CO Yield Research Articles

Polyoxometalates-Mediated Selectivity in Pt Single-Atoms on Ceria for Environmental Catalysis.

Optimizing the reactivity and selectivity of single-atom catalysts (SACs) remains a crucial yet challenging issue in heterogeneous catalysis. This study demonstrates selective catalysis facilitated by a polyoxometalates-mediated electronic interaction (PMEI) in a Pt single-atom catalyst supported on CeO2 modified with Keggin-type phosphotungstate acid (HPW), labeled as Pt1/CeO2-HPW. The PMEI effect originates from the unique arrangement of isolated Pt atoms and HPW clusters on CeO2 surface. Electrons are transferred from ceria support to the electrophilic tungsten in HPW clusters, and subsequently, Pt atoms donate electrons to the now electron-deficient ceria. This phenomenon enhances the positive charge of Pt atoms, moderating O2 activation and limiting lattice oxygen mobility compared to the conventional Pt1/CeO2 catalyst. The resulting electronic structure of Pt combined with the strong and local acidic environment of HPW on Pt1/CeO2-HPW leads to improved degradation of NH3, N2 selectivity in the NO conversion, and CO2 yield when inputting volatile organic compounds. This study sheds the light on the design of SACs with balanced reactivity and selectivity for environmental catalysis applications.

Biphase TiO2\\Zn-tetracarboxy-phthalocyanine twin S-scheme heterojunction nanowires with efficient charge transfer and CO2 photocatalytic conversion

Constructing heterojunction photocatalysts with proper charge transfer channels has been confirmed to be a promising strategy for CO2 photoreduction into chemical fuels. However, promoting photoinduced charge separation in traditional heterojunction catalysts still remains a big obstacle for practical applications. In this work, the TiO2(B)-Anatase\\ZnTcPc twin S-scheme heterojunctions are designed and constructed by loading Zn (II) tetracarboxy phthalocyanine (ZnTcPc) on the prepared TiO2(B)-Anatase biphase TiO2 nanowires by self-assemble strategy. The TiO2(B)-Anatase\\ZnTcPc twin S-scheme heterojunctions effectively promote charge transport across the multi-heterointerfaces and enhance visible light absorption and CO2 adsorption. Thus the optimized hybrid photocatalyst exhibits a remarkable photocatalytic CO2 reduction performance, and the CO yield reaches 237.8μmol g−1h−1. The CO2 photoreduction mechanism and charge transfer properties in the twin S-scheme heterojunction are also investigated and characterized. This research offers a viable approach to enhancing the heterojunction system for excellent photocatalytic performance.

Multi-species defect engineering synergistic localized surface plasmon resonance boosting photocatalytic CO2 reduction

Inadequate charge carrier kinetics and a scarcity of active sites still challenge photocatalytic CO2 reduction reaction (CO2RR). We exploit the synergy between multi-species defect engineering and the localized surface plasmon resonance (LSPR) effect in Bi/BiV1-mO4-m to address these limitations. Theoretical calculations show that V and O defects collectively modulate the work function of BiVO4, which induces hot electrons to transfer from Bi nanoparticles to BiV1-mO4-m. These electrons are then captured by O defects, confirmed by femtosecond transient absorption spectroscopy. Electron density is significantly increased at the O defects, enhancing CO2 adsorption and establishing it as a new reaction site. Bi/BiV1-mO4-m achieves photocatalytic CO2RR in pure water; Bi/BiV1-mO4-m achieves direct solar-driven photocatalytic CO2RR with a CO yield of 501 μmol/g/h under concentrated sunlight.

Ni-Doped Pr0.7Ba0.3MnO3-δ Cathodes for Enhancing Electrolysis of CO2 in Solid Oxide Electrolytic Cells.

