Lawrence Berkeley National Laboratory (LBNL) scientists have developed a new electrocatalyst that can directly convert carbon dioxide into multicarbon fuels and alcohols using record-low inputs of energy. The work is the latest in a round of studies tackling the challenge of a creating a clean chemical manufacturing system that can put carbon dioxide to good use.

Schematic of a new catalyst made of copper nanoparticles that converts carbon dioxide to multicarbon products (ethylene, ethanol, and propanol). At top left are scanning electron microscope images of the copper nanoparticles. The transformation of the nanoparticles from spheres to cube-like structures is key to keeping the energy input low for the reactions. Image Credit: Dohyung Kim/Berkeley Lab. Click image for the largest view.

In the new study, published this week in the Proceedings of the National Academy of Sciences (PNAS), a team led by LBNL scientist Peidong Yang discovered that an electrocatalyst made up of copper nanoparticles provided the conditions necessary to break down carbon dioxide to form ethylene, ethanol, and propanol.

All those products contain two to three carbon atoms, and all are considered high-value products in modern life. Ethylene is the basic ingredient used to make plastic films and bottles as well as polyvinyl chloride (PVC) pipes. Ethanol, commonly made from biomass, has already established its place as a biofuel additive for gasoline. While propanol is a very effective fuel, it is currently too costly to manufacture to be used for that purpose.

To gauge the energy efficiency of the catalyst, scientists consider the thermodynamic potential of products – the amount of energy that can be gained in an electrochemical reaction – and the amount of extra voltage needed above that thermodynamic potential to drive the reaction at sufficient reaction rates. That extra voltage is called the overpotential; the lower the overpotential, the more efficient the catalyst.

Yang, a senior faculty scientist at LBNL’s Materials Sciences Division said, “It is now quite common in this field to make catalysts that can produce multicarbon products from CO2, but those processes typically operate at high overpotentials of 1 volt to attain appreciable amounts. What we are reporting here is much more challenging. We discovered a catalyst for carbon dioxide reduction operating at high current density with a record low overpotential that is about 300 millivolts less than typical electrocatalysts.”

The researchers characterized the electrocatalyst at LBNL’s Molecular Foundry using a combination of X-ray photoelectron spectroscopy, transmission electron microscopy, and scanning electron microscopy.

The catalyst consisted of tightly packed copper spheres, each about 7 nanometers in diameter, layered on top of carbon paper in a densely packed manner. The researchers found that during the very early period of electrolysis, clusters of nanoparticles fused and transformed into cube-like nanostructures. The cube-like shapes ranged in size from 10 to 40 nanometers.

Study lead author Dohyung Kim, a graduate student in LBNL’s Chemical Sciences Division and at UC Berkeley’s Department of Materials Science and Engineering, “It is after this transition that the reactions to form multicarbon products are occurring. We tried to start off with pre-formed nanoscale copper cubes, but that did not yield significant amounts of multicarbon products. It is this real-time structural change from copper nanospheres to the cube-like structures that is facilitating the formation of multicarbon hydrocarbons and oxygenates.”

Exactly how that is happening is still unclear, said Yang, who is also a professor at UC Berkeley’s Department of Materials Science and Engineering.

“What we know is that this unique structure provides a beneficial chemical environment for CO2 conversion to multicarbon products,” he said. “The cube-like shapes and associated interface may be providing an ideal meeting place where the carbon dioxide, water, and electrons can come together.”

This latest study exemplifies how carbon dioxide reduction has become an increasingly active area in energy research over the past several years. Instead of harnessing the sun’s energy to convert carbon dioxide into plant food, artificial photosynthesis seeks to use the same starting ingredients to produce chemical precursors commonly used in synthetic products as well as fuels like ethanol.

Researchers at LBNL have taken on various aspects of this challenge, such as controlling the product that comes out of the catalytic reactions. For instance, in 2016, a hybrid semiconductor-bacteria system was developed for the production of acetate from CO2 and sunlight. Earlier this year, another research team used a photocatalyst to convert carbon dioxide almost exclusively to carbon monoxide. More recently, a new catalyst was reported for the effective production of synthesis gas mixtures, or syngas.

Researchers have also worked on increasing the energy efficiency of carbon dioxide reduction so that systems can be scaled up for industrial use.

A recent paper led by LBNL researchers at the Joint Center for Artificial Photosynthesis leverages fundamental science to show how optimizing each component of an entire system can accomplish the goal of solar-powered fuel production with impressive rates of energy efficiency.

