scholarly journals Combining scaling relationships overcomes rate versus overpotential trade-offs in O2 molecular electrocatalysis

2020 ◽  
Vol 6 (11) ◽  
pp. eaaz3318 ◽  
Author(s):  
Daniel J. Martin ◽  
Brandon Q. Mercado ◽  
James M. Mayer
Keyword(s):  
Energy Efficiency ◽  
Reaction Rate ◽  
Electrical Energy ◽  
Reduction Reaction ◽  
Iron Porphyrin ◽  
Scaling Relationships ◽  
Anionic Ligand ◽  
Trade Offs ◽  
Rate Versus ◽  
Molecular Catalysts

The development of advanced chemical-to-electrical energy conversions requires fast and efficient electrocatalysis of multielectron/multiproton reactions, such as the oxygen reduction reaction (ORR). Using molecular catalysts, correlations between the reaction rate and energy efficiency have recently been identified. Improved catalysis requires circumventing the rate versus overpotential trade-offs implied by such “scaling relationships.” Described here is an ORR system—using a soluble iron porphyrin and weak acids—with the best reported combination of rate and efficiency for a soluble ORR catalyst. This advance is achieved not by “breaking” scaling relationships but rather by combining two of them. Key to this behavior is a polycationic ligand, which enhances anionic ligand binding and changes the catalyst E1/2. These results show how combining scaling relationships is a powerful way toward improved electrocatalysis.

O2 Reduction Reaction by Biologically Relevant Anionic Ligand Bound Iron Porphyrin Complexes

2013 ◽  
Vol 52 (22) ◽  
pp. 12963-12971 ◽  
Author(s):  
Subhra Samanta ◽  
Pradip Kumar Das ◽  
Sudipta Chatterjee ◽  
Kushal Sengupta ◽  
Biswajit Mondal ◽  
...  
Keyword(s):  
Reduction Reaction ◽  
Iron Porphyrin ◽  
Biologically Relevant ◽  
Anionic Ligand ◽  
O2 Reduction ◽  
Iron Porphyrin Complexes

An NADH-Inspired Redox Mediator Strategy to Promote Second-Sphere Electron and Proton Transfer for Cooperative Electrochemical CO2 Reduction Catalyzed by Iron Porphyrin

2020 ◽  
Author(s):  
Peter T. Smith ◽  
Sophia Weng ◽  
Christopher Chang
Keyword(s):  
Proton Transfer ◽  
Co2 Reduction ◽  
Iron Porphyrin ◽  
Redox Mediators ◽  
Reservoir Properties ◽  
Proton Reduction ◽  
Electrochemical Co2 Reduction ◽  
Starting Point ◽  
Rate Improvement ◽  
Molecular Catalysts

We present a bioinspired strategy for enhancing electrochemical carbon dioxide reduction catalysis by cooperative use of base-metal molecular catalysts with intermolecular second-sphere redox mediators that facilitate both electron and proton transfer. Functional synthetic mimics of the biological redox cofactor NADH, which are electrochemically stable and are capable of mediating both electron and proton transfer, can enhance the activity of an iron porphyrin catalyst for electrochemical reduction of CO<sub>2</sub> to CO, achieving a 13-fold rate improvement without altering the intrinsic high selectivity of this catalyst platform for CO<sub>2</sub> versus proton reduction. Evaluation of a systematic series of NADH analogs and redox-inactive control additives with varying proton and electron reservoir properties reveals that both electron and proton transfer contribute to the observed catalytic enhancements. This work establishes that second-sphere dual control of electron and proton inventories is a viable design strategy for developing more effective electrocatalysts for CO<sub>2</sub> reduction, providing a starting point for broader applications of this approach to other multi-electron, multi-proton transformations.

scholarly journals Characterizing Color Quality, Damage to Artwork, and Light Intensity of Multi-Primary LEDs for Museums

