The Carbon Age: Dark element, brighter future

New materials built on carbon's many forms will function as building blocks for cleaner batteries, water, and air. EnerG2 CTO Aaron Feaver outlines the green-tech opportunities.

Editors' note: This is a guest column. See Aaron Feaver's bio below.

Humankind has seen the Stone Age, the Golden Age, and the Iron Age. Some would argue the 20th century should be called the Silicon Age. Based on the events of its first 10 years, the 21st century may very well become known as the Carbon Age.

A computer-rendered view inside a carbon nanotube ghutchis/Flickr

An important tension is unfolding between two types of carbon--atmospheric carbon in the form of carbon dioxide emissions, and elemental carbon as a building block for a new generation of devices designed to manage and abate those same pollutants. Our way of life has become dependent on energy generated by the process of extracting carbon from the earth in the form of fossil fuels and then burning it to form carbon dioxide. Meanwhile, we have begun developing carbon in solid form as an advanced material to counter the effects of its atmospheric cousin.

From the days of Thomas Edison, when an exhaustive list of carbon fibers were pyrolyzed, or thermochemically decomposed sans oxygen, from natural materials to form the filaments of the first successful lightbulb, to the development of activated carbon as the first commercial nanomaterial, to the discovery of buckyballs and the invention of carbon nanotubes, carbon has always generated an abundance of near-term change, cutting-edge breakthroughs, and even economic prosperity.

Our future will be brighter because new materials built on the many allotropes of carbon will function as the base-building blocks for a host of solutions--including cleaner batteries, cleaner water, and cleaner air--that will benefit our society, our economies, and our planet.

There are legions of carbon-based innovations to watch between now and 2020. As the research deepens and expands, and the technologies are fully developed and rolled out, new products and processes will be embraced by the automotive industry for hybrid electric vehicles, by electronics manufacturers for enhancing the life and usability of consumer goods, and by a variety of industrial customers to deliver an ever-increasing breadth of new ways to improve energy efficiency.

Here are the highlights of what we can expect:

Lithium ion batteries
They are among the best-performing batteries because of their combination of relatively high power and energy density. They also, unfortunately, have a very high cost. While relatively well known in the market, the role of their carbon ingredients is less understood and appreciated. These batteries use a lithium-based oxide cathode, which can store an abundance of lithium but is not conductive.

In many cases, carbon is added to this cathode as a conductivity enhancer to reduce resistance and increase the power capability of the cell. In addition, the active component of the anode is nearly 100 percent carbon. Look for enhancements in lithium ion battery performance to continue, but this time based on carbon anode advancements. The graphite anode will be replaced with high surface area carbons, or carbon-based nanocomposites comprised of carbon- and lithium-alloying elements such as silicon, aluminum, and tin, which will enable doubling or tripling energy and power density. This will result in longer-lived batteries with more power and energy for all kinds of applications, including consumer electronics such as laptops and cell phones, as well as hybrid or plug-in vehicles.

Carbon fiber
It is spurring a new generation of lightweight vehicles that could entirely eschew steel. Prices are dropping as volumes increase. Lightweight carbon fiber, combined with lightweight aluminum, is dramatically decreasing the weight of vehicles and increasing fuel efficiency. This trend can continue, if carbon fiber technology advances and becomes less costly. As is the case in aerospace, where half of efficiency gains are from engine improvements and half of the gains are from weight reduction, automobiles will begin to move into a new paradigm where "lightweighting" is seen as a major way to increase miles per gallon.

We currently all drive vehicles that are an order of magnitude heavier than the passengers they carry. By combining the energy and power improvements derived from carbon in energy storage systems with carbon-based lightweight vehicles, we may soon see reasonably priced all-electric automobiles that take off like Ferraris, have a 500- mile driving range, and have the capability to safely carry five passengers and all their luggage.

Wholly dependent on the performance of their carbon electrodes, they store and release energy an order of magnitude faster than batteries. Ultracapacitors are typically used for power supply and kinetic energy recapture in industrial environments, grid augmentation, portable electronics, and energy storage for critical infrastructure and heavy hybrids like buses and garbage trucks. Look for ultracapacitors to enter the mainstream automotive industry as energy storage for start-stop, regenerative braking, and rapid acceleration in micro, mild, full, and plug-in hybrid vehicles.

Ultracapacitors, which charge and discharge power rapidly, are being considered as a complement to batteries for different applications, including electric vehicles.
Advanced carbon-based materials can be used in a number of energy-related areas, including ultracapacitors, which store electrical charge on porous carbon electrodes. Creating a material with a lot of surface area, storage devices can hold more charge. Ultracapacitors, which charge and discharge power rapidly, are being considered as a complement to batteries for different applications, including electric vehicles. Energ2

Enhancements to the carbon in ultracapacitors will enable increased voltage rating of devices, which will exponentially increase their energy and power. By 2012, we should anticipate that widespread adoption of microhybrids will begin, and engineered carbon will help usher in an era in which combustion engines no longer idle in traffic.

They combine the properties of batteries and ultracapacitors to deliver a device with higher power than a battery and higher energy density than an ultracapacitor. Pseudocapacitors are not widely available now, but look for a Japanese- and Korean-led push to introduce lithium ion-based devices, with carbon serving as a majority of the electrode material.

These devices will likely contain one carbon electrode that closely resembles an ultracapacitor and one graphitic carbon similar to a lithium ion anode. Both of these carbon materials will be tuned for this unique application, in terms of pore size, particle size, and surface area.