This new PNAS study focuses on the efficiency of the catalyst rather than an entire system, but the researchers point out that the catalyst can be hooked up to a variety of renewable energy sources, including solar cells.

“By utilizing values already established for other components, such as commercial solar cells and electrolysers, we project electricity-to-product and solar-to-product energy efficiencies up to 24.1 and 4.3 percent for two-to-three carbon products, respectively,” said Kim.

Kim estimates that if this catalyst were incorporated into an electrolyzer as part of a solar fuel system, a material only 10 square centimeters could produce about 1.3 grams of ethylene, 0.8 grams of ethanol, and 0.2 grams of propanol a day.

“With continued improvements in individual components of a solar fuel system, those numbers should keep improving over time,” he said.

Doubtless, this is big news. Low energy input is key to producing synthesized fuels. The mere passing over catalysts would be a revolution. One can imagine an shortage of CO2 someday. Wouldn’t that be an interesting problem?

Lawrence Berkeley National Laboratory (LBNL) scientists have harnessed the power of photosynthesis to convert carbon dioxide into fuels and alcohols at efficiencies far greater than plants. The achievement marks a significant advance in the effort to move toward sustainable sources of fuel.

Schematic of a solar-powered electrolysis cell which converts carbon dioxide into hydrocarbon and oxygenate products with an efficiency far higher than natural photosynthesis. Power-matching electronics allow the system to operate over a range of sun conditions. Image Credit: Clarissa Towle/Berkeley Lab. Click image for the largest view.

Many systems have successfully reduced carbon dioxide to chemical and fuel precursors, such as carbon monoxide or a mix of carbon monoxide and hydrogen known as syngas.

This new work, described in a study published in the journal Energy and Environmental Science, is the first to successfully demonstrate the approach of going from carbon dioxide directly to target products, namely ethanol and ethylene, at energy conversion efficiencies rivaling natural counterparts.

The LBNL researchers did this by optimizing each component of a photovoltaic-electrochemical system to reduce voltage loss, and creating new materials when existing ones did not suffice.

Study principal investigator Joel Ager, a LBNL scientist with joint appointments in the Materials Sciences and the Chemical Sciences divisions said, “This is an exciting development. As rising atmospheric CO2 levels change Earth’s climate, the need to develop sustainable sources of power has become increasingly urgent. Our work here shows that we have a plausible path to making fuels directly from sunlight.”

That sun-to-fuel path is among the key goals of the Joint Center for Artificial Photosynthesis (JCAP), a DOE Energy Innovation Hub established in 2010 to advance solar fuel research. The study was conducted at JCAP’s Berkeley Lab campus.

The initial focus of JCAP research was tackling the efficient splitting of water in the photosynthesis process. Having largely achieved that task using several types of devices, JCAP scientists doing solar-driven carbon dioxide reduction began setting their sights on achieving efficiencies similar to those demonstrated for water splitting, considered by many to be the next big challenge in artificial photosynthesis.

Another research group at LBNL is tackling this challenge by focusing on a specific component in a photovoltaic-electrochemical system. In a study published today, they describe a new catalyst that can achieve carbon dioxide to multicarbon conversion using record-low inputs of energy.

For this JCAP study, researchers engineered a complete system to work at different times of day, not just at a light energy level of 1-sun illumination, which is equivalent to the peak of brightness at high noon on a sunny day. They varied the brightness of the light source to show that the system remained efficient even in low light conditions.

When the researchers coupled the electrodes to silicon photovoltaic cells, they achieved solar conversion efficiencies of 3 to 4 percent for 0.35 to 1-sun illumination. Changing the configuration to a high-performance, tandem solar cell connected in tandem yielded a conversion efficiency to hydrocarbons and oxygenates exceeding 5 percent at 1-sun illumination.

Ager, who also holds an appointment as an adjunct professor at UC Berkeley’s Materials Science and Engineering Department, “We did a little dance in the lab when we reached 5 percent.”

Among the new components developed by the researchers are a copper-silver nanocoral cathode, which reduces the carbon dioxide to hydrocarbons and oxygenates, and an iridium oxide nanotube anode, which oxidizes the water and creates oxygen.

“The nice feature of the nanocoral is that, like plants, it can make the target products over a wide range of conditions, and it is very stable,” said Ager.

The researchers characterized the materials at the National Center for Electron Microscopy at the Molecular Foundry, a DOE Office of Science User Facility at LBNL. The results helped them understand how the metals functioned in the bimetallic cathode. Specifically, they learned that silver aids in the reduction of carbon dioxide to carbon monoxide, while the copper picks up from there to reduce carbon monoxide further to hydrocarbons and alcohols.

