Part Of CO2 Research Articles

Single-atom Zr-doped CoOOH with enhanced electrical conductivity as a signal amplifier and detection probe for the indirect non-enzymatic electrochemical determination of malathion in foods

Herein, a novel electrochemical sensor based on zirconium-doped cobalt oxyhydroxide (ZrCoOOH) was proposed for highly sensitive non-enzymatic determination of malathion (MAL). The doping of Zr can improve the electrical conductivity of CoOOH, of which the transfer resistance was reduced from 241.1 Ω to 140.2 Ω. Furthermore, the X-ray photoelectron spectroscopy confirmed that part of Co2+ was converted to Co3+ due to the introduction of Zr. The Co3+ in ZrCoOOH could react with MAL to form Co2+, which enhanced the electrooxidation current of Co2+. Therefore, the peak current of Co2+ was served as detection probe for MAL. Under optimal conditions, the developed sensor established the linear relationship for MAL in the concentration range of 0.001–10.0 μM with a low limit of detection (0.64 nM). The constructed sensor was employed to detect MAL in food samples (peach, kiwi fruit, spinach and tomato), verifying the accuracy and practicability of the sensor.

Investigation of the effect of partial Co substitution by Ni and Fe on the interface bond strength of WC cemented carbide based on first-principles calculations

In this work, the effect of Ni and Fe replacing part of Co on the interfacial properties of WC cemented carbides was evaluated by using first-principles calculations and WC/Co and WC/CoNiFe cemented carbides were prepared by powder metallurgy. The effects of replacing part of the Co by Ni and Fe on the interfacial electronic structure, interfacial bond strength, microstructure and mechanical properties of WC cemented carbides was investigated by establishing the WC/Co and WC/CoNiFe interfacial models and examining the porosity, KPFM and microhardness of the actual samples. The results indicate that the substitution of partial Co by Fe and Co has little effect on the interface binding energy and interface structure of WC cemented carbides. Co, Ni, and Fe atoms can all form strong covalent and metallic bonds with W atoms, with atomic bonding strength W-Fe>W-Co>W-Ni. Fe atoms play a major role in the strength of the WC/CoNiFe interface. The porosity of the WC/CoNiFe cemented carbide sample is 0.78 %, which is significantly smaller than that of the WC/Co cemented carbide and the porosity distribution is relatively homogeneous. The hardness of WC/CoNiFe cemented carbide is lower (1182 HV) than that of the WC/Co cemented carbide (1320 HV) but the distribution is much more uniform than that of the WC/Co cemented carbide.

Intermittent CO2 injection: injectivity and capacity

Сarbon capture and storage (CCS), especially offshore, involves a chain of complex and expensive infrastructure connecting emitters to the disposal site. The classic example of an industrial cluster sending CO2 by a large pipeline to a nearby storage site is considered the most favorable solution in term of techno-economics. However, many emitters are located either too far from suitable offshore geology or are dispersed in harder to reach locations, making pipeline transport uneconomical. In these instances, ship transport is a viable option for shuttling CO2 from source to sink. The Northern Lights project in Norway will implement this approach, using shuttle tankers to deliver CO2 to an onshore receiving terminal. One should note that onshore terminals add significant cost to CCS, and their permanence can hinder flexibility and delay future expansion to new regions. High costs can also hinder small emitters to embark on CCS journey until the larger infrastructure is in place and the price for joining the value chain drops. Direct injection from ships can be a good supplement to the offshore transport portfolio, allowing ships to offload CO2 directly to the injection well on a periodic basis. While direct ship injection introduces a planned intermittency into the CCS chain, intermittency can also be caused by planned maintenance and technical issues along the value chain; energy supply and demand (where either less emissions are available due to, for example, higher renewables production or less energy is available for injection, in, for example, offshore renewable energy driven case); seasonal variations (part of CO2 used in agriculture or seasonal variation of injection temperature). The effect of intermittency, in general, is not fully understood. Part 1: aspects of intermittency on the storage reservoirLittle is known about the impact of injectivity CO2 injection on storage performance, i.e. injectivity and capacity. Recent studies indicate that cycling injection can delay bottom-hole pressure build-up, thus increasing capacity of the reservoir. On the other hand, evidence from field tests show that pressure relief can cause dissolved CO2 to exsolve into bubbles that block pores and reduce injectivity. Salt precipitation is another aspect that can be either positively or negatively impacted by flow cycling. In this case, repeated drainage-imbibition cycles may dissolve salt crystals formed in a previous cycle, improving injectivity, or it may continue to feed the system with new saltwater, thus impairing injectivity. The topic of salt precipitation is an active area of research.Part 2: how to deal with itWe present results of the recent study down for NEMO Maritime AS in a research council of Norway sponsored NEMO project. The talk will briefly highlight simulation outcomes on the near wellbore and field scale.Part 3: where do we go from hereFinally, we shortly introduce a recently funded CTS project which will focus on several aspects of direct injection from ships, including full-chain LCA/TEA based on Strategy CCUS H2020 project approach and scenarios. The project focuses on four different regions of Europe, including Baltics.

