Hybrid Energy Harvesters for Hydrogen Production

David Novitski is a new guest web-writer for Energy and Environmental Science. David is a PhD student in Dr. Steven Holdcroft’s group at Simon Fraser University. When not in the lab, he enjoys eating food, contemplating the universe, and mountain biking.

Researchers in Atlanta, GA have developed a device that produces hydrogen gas from waste heat, solar, and/or mechanical energies.

A hybrid energy cell for self-powered water splitting

Recent research conducted at Georgia Institute of Technology by Yang and coworkers have developed a new hybrid energy harvesting device to aid in the effort of hydrogen fuel production. Currently, hydrogen gas for use in industry is predominantly generated by steam reformation of methane or natural gas. This method produces greenhouse gas, requires high temperatures, and utilizes non-renewable resources.

Electrolytic production of hydrogen from water is one popular contender, due to its simplicity and abundance of reactants, however it is currently a more expensive process than through steam reformation. By developing a hybrid device that can take advantage of multiple modes of otherwise wasted energy, an “ambient” fuel generator can be realized.

The novelty in the present work is the combination of solar, thermal, and mechanical energies in the electrolysis of water. By matching a Si-pyramid solar cell with a Bi2Te3 based thermoelectric cell, along with a polyamide-perfluoroalkoxy based triboelectric nanogenerator, simultaneous energy harvesting can occur under a variety of environmental conditions. The group has reported H2 gas production at a rate of 4 x10-4 mL/s under hybrid generation mode. The technology can also be made to charge a Li-ion battery for on-demand hydrogen production, to compensate for environmental fluctuations.

With optimization, technology such as this can one day exist as a remote platform on the open ocean, passively generating hydrogen gas to be either pipelined to land, or used immediately for fuel cell powered ships.

David Novitski EES guest web-writer

by David Novitski

Interested? Read the full communication in Energy and Environmental Science here:

A hybrid energy cell for self-powered water splitting
Ya Yang, Hulin Zhang, Zong-Hong Lin, Yan Liu, Jun Chen, Ziyin Lin, Yu Sheng Zhou, Ching Ping Wonga and Zhong Lin Wang
Energy Environ. Sci., 2013, Advance Article
DOI: 10.1039/C3EE41485J

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Towards the 3rd breakthrough of Mg rechargeable batteries

Martina Congiu is a new guest web-writer for Energy and Environmental Science. Martina is currently a Research Technician in Dr Henry Snaith’s group at the University of Oxford. During her free time from work, she loves cooking and cycling in the outskirts of Oxford.

If I say rechargeable batteries, most people think immediately about Li-ion batteries as the most successful achievement in this field. However, some issues related to safety, energy density and price are now forcing Li-ion battery research through big challenges, highlighting Mg batteries as a promising alternative technology for energy storage and conversion.

In their recent PCCP Perspective, Doron Aurbach and co-authors provide a closer look at Mg rechargeable batteries and guide the reader through 23 years of research since the first breakthrough in 1990 by Gregory et al. Gregory’s group demonstrated that Mg organo-borate moieties in solution, such as Mg(BBu2Ph2)2 in THF, allow magnesium to be deposited/dissolved successfully in a reversible process, despite the absence of highly reducing Grignard reagents.

This work led to a 2nd breakthrough in 2000 by Aurbach et al. who developed new electrolyte solutions comprised of ethereal solvents and complexes of the Mg(AlCl4-nRn)2 type (R = alkyl or aryl groups), with 100% reversibility of Mg deposition and anodic stability of 2.1 V vs. Mg.

Some companies, including Sony, LG and Toyota, already have prototypes of high energy density Mg rechargeable batteries with 2-3 V anodic stability. Compatibility needs to be enhanced in order to allow further developments of efficient rechargeable batteries.

by Martina Congiu

Interested in a better understanding about this field? Read more from the Perspective article:

Mg rechargeable batteries: an on-going challenge
Hyun Deog Yoo, Ivgeni Shterenberg, Yosef Gofer, Gregory Gershinsky, Nir Pour and Doron Aurbach
DOI: 10.1039/C3EE40871J

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This week’s HOT articles

Take a look at our selection of exciting articles that have been recently published online:

$ per W metrics for thermoelectric power generation: beyond ZT
Shannon K. Yee, Saniya LeBlanc, Kenneth E. Goodson and Chris Dames  
DOI: 10.1039/C3EE41504J