Solid Oxide Electrolysis Cells (SOECs) can electro-reduce carbon dioxide to carbon monoxide, which not only effectively utilizes greenhouse gases, but also converts excess electrical energy into chemical energy. Perovskite-based oxides with exsolved metal nanoparticles are promising cathode materials for direct electrocatalytic reduction of CO2 through SOECs, and have thus received increasing attention. In this work, we doped Pr0.7Ba0.3MnO3-δ at the B site, and after reduction treatment, metal nanoparticles exsolved and precipitated on the surface of the cathode material, thereby establishing a stable metal-oxide interface structure and significantly improving the electrocatalytic activity of the SOEC cathode materials. Through research, among the Pr0.7Ba0.3Mn1-xNixO3-δ (PBMNx = 0-1) cathode materials, it has been found that the Pr0.7Ba0.3Mn0.9Ni0.1O3-δ (PBMN0.1) electrode material exhibits greater catalytic activity, with a CO yield of 5.36 mL min-1 cm-2 and a Faraday current efficiency of ~99%. After 100 h of long-term testing, the current can still remain stable and there is no significant change in performance. Therefore, the design of this interface has increasing potential for development.

Experimental study on co-gasification of cellulose and high-density polyethylene with CO2

Co-gasification of biomass and waste plastic with CO2 presents an effective strategy for integrating biomass conversion, waste utilization and carbon recycling. In this study, the co-gasification of cellulose and high-density polyethylene with CO2 was investigated experimentally. The effects of mixing ratio and temperature on co-gasification characteristics, including gas yield, product gas composition, lower heating value of syngas and gasification efficiency, were comprehensively evaluated. Additionally, the interaction between cellulose and high-density polyethylene was analyzed. The results suggested that increasing the polyethylene content in feedstock resulted in decreased yields of H2 and CO, increased CH4 yield, increased lower heating value of syngas and reduced gasification efficiency. The interaction between cellulose and high-density polyethylene enhanced the gas yield, with the most significant effect at 40 % polyethylene content. In the range of 900 °C–1000 °C, increasing the temperature resulted in increased gas yield, reduced lower heating value of syngas and increased gasification efficiency. The positive interaction between cellulose and high-density polyethylene on gas yield was more significant at higher temperatures. This work shed light on reaction characteristics for co-gasification of biomass and high-density polyethylene with CO2, laying the foundation for the design and application of this technology.

Synergy Effect of High K-Low Ca-High Si Biomass Ash Model System on Syngas Production and Reactivity Characteristics during Petroleum Coke Steam Gasification

The synergy effect of high K-low Ca-high Si biomass ash-based model system (BAMS) on the synthesis gas output and reaction characteristics of petroleum coke (PC) steam gasification process was studied using three biomass ash (BA) components, KCl, SiO2, and CaCO3, which were used as the model compounds. In the ternary model system, the steam gasification experiment of PC was conducted using a fixed bed reactor and gas phase chromatography. The synergistic effects of binary and ternary components in the ternary model system on the gasification of PC were obtained. These investigations were based on the data from the gas analysis and examined the gasification reaction process, syngas release behavior, and reaction characteristics. This study examined the effects of binary and ternary components in the ternary model system on the evolution of semi-char structure during PC gasification. This correlation revealed the synergistic effect of the model system on PC gasification. Scanning electron microscope (SEM) and Raman spectroscopy were used to characterize the structure and surface microstructure of the gasification semi-char. The results showed that the yields of different gases in the ternary model system were in H2 > CO > CO2. Compared with single PC gasification, the yields of H2, CO, syngas, and carbon conversion were increased by 29.42 mmol/g, 20.40 mmol/g, 56.68 mmol/g, and 0.35, respectively. All other components in the ternary model system with high K-low Ca-high Si demonstrated catalytic effect, except for SiO2 and the Ca-Si system, which showed inhibitory effects on syngas release and reaction features. Integrating SEM and Raman spectroscopic analyses, it was elucidated that CaCO3 and KCl diminished the degree of graphitization in semi-char through interactions with the carbonaceous matrix. This phenomenon facilitated the gasification process and exhibited a synergistic effect. Secondly, SiO2 will react with CaCO3 and KCl, producing inert silicates and inactivating these compounds, leading to the decline of catalysis.