Supported catalysts derived from cobalt phyllosilicates for chemical vapor deposition growth of single-walled carbon nanotubes

Chemical vapor deposition (CVD) growth of single-walled carbon nanotubes (SWNTs) using supported catalyst is problematic due to possible metal coalescence during reaction. Thus, the development of supported catalyst that resists sintering is crucial for synthesizing SWNTs with a narrowly distributed chirality. Here, silica-supported phyllosilicate materials containing Co are prepared for catalytically growing carbon nanotubes. Owing to the incorporation of Co in the phyllosilicate, only part of Co2+ is reduced under CVD reaction environment, leading to the formation of immobilized metallic particles which subsequently catalyze the growth of SWNTs at 850 °C. With the addition of Pd promoter, the reducibility and carburization of the Co particles is enhanced, leading to the preferential synthesis of (6, 5) SWNTs at 600 °C. This work extends the application of phyllosilicates in catalytic synthesis of SWNTs, thus providing a new avenue for chirality-selective synthesis of SWNTs.

The generation mechanism of CO and CO2 in coal spontaneous combustion by mathematical statistical and other methods

At present, the mechanism of CO and CO2 production in coal spontaneous combustion is controversial. With the hope of exploring the generation mechanism of CO and CO2 in the low-temperature oxidation of coal, in this study, the correlation between the relative contents of three active functional groups, –CH3/–CH2, -C = O, and –COOH and the generation law of CO and CO2 in the low-temperature oxidation of coal samples with different metamorphic degrees was explored by means of principal component analysis, Pearson linear analysis, and Fourier transform infrared spectroscopy. The results indicate that –CH3/–CH2, -C = O, and –COOH in low-rank lignite (HC) are significantly correlated with the concentrations of CO and CO2. The -C = O and –COOH in medium-rank bituminous coal (BC) are closely correlated with the concentrations of CO and CO2. The concentrations of CO and CO2 in high-rank anthracite (CQ) show the highest correlation with the relative content of –CH3/–CH2, followed by their correlation with the relative content of -C = O, and their correlation with the relative content of –COOH is relatively low. Thus, it can be concluded that the generation mechanism of CO and CO2 varies with the metamorphic degrees of coal in coal spontaneous combustion. CO and CO2 generated from low-rank HC mainly come from continuous generation and oxidation of inherent and secondary alkyl chains and those generated from medium-rank BC mainly come from the oxidation of oxygen-containing functional groups. Besides, for high-rank CQ, CO is mainly generated from the process in which alkyl chains in coal oxidize to form carbonyl groups which then break to form CO, and a small part of CO comes from the coal-oxygen free radical reaction. As for CO2, its sources are more complex. A big portion of CO2 comes from the free radical reaction and CO2 may also come from the direct conversion of CO at high temperature and in the presence of water. Finally, the reaction mechanism of C = O· and ·OH free radicals was studied by quantum chemical calculation. The calculation results reveal that the free radical reaction can occur spontaneously and release a certain amount of heat under certain conditions, thus playing a positive role in promoting coal spontaneous combustion.

