by 50.44% and 35.59% compared with pure EP, respectively. Moreover, the maximum peak value of CO production rate from EP/6RaAHP‐4 decreased by 62.64% compared with that from EP/6AHP. The excellent flame retardant effect of EP/6RaAHP‐4 composites was obtained because RaAHP‐4 changed the formation of the char residue layer during the combustion process. In comparison, the compactness, expansion degree, and carbonization quality of the char residue layer from the samples with RaAHP‐2 or RaAHP‐4 have been significantly improved, which acted as a valuable barrier for heat and mass transfer. The above results showed that the one‐step synthesis method had high potential application in the large‐scale production of hydrophobic AHP.

Tailored Persistent Radical‐containing Heterotrimetal‐Organic Framework for Boosting Efficiency of Visible/NIR Light‐driven Photocatalytic CO2 Reduction

AbstractPromoting light absorption range of photocatalysts is of great significance to improve solar light‐driven photocatalytic CO2 reduction efficiency. Herein, a new viologen‐based multicomponent heterotrimetallic metal–organic framework (MOF) [Cu3Th6(µ3‐O)4(µ3‐OH)4(cpb)12][FeIII(CN)6]6 (IHEP‐14) with an unprecedented (6, 18)‐connected she‐d topology is presented. Upon UV irradiation, this MOF undergoes ligand and iron photoreduction, and a single‐crystal‐to‐single‐crystal transformation to generate persistent radical‐containing MOF [Cu3Th6(µ3‐O)4(µ3‐OH)4(cpb•)12][FeII(CN)6]6 (IHEP‐15). This radical‐containing MOF shows excellent stability without fading after at least 2 months in air. Besides extending the photoabsorption to a wider wavelength range covering from 200 to 2,500 nm, the generation of persistent radical in IHEP‐15 also largely enhances its CO2 adsorption capacity by a factor of three due to the strong affinity between π orbital of the radical and the π system of CO2. These attributes endow IHEP‐15 with excellent visible/NIR light‐driven CO2 photoreduction activity, with CO production rates under visible and NIR irradiation of 570.3 and 209.3 µmol h−1 g−1, respectively. Notably, the latter is a record high for NIR‐induced CO production among all MOFs reported so far.

Construction of polyphosphazene-functionalized Ti3C2TX with high efficient flame retardancy for epoxy and its synergetic mechanisms

As a promising flame retardant, Titanium carbide (Ti3C2TX) MXene has shown synergetic flame retardancy with various modifying agents, especially phosphorus/nitrogen-containing flame retardants. However, the synergetic flame-retardancy mechanism of Ti3C2TX and modifying agent are unclear due to the complexity of reactions during the combustion process. Herein, polyphosphazene-functionalized Ti3C2TX nanosheets (MXene-PZN) were prepared and then added to epoxy resin (EP) to prepare the EP/MXene-PZN composites. Subsequently, the mechanical properties and the flame-retardant performance and mechanism were systematically investigated. The results showed an improved interfacial interaction and excellent compatibility of MXene-PZN nanosheets in the EP matrix, resulting in the storage modulus and tensile strength of EP/MXene-PZN-2.0 being increased by 46.5% and 68.4% respectively, as 2 wt% MXene-PZN was added into the EP matrix. Moreover, the flame-retardant tests showed that the peak heat release rate and total heat release of EP/MXene-PZN-2.0 were reduced by 44.8% and 54.8%, respectively, compared with pure EP, while 49.4% and 41.9% decrease in the peak CO production rate and the peak CO2 production rate were also achieved. Finally, focusing on the main existing forms of MXene-PZN in the EP matrix during different combustion stages, the flame-retardant mechanism of MXene-PZN functioned both in the condensed phase and gaseous phase was established. Thus, this work demonstrates a facile yet promising strategy to design efficient synergetic flame retardants.

Constructing metal-free heterophotocatalyst using two-dimensional carbon nitride sheets and violet phosphorene for highly efficient visible-light photocatalysis

Two-dimensional (2D) carbon nitride sheets (CNs) with nanoscale thickness have great potential in solar energy conversion owing to their intrinsic bandgap. However, their photocatalytic efficiency falls far below the practical requirements because the generated electron-hole pairs rapidly recombine. We construct a metal-free 2D p–n junction heterophotocatalyst from CNs and violet phosphorene (VP) using a simple electrostatic self-assembly method. The experimental results and density functional theory calculations show that the built-in electric field of the p–n junction promotes photogenerated carrier transport at the heterojunction interface, thereby promoting the separation of photogenerated electron-hole pairs. Under visible-light illumination, the visible-light photocatalytic hydrogen and CO production rates of the CNs/VP heterojunction were increased by 5.85 and 1.51 times, respectively, when compared to that of CNs. This study provides new insights into the design of metal-free heterogeneous photocatalysts with high catalytic activity.

Plasmonic Titanium Nitride/g-C3N4 with Inherent Interface Facilitates Photocatalytic CO2 Reduction

Plasmonic metal nitride is a practical alternative for plasmonic gold nanoparticles owing to its low-cost, tunable plasmonic resonance in the visible-light and near-IR region. However, an efficient charge transfer between plasmonic metal nitride nanoparticles and graphitic carbon nitride g-C3N4 through the formation of chemical bonds remains challenging. Herein, a facile strategy for the fabrication of plasmonic titanium nitride/g-C3N4 with intimate contact toward an enhanced photocatalytic CO2 reduction is proposed. The functionalization of TiN nanoparticles with amino groups enables the copolymerization with g-C3N4 precursors, offering intimate contact between them by the covalent bonds. This intimate contact could facilitate the electron transfer between TiN nanoparticles and g-C3N4. Under optimized conditions, the representative g-C3N4-2.8TiN has the highest CO production rate of ∼820 μmol g–1 h–1 with an apparent quantum yield of 3.5% at 400 nm and even 0.43% at 550 nm, which are some of the highest reported values for g-C3N4-based materials. This work offers promising opportunities to fabricate low-cost plasmonic nanoparticle/semiconductor systems for solar energy applications.

Photo-Assisted Catalytic CO2 Hydrogenation to CO with Nearly 100% Selectivity over Rh/TiO2 Catalysts

Photo-assisted catalytic CO2 hydrogenation represents a promising route to convert CO2 into value-added chemicals under mild conditions, but challenges remain in the design and development of highly active and selective catalysts. Herein, we synthesized highly efficient catalysts comprising Rh nanoparticles supported on TiO2 nanosheets for photo-assisted catalytic CO2 hydrogenation, which achieved a high CO production rate of 20.6 mmol gcat–1 h–1 (5.15 mol gRh–1 h–1) with nearly 100 % selectivity and excellent stability at 250 °C under light irradiation, outperforming most reported metal-based catalysts. X-ray photoelectron spectroscopy revealed that the electrons transfer from Rh nanoparticles to TiO2, hinting a strong interaction between Rh and the TiO2 support. Under illumination, the accumulated hot electrons on TiO2 surfaces could effectively promote the activation of CO2 molecules. In situ diffuse reflectance infrared Fourier transform spectroscopy results revealed that formate was the critical intermediate in the reverse water–gas shift reaction process, and light irradiation could effectively facilitate the activation and conversion of reactants and intermediate species, thereby improving CO production. This work provides a new strategy for the integration of solar and thermal energy for an efficient RWGS reaction under mild conditions.