Because carbon dioxide is a stubbornly stable molecule, breaking it up typically involves a significant input of energy.

Study lead author Gurudayal, postdoctoral fellow at Berkeley Lab said, “Reducing CO2 to a hydrocarbon end product like ethanol or ethylene can take up to 5 volts, start to finish. Our system reduced that by half while maintaining the selectivity of products.”

Notably, the electrodes operated well in water, a neutral pH environment.

Gurudayal added, “Research groups working on anodes mostly do so using alkaline conditions since anodes typically require a high pH environment, which is not ideal for the solubility of CO2. It is very difficult to find an anode that works in neutral conditions.”

The researchers customized the anode by growing the iridium oxide nanotubes on a zinc oxide surface to create a more uniform surface area to better support chemical reactions.

LBNL chemist Frances Houle, JCAP deputy director for Science and Research Integration, who was not part of the study said, “By working through each step so carefully, these researchers demonstrated a level of performance and efficiency that people did not think was possible at this point. This is a big step forward in the design of devices for efficient CO2 reduction and testing of new materials, and it provides a clear framework for the future advancement of fully integrated solar-driven CO2-reduction devices.”

Its a big step forward indeed. Costing out fuel molecule builds by the energy inputs has so far defeated any competitiveness with fossil fuels. But those days could be numbered. Someday oil and natural gas prices will go up, the economic shock will be severe and these kinds of technologies need to be project ready by then.

Lancaster University physicists are developing methods of creating renewable fuel from water using quantum technology. Fundamental problems remain before this can be adopted commercially due to inefficiency, but a new study demonstrates that the novel use of nanostructures could increase the maximum photovoltage generated in a photoelectrochemical cell, increasing the productivity of splitting water molecules.

Renewable hydrogen can already be produced by photoelectrolysis where solar power is used to split water molecules. Despite significant research effort over the past four decades, fundamental problems remain before this process can be adopted commercially due to inefficiency and lack of cost-effectiveness.

The Lancaster study, which formed part of the PhD research of Dr. Sam Harrison, has been published in Nature’s Scientific Reports.  The study provides the basis for further experimental work into the solar production of hydrogen as a renewable fuel.

The study demonstrates that the novel use of nanostructures could increase the maximum photovoltage generated in a photoelectrochemical cell, increasing the productivity of splitting water molecules.

Dr. Manus Hayne said, “To the authors’ best knowledge, this system has never been investigated either theoretically or experimentally, and there is huge scope for further work to expand upon the results presented here.”

For all the alternative energy effort already expended, fossil fuels account for almost 90% of energy consumption in 2015, with absolute demand still increasing due to a growing global population and increasing industrialization.

Dr. Hayne explained, “Fossil-fuel combustion releases carbon dioxide into the atmosphere, causing global climate change, and there is only a finite amount of them available for extraction. We clearly need to transition to a renewable and low-greenhouse-gas energy infrastructure, and renewable hydrogen is expected to play an important role.”

Photovoltaic solar cells are currently used to convert sunlight directly into electricity but solar hydrogen has the advantage that it can stored, so it can be used as and when needed or used to build synthetic fuels that store much easier or hold more energy.

Hydrogen is also very flexible, making it highly advantageous for remote communities. It can be converted to electricity in a fuel cell, or burned in a boiler or cooker just like natural gas. It can even be used to fuel aircraft.

Hydrogen is a major component of fuels. It makes hydrocarbons liquid and gaseous. Its fundamental and any way to get H2 for processing cheaply in big volume is going to be welcome. Go Lancaster U!!!

Sweden’s University of Borås researchers are finding values and ways to obtain them from the problematic plant residue lignin. Lignin, a substance considered as a waste product in biomass and ethanol production, would then reach its proper value as bio-oil in new products.

Lignin is a natural substance in biomass, but it is unwanted in processes like production of paper or ethanol. In those processes lignin is considered as waste, and is used as fuel in heat and power plants. At the University of Borås, Sweden, a team of researchers investigate methods to extract and refine lignin for better purposes than burning it.

While the commercial lignocellulose to ethanol plants use the lignin after pretreatment as biomass feedstock to heat and power the plants, in the Horizon 2020 project AGROinLOG, lignin will instead be transformed into bio-oil based products.

Swarnima Agnihotri With Lignin Samples. Image Credit: University of Borås. Click image for the largest view.

