Performance For CO2 Conversion Research Articles

Plasma-induced black bismuth tungstate as a photon harvester for photocatalytic carbon dioxide conversion

The Bi QDs are reduced in situ on the surface of black Bi2WO6 nanosheets using a novel plasma treatment, which shows a superior CO2 conversion performance.

Efficient Electrochemical Reduction of CO2 to CO in Ionic Liquid/Propylene Carbonate Electrolyte on Ag Electrode

The electrochemical reduction of CO2 is a promising way to recycle it to produce value-added chemicals and fuels. However, the requirement of high overpotential and the low solubility of CO2 in water severely limit their efficient conversion. To overcome these problems, in this work, a new type of electrolyte solution constituted by ionic liquids and propylene carbonate was used as the cathodic solution, to study the conversion of CO2 on an Ag electrode. The linear sweep voltammetry (LSV), Tafel characterization and electrochemical impedance spectroscopy (EIS) were used to study the catalytic effect and the mechanism of ionic liquids in electrochemical reduction of CO2. The LSV and Tafel characterization indicated that the chain length of 1-alkyl-3-methyl imidazolium cation had strong influences on the catalytic performance for CO2 conversion. The EIS analysis showed that the imidazolium cation that absorbed on the Ag electrode surface could stabilize the anion radical (CO2•−), leading to the enhanced efficiency of CO2 conversion. At last, the catalytic performance was also evaluated, and the results showed that Faradaic efficiency for CO as high as 98.5% and current density of 8.2 mA/cm2 could be achieved at −1.9 V (vs. Fc/Fc+).

Robust route to highly porous graphitic carbon nitride microtubes with preferred adsorption ability via rational design of one-dimension supramolecular precursors for efficient photocatalytic CO2 conversion

Abstract The ability to create well-ordered graphitic carbon nitride (g-C3N4) assemblies with good surface adsorption for CO2 represents an important endeavor towards achieving high photocatalytic CO2 reduction activity that yet remains a significant challenge. Herein, a simple yet robust double-solvent-induced self-assembly strategy is, for the first time, developed to yield supramolecular precursors using a single monomer for crafting one-dimensional (1D), highly porous g-C3N4 microtubes that possess remarkable photocatalytic CO2 conversion performance. Intriguingly, the introduction of water and isopropanol triggers the self-assembly of dicyandiamide under hydrothermal conditions to form a melamine-cyanaurate-like complex (MCC) composed of 1D hexagon-shaped, micron-sized crystals with outstanding thermal stability. Subsequent thermal pyrolysis converts these pillar-like crystals into 1D mesoporous g-C3N4 microtubes (denoted MCNM) comprising well-packed nano-leaf-like frameworks (i.e., hierarchical structure). Such unique microtubes are oxygen-doped g-C3N4 and mechanically stable, exhibiting improved visible-light harvesting ability, enhanced charge transfer, increased active sites, and preferred adsorption and activation for CO2, as revealed by a suite of characterization techniques. Consequently, in sharp contrast to bulk g-C3N4, the MCNM manifests a markedly improved photocatalytic activity with a CO evolution rate of 45.16 μmolh−1, reflecting an 11.0-fold enhancement and an apparent quantum efficiency of 2.55% at 420 nm. As such, the double-solvent-induced self-assembly may stand out an effective route to organized supramolecular precursors for preparing hierarchically structured g-C3N4 for efficient photocatalysis.

Porous organic polymers containing zinc porphyrin and phosphonium bromide as bifunctional catalysts for conversion of carbon dioxide

Cycloaddition reaction using CO2 as a starting material to form a cyclic carbonate has been applied to chemical fixation of CO2. In order to further increase the reaction efficiency, herein, a bifunctional catalyst (CPBrs) containing metalloporphyrin and quaternary phosphonium salt groups was prepared, and the related catalytic performance for CO2 conversion was also studied. The catalytic system possesses multiple active sites of zinc porphyrin (Lewis acids) and quaternary phosphonium bromide salts (nucleophilic reagents), which can cooperatively work together to enhance the efficiency of cycloaddition reaction. At the same time, CPBrs (CPBr-1 and CPBr-2) are microporous polymers with permanent microporous pore structure and high specific surface areas (342–370 m2 g−1). Their moderate capacities (5.76 and 8.81% at 1 bar/273 K) to capture carbon dioxide were also beneficial for CO2 conversion. The activity of the bifunctional catalyst is higher than that of the catalyst with a single component. The corresponding highest yield to catalyze cycloaddition reaction between methyl substituented propylene oxide and CO2 is up to 95% (2.5 MPa, 90 °C). What is more, the porous nature of catalysts provides the recoverability of the catalyst, and the efficiency of the catalyst CPBr-2 remains high (above 90% yield) after five catalytic recycle.