Heritage ◽  
2021 ◽  
Vol 4 (1) ◽  
pp. 188-197
Author(s):  
Dorukalp Durmus
Keyword(s):  
Energy Efficiency ◽  
Appearance Model ◽  
Light Sources ◽  
Great Flexibility ◽  
Oil Paintings ◽  
Damage Reduction ◽  
Output Variability ◽  
Color Quality ◽  
Trade Offs

Light causes damage when it is absorbed by sensitive artwork, such as oil paintings. However, light is needed to initiate vision and display artwork. The dilemma between visibility and damage, coupled with the inverse relationship between color quality and energy efficiency, poses a challenge for curators, conservators, and lighting designers in identifying optimal light sources. Multi-primary LEDs can provide great flexibility in terms of color quality, damage reduction, and energy efficiency for artwork illumination. However, there are no established metrics that quantify the output variability or highlight the trade-offs between different metrics. Here, various metrics related to museum lighting (damage, the color quality of paintings, illuminance, luminous efficacy of radiation) are analyzed using a voxelated 3-D volume. The continuous data in each dimension of the 3-D volume are converted to discrete data by identifying a significant minimum value (unit voxel). Resulting discretized 3-D volumes display the trade-offs between selected measures. It is possible to quantify the volume of the graph by summing unique voxels, which enables comparison of the performance of different light sources. The proposed representation model can be used for individual pigments or paintings with numerous pigments. The proposed method can be the foundation of a damage appearance model (DAM).

scholarly journals Effect of Different SiO2 Polymorphs on the Reaction Between SiO2 and SiC in Si Production

2021 ◽  
Vol 52 (2) ◽  
pp. 792-803
Author(s):  
Marit Buhaug Folstad ◽  
Eli Ringdalen ◽  
Halvard Tveit ◽  
Merete Tangstad
Keyword(s):  
Amorphous Silica ◽  
Reaction Rate ◽  
Reduction Reaction ◽  
Minor Effect ◽  
Target Temperature ◽  
Heating Rates ◽  
Significant Difference ◽  
Sio2 Polymorphs ◽  
A Minor ◽  
Final Composition

AbstractThis work investigates the phase transformations in silica (SiO2) during heating to a target temperature between 1700 °C and 1900 °C and the effect of SiO2 polymorphs on the reduction reaction 2SiO2 + SiC = 3SiO + CO in silicon production. Different heating rates up to target temperature have been used to achieve the different compositions of quartz, amorphous silica and cristobalite. The different heating rates had a minor effect on the final composition, and longer time at temperatures > 1400 °C were necessary to achieve greater variations in the final composition. Heating above the melting temperature gave more amorphous silica and less cristobalite, as amorphous silica also may form from β-cristobalite. Isothermal furnace experiments were conducted to study the extent of the reduction reaction. This study did not find any significant difference in the effects of quartz, amorphous silica or cristobalite. Increased temperature from 1700 °C to 1900 °C increased the reaction rate.

scholarly journals Specific Electrical Energy Consumption and CO2 Emissions Assessment of Agrifood Industries in the Central Region of Portugal

2014 ◽  
Vol 675-677 ◽  
pp. 1880-1886 ◽  
Author(s):  
Pedro D. Silva ◽  
Pedro Dinis Gaspar ◽  
J. Nunes ◽  
L.P.A Andrade
Keyword(s):  
Energy Efficiency ◽  
Energy Consumption ◽  
Food Safety ◽  
Central Region ◽  
Electrical Energy ◽  
Electrical Energy Consumption ◽  
Reference Levels ◽  
Energy Characteristics ◽  
Result Analysis