Performance of a novel CLOU oxygen carrier (CuO/ZrO2/TiO2/MgO) in the combustion of high-rank coal: Anthracite and bituminous

Coal is the largest contributor to global CO2 emissions, and current reserves are projected to last approximately 150 years, with 71.6 % being high-rank coals (anthracite and bituminous). Chemical looping combustion is an economical CO2 capture method that uses oxygen carrier materials to supply oxygen for combustion. Copper is the most reactive due to its oxygen uncoupling capability, though it has poor stability. In our research, we developed a novel modified copper-based oxygen carrier with enhanced stability in oxygen uncoupling cycles by increasing the ZrO2 ratio at the expense of TiO2 to reduce phase interactions. The modified oxygen carrier (40 % CuO, 30 % ZrO2, 15 % TiO2, 15 % MgO) was used to combust bituminous and anthracite coal in a fixed-bed system. While bituminous coal had a high combustion rate, its efficiency was 63 %, yielding 18 mol/kg of CO2, compared to 90 % efficiency and 56 mol/kg CO2 for anthracite. The lower efficiency for bituminous was due to the rapid release of volatiles. Adding steam improved bituminous combustion efficiency to 75 % and CO2 yield to 21 mol/kg, with no significant change for anthracite. A blend of 25 % bituminous and 75 % anthracite showed better combustion efficiency, rate, and CO2 yield. This blend test was stable over 10 cycles, as confirmed by SEM, XRD, and BET analyses.

Decorating nitrogen-deficient crystalline g-C3N4 with Ti3C2(OH)2 for photocatalytic CO2 reduction and RhB degradation enhancement

Visible light responding photocatalytic technology has shown great potential to mitigate the greenhouse effect and global pollution issues in recent years. Herein, alkalized titanium carbide Ti3C2Tx (TCOH) is combined with nitrogen-deficient g-C3N4 (CN-Nx) by simply mixing for photocatalytic CO2 reduction and RhB degradation. TCOH replaces noble metals as a co-catalyst for CN-Nx due to its full-spectrum absorption properties and excellent conductivity, which effectively enhances the overall light absorption capacity of CN-Nx. Additionally, a large Fermi energy level difference between TCOH and CN-Nx leads to a built-in electric field forming at their interface when combined. This built-in electric field can enhance the photogenerated electron-hole pair separation and reduce the recombination rate. So the visible light utilization ranges of optimized 2TCOH-30 %/CN-N0.02 expanded from 477 nm (CN-N0.02) to 481 nm, and the average lifetimes of the photogenerated carriers is 4.37 ns, which is 2.64 times longer than CN-N0.02. Moreover, the CO yield reaches 67.55 μmol/g during photocatalytic CO2 reduction of 2TCOH-30 %/CN-N0.02, which is 4.06 and 2.54 times than 2TCOH and CN-N0.02. During the RhB degradation, 2TCOH-30 %/CN-N0.02 can remove approximately 98.3 % of RhB in 15 min, which is1.6 and 1.4 times of 2TCOH and CN-N0.02. Also, 2TCOH-30 %/CN-N0.02 shows excellent stability, the photocatalytic capacity for CO2 reduction and RhB degradation has no significant degradation after six times circles.

Pd Nanoparticle-Modified BiOBr/CdS S-Scheme Photocatalyst for Enhanced Conversion of CO2.

S-scheme heterojunction photocatalyst-coupled plasma-resonance effect can enhance the response range and absorption of light and charge transfer, and, at the same time, obtain strong redox ability, which is an effective way to improve CO2 conversion. In this work, plasma S-scheme heterojunctions of Pd/BiOBr/CdS with heterogeneous interfaces have been successfully constructed by a simple hydrothermal method. The possible reaction mechanism was proposed by in situ infrared, ultraviolet-visible spectroscopy (UV-vis), electron paramagnetic resonance (ESR), density functional theory (DFT), and electrochemical techniques. It was proved that the plasma S-scheme heterojunction can enhance the charge separation efficiency and improve the photocatalytic activity. When the loading ratio is Pd0.6-10%-BiOBr/CdS, it has the best performance, and the CO yield is 30.24 μmol/g, which is 15 and 30 times that of pure BiOBr and CdS, respectively. The results show that with the strong absorption of photon energy and the special electron transfer mode of S-scheme heterojunction, the charge can be effectively separated and transferred, and the photocatalytic activity is significantly improved. This study provides a useful strategy for charge transfer kinetics of plasma S-scheme heterojunction photocatalysts.

