Co-CoO_x supported onto TiO_(2) coated with carbon as a catalyst for efficient and stable hydrogen generation from ammonia borane

Ammonia borane(AB) can be catalytically hydrolyzed to provide hydrogen at room temperature due to its high potentaial for hydrogen storage. Non-precious metal heterogeneous catalysts have broad application in the field of energy catalysis. In this article, catalysts precursor is obtained from Co-Ti-resorcinol-formaldehyde resin by sol–gel method. Co/TiO_(2)@N-C(CTC) catalyst is prepared by calcining the precursor under high temperature conditions in nitrogen atmosphere. Co-CoO_x/TiO_(2)@N-C(COTC) is generated by the controllable oxidation reaction of CTC. The catalyst can effectively promote the release of hydrogen during the hydrolytic dehydrogenation of AB. High hydrogen generation at a specific rate of 5905 m L min^(-1) g_(Co)^(-1) is achieved at room temperature. The catalyst retains its 85% initial catalytic activity even for its fifth time use in AB hydrolysis. The synergistic effect among Co, Co_(3)O_(4) and TiO_(2) promotes the rate limiting step with dissociation and activation of water molecules by reducing its activation energy. The applied method in this study promotes the development of non-precious metals in catalysis for utilization in clean energy sources.

Methane Generation and Capture of U.S.Landfills

Analysis of the U.S.EPA(Environmental Protection Agency)database of 2,549 MSW(Municipal Solid Waste)landfills showed that there were 1,164 operating landfills in which 348 million short tons(316 million metric tons)of waste were landfilled in 2017.In total,these landfills occupy about 370 million square meters of land so it is not possible to monitor the generation of LFG(Landfill Gas)generation accurately,or collect most of the LFG generated.This study was based on the hypothesis that,on the average,methane generation is proportional to the tonnage of wastes landfilled annually.The Landfill Methane Outreach Program of the EPA(EPA-LMOP)compiles annual operating data of all methane-capturing landfills.Our analysis of the 2018 data for 396 LMOP operating landfills showed that 210 million short tons of wastes were deposited and 5.06 million short tons of methane were captured,i.e.,an average capture of 0.024-ton CH4/ton waste.On the basis of the anaerobic reaction of the DOC(Degradable Organic Carbon)in landfilled wastes,the average rate of methane generation from all operating U.S.landfills was estimated to be 0.05 ton of CH4 per ton of annual capacity;this number corresponds to bioreaction of about one half of the total organic carbon in MSW.On this basis,the average rate of CH4 emission from the 396 LMOP landfills was estimated to be 0.026-ton CH4 per annual ton of deposition and the average efficiency of LFG capture,48%.Adding up all 1,164 operating landfills,their total emission of methane was estimated at 11.9 million metric tons of CH4.At CH4/CO2 equivalence of 25,this number corresponds to CO2-eq emissions of 270 million metric tons,i.e.,5.1%of the U.S.energy related carbon dioxide emissions.

Co-thermal in-situ reduction of inorganic carbonates to reduce carbon-dioxide emission

Thermal decomposition of inorganic metal carbonates is the main path to prepare metal oxides;nonetheless,it is always accompanied by the emission of large amounts of CO_(2) as one of the gas products.This study reports a concept of co-thermal insitu reduction of inorganic carbonates by using the energy released by carbonate decomposition under pure hydrogen atmosphere,which reduces the decarboxylation temperature and significantly inhibits the CO_(2) emissions.A combination of hydrogen–deuterium exchange,isotope experiment,and density functional theory calculations demonstrates that the CO results from the selective cleavage of Ca–O bonds at the surface of CaCO_(3) via the direct hydrogenation mechanism at relatively low temperature.However,it undergoes the reverse water–gas shift reaction path at high temperature,i.e.,CO being produced by the reduction of CO_(2) released by the decomposition of carbonates.This study sheds light on the potential of green hydrogen technology for inorganic carbonate valorization toward high value-added products,which can facilitate the large-scale industrial applications.

Total entropy generation rate minimization configuration of a membrane reactor of methanol synthesis via carbon dioxide hydrogenation

The total entropy generation rate,internal exergy loss and exergy efficiency of the membrane reactor of methanol synthesis via carbon dioxide hydrogenation are compared,and the results show that the total entropy generation rate minimization is equivalent to the internal exergy loss minimization and the exergy efficiency maximization under the fixed inlet exergy.Therefore,this paper optimizes the membrane reactor with total entropy generation rate minimization as an optimization objective under a fixed methanol production rate.The optimal temperatures curves of exterior walls for three optimal membrane reactors with different boundary conditions are obtained by using optimal control theory and nonlinear programming.The influences of other geometric and operating parameters on optimization results of optimal membrane reactors are analyzed.The results indicate that when inlet temperatures of the reaction mixture and mixture in the permeable tube are unfixed,the optimizing curve of exterior wall temperature makes the total entropy generation rate of membrane reactor reduce by 12.39%compared with the total entropy generation rate of a reference membrane reactor with a linear exterior wall temperature.Decreasing the inlet molar flow rate of sweep gas and gas hourly space velocity and increasing inlet pressure of reaction mixture,the inlet pressure of mixture in the permeable tube and heat transfer coefficients are favorable for decreasing the total entropy generation rate in the membrane reactor.As the porosity of catalyst bed and reactor length increases,the minimum total entropy generation rate decreases first and then increases.From the perspective of engineering application,this paper establishes two membrane reactors(membrane reactor heated by three-stage furnaces of the same length and membrane reactor heated by threestage furnaces of different lengths),respectively.The minimum total entropy generation rates of the two reactors are reduced by11.67%and 11.79%compared with the total entropy generation rate in the reference membrane reactor,respectively.The obtained results are beneficial to the optimal design of energy-efficient membrane reactors.