Quantitative evolved gas analysis: Winchcombe in comparison with other CM2 meteorites

AbstractTwo bulk Winchcombe along with six other CM2 meteorite samples were subjected to quantitative evolved gas analysis. The observed release patterns for almost all volatile species demonstrate close similarity for all the samples and especially between those for Winchcombe. This can be considered as a fingerprint for this petrological type of meteorites. We identified several gases including H2, H2O, O2, CO, CO2, and SO2 released in different temperature ranges. The sources and mechanisms of their release were also established. Some of the gases, H2, CO, and CO2, are released as a result of oxidation of macromolecular organic material from oxygen derived from oxygen‐bearing minerals (a part of CO2 is also released as a result of decomposition of carbonates). The others, O2 and H2O, are associated with the phase transformation/decomposition of phyllosilicates and (oxy)hydrates, while a high‐temperature release of SO2 is associated mostly with the decomposition of sulfides and in few cases also with sulfates. A low‐temperature release of SO2 is due to evaporation and oxidation of elemental sulfur from the meteoritic matrix and organic material. The total concentrations of H (mostly represented by H2O), C, and S, calculated according to calibration of the quadrupole mass spectrometer with reference gases and decomposition of solid samples (CaSO4·2H2O and NaHCO3) are in reasonable agreement with those determined by independent methods. Variations in the ratio of the carbon amounts released as CO2 and CO (/CCO) between the samples could be an indicator of their terrestrial weathering.

Mercury removal over Ce-doped LaCoO3 supported on CeO2 at low temperatures from coal combustion flue gas

Mercury has a significant impact on environment and is mainly derived from coal-fired power plant. Herein, we report a potential route for efficient removal of Hg0 via oxidation reactions using Ce-doped LaCoO3 supported on CeO2 catalyst. Catalyst characterization results proved that Ce can successfully substitute a desired part of Co into the LaCoO3 crystal lattice via a sol–gel method. The Hg0 removal experiments suggest that Hg0 removal efficiency decreased in the order of La0.875Ce0.125CoO3/CeO2 > La0.875Ce0.125CoO3 > LaCoO3. The presence of O2 provided more active oxygen and resulted in approaching 100% Hg0 removal efficiency. Introducing H2O and sole SO2 would significantly reduce the Hg0 removal efficiency as a result of competitive adsorption on the actives sites of the catalyst. On the other hand, SO2 could reacted with Hg0 in the presence of O2 and thereby recover the high Hg0 removal efficiency and the La0.875Ce0.125CoO3/CeO2 catalyst presented a good performance towards sulfur resistance. Furthermore, the catalyst still exhibited a high Hg0 removal efficiency performance after five times consecutive recycles.

Enhancing hydrogen storage properties of MgH2 using FeCoNiCrMn high entropy alloy catalysts

Herein, we report the successful preparation of the FeCoNiCrMn high entropy alloy (HEA) loaded MgH2 and HEA's effect on the hydrogen storage properties of Mg/MgH2. The HEA shows high catalytic activity toward hydrogen dissociation and recombination reaction, and successfully suppressed activation energy of dehydrogenation reaction from 151.9 to 90.2 kJ mol–1. Moreover, part of Co and Ni can react with Mg, and produce Mg2Co/Mg2CoH5 and Mg2Ni/Mg2NiH4 during the hydrogen storage processes, further enhancing dehydrogenation reaction through the “hydrogen pumping” mechanism. As a result, the MgH2–5 wt% HEA composite can release 5.6 wt% of H2 at 280 °C within 10 min, and absorb 5.5 wt% H2 within 0.5 min at 150 °C. The loaded HEA shows robustness against particle aggregation, leading to stable reversible hydrogen storage processes at least 50 times. These findings show the synergistic effects of HEA on Mg-based hydrogen storage materials, providing an additional degree of freedom for catalyst design.