Just as ultracapacitors have bridged the difference between electrolytic capacitors and batteries, pseudocapacitors will further blur the line between ultracapacitors and batteries. There are many areas--including transportation, industrial, and renewable energy/grid applications--that will be enabled by an energy storage system where a million cycles (think ultracapacitors) is overkill, but where 1,000 cycles (think lithium ion batteries) is inadequate; this is where an energy/power compromise between the two technologies is needed.

Catalyst support platforms
They will be needed for a multitude of industrial and environmental applications, such as biofuels, hydrocarbon cracking and, potentially, reuse of atmospheric carbon dioxide. As developing countries embrace an appetite for first-world lifestyles, we will need to find ways to do more with less. Catalysts are a route for reducing the amount of energy needed to perform a huge array of industrial processes that--while invisible to most of us--are used to produce the products that we use every day.

Carbon materials are ideal catalyst supports because they can be relatively inert at high temperatures, are electrically conductive, are porous with a high surface area, and, especially in the case of synthetic nanocarbons, can readily accommodate the addition of catalyst materials in their manufacturing processes.

As nanoscale catalysts become mainstream and move into more established industries, watch for low-cost nanostructured carbon to be a key support material for improving the efficiency of the reactions that enable everything from drugs to bulk chemicals to food to energy.

Fuel cells
They were actually invented before the internal combustion engine, but the technology quickly fell by the wayside, as diesel- and gasoline-fueled engines became more ubiquitous. Various types of fuel cells have experienced a brief resurgence over the last 10 years, as the promise of the hydrogen economy gained momentum. These devices use an electrochemical reaction, rather than combustion to oxidize various fuels, and the result is direct generation of electrons at the electrode.

Carbon can be used in many fuel cell chemistries but is most often used as an electrode in one type of fuel cell--the proton exchange membrane fuel cell, or PEM. Carbon is combined with a catalyst to create the "triple point," where fuel, oxidant, and catalyst comingle in an electrically conductive environment that enables the reaction. As hydrogen research begins to develop low-cost methods for production and storage of this high-energy gas, look for a rejuvenation of PEM fuel cells as an energy source. By replacing platinum with a cheaper nanoscale catalyst, carbon will drive substantial cost reductions while improving efficiency in PEM fuel cells.

Capacitive deionization
This is a relatively new technology for desalination and water treatment. Even as our reliance on--and conflicts over--petroleum decrease, new battles (both philosophical and physical) will be fought over fresh water. Capacitive deionization of salt water creates freshwater by the adsorption of ions in an electric field at the surface of porous carbon electrodes.

In many ways, capacitive deionization uses a structure like an ultracapacitor, with contaminated or salt water as the electrolyte. The process is constantly recyclable, and contaminants are removed from the system without the need to change a filter.

In the United States, we have already seen internal strife, as states vie for the water resources of the Colorado River. This conflict pales in comparison to that surrounding the stressed Himalayan Watershed, which supplies 47 percent of the world's population with water. Watch for capacitive deionization to become more mainstream, as population centers look to the oceans for their water supplies, and as the carbon technology enabling it becomes less expensive.

Adsorbed natural gas storage
Also known as ANG storage, this technology makes use of activated microporous carbons that function just like a natural-gas sponge. ANG storage containers enabled by advanced carbon technology allow for increased safety, more flexible form factors for vehicular applications, and decreased cost, due to compressor inefficiencies. These attributes will all contribute toward wider adoption of natural gas as a transportation fuel, and this can substantially reduce carbon emissions.

The right carbon will allow ANG vehicles to reach performance parity with gasoline at a much lower cost to the environment. In the future, net-zero carbon dioxide methane--produced by combining renewable energy, carbon from atmospheric carbon dioxide, and hydrogen from water--could be used to power hybrid vehicles.

While many are working on hydrogen as the ultimate clean fuel, the relative ease of storing methane in carbon-based ANG systems, as well as its compatibility with fuel cells, internal combustion engines, and grid-level power plants, could make renewable methane a more affordable clean fuel of the future.

Hydrogen storage
It can be accomplished using high-density solid materials instead of compressed or liquefied hydrogen. Research is focused on chemical compounds that reversibly store and release hydrogen during an exothermic or endothermic reaction. Carbon will be used as a support matrix in improving the cyclability and kinetics of these solid-state hydrogen materials.

Heat needs to be added and removed for these reactions to take place, and the materials often need to be maintained at the nanoscale; both of these attributes can be improved through the addition of carbon. By inserting high-density hydrogen storage compounds into the nanopores of custom-designed carbons, those materials can remain confined at the nanoscale, while in intimate contact with a heat conduction medium--the carbon--to improve heat flow in or out of the system, as they undergo thermodynamically active changes.

Batteries are the leading technology for portable energy storage, but look for hydrogen storage and fuel cells to become competitive, as the research evolves over the next 10 years.

Every generation has its own favorite elements on the periodic table. In the Middle Ages and Renaissance, gold and silver were economic motivators; later on, sulfur for gunpowder became a force to be reckoned with; the nuclear era brought uranium to the top; information technology made silicon a star; and now some clean-technology analysts are focused on lithium. From my perspective, however, the future is about carbon.

Carbon may present itself in a dark, black form, but I believe that it presages brighter days ahead for all of us. That's part of the supreme irony: when it appears as part of carbon dioxide, carbon pollutes the atmosphere; when it's deployed in its pure and unadulterated form, however, it can play a major role in scrubbing clean our skies and our waterways--and that's welcome news for the many generations to come.

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