Controlled synthesis of hierarchical CoxMn3−xO4 array micro-/nanostructures with tunable morphology and composition as integrated electrodes for lithium-ion batteries
Le Yu, Lei Zhang, Hao Bin Wu, Genqiang Zhang and Xiong Wen (David) Lou   
DOI: 10.1039/C3EE41181H

Oxygen-tolerant coenzyme A-acylating aldehyde dehydrogenase facilitates efficient photosynthetic n-butanol biosynthesis in cyanobacteria
Ethan I. Lan, Soo Y. Ro and James C. Liao  
DOI: 10.1039/C3EE41405A

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Cobalt redox couple boosts thermoelectric cells: EES article in Chemistry World

Scientists in Australia have improved a technology that recycles waste heat into useable energy by using ionic liquids containing cobalt redox couples as the electrolytes in thermoelectric cells.

Thermoelectrochemical devices generate power when a temperature gradient exists across a redox couple. The power generated is not yet enough to use as a primary energy source, but thermoelectric cells are useful for harvesting waste energy from energy production.

Aqueous or organic solutions traditionally form the electrolyte in thermoelectrochemical cells. The volatility of water and most organic solvents restrict working temperatures as the solvent can evaporate, reducing the long term stability and power output of the cells. Ionic liquids have extremely low vapour pressures, because of the strong ionic interactions, so do not easily evaporate. Their low thermal conductivity compared to water also helps ionic liquids maintain the temperature gradient across the device.

Interested to know more? 

Read the article in EES:

High Seebeck coefficient redox ionic liquid electrolytes for thermal energy harvesting
Theodore J. Abraham, Douglas R. MacFarlane and Jennifer M. Pringle  
Energy Environ. Sci., 2013, Advance Article
DOI: 10.1039/C3EE41608A

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UPDATE – Challenges in Chemical Renewable Energy (ISACS12)

Early Bird Deadline – 12 July 2013

Don’t forget that early bird registration for Challenges in Chemical Renewable Energy (ISACS12) closes this Friday. Make sure you register for this significant conference before 12 July 2013 to guarantee your place at the reduced fee.

For full details including themes and speaker details, please visit the dedicated website.

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Mg rechargeable batteries: an on-going challenge

Alexander Forse is a guest web-writer for Energy and Environmental Science. Alexander is a PhD student in Professor Clare Grey’s group at the University of Cambridge.
When not in the lab, he enjoys playing football, skateboarding and producing electronic music.

In their recent perspective article in Energy and Environmental Science, Professor Doron Aurbach and co-workers highlight key developments in magnesium-ion battery technology.

Mg rechargeable batteries: an on-going challengeRechargeable batteries are ubiquitous in portable electronics, and are expected to play an important role in electric vehicles and grid storage in the future. While lithium-ion technology is the current state of the art, concerns remain about the supplies of lithium on Earth. As such, alternative systems such as magnesium-ion batteries are being developed. Magnesium is the fifth most abundant element in the Earth’s crust and its bivalency means that it can in principle store more energy per unit volume than lithium metal.

A key requirement in magnesium-ion battery technology is reversible deposition of magnesium on the magnesium metal anode. However, most organic solvents and simple magnesium salts react with magnesium to form a so-called passivation layer on the anode, precluding reversible magnesium deposition and further charge-discharge cycles. Vital progress was made with the discovery of electrolytes that were stable in the presence of the magnesium anode. In particular, reaction of AlCl3-nRn lewis acids with R2Mg lewis bases in ether solvents yielded electrolyte solutions which were stable up to voltages of 2.1 V vs. magnesium metal. The combination of these so-called dicholoro-complex (DCC) electrolytes with Chevrel phase intercalation cathodes (e.g. Mo6S8) and magnesium anodes yielded the first working prototypes for reversible magnesium-ion batteries.

While these first prototypes constituted a great breakthrough, relatively low energy densities and lacking performance at high rates precluded their commercialisation. Ongoing work focuses on finding new electrolytes with wider electrochemical stability windows, as well as new cathode and anode materials. One interesting possibility is to replace the magnesium anode with metal alloys of bismuth and antinomy, sidestepping the problems associated with the reactivity of magnesium and allowing more conventional electrolytes to be used.