Effectiveness and safety of pulse oximetry in remote patient monitoring of patients with COVID-19

Abstract Context A surge of COVID cases globally is often portrayed as “very likely”, which overwhelms health systems and challenges their capacities. A mitigation strategy is seen by remotely monitoring COVID patients in out-of-hospital settings to determine the risk of deterioration. Description of the problem We need an indicator to enable remote monitoring of COVID patients at home that can be measured by a handy tool; pulse oximetry which measures peripheral blood oxygen saturation (SpO2). Evidence shows that SpO2 is a reliable indicator of deterioration among COVID patients. The UK initiated a national programme (COVID Oximetry @ Home (CO@H)) to assess the theory. The concept can be potentially applied in other countries in various settings. As part of CO@H, we conducted a systematic review of the evidence on the safety and effectiveness of pulse oximetry in remote monitoring of COVID patients. Results Our review confirms the safety and potential effectiveness of pulse oximetry in remote home monitoring among COVID patients. We identified 13 research projects involving 2,908 participants that assessed the proposed strategy. Evidence shows the need to monitor at-rest and post-exertional SpO2. At-rest SpO2 of ≤ 92% or a decrease of 5% or more in post-exertional SpO2 should indicate care escalation. The recommended method for measuring at-rest SpO2 is after 5-10 min of rest, and assessing post-exertional SpO2 is after conducting a 1-min sit-to-stand test. We could not find explicit evidence on the impact on health service use compared with other models of care. Lessons Remote monitoring of COVID patients could alleviate the pressure on health systems and save hospital resources. Monitoring SpO2 by pulse oximetry can be widely applied, including in resource-limited settings, as the tool is affordable, reliable, and easy to use. Key messages • Adopting relevant health technologies in remote patient monitoring is critical to combat the pandemic. • Pulse oximetry is an affordable, easy to use and widely available tool to monitor patients with COVID-19 at home.

Numerical analysis of CO2 capture process with potassium-based sorbent in a three-dimensional fluidized bed

CO2 capture process with potassium-based sorbents in fluidized beds is an emerging technology in industries, yet the in-furnace solid transportation and thermal characteristics are still lacking. In this work, the CO2 process capture with K2CO3 adsorbents in a three-dimensional fluidized bed is numerically explored using a recently developed reactive multiphase particle-in-cell model under the Eulerian-Lagrangian framework. After model validation, the spatial distribution of K2CO3 particles and the effect of key operating parameters on the flow and thermal behaviours in the fluidized bed are investigated. The results indicate that elevating the particle size distribution enhances CO2 capture and increases the absorbent temperature due to the extended residence time of K2CO3 particles and the resulting enhanced exothermic carbonation reactions. Enlarging the inlet gas velocity increases the gas concentration in the reactor outlet because a part of CO2 without enough time to react with K2CO3 particles is entrained out of the reactor by bubbles with the increase of gas velocity, indicating the optimal inlet gas velocity (0.71 m/s) for CO2 capture using K2CO3 adsorbents in this fluidized bed. The particle temperature rises with enlarging inlet gas velocity due to enhanced exothermic carbonation reactions. The results obtained can help to understand the regularity of CO2 capture process based on K2CO3 absorbents in fluidized beds.

The active pairs of Co-Co2C adjusted by La-doped CaTiO3 with perovskite phase for higher alcohol synthesis from syngas

Catalytic conversion of syngas (CO + H2) to higher alcohols is desirable, but a high C2+OH selectivity is challenging to achieve due to the difficult equilibrium between dissociatively adsorbed CO and non-dissociatively adsorbed CO. In this work, Ca1-xLaxTi1-xCoxO3 catalysts are facilely prepared by using citrate complexing method, and a part of metal Co is transformed to Co2C during reaction. In the process of reaction, the synergistic effects among metal Co, Co2C and oxygen vacancies boost the conversion of syngas to higher alcohols. Metal Co nanoparticles are used to promote the dissociative adsorption CO and C–C coupling, subsequently combine with *CO adsorbed on Co2C to produce alcohols. Besides, oxygen vacancy can be used to activate oxygen-containing compounds and enhance higher alcohols synthesis. The surface Co2C/Co ratio has significant influences on catalytic activity and stability of catalysts, which can be adjusted by the Co/Ti ratio. The C0.7L0.3T0.7C0.3O3 catalyst exhibits the highest selectivity of higher alcohols due to the moderate surface Co2C/Co ratio, which has an appropriate balance between *C, *CO and C–C coupling.