Plasma-catalytic dry reforming of CH4: Effects of plasma-generated species on the surface chemistry

By means of steady-state experiments and a global model, we studied the effects of plasma-generated reactive species on the surface chemistry and coking in plasma-catalytic CH4/CO2 reforming at reduced pressure (8–40 kPa). We used a hybrid ZDPlasKin-CHEMKIN model to predict the species densities over time. The detailed plasma-catalytic mechanism consists of the plasma discharge scheme, a gas-phase chemistry set and a surface mechanism. Our experimental results show that the coupling of Ni/SiO2 catalyst with plasma is more effective in CH4/CO2 activation and conversion than unpacked DBD plasma, with syngas being the main products. The highest total conversion of 16 % was achieved at 8000 V and 473 K, with corresponding CO and H2 yields of 15 % and 12 %, respectively. The reactants conversion and product selectivity are well captured by the kinetic model. Our simulation results suggest that vibrational species and radicals can accelerate the dissociative adsorption and Eley-Rideal (E-R) reactions. Path flux analysis shows that E-R reactions dominate the surface reaction pathways, which differs from thermal catalysis, indicating that the coupling of non-equilibrium plasma and catalysis can effectively shift the formation and consumption pathways of important adsorbates. For instance, our model suggests that HCOO(s) is primarily generated through the E-R reaction CO2(v) + H(s) → HCOO(s), while the hydrogenation reaction HCOO(s) + H → HCOOH(s) is the main source of HCOOH(s). Carbon deposition on the catalyst surface is primarily formed through the stepwise dehydrogenation of CH4, while the E-R reactions enhanced by plasma-generated H and O atoms dominate the consumption of carbon deposition. This work provides new insights into the effects of reactive species on the surface chemistry in plasma-catalytic CH4/CO2 reforming.

CO enhancement in coal gasification with CO2: Effect of minerals

To investigate the effect of minerals in brown coal on CO yield in a CO2 atmosphere, we impregnated pickled coal with nitrate and quartz to simulate the mineral content and assessed their impact on CO yield during gasification. It demonstrated that the reaction of Ca2+ and Fe3+ forming CaFe2O4 enhanced the CO yield. In the 100 % CO2 atmosphere, pickled coal containing CaFe2O4 produced five fold the amount of CO as after-pickling coal. The effect of minerals on CO generation under the CO2 atmosphere was explored by adding specific amounts of 1.96 wt% Ca, 1.80 wt% Fe, 6.83 wt% Al, 0.53 wt% Mg, and 11.64 wt% Si to acid-washed brown coal. The results show that the addition of Ca2+ contributes to the enhancement of CO, whereas the combined addition of Ca2+ and Fe3+ increases CO yield. CaFe2O4 enhances CO yield for two reasons: firstly, it is oxidized by CO2 to produce CO; secondly, CaFe2O4 can further react with CO2 to form Ca2Fe2O5, Ca2Fe2O5 then reacts with carbon in the brown coal to generate CO. This study has significant implications for the utilization of brown coal resources.

In-situ exsolved Ni nanoparticles for boosting CO2 reduction in solid oxide electrolysis cell

Due to their excellent high Faraday efficiency, perovskite solid oxide cells (SOECs) have attracted considerable attention. Nevertheless, they still face significant challenges in terms of stability and electrocatalytic activity during CO₂ electrolysis. In this study, Ni particles in La0.65Ba0.35Mn1-xNixO3-δ are successfully separated by a unique in-situ exsolved method of metal nanoparticles, which are uniformly anchored to the electrode surface as Ni nanometal particles. This effectively suppresses the generation of carbon deposits on the cathode surface. Under test conditions of 850 °C, 1.6 V and 50 sccm flow rate, the CO yield of the modified cathode material reached 5.9 mL min−1 cm−2, which is nearly four times higher than that before doping. The synergistic effect of in-situ exsolution of Ni metal nanoparticles with oxygen defects generated by the perovskite, creating more active locations for CO2 adsorption and electrolysis, is responsible for the significant improvement in electrochemical performance. This work provides new strategies and ideas for the development of efficient and durable SOEC cathode materials.