The researcher Swarnima Agnihotri has spent a year at the University of Borås refining the methods to extract the lignin from the lignin rich wheat straw.

She explains, “If biofuels are to become a reality, we need to realize the industrial potential of lignin and get more value from it,” she said. “Seeing the complexity and richness of its functional groups, there are various potential applications of lignin by converting it in a variety of value added products like high performance carbon fiber, bio-oil and vanillin, to name a few.”

The project aims at utilizing an agricultural residue, wheat straw, which is available in surplus in Sweden, and also in other European countries.

When asked for the press release what is there to gain for the society or industry from her part of the project, Agnihotri said, “Wheat straw lignin valorization will add value to the whole process, and in turn provide benefit to industry, as well as further insight in creating value from lignin, which has been considered a waste until now.”

Integration of lignocellulose based feedstock in ethanol plants is not new. There are a number of techniques already producing ethanol from lignocelluloses at commercial scale.

“It is the high investment costs and the low profitability of the process which needs to be addressed. The goal with this AGROinLOG project will be to see the possibilities of adding a high valuable byproduct, eg. bio-oil, to the whole production chain, and therefore increase the profitability of the process,” she said.

She addressed the project challenges by saying, “Finding a cost effective biomass fractionation process was a challenge. There is a lot of ongoing research on pretreatment for a better lignin extraction from lignocelluloses, but still the main challenge is to bring the cost down. The results are interesting and motivating.”

Next up: “Now, when we have optimized an efficient pretreatment process for effective lignin extraction from wheat straw, we will scale up the process, and the pure lignin obtained will be transformed into bio-oil through a hydrothermal liquefaction process done, that is, extracting liquid and get a concentrated oil. The bio-oil product obtained will be a high valuable byproduct since it can be further upgraded in refineries to obtain green chemicals and biofuels,” she said.

While this may seem out at the edge of research for new fuels to Americans, remember, the Europeans labor under astonishingly high taxes on fuels. They have a much larger costs basis to work with over there. Still there is a lot of lignin getting burned worldwide and if the Swedes can cut those costs and come up with the value added products the products will surely be welcomed.

Cardiff University scientists have catalyzed methanol from methane using oxygen from the air. Methanol is currently produced by breaking down natural gas at high temperatures. But researchers have discovered they can produce methanol from methane through simple catalytic action that allows methanol production at low temperatures using oxygen and hydrogen peroxide. The findings have major implications for cleaner, greener industrial processes worldwide.

Methanol is currently produced by breaking down natural gas at high temperatures into hydrogen gas and carbon monoxide before reassembling them – expensive and energy-intensive processes known as ‘steam reforming’ and ‘methanol synthesis.’

The findings, rich in industrial implication, have been published in Science.

Professor Graham Hutchings, Director of Cardiff Catalysis Institute, said, “The quest to find a more efficient way of producing methanol is a hundred years old. Our process uses oxygen – effectively a ‘free’ product in the air around us – and combines it with hydrogen peroxide at mild temperatures which require less energy.

“We have already shown that gold nanoparticles supported by titanium oxide could convert methane to methanol, but we simplified the chemistry further and took away the titanium oxide powder. The results have been outstanding,” he said. “Commercialization will take time, but our science has major implications for the preservation of natural gas reserves as fossil fuel stocks dwindle across the world.”

“At present global natural gas production is ca. 2.4 billion tons per annum and 4% of this is flared into the atmosphere – roughly 100 million tons. Cardiff Catalysis Institute’s approach to using natural gas could use this “waste” gas saving CO2 emissions. In the US there is now a switch to shale gas ,and our approach is well suited to using this gas as it can enable it to be liquefied so it can be readily transported.”

Dr. James J. Spivey, Professor of Chemical Engineering at Louisiana State University and Editor-in-Chief of Catalysis Today, said, “This research is of significant value to the scientific and industrial communities. The conversion of our shale resources into higher value intermediates like methanol provide new routes for chemical intermediates.”

Cardiff Catalysis Institute has a worldwide reputation for outstanding science. The Institute works with industry to develop new catalytic processes and promote the use of catalysis as a sustainable 21st century technology.

This is a breakthrough and disruptive technology on a large scale. While methanol isn’t a common consumer product it is a major chemical raw material. One would expect that this technology will make many methanol products less expensive as well as promote marginal priced methanol products such as fuel to be much more competitive. All pluses for consumers. Methanol is also a great way to have a near hydrogen economy without a storage issue. A welcome breakthrough indeed.


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