East Africa Region Energy Projection with the Carbon Emissions for Conventional Energy

In this study we analyzed the generation and the potential of the electricity capacity of energy mix in East Africa from 2020 to 2040 including CO2 emission. The predicted results show that the electricity generated from hydro will dominate compared to gas, oil, coal, Solar PV, bio-energy and other renewable energy. Some forms of energies such as bio-energy, solar PV will contribute less, while the contribution of nuclear will remain insignificant. The oil will continue to emit a lot carbon dioxides compared to the emission from gas and coal. The emission of CO2 from total final consumption (TFC) of oil will be high compared to its emission from power generation (PG) of oil. More importantly, the results show a linear relationship between the energy outlook and time. This approach of modeling the energy in a linear form simplifies significantly the analysis of the electricity generation and capacity. Due to this high emission of CO2, a new policy and a transition from conventional to renewable should be implemented with clean and energy efficiency technology.

Energy Outlook in East Africa Region and the Carbon Emissions for Conventional En-ergy Projection (Part I)

In this investigation, we focus on the current energy sources and future projects situation in East Africa up to 2040. Electricity generation potential of energy mix and electrical capacity will be analyzed. For both electricity generation and electrical capacity, the data source shows that some forms of energies such bio-energy, solar PV, etc. will contribute less as well as with insignificant contribution of nuclear energy. Whereas hydro is dominating comparing with gas, oil, coal, solar PV, bio-energy and other renewables energies. From 2000 up to 2012, hydro and oil were only the one source of electricity generation. Starting from 2020, other forms of energies will appear and continue to increase at different rate. The international trade of electricity in this region will appear in 2020 and continue to increase as predicted by the data. Up to 2040, hydro will play a big role in electricity generation with other renewable energy sources, such as coal, oil, Gas, bio- energy and solar PV that will continue to increase at different rate. The share of solar PV in energy generation will slowly increase compared to other sources. The capacity of hydro and renewable energy sources will be high compared with other sources of energy such as bioenergy, coal, oil, PV solar, and gas. The results show also that bio-energy will increase slowly in electricity generation in comparison with other source of energies. The present report shows that oil will continue to emit a lot carbon dioxide compared to gas and coal. The emission of CO2 from total final consumption (TFC) of oil will continue to be high in comparing with CO2 emission from power generation (PG) of oil. But the emission of carbon dioxide from power generation of coal from 2025 until 2040 will be high compared with emission of CO2 generated from FTC of coal. In this period, the emission from TFC for gas will remain insignificant. The total final consumption emission of oil in general will dominate other emissions from both coal and gas. Due to this high emission of CO2, new technologies should be introduced in order to reduce gas pollution from TFC.

Highly efficient multi-metal catalysts for carbon dioxide reduction prepared from atomically sequenced metal organic frameworks

The precise control on the combination of multiple metal atoms in the structure of metal-organic frameworks(MOFs)endowed by reticular chemistry,allows the obtaining of materials with compositions that are programmed for achieving enhanced reactivity.The present work illustrates how through the transformation of MOFs with desired arrangements of metal cations,multi-metal spinel oxides with precise compositions can be obtained,and used as catalyst precursor for the reverse water-gas shift reaction.The differences in the spinel initial composition and structure,determined by neutron powder diffraction,influence the overall catalytic activity with changes in the process of in s itu formation of active,metal-oxide supported metal nanoparticles,which have been monitored and characterized with in situ X-ray diffraction and photoelectron spectroscopy studies.

Analysis of electric vehicle charging using the traditional generation expansion planning analysis tool WASP-IV

Electric vehicles(EV)are proposed as a measure to reduce greenhouse gas emissions in transport and support increased wind power penetration across modern power systems.Optimal benefits can only be achieved,if EVs are deployed effectively,so that the exhaust emissions are not substituted by additional emissions in the electricity sector,which can be implemented using Smart Grid controls.This research presents the results of an EV roll-out in the all island grid(AIG)in Ireland using the long term generation expansion planning model called the Wien Automatic System Planning IV(WASP-IV)tool to measure carbon dioxide emissions and changes in total energy.The model incorporates all generators and operational requirements while meeting environmental emissions,fuel availability and generator operational and maintenance constraints to optimize economic dispatch and unit commitment power dispatch.In the study three distinct scenarios are investigated base case,peak and off-peak charging to simulate the impacts of EV’s in the AIG up to 2025.