Read more in the perspective article in Energy and Environmental Science:

Mg rechargeable batteries: an on-going challenge
Hyun Deog Yoo, Ivgeni Shterenberg, Yosef Gofer, Gregory Gershinsky, Nir Pour and Doron Aurbach
Energy Environ. Sci., 2013, Advance Article
DOI: 10.1039/C3EE40871J

By Alexander Forse

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This week’s HOT articles

These articles are HOT as recommended by the referees…

Take a look at our selection of exciting articles that have been recently published online:

Post-combustion carbon dioxide capture using electrochemically mediated amine regeneration
Michael C. Stern, Fritz Simeon, Howard Herzog and T. Alan Hatton
DOI: 10.1039/C3EE41165F

Improving the long-term stability of PBDTTPD polymer solar cells through material purification aimed at removing organic impurities
William R. Mateker, Jessica D. Douglas, Clément Cabanetos, I. T. Sachs-Quintana, Jonathan A. Bartelt, Eric T. Hoke, Abdulrahman El Labban, Pierre M. Beaujuge, Jean M. J. Fréchet and Michael D. McGehee
DOI: 10.1039/C3EE41328D

New materials based on a layered sodium titanate for dual electrochemical Na and Li intercalation systems
Mona Shirpour, Jordi Cabana and Marca Doeff
DOI: 10.1039/C3EE41037D

Towards high energy density sodium ion batteries through electrolyte optimization
Alexandre Ponrouch, Rémi Dedryvère, Damien Monti, Atif E. Demet, Jean Marcel Ateba Mba, Laurence Croguennec, Christian Masquelier, Patrik Johansson and M. Rosa Palacín
DOI: 10.1039/C3EE41379A

Charge transport in lithium peroxide: relevance for rechargeable metal–air batteries
Maxwell D. Radin and Donald J. Siegel
DOI: 10.1039/C3EE41632A

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William Hague learns about EES

Energy & Environmental Science (EES) Editor-in-chief Nathan Lewis and EES Advisory Board member Harry Gray describe the journal EES and the story of its continuing success to William Hague, the British Foreign Secretary and First Secretary of State, during his recent visit to Caltech, USA.

From left to right: Harry Gray, Nathan Lewis and William Hague

Here they are holding an issue of EES.

Harry Gray, Nathan Lewis, William Hague, Energy & Environmental Science

From left to right: Harry Gray, Nathan Lewis and William Hague

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The Hidden Value Of Carbon Dioxide – EES article in C&EN News

Thomas Jaramillo and co-workers developed of a very sensitive experiment to identify and quantify CO2 electroreduction products. Their results, presented in their recent EES article, provide a comprehensive view of the reaction chemistry.

A recent C&EN article discussNew insights into the electrochemical reduction of carbon dioxide on metallic copper surfaceses the work of Jaramillo’s group. The C&EN article focuses on recent developments towards the interesting goal of converting CO2 into useful products using electrochemistry: “Carbon dioxide gets a lot of attention—most of it negative—as a greenhouse gas. But if CO2 could be converted in a cost-effective manner to valuable products, the ubiquitous small molecule so often reviled for its role in climate change might start to lose its bad rap.”

Read more in the C&EN article here…

…and read the article in EES:

New insights into the electrochemical reduction of carbon dioxide on metallic copper surfaces
Kendra P. Kuhl, Etosha R. Cave, David N. Abram and Thomas F. Jaramillo
DOI: 10.1039/C2EE21234J

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Thermoelectric cost analysis – EES article in Chemistry World

Scientists from the US have derived a metric to analyse the cost of power generation using thermoelectric technology. The metric shows that thermoelectric devices have greater potential in large-scale power generation than previously thought.

Thermoelectric generators convert heat into electricity by a physical phenomenon called the Seebeck effect. They are compact, robust, and have no moving parts. This means they are useful for low-maintenance applications, such as in spacecrafts. However, their device efficiencies – the power produced for a certain heat flow – are low, so they are not used for large-scale power generation.

Thermoelectric research has typically focussed on the dimensionless figure-of-merit ZT, a metric that relates directly to device efficiency. Shannon Yee from the University of California Berkeley, part of the team that performed the analysis, explains that for power generation to be commercially viable, what really matters is a technology’s capital cost per watt and not just its device efficiency: ‘we found that the design that minimises a system’s cost per watt value is generally very different to the design that maximises efficiency.’

Interested to know more? Read the full news article in Chemistry World here…

Read the article by Yee, Dames et al. in EES:

$/W Metrics for Thermoelectric Power Generation: Beyond ZT
Shannon K Yee, Saniya LeBlanc, Ken Goodson and Chris Dames
DOI: 10.1039/C3EE41504J

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