Microenvironment modulation of Fe-porphyrinic metal–organic frameworks for CO2 photoreduction

Photocatalytic CO2 reduction to fuels and chemicals is a promising pathway towards carbon resource recovery. Herein, three isomorphic Fe-porphyrinic MOFs, Zr6O4(OH)4(Fe-TCPP)3 (MOF-525, Fe-TCPP = iron 5,10,15,20-tetra(4-carboxyphenyl)-porphyrin), Zr6O4(OH)4(Fe-TCPP-NO2)3 (MOF-525-NO2, Fe-TCPP-NO2 = iron 5,10,15,20-tetra(2-nitro-4-carboxyphenyl)-porphyrin), and Zr6O4(OH)4(Fe-TCBPP-NO2)3 (MOF-526-NO2, Fe-TCBPP-NO2 = iron 5,10,15,20-tetra[4-(4′-carboxyphenyl)-2-nitrophenyl]-porphyrin) were synthesized and employed as photocatalysts for CO2 reduction. Among them, MOF-525-NO2 exhibited the highest catalytic activity with CO and H2 yields of 10.36 and 0.46 mmol·g−1 without any photosensitizer under visible light. Mechanism investigations suggested that the micro-environments of these MOFs were adjusted by introducing porphyrinic fragments with different lengths and functional groups, resulting in stronger CO2 affinity, faster photocurrent response, and efficient photogenerated electron-hole separation and transfer, which finally promoted the efficiency for photocatalytic CO2 reduction.

In situ constructing 2D/2D layered BiOBr/Bi2O2CO3 heterostructure for efficient photocatalytic reduction CO2 to CO

Photocatalytic reduction of CO2 to valuable energy materials is necessary for sustainable development. It is a considerable challenge to prepare photocatalysts for CO2 photoreduction with excellent separation capability of carriers by simple way. Herein, the BiOBr/Bi2O2CO3 type-II heterostructure was constructed by in situ conversion at room temperature. Combining the advantages of the 2D/2D layered structure can form a close contact interface and the type-II heterostructure can facilitate the transport of photogenerated charges, the BiOBr/Bi2O2CO3 composite showed significant enhancement in photocatalytic CO2 reduction performance. The most obvious performance enhancement was observed for 2.0-BiOBr/Bi2O2CO3, where CO yield could reach 29.55 μmol·g−1 for 3 h under light irradiation, it is 11 and 4 times higher than Bi2O2CO3 and BiOBr, respectively. And the sample exhibits excellent cycling stability in photocatalytic tests. In situ Fourier Transform Infrared spectroscopy confirmed that the important intermediates of the reaction are *COOH and *CO. The photocatalytic reduction mechanism of CO2 to CO in the BiOBr/Bi2O2CO3 type-II heterostructure was further analyzed. This study provides feasible solutions for selecting photocatalytic materials and designing facile preparation of efficient 2D/2D catalysts for photocatalytic reduction of CO2.

Effects of MOF-MoO3-x derivatives synthesis and oxygen defect engineering on photocatalytic CO2 reduction

Photocatalytic conversion of CO2 into valuable fuels is considered a promising approach for the development of sustainable and renewable energy sources. In this study, we utilized Mo-MOF as a precursor to obtain MoO3 by pyrolytic derivatization and treated it to obtain MOF-MoO3-x containing oxygen vacancies as a catalyst for the photocatalytic reduction of CO2 to CO. MOF derivatization altered the morphology of the MoO3, which made the formation of oxygen vacancies easier and facilitated the separation of electron-hole pairs. Meanwhile, the increased specific surface area and the appearance of surface oxygen vacancies enhanced the CO2 adsorption and activation capabilities of MOF-MoO3-x. As a result, MOF-MoO3-x demonstrated a significant enhances in the photoreduction activity of CO2. Its CO yield was 29.1 μmolg−1h−1, which was 3.7 times higher than that of MOF-MoO3 and 2.4 times higher than that of H-MoO3-x. This innovative strategy may provide a new avenue for improving the comprehensive performance of photocatalysts and developing renewable energy sources.