High-efficiency CuCe(rod) catalysts for CO2 hydrogenation with high Cu content

Cu catalysts have been widely used in CO2 utilization due to their low reduction temperature and excellent CO2 hydrogenation performance. It is important to well design Cu catalyst with high efficiency and durability for CO2 hydrogenation. In this work, CuCe(rod) catalysts with various Cu contents were prepared. The physicochemical properties of the CuCe(rod) catalysts were described by XRD, TEM, N2-physisorption and H2-TPR.The effect of Cu content on catalytic performance of CO2 hydrogenation with CuCe(rod) catalysts was also studied. Results showed that a high Cu content enhanced CO2 conversion. The 40CuCe(rod) catalyst exhibited the best CO2 conversion performance. At the reaction temperature of 400 °C, the CO production rate (CO2 conversion) and CO selectivity based on the 40CuCe(rod) catalyst could reach 1.69 mol/gcat/h (41.1%) and nearly 100%, respectively. The analysis of kinetic measurements revealed that the activation energy of the 40CuCe(rod) catalyst was lower than that of other catalysts with different Cu contents during a reverse water–gas shift reaction. The lower activation energy and the interface structure of Cu-Ox-Ce were closely related to CO2 hydrogenation activity and remarkable stability for 96 h with minimal loss of CO2 conversion activities.

Control of the pH for marine microalgae polycultures: A key point for CO2 fixation improvement in intensive cultures

Recently, CO2 recycling for the production of valuable microalgae has acquired substantial interest. Most studies investigating CO2 conversion efficiency in algal cultures were based on single species, although a stabilising effect of algal diversity on biomass production was recently highlighted. However, addition of CO2 into polyalgal cultures requires a careful control of pH; performance of CO2 conversion, growth and carbon biomass production are affected by pH differently, depending on the species of microalgae. This study investigates the efficiency of CO2 conversion by natural marine algal assemblage cultivated in open, land-based raceways (4.5 m3, 10 m2), working as high rate algal ponds (HRAP). Ponds were enriched with nitrogen and phosphate, pure CO2 was added and algal cultures were grown under three different fixed pH levels: pH 6, 7 and 8. The highest conversion of photosynthetically fixed CO2 into carbon biomass (40 %) was reached at pH 7, an intermediate level, due to the partial CO2 asphyxiation of algal predators (copepods, ciliates), while being under the suboptimal conditions for the development of marine amoebae. Under this pH, the theoretical maximal biological conversion of available CO2 into carbon biomass was estimated to be 60 % in naturally inoculated open ponds.

Effective Driving of Ag-Loaded and Al-Doped SrTiO3 under Irradiation at λ > 300 nm for the Photocatalytic Conversion of CO2 by H2O

Al-doped strontium titanite (Al–SrTiO3) containing numerous stepwise edges on the surface was found to exhibit an excellent performance in the photocatalytic conversion of CO2 by H2O as an electron...

B-O Bonds in Ultrathin Boron Nitride Nanosheets to Promote Photocatalytic Carbon Dioxide Conversion.

Limited by the chemical inertness of CO2 and the high dissociation energy of the C═O bond, photocatalytic CO2 conversion is highly challenging. Herein, we prepare ultrathin oxygen-modified h-BN (O/BN) nanosheets containing B-O bonds. On the O/BN surface, CO2 can be chemically captured and is bonded with the B-O bond, leading to the formation of an O-B-O bond. This new chemical bond acting as an electron-delivery channel strengthens the interaction between CO2 and the surface. Thus, the reactants can continuously obtain electrons from the surface through this channel. Therefore, the majority of gaseous CO2 directly converts into carbon active species that are detected by in situ DRIFTS over O/BN. Moreover, the activated energies of CO2 conversion are significantly reduced with the introduction of the B-O bond evidenced by DFT calculations. As a result, O/BN nanosheets present an enhanced photocatalytic CO2 conversion performance with the H2 and CO generation rates of 3.3 and 12.5 μmol g-1 h-1, respectively. This work could help in realizing the effects of nonmetal chemical bonds in the CO2 photoreduction reaction for designing efficient photocatalysts.