Environmental impacts of the production of synthetic natural gas from industrial carbon dioxide

Power-to-Gas technologies (PtG) are regarded as promising options to defossilize the energy system by converting and storing renewable electricity to gases. When combined with carbon capture and utilization from large point sources, such as energy intensive and hard-to-abate sectors, where a major part of CO 2 emissions cannot be avoided, PtG technologies can also play a role to mitigate CO 2 emissions. However, these technologies have several environmental impacts throughout their lifetimes that must be assessed, due to the use of resources, materials, and energy, as well as the formation of chemical by-products. Using a Life Cycle Assessment (LCA) methodology, this paper aims to assess the most significant environmental impacts of an integrated PtG system including the conversion of renewable energy to hydrogen through water wind-based electrolysis, that is further converted to synthetic natural gas (SNG) by reacting with captured CO 2 from a cement plant flue gas. More precisely, the present work innovates on both the technical and methodological perspectives. An advanced CO 2 capture process is implemented, using mixed amines solvent and innovative configuration to reduce the energy consumption to 2.3 GJ per tCO 2 captured, and include an optimized heat integration with the CO 2 conversion step. A hybrid approach combining physical and economic input data is also considered for the life cycle inventory. Additionally, both subdivision and system expansion via substitution approaches are applied to consider the multi-functionality of the systems. Simulation results show that the PtG process with CO 2 captured from cement plants flue gas reduces the overall GHG emissions by 76%. Similarly, the fossil resource scarcity is drastically reduced by over 80% thanks to the heat integration between the CO 2 capture and the CO 2 conversion processes, but also thanks to the substitution of natural gas by the CO 2 -based SNG. Nevertheless, environmental impacts of PtG are higher than conventional natural gas production for other impact categories, including freshwater eutrophication, terrestrial acidification, and mineral resource scarcity. Both data uncertainties, assessing the knowledge base underlying the input data parameters, and sensitivity analysis, assessing the value range of the parameters respectively to the environmental indicators, are conducted to test the results and highlight the uncertainty hotspots.

Preparation of low binder WC-Co-Ni cemented carbides with fine WC grains and homogeneous distribution of Co/Ni

Fine grained WC-Co-Ni cemented carbides with a low binder content have been successful manufactured via the powder metallurgy method. The WC-Co-Ni composite powder with homogeneous distributions of Co and Ni was synthesized by chemical co-precipitation with the raw materials of WC powder, oxalic acid and chlorides of Co and Ni. In this study, the effects of cobalt and nickel contents on the properties of cemented carbides were investigated systematically. The experimental results demonstrated that the alloy prepared by vacuum sintering had uniform grain size distribution and no abnormal growth of WC grains. When the cobalt content was 4 wt% and 5 wt%, the obtained composites almost completely consolidated with excellent hardness and fracture toughness. Among them, for the sample WC-4 wt%Co, the relative density could reach 99.37%, and the Vickers hardness and fracture toughness were 2010 HV30 and 8.55 MPa·m1/2, respectively. When Ni was added to replace part of Co, the relative density of WC-Co-Ni decreased and the fracture toughness was improved without basically sacrificing the hardness. For the sample WC-2 wt%Co-2 wt%Ni, the hardness decreased to 1921 HV30, while the fracture toughness increased to 8.97 MPa·m1/2.

Reaction mechanism of CO/CO2 with low-carbon aluminium-killed molten steel during the ladle furnace (LF) refining process

ABSTRACT The reaction mechanism of CO/CO2 with low-carbon aluminium-killed molten steel in ladle furnace was investigated through thermodynamic analysis, simulation, and experiments. When a [O]×a [C] in molten steel is less than p CO/(p Θ × K Θ CO), CO/CO2 gas is dissolved in the metal phase and decomposed into oxygen and carbon. When a [O] × a [C] is equal to or close to p CO/(p Θ × K Θ CO), CO no longer reacts with molten steel, part of CO2 is decomposed to CO, and oxygen atoms selectively oxidise other elements. The experimental results showed that the CO reaction rate increases with an increase in the aluminium content in molten steel, whereas the opposite occurs for the decomposition rate of CO2. The industrial test of the CO2 bottom blowing was conducted in a 100 t LF. Compared with argon, the stirring effect was weakened, and carburisation and selective oxidation of the elements were noted.