This paper provides a characterization of the electrical energy consumption of agrifood industries located in the central region of Portugal that use refrigeration systems to ensure the food safety. The study is based on the result analysis of survey data and energy characteristics of the participating companies belonging to the following agrifood sectors: meat, dairy, horticultural, distribution and wine. Through the quantification of energy consumption of companies is possible to determine the amount of greenhouse gases (GHGs) emissions indexed to its manufacturing process. Comparing the energy and GHGs emissions indexes of companies of a sector and between sectors is possible to create reference levels. With the results of this work is possible to rating the companies in relation to reference levels of energy and GHGs emissions and thus promote the rational use of energy by the application of practice measures for the improvement of the energy efficiency and the reduction of GHGs emissions.

scholarly journals Energy efficiency trade-offs in small to large electric vehicles

2020 ◽  
Vol 32 (1) ◽  
Author(s):  
Martin Weiss ◽  
Kira Christina Cloos ◽  
Eckard Helmers
Keyword(s):  
Energy Efficiency ◽  
Electric Vehicles ◽  
Trade Offs

Reduction Kinetics of Mill Scale Briquettes by Using A3 Fine Coal as a Reductant

2021 ◽  
Vol 21 (4) ◽  
pp. 2563-2567
Author(s):  
Nguyen Hoang Viet ◽  
Pham Ngoc Dieu Quynh ◽  
Nguyen Thi Hoang Oanh
Keyword(s):  
Reaction Rate ◽  
Reduction Process ◽  
Reduction Reaction ◽  
Reaction Rate Constant ◽  
Reduction Degree ◽  
Furnace Temperature ◽  
Time Duration ◽  
Mill Scale ◽  
Fine Coal ◽  
Kinetics Of

In this work, a mixture of mill scale with 5 wt% molasses as binder was pressed under pressure of 200 MPa to prepare briquettes. The reduction process was performed at the temperature of 1000, 1050, 1100, 1150 and 1200 °C in the bed of A3 fine coal as the reductant. The degree of reduction was evaluated at time duration of 15, 30, 45, 60, 90 and 150 minutes, after the furnace temperature reached the predetermined reduction temperature. The highest reduction degree is 94.7% at the reduction process temperature of 1200 °C. Reaction rate constant (k) increased from 4.63×10-4 to 5.03×10-3 min-1 when the temperature increased from 1000 to 1200 °C. The apparent activation energy of the reduction reaction (Ea) is about 95.6 kJ/mole.

Increase of energy efficiency ratio of a direct evaporative cooler by dynamic behavior with energy and exergy analysis

2021 ◽  
pp. 095440622110420
Author(s):  
Behzad Omidi Kashani
Keyword(s):  
Energy Efficiency ◽  
Electrical Energy ◽  
Coefficient Of Performance ◽  
Dynamic State ◽  
Circulation Rate ◽  
Cooling Load ◽  
Efficiency Ratio ◽  
Static State ◽  
Circulation Pump ◽  
Water Rate

The present research is about increasing the energy efficiency ratio (EER) in current direct evaporative coolers (DEC) in Iran. Increasing the cooling load and reducing the electrical energy consumption simultaneously (increasing the energy efficiency ratio (EER)) in DEC are the main goals of manufacturers and consumers of this device. When the circulation water pump runs continuously (static state), the circulation water rate is about 1.89 to 2.90 times of the amounts recommended in the reasonable standards. In order to adjust the circulation water rate to the recommended amount by standards, the present study has utilized repetitive cyclic scheduling programs to reduce the circulation rate to the optimal amount, (by turning the circulation pump on and off by dynamic pattern operation). In other words, the circulation pump stays on only for a certain period of a working cycle, and then the pump stays off for the rest of it. The cooling load and EER were measured based on ASHRAE 133 (2015). The results indicated that the cooling load in the dynamic state increased by 5.03 and 6.18 percent compared to the static state at low and high fan speeds, respectively. Moreover, in comparison with the static state, the amount of electrical energy consumed (kW-hr) in the dynamic state decreased by 8.8 and 4.2 percent at low and high fan speeds, respectively. Finally, the coefficient of performance (COP or EER) of the DEC in the dynamic state is increased by 15.16 and 10.78 in comparison with the static state at low and high fan speeds, respectively.

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