Novel HBD-Containing Zn (dobdc) (datz) as efficiently heterogeneous catalyst for CO2 chemical conversion under mild conditions

A novel Zn-based metal–organic framework Zn (dobdc) (datz) [Zn2(H2dobdc) (datz)2·1.5DMF] with plentiful hydrogen bond donors (HBD) groups was facilely synthesized from mixed ligands. The dual activation of metal Zn sites and HBD groups for epoxides by forming Zn–O adduct and hydrogen bonds facilitated the ring-opening of epoxide substrate, which is critical for the subsequent CO2 fixation. Also, the existence of micropores and N-rich units in Zn (dobdc) (datz) afforded affinity towards CO2, which is beneficial to further improvement on catalytic CO2 conversion performance. Satisfactorily, Zn (dobdc) (datz)/Bu4NBr system was proved efficient heterogeneous catalyst for the CO2 cycloaddition with epoxides, and 98% propylene carbonate yield was obtained under mild conditions (80 °C, 1.5 MPa and solvent-free). In addition, Zn (dobdc) (datz)/Bu4NBr exhibited remarkable versatility to different epoxides and could be completely recycled over six runs with high catalytic activity. The highly stable, easily recycle and solvent-free Zn-based MOF reported here displays eco-friendly and efficient performance to CO2 conversion.

B-Doped and NH2-functionalized SBA-15 with hydrogen bond donor groups for effective catalysis of CO2 cycloaddition to epoxides

The novel B-SBA-15-NH2 catalyst with Lewis acid–base properties and hydrogen bond donor groups exhibited good catalytic performance for CO2 conversion under metal- and solvent-free conditions.

Reverse water-gas shift in a packed bed DBD reactor: Investigation of metal-support interface towards a better understanding of plasma catalysis

Palladium-loaded ZnO (Pd/ZnO) catalyst was synthesized by co-precipitation method and evaluated for plasma-catalytic reverse water-gas shift (RWGS) reaction. A CO2 conversion of 32.5 % was achieved on “Pd/ZnO + Plasma”, and was around two times higher than that of “ZnO + Plasma” (17.3 %). Catalyst characterization by X-ray diffraction, high-resolution transmission electron microscopy, temperature-programmed reduction and quasi in situ X-ray photoelectron spectroscopy revealed the possible formation of ZnOx@PdZn (ZnOx decorated PdZn alloy) at the interface of Pd active phase and ZnO support. The role of ZnOx@PdZn in plasma-catalytic CO2 conversion was systematically investigated by plasma-excited CO2 temperature-programmed desorption and in situ Fourier transform infrared spectroscopy. It was found that ZnOx@PdZn at Pd-ZnO interface improved significantly plasma-catalytic CO2 conversion by promoting the production of bidentate carbonate and bidentate formate species. In situ Raman spectroscopy studies proved that the ZnOx@PdZn remained largely intact during the RWGS process. Our in situ spectroscopic findings thus unveil that the ZnOx@PdZn at Pd-ZnO interface favors the activation of CO2, and, consequently, leads to a higher plasma-catalytic performance for CO2 conversion.

Carbon dioxide conversion in an atmospheric pressure microwave plasma reactor: Improving efficiencies by enhancing afterglow quenching