Anchoring MnWO4 Nanorods on LaTiO2N Nanoplates for Boosted Visible Light-Driven Overall CO2 Reduction.

The photocatalytic conversion of CO2 into hydrocarbon fuel holds immense potential for achieving a carbon closed loop and carbon neutrality. Developing efficient photocatalysts plays a pivotal role in enabling the widespread application of photocatalytic CO2 reduction on a large scale. Herein, a novel S-scheme MnWO4/LaTiO2N heterojunction composite is successfully synthesized by a hydrothermal method. This composite catalyst demonstrates excellent photocatalytic activity in the reduction of CO2 to CO and CH4 using water molecules as electron donors under visible light irradiation, and the optimized 30% MnWO4/LaTiO2N composite displays significantly enhanced CO and CH4 yields of 3.94 and 0.81 μmol g-1 h-1, respectively, and the corresponding utilized photoelectron number reaches 14.7 μmol g-1 h-1, which is approximately 7.7 and 12.9 times that of LaTiO2N and MnWO4. The enhancement in photocatalytic activity of the composites can be ascribed to the construction of an S-scheme heterojunction, which exhibits improved charge transfer dynamics, retains the strongest redox capacity, and effectively suppresses back reactions. In situ Fourier-transform infrared imaging provides evidence, to a certain extent, for the existence of a temporal gradient order in the generation of multiple products during the photocatalytic reduction of CO2.

Chemically bonded to construct S-scheme CNQDs/Bi2WO6 heterostructure: The Bi-N bonds as interfacial electronic channel boosting the efficient photocatalytic CO2 reduction under simulated sunlight

Photoinduced carrier separation efficiency plays a crucial role in determining the photocatalytic activity of photocatalysts, but it remains a challenge to accurately and efficiently control charge separation. Hence, we successfully prepared S-scheme CNQDs/Bi2WO6 heterostructure via a simple hydrothermal method. The theoretical calculations demonstrate that Bi-N bonds at the interface between CNQDs and Bi2WO6 serve as an electron transfer channel to facilitate charge transfer at the atomic level, which plays a vital role in driving the photoreduction of CO2 to CO. Interestingly, S-scheme heterostructure not only remains strong reducing ability of CNQDs, but also significantly reduces the energy barrier of *CO2 *COOH and release the product CO easily. The CO yield of the CNQDs/Bi2WO6 sample (26.24 µmol/g) was 11 times higher than that of the pure Bi2WO6 (2.43 µmol/g) without any sacrificial agents under 300 W xenon lamp. This work highlights the critical role of chemical bonding interfaces in the design of efficient S-scheme heterostructure photocatalysts.

Ceria-boosted Ni/Al2O3 catalysts for enhanced H2 production via acetic acid dry reforming

Acetic acid dry reforming (ADR) is a promising route for sustainable H2 generation. However, coke inhibition during ADR is the main challenge and not resolved by using suitable promoted catalysts. In this work, Ce promotion on 10%Ni/Al2O3 catalysts with 1-5 wt%Ce was evaluated for ADR at varied temperatures of 923–998 K and stoichiometric feed in a fixed-bed rig. CeO2 addition of 1–3% enhanced metal dispersion, and surface area whilst basic CeO2 character significantly boosted the concentration and density of basic sites on catalysts. Particularly, the CO2 uptake of promoted catalysts was about 2.49–3.73 times greater than that of counterpart sample. CH3COOH and CO2 conversions were enhanced with rising Ce loading and the highest reactant conversions were observed at 3 wt%Ce. The improved adsorption of acidic CH3COOH and CO2 molecules due to increasing amount of basic sites as well as redox attributes of CeO2 promoter could be responsible for the enhancement in ADR activity and yield of H2 and CO. The mechanistic two-step pathway for coke suppression induced by CeO2 promotion was elaborated in this work. Generally, carbonaceous species formation on 3%Ce–10%Ni/Al2O3 was considerably reduced about 1.6–2.0 times. H2/CO ratio varied from 0.59 to 0.65 relying on ADR temperature over 3%Ce–10%Ni/Al2O3. These H2/CO values, two times higher than theoretical H2/CO ratio in ADR, are compatible for downstream gas-to-liquid processes to selectively yield high molecular weight olefins. Water formation rate increased from 8.67 × 10−6 to 4.71 × 10−5molH2O gcat−1 s−1 with rising temperature within 923–998 K on 3%Ce–10%Ni/Al2O3.