Effect of deposition current density on the Co–Ni/SiO2 alloy composite coatings using scanning jet electrodeposition

Co–Ni/SiO2 alloy composite coatings were electrodeposited on copper substrate by scanning jet electrodeposition at various current densities to study its effect on the morphologies, texture orientation, microhardness, adhesion force, wear resistance, and corrosion resistance of Co–Ni/SiO2 alloy composite coatings. The structure and performance of the material were characterized using a scanning electron microscope, XRD diffractometer, nanoindentation, scratch tester, friction and wear tester, and electrochemical methods. The morphologies of the Co–Ni/SiO2 alloy composite coatings changed from sparse and slender structures to dense starfish structures with an increase in current density. A part of Co precipitated in the form of a face-centered cubic structure and formed a solid solution with Ni, while another part of Co precipitated in the structure of the composite coating in the form of a hexagonal close-packed structure. The Co–Ni/SiO2 alloy composite coating exhibited excellent adhesion force, wear resistance, and corrosion resistance when the deposition current density was 130 A dm−2. Once the current density was exceeded, some microcracks appeared on the surface of the composite coating, after which the adhesion force and corrosion resistance decreased. The present study suggests that current density at 130 A dm−2 is more suitable than low current density for jet electrodeposition to prepare high-density and high-quality composite coating.

Efficient Electrochemical/Electroless Deposition Synthesis Routines for CO Tolerant Catalysts

Composite catalysts containing Pt and Mo-oxides are promising materials for anodic catalyst preparation in PEMFCs due to their high tolerance for CO-poisoning. The search for optimal preparation methods for these materials is an important task in modern electrochemical energetics.Two synthetic routines, namely electrodeposition and deposition under open-circuit conditions, were used for Pt-MoO x catalyst preparation. The prepared catalysts were characterized by a variety of modern physical methods (XRD, XPS, SEM, EDX); it was established that the material prepared by electroless deposition contains platinum shell upon platinum core. The materials obtained were tested in the reactions of CO adsorbate electrodeposition and dissolved CO-oxidation.It was found that molybdenum oxides in the composites prepared by electrodeposition broaden the major peak of CO-oxidation, but the peak maximum does not shift toward less positive values. Therefore, the CO monolayer is destabilized as a result of the contact with molybdenum oxides; however, only a small part of CO can be oxidized at these low potentials. Nevertheless, these catalysts are suitable for dissolved carbon monoxide oxidation. aPt·b(H x -2MoO3) composites were synthesized by the redox reaction of K2PtCl4 with reduced forms of hydrogen containing molybdenum bronzes. The CO desorption peak is broadened and shifted toward less positive potentials. aPt·b(H x -2MoO3) catalysts demonstrate high catalytic activity in the reaction of both adsorbed and dissolved CO oxidation. Therefore, one can conclude that both electrodeposition and electroless deposition are suitable methods for preparing PEMFC anode catalysts. Figure 1

Stable Structure and Electronic Structure for Mg(MgxVyNiz)O4 As Cathode Material for Magnesium Secondary Battery in Discharge Process Using First-Principle Calculation