Microwave plasma is effective for decomposing CO2, which is a major contributor to global warming. Atmospheric pressure microwave plasma is of particular interest due to its vacuum-free configuration. Here, we investigated the CO2 conversion performance of a microwave plasma system operating at atmospheric pressure. CO2 conversion efficiency and energy efficiency were measured for various CO2 flow rates and input power levels. Lower CO2 flow and higher power yielded an enhanced CO2 conversion efficiency and lower energy efficiency. The afterglow temperature in the reactor was also measured. At a specific energy input (SEI) of 7.25 eV/molecule, a temperature of 1342 K was observed 12 cm below the gas injection nozzle. To improve the efficiencies of the plasma system, we propose an afterglow quenching method with enhanced heat transfer characteristics. This was achieved using a water-cooled quenching rod inserted into the plasma reactor to cool the afterglow gas stream, thus limiting the recombination reaction of CO to form CO2. At a SEI of 7.22 eV/molecule, CO2 conversion increased from 30.1% to 36.1% with the quenching rod; at 2.46 eV/molecule, the increment of CO2 conversion efficiency was 29 %. An energy efficiency of 28.9 % was achieved using an SEI of 1.19 eV/molecule. By tracking down the heat loss to cooling water flowing through the applicator, exhaust port, and quenching rod, we determined the energy distribution from the plasma plume to the exit gas stream. The quenching rod increased the chemical enthalpy of the product gas by reducing CO recombination.

NH2-UiO-66/g-C3N4/CdTe composites for photocatalytic CO2 reduction under visible light

To boost the photocatalytic activity of NH2-UiO-66 toward CO2 under visible light, CdTe quantum dots and g-C3N4 nanocrystals were introduced to form NH2-UiO-66/g-C3N4/CdTe composites via a two-step synthetic strategy. g-C3N4 and CdTe in different visible light ranges possessed a strong absorption ability, and, thereby, greatly extended the range of photoresponsive wavelength of the composites. Mott-Schottky analysis revealed that the energy level of the conduction band of g-C3N4 and CdTe was higher than the LUMO level of NH2-UiO-66, benefiting for the photogenerated carriers separation and electron injection from g-C3N4 and CdTe to NH2-UiO-66, leading to a high concentrated Zr (iii) formation. Finally, the NH2-UiO-66/g-C3N4/CdTe composites exhibited the superior photocatalytic performance for CO2 conversion in the acetonitrile/ethanol system upon visible light irradiation (≥400 nm) with a HCOOH generation rate of 24.6 µmol g−1 h−1 that was ∼7.5 times higher than that of NH2-UiO-66 alone.

(Invited) Dilute Cu Alloying in Au Nanostructures for Highly Selective and Long-Term Stability of CO2 Reduction

Electrochemical CO2 reduction can produce value-added chemical or fuels in moderate reaction environment. For efficient CO2 reduction to a target product with high selectivity, vast research works have been carried out over a few decades. Particularly, CO2 conversion performance using Au and Ag based catalysts for CO production has reached to economically viable level according to recent techno-economic analysis [1]. In various routes to improve catalytic property, metal alloys are shown effective by tailoring intermediate binding energy of CO2 reduction reaction (CO2RR). For example, bimetallic AuCu alloys, such as AuCu, AuCu3 and Au3Cu, have shown synergetic effects which lead to higher catalytic activities (i.e. overpotential, stability) although CO selectivity is still lower than state-of-art records (over 95%) [2-4]. Herein, we demonstrate the dilute Cu alloying in Au nanostructure for highly selective CO production with long-term stability. To synthesize nanostructured Au with controlled Cu alloying, we firstly formed Cu/Au bilayers by employing the electrochemical deposition (ED) and underpotential deposition (UPD) of Cu on 200-nm-thick Au thin films on Si substrates. ED and UPD processes were conducted at applied potentials of –0.1 and 0.3 V (vs. Ag/AgCl), respectively, in 50 mM H2SO4 electrolyte with 50 mM CuSO4. We carried out electrodepositon for 10s and 60s while underpotentially deposited Cu sample were only prepared for 60s. The Cu-covered Au surfaces were then electrochemically treated for nanostructuring with the same method previously reported by our research group [5]. Specifically, we electrochemically oxidized the Cu/Au bilayers at 2.5 V (vs. RHE) for 40 minutes in 0.2 M KHCO3 solution (pH = 8.5). Then electro-reduction was sequentially followed under constant current density of –0.5 mA cm–2 for about 10 minutes in the same solution. We denote the prepared samples by Nano-ED-CuAu-10s, -60s and Nano-UPD-CuAu in accordance with the type of Cu deposition processes. Additionally, nanostructured Au without Cu was prepared for the comparison. As a result of the electrochemical treatment, nanoporous structures were formed for all samples. The heights of the nanostructures were 200, 215, 225 and 240 nm for Nano-Au, Nano-UPD-CuAu, Nano-ED-CuAu-10s and 60s. XPS investigations clearly show the appearance of Cu 2p peak and slight shift of Au 4f peak position to the higher binding energy (~0.1 eV) when Cu was incorporated in Au nanostructures. In addition, the surface concentration of Cu were found to be 2, 11 and 13% for Nano-UPD-CuAu, Nano-ED-CuAu-10s and 60s, respectively. Our nanostructured CuAu and Au exhibit low CO2RR overpotential and high selectivity for CO in CO2 saturated 0.2 M KHCO3. For instance, the selectivity of CO2RR for all electrodes is around 50 – 70% (Nano-Au : 47%, Nano-UPD-CuAu : 65% Nano-ED-CuAu-10s : 69%, Nano-ED-CuAu-60s : 57%) at low overpotential (–0.34 V (vs. RHE)). It is noted that bare Au thin film shows almost no CO production. At higher applied potential (–0.59 V), the CO selectivity increases over 90% and notably, Nano-UPD-CuAu shows almost unity CO production (~99.5%) with nearly completely suppressing H2 evolution. In addition, Cu-Au nanostructures show the remarkably improved durability as compared to nanostructured Au catalysts. Whereas the CO selectivity at –0.49 V for Nano-Au drops from 92% at 30 minutes to below 80% in about 4.5 hours, Nano-UPD-CuAu retains the same performance for about 7 hours. Surprisingly, Nano-ED-CuAu samples are stable for 12 hours showing the selective CO production over 80%. These results indicate that dilute Cu-Au alloy nanostructures can be effective to improve stability with highly selective CO production. Additionally, in the presentation, we will introduce an in-situ tailoring technique to re-active the degraded Au catalysts by utilizing Cu impurities in electrolyte during CO2 electroreduction process for robust and efficient CO2 reduction. [1] Jouny et al., Ind. Eng. Chem. Res. 57, 2165 (2018) [2] Kim et al., Nat. Commun. 5, 4948 (2014) [3] Kim et al., Appl. Catal. B, 213, 211 (2017) [4] Kim et al., ACS Energy Lett., 3, 2144 (2018) [5] Kim et al., J. Mater. Chem. A., 6, 5119 (2018)