Study on the pathways of thermochemical sulfate reduction between sulfates and alkanes at low temperatures

To reduce the energy consumption of heavy oil thermal recovery, low-temperature hot water flooding is becoming popular. The occurrence of thermochemical sulfate reduction (TSR) reactions during the hot water flooding process generates H2S, which can corrode equipment and jeopardize personnel safety. Preventing and managing H2S requires studying TSR reactions. The study investigated the reactivity of SO42-, HSO4-, and [MgSO4]CIP in the TSR reaction during heavy oil low-temperature hot water flooding. The results indicated that during low-temperature hot water flooding, no significant thermal cracking of heavy oil occurs, only a minor aquathermolysis takes place, while the TSR reaction proceeds vigorously. The TSR reaction leads to increased yields of H2S, CH4, and CO2, as well as a higher S content in the heavy oil. Based on experimental results, numerical simulations of the reaction process between SO42- and CH4 were conducted using density functional theory and transition state theory. The results indicated that the reduction of SO42- to produce SO32- is the rate-limiting step in the entire reaction pathway between SO42- and CH4. Further analysis of the reaction barriers and chemical reaction rates of the three sulfates (SO42-, HSO4-, and [MgSO4]CIP) and C1-C5 alkanes was conducted based on the limiting step. Through macro and micro analysis, this study not only confirmed previous findings regarding the order of alkanes participating in TSR reactions from the perspective of microscopic molecular but also clarified the oxidation order of sulfate species under heavy oil low-temperature thermal water flooding conditions, with the sequence being HSO4- > [MgSO4]CIP>SO42-. This study provides a foundational understanding of TSR reactions during heavy oil low-temperature hot water flooding and is of significance for the prediction and management of H2S.

Encapsulating Halide Perovskite Quantum Dots in Metal–Organic Frameworks for Efficient Photocatalytic CO2 Reduction

Halide perovskite has shown great potential in photocatalysis owing to its diversity, suitable energy band alignment, rapid charge transfer, and excellent optical properties. However, poor stability, especially under humid conditions, hinders their practical application in photocatalysis. In this work, we report the encapsulation of inorganic–organic hybrid perovskite QDs into MIL-101(Cr) through an in situ growth strategy to prepare a series of MAPbBr3@MIL-101(Cr) (MA = CH3NH3+) composites. The perovskite precursors, i.e., MABr and PbBr2, were successively introduced into the pores of MOF, where the perovskite quantum dots were self-assembled in the confined environment. In photocatalytic CO2 reduction, 11%MAPbBr3@MIL-101(Cr) composite displayed the best performance among the composites with a total CO and CH4 yield of 875 μmol g−1 in 9 h, which was 8 times higher than that of the pure MAPbBr3. Such high gas production efficiency could be maintained for 78 h at least without structural and morphologic decomposition. The remarkable stability and catalytic activity of composites are mainly due to the synergistic effect and improved electron transfer between MAPbBr3 and MIL-101(Cr). Moreover, these composites revealed a novel mechanism, showing switched CH4 selectivity with the controlling of the perovskite location and contents. Those with perovskites encapsulated in the mesopores of MIL-101(Cr) were more preferential for CO production, while those with perovskites encapsulated in both meso- and micropores could produce CH4 dominantly.