1. Introduction Magnesium secondary batteries are expected to be applied as a next generation battery materials having higher volume energy density than lithium ion batteries. In our laboratory, we are conducting research and development on cathode materials for magnesium secondary batteries. In recent years, the spinel MgCo2O4 and MgCo1.5Mn0.5O4 in which part of Co is substituted with Mn have been synthesized and measured the battery characteristics of average structure1). From this previous study, it became clear that the Mg/Co cation mixing become decreasing and the first discharge capacity became increasing with the substitution of Mn atom. The first-principle calculation was also performed for the spinel MgCo2O4 and MgCo1.5Mn0.5O4 in pristine and discharge process and reported that the structure changed from a spinel structure to a rock salt structure during discharge2). From the first-principle calculation, it was found that the structure change of MgCo1.5Mn0.5O4 was remarkable because the bond between Mg and O was weakened especially by the influence of Mn. In our laboratory, we have also reported that spinel type Mg(MgxVyNiz)O4 with mixed valence vanadium ions as a host structure has better cycle characteristics than MgCo2O4 system3). However, the local structure in the charge / discharge process and the structural change when Mg is inserted have not been elucidated. The purpose of this study is to investigate the stable structure of Mg(MgxVyNiz)O4 at pristine and discharge process by using the first-principles calculation, and to clarify the mechanism of Mg insertion.2. Calculation method The stable structure of the spinel Mg(Mg0.31V1.69)O4 and Mg(Mg0.31V1.56Ni0.13)O4 inserted Mg atoms (shown as Mg1+y(Mg0.31V1.69)O4 and Mg1+y(Mg0.31V1.56Ni0.13)O4 (y = 0.125~0.75); y is equal to the amount of Mg atoms), were obtained by GGA+U method (VASP code) in discharge process. The cell size of the spinel Mg(Mg0.31V1.69)O4 and Mg(Mg0.31V1.56Ni0.13)O4 were (2×1×1).3. Results and discussion The stable structures of the spinel Mg(Mg0.31V1.69)O4 and Mg(Mg0.31V1.56Ni0.13)O4 at pristine obtained by the first-principle calculation are shown in Fig. 1. In previous study, it was reported that the 8a site was occupied by only Mg atom, and the 16d site was occupied by V, Mg and Ni atom from the average structure analysis measured by the synchrotron X-ray diffraction.3) Models are created based on the results of Rietveld analysis in this study. In both Fig. a-1) and b-1), Mg at 16d site tends to coordinate relatively close to each other in the crystal. It is found from b-1) that Ni also tends to coordinate to positions close to each other. Fig. 1.a-2) and b-2) show the stable structure at the discharge with y=0.25 of Mg inserted into the vacancy 16c site the spinel Mg(Mg0.31V1.69)O4 and Mg(Mg0.31V1.56Ni0.13)O4 at pristine, respectively. Green circles in Fig. 1 a-2) and b-2) are indicated the Mg inserted into the hole 16c site. The Mg before the structural relaxation is indicated by a black dotted circle, and the Mg moved after the structural relaxation is indicated by an arrow and a red circle in in Fig. 1 a-2) and b-2), respectively. As shown in Fig. a-2) and b-2), the structure of Mg become stable when it is inserted into the 16c site near Mg, which is mixed to the 16d site. The model in which the inserted Mg coordinated away from each other in the crystal has high total energy. In both a-2) and b-2), it is found that the Mg atoms at the 8a site near the inserted Mg have moved to the 16c site. When Mg are inserted into spinel Mg(Mg0.31V1.69)O4 and Mg(Mg0.31V1.56Ni0.13)O4, it becomes clear that the structural change to rocksalt is occurred around Mg at 16d site. This structural change during discharge is also observed in the spinel type MgCo2-xMnxO4 system. Since the distance between the nearest 8a site and 16c site is about 1.7 to 1.8 Å, it is considered that repulsion between cations occurs. On the lecture, we will show the electron density and discuss the electronic state in detail. Acknowledgement This work was partly supported by ALCA-SPRING Grant Number JPMJAL1301, Japan. We are deeply grateful for the cooperation.1) Y. Idemoto, Y. Mizutani, C. Ishibashi, N. Ishida and N. Kitamura, Electrochemistry 87, 220 (2019).2) C. Ishibashi, Y. Mizutani, N. Ishida, N. Kitamura, Y. Idemoto, Bull. Chem. Soc. Jpn. 92, 1950 (2019).3) Y. Idemoto, N. Kawakami, N. Ishida, N. Kitamura, Electrochemistry 87, 281 (2019). Figure 1

Surface metal valence state regulating on hematite to weaken dependence of charge transport to catalyst loading