Simultaneous methanogenesis and acetogenesis from the greenhouse carbon dioxide by an enrichment culture supplemented with zero-valent iron

Abstract The microbial reduction of CO2 into value-added products is gaining considerable attention and can play a significant role in the field of environment and energy research. A novel strategy for biotransformation of CO2 was tested with zero valent iron (ZVI) and enrichment cultures for methane and acetate production under anaerobic conditions at room temperature. The favorable performance of CO2 conversion (81.67% of conversion rate) was achieved in ZVI-amended treatments by enhanced methanogenesis and acetogenesis simultaneously. The enrichment consortium of microorganisms containing Methanosarcina spp. and Clostridiaceae was responsible for methane and acetate production, and accounted for 25.89% and ∼4.83% of CO2 conversion, respectively. Scanning electron microscopy (SEM) observation and mass balance analysis of hydrogen detected in the headspace indicated that direct electron transfer and utilization possibly occurred with these microbes, especially methanogens. Interestingly, X-ray Photoelectron Spectroscopy (XPS) confirmed carbonation mineral (FeCO3) as the major strategy of CO2 consumption under the experimental conditions. These observations collectively revealed that supplementation of ZVI can be a favorable electron donor to stimulate and accelerate the biotransformation of CO2 into methane and acetate by the enrichment culture of microorganisms, and the information presents available alternative biochemical pathways for energy recovery from greenhouse gas under anaerobic conditions.

Z-scheme Photocatalytic CO2 Conversion on Three-Dimensional BiVO4/Carbon-Coated Cu2O Nanowire Arrays under Visible Light

Cuprous oxide (Cu2O) is one of the most promising materials for photoreduction of CO2 because of its high conduction band and small band gap, which enable the production of high-potential electrons under visible-light irradiation. However, it is difficult to reduce the CO2 using a Cu2O-based photocatalyst due to fast charge recombination and low photostability. In this work, we enhanced the photocatalytic CO2 conversion activity of Cu2O by hybridization of Cu2O NWAs, carbon layers, and BiVO4 nanoparticles. By construction of a Z-scheme charge flow on a 3-D NWA structure, the BiVO4/carbon-coated Cu2O (BVO/C/Cu2O) NWAs show significantly enhanced charge separation and light harvesting property. As a result, CO formation rate of BVO/C/Cu2O was 9.4 and 4.7 times those of Cu2O mesh and Cu2O NWAs, respectively, under visible light irradiation. In addition, the material retained 98% of its initial photocatalytic CO2 conversion performance after five reaction cycles (20 h) because of the protective carbon layer a...