The highly selective catalytic hydrogenation of CO_(2)to CO over transition metal nitrides

Three transition metal-like facet centered cubic structured transition metal nitrides,γ-Mo_(2)N,β-W_(2)N andδ-NbN,are synthesized and applied in the reaction of CO_(2)hydrogenation to CO.Among the three nitride catalysts,theγ-Mo_(2)N exhibits superior activity to target product CO,which is 4.6 and 76 times higher than the other two counterparts ofβ-W_(2)N andδ-NbN at 600℃,respectively.Additionally,γ-Mo_(2)N exhibits excellent stability on both cyclic heating-cooling and high space velocity steady state operation.The deactivation degree of cyclic heating-cooling evaluation after 5 cycles and long-term stability performance at 773 and 873 K in 50 h are all less than 10%.In-situ XRD and kinetic studies suggest that theγ-Mo_(2)N itself is able to activate both of the reactants CO_(2)and H_(2).Below 400℃,the reaction mainly occurs at the surface ofγ-Mo_(2)N catalyst.CO_(2)and H_(2)competitively adsorbe on the surface of catalyst and CO_(2)is the relatively stronger surface adsorbate.At a higher temperature,the interstitial vacancies of theγ-Mo_(2)N can be reversibly filled with the oxygen from CO_(2)dissociation.Both of the surface and bulk phase sites ofγ-Mo_(2)N participate in the high temperature CO_(2)hydrogenation pathway.

A preliminary study of impact of reduced system inertia in a low-carbon power system

One of the important features of low-carbon electric power system is the massive deployment of renewable energy resources in the advent of a new carbon-strained economy.Wind generation is a major technology of generating electric power with zero carbon dioxide emission.In a power system with the high penetration of wind generation,the displacement of conventional synchronous generators with variable speed wind turbines reduces system inertia.This leads to larger system frequency deviation following a loss of large generation.In this paper,the impact of the reduction of system inertia on system frequency is analyzed as the result of the integration of a significant amount of wind generation into power systems.Furthermore,we present a preliminary study of the impact of the distribution of the inertia contributions from those online conventional synchronous generators on the rate of change of frequency(ROCOF)based on the total energy injected into the system due to the fault.The total fault energy is represented using Hamiltonian formulism.With the IEEE 39-bus system,it is shown that for a fault with the given injected total energy,clearing time,and location,the distribution of inertia contributions can significantly affect the magnitude of ROCOF.Moreover,for such a fault with different locations,the average of the magnitudes of ROCOF caused by the fault at different locations is larger when the distribution of the inertia contributions is more dispersed.

Atomically dispersed indium and cerium sites for selectively electroreduction of CO_(2)to formate

Currently,single-atom combo catalysts(SACCs)for carbon dioxide reduction reaction(CO_(2)RR)to the formation of HCOOH are still very limited,especially the lanthanide-based SACCs.In this work,the novel SACCs with atomically dispersed In and Ce active sites were successfully prepared on the nitrogen-doped carbon matrix(InCe/CN).Both aberration-corrected high-angle annular dark-field scanning transmission electron microscopy(AC-HAADF-STEM)images and the extended X-ray absorption fine structure(EXAFS)spectra proved the well-isolated In and Ce atoms.The as-prepared InCe/CN shows a high Faradaic efficiency(FE)(77%)and current density of HCOOH formation(j_(HCOOH))at-1.35 V vs.reversible hydrogen electrode(RHE),much higher than the single atom catalysts.Theoretical calculations have indicated that the introduced Ce single atom sites not only significantly promote electron transfer but also optimize the In-5p orbitals towards higher selectivity towards the HCOOH formation.This work innovatively extends the design of SACCs towards the main group and Ln metals for more applications.

Unraveling the interfacial effect of PdBi bimetallic catalysts on promoting CO_(2)electroreduction to formate

Through interface engineering and content control strategy,a PdBi bimetallic interface structure was constructed for the first time to selectively convert CO_(2)to formate with a remarkably high Faraday efficiency(FEformate)of 94%and a partial current density(jformate)of 34 mA·cm^(−2)at−0.8 V vs.reversible hydrogen electrode(RHE)in an H-cell.Moreover,the PdBi interface electrocatalyst even exhibited a high current density of 180 mA·cm^(−2)with formate selectivity up to 92%in a flow cell and could steadily operate for at least 20 h.Electrochemical in-situ attenuated total reflection surface enhanced infrared absorption spectroscopy(ATR-SEIRAS)confirmed that the PdBi interface could greatly weaken the adsorption of*CO intermediates due to electronic and geometric effects.Density functional theory(DFT)calculations also established that the PdBi interface regulated the CO_(2)-to-formate pathway by reducing the energy barrier toward HCOOH and largely weakening the adsorption of*CO intermediates on the catalyst surface.This study reveals that the unique PdBi bimetallic interface can provide a novel platform to study the reaction mechanism through combining in-situ ATR-SEIRAS and DFT calculations.