Generally, the loading of oxygen evolution catalyst (OEC) must be carefully controlled to an extremely thin level or the photo-generated holes will mainly charge the catalyst rather than oxidizing water. To overcome the extreme sensitivity of charge transport to catalyst thickness, we proposed the iron valence state regulating on hematite to negatively shift the surface defect state, thereby suppressing the severe OEC charging. In detail, a fluorine layer (FeOxFy) was inserted between Fe2O3 and OEC (ZIF-67) to reduce the oxidation state of iron atoms, forming a case where only part of Co(II) can be oxidized (build a rapid Co(II)/Co(III) cycle). Even in the case of thicker OEC (~10 nm), Fe2O3@[email protected] exhibits increased photocurrent density of 2.56 mA cm−2 at 1.23VRHE (~170% higher than Fe2O3@ZIF-67), accompanied by a rapid decrease in sensitivity to OEC loading. Above pretreatment not only relaxed the catalyst process requirements, but also provide new insights into interfacial catalysis process.

Characteristics and implication of multilayer dawsonite in heterogeneity reservoir of the Honggang anticline, southern Songliao Basin, NE China

Reservoir heterogeneity is one of the key factors regarding the long-term fate of the injected CO2. Natural CO2 reservoir and ancient CO2-bearing reservoir is a natural analog to investigate the influence of reservoir heterogeneity on the migration of CO2 and CO2-rock interaction with geological timescale. Dawsonite cements are detected in both sandstone and mudstone of the Upper Cretaceous Qingshankou reservoir in Honggang anticline of the southern Songliao Basin, China. Here, we present results of a petrographic characterization of this reservoir based on polarizing microscope, X-ray diffraction, and fluid inclusion data. These data were used to identify the vertical distribution characteristic of dawsonite and to identify the migration characteristics for the supercritical CO2 in heterogeneity reservoir. Our analytical results show that as the “CO2 trace mineral,” dawsonite appears as multilayered zones of cementation that are separated by mudstone interlayers. These multilayered dawsonite could be one of the geological produces for supercritical CO2 flooding through the heterogeneous rock, acting as the lateral migration and upward diffusion. Supercritical CO2 could move through the thinner mudstone interlayer, with the product of dawsonite developing in the mudstone as its “footprint,” although the vertical distance of diffusion in low-permeability caprock is limited. Combined with the truth that most of the present CO2 gas reservoirs (in K1q4) are in the deeper layers than the dawsonite-bearing sandstone (K1q4-K2y1) (developed in non-CO2 reservoir), we can deduce that CO2 was at some time abundant in the Honggang anticline but had now part of CO2 been migrated, with the other part consumed by the reaction with the primary rock and captured as new carbonate minerals. The dawsonite-bearing sandstones also record a sequence of hydrocarbon filling events. Combined with the truth that the injection time of CO2 is later than that of hydrocarbon, the early hydrocarbon should be deasphalted by the injection and migration of mantle CO2. Therefore, CO2 could also be stored as long-term carbonate minerals after the termination of a CO2-EOR project.

Metallic Co, CoS, and P co-doped N enriched carbon derived from ZIF-67 as an efficient catalyst for hydrogen evolution reaction

Exploring non-precious materials with efficient electrocatalytic performance to replace the precious Pt-based materials for hydrogen evolution reaction (HER) is still a great challenge now. Herein, metallic Co, CoS, and P co-doped N enriched carbon (CoSP/NC) was successfully fabricated by using ZIF-67 as precursor via a facile pyrolysis, sulphurization, and phosphorization process for HER application. ZIF-67 was transformed into metallic Co doped N enriched carbon (Co/NC) undergoing the treatment of high temperature. After being sulphurized, part of metallic Co was transformed into CoS and attached firmly on the surface of the catalyst. P element was well dispersed on the catalyst during the phosphorization process. The fabricated CoSP/NC exhibits the optimal HER activity with the superior overpotential of 183 mV at 10 mA cm−2 and the lowest Tafel slope of 64.25 mV dec−1. Furthermore, CoSP/NC shows superior durability. The excellent HER performance may be ascribed to the abundant active sites, firm structure, and superior electrical conductivity of the carbon. Thus, this work provides a new strategy to fabricate non-precious materials with excellent HER performance for the following researchers.