Advances in state-of-art valorization technologies for captured CO2 toward sustainable carbon cycle

ABSTRACTValorization of captured CO2 is an important but challenging topic since CO2 is a stable and relatively inert compound. Nonetheless, CO2 valorization technologies should be sought after, because they can offer an opportunity for the sustainable carbon cycle towards a circular economy by creating value-added products and generate revenues from CO2. This paper provides an overview of state-of-the-art valorization technologies for captured CO2, including (1) supercritical CO2 as a reactive solvent, (2) mineralization of CO2 as inorganic carbonates, (3) catalytic reduction of CO2 into organic fuel for transport, (4) transformation of CO2 to value-added chemicals, and (5) biological CO2 utilization. The principles and application, in terms of CO2 conversion performance and environmental benefits of each technology, are reviewed in detail. In addition, the perspectives and prospects of CO2 valorization technologies as a portfolio solution are provided to achieve the effective CO2 reduction while minimizing social and economic costs in the near future.

Order engineering on the lattice of intermetallic PdCu co-catalysts for boosting the photocatalytic conversion of CO2 into CH4

Order engineering has been performed on PdCu co-catalysts for enhanced photocatalytic performance in conversion of CO2 to CH4 based on the disorder–order transformation from an A1 alloy phase to a B2 intermetallic phase.

Enhanced carbon dioxide conversion to formate on a multi-functional synergistic photoelectrocatalytic interface

As one of the main greenhouse gases, the conversion of CO2 into useful chemicals is of great significance to global warming, climate change and energy supply. Herein, a multi-functional synergistic photoelectrocatalytic (PEC) interface is employed to realize enhanced PEC CO2 reduction by using intrinsic Au doped TiO2 as the light harvester, nanotube photonic crystal (NTPC) as optical channels and Cu nanoparticles (NPs) as CO2 electrocatalyst. Formic acid is produced as the main product with a selectivity of 98% and a Faraday efficiency of 82.6% under simulated sunlight illumination and an applied potential of −1.0V vs. Ag/AgCl. Its yield ratio is up to 1019.3μmolL−1cm−2 after an 8h reduction, nearly 6.3 times higher than that on the traditional TiO2 NTs. Such enhanced PEC CO2 conversion performance is due to a synergistic catalytic effect on this multi-functional interface. The extraordinary localized surface plasmon resonance sensitized by the intrinsic Au NPs expands the light absorption region to the visible region. The photonic crystal layer structure raises the multi-reflection of incident light. The electrocatalyst of Cu NPs synergistically promotes PEC activity toward CO2 reduction. The calculated enhancement factors of photonic crystal layer, intrinsic Au NPs, and Cu NPs are 813%, 91%, and 2028%, respectively. This work provides an effective approach for photocathode design to promote the efficiency of PEC CO2 conversion.

Heterojunction p-n-p Cu2O/S-TiO2/CuO: Synthesis and application to photocatalytic conversion of CO2 to methane

Photocatalytic conversion of CO2 to fuel is a topic of great current interest. The problem is a challenging one, requiring a photocorrosion-stable, industrially-scalable, broad-spectrum light absorbing semiconductor, the energy bands of which align with the CO/CO2 and H2O/O2 potentials. Herein we report the synthesis of a unique p-n-p heterojunction material architecture, Cu2O/S-doped TiO2 micro-blocks covered with CuO nanowires, using anodization and annealing processes. The photocatalytic material shows excellent performance in the photocatalytic conversion of CO2 and water vapor to methane under AM 1.5G illumination. The heterojunction material architecture exhibits a methane yield of 2.31μmolm−2h−1, a rate approximately ten times higher than TiO2 nanotube array films synthesized using similar anodization conditions. The improved performance of the heterojunctioned material architecture appears due to improved light absorption and efficient separation of the photogenerated charge.