The syngas produced would need to be sequestered, but the technology itself does do the *removal* process, so it at least has CDR potential. Those other papers look very interesting. It would be great to see a comparison of the energy efficiency of these various technologies. I would also note that, at least in my personal opinion, we should avoid encouraging the use of hydrogen as a fuel, given its numerous disadvantages and inefficiencies compared to other options.
-- Adam Dorr University of California Los Angeles School of Public Affairs Urban Planning PhD Candidate adamd...@ucla.edu adamd...@gmail.com On Fri, Jul 29, 2016 at 4:03 PM, Greg Rau <gh...@sbcglobal.net> wrote: > If hydrocarbon fuel is being produced from CO2 and then ultimately > combusted in an ICE, how is this CDR? How is this producing negative > emissions? I haven't seen the paper either, but are they actually using > air CO2, or more likely, some highly concentrated source and at what cost? > Anyway, those interested in true electrochemical CDR with H2 fuel > production powered by your choice of renewable or nuclear electricity (and > without exotic chemicals), I can humbly offer these: > http://pubs.acs.org/doi/abs/10.1021/acs.est.5b00875 > http://www.pnas.org/content/110/25/10095.full > http://pubs.acs.org/doi/abs/10.1021/es800366q > > Greg > > > ------------------------------ > *From:* Adam Dorr <adamd...@ucla.edu> > *To:* geoengineerin...@gmail.com > *Cc:* geoengineering <geoengineering@googlegroups.com> > *Sent:* Friday, July 29, 2016 12:34 PM > *Subject:* Re: [geo] Fwd: solar cell captures CO2 and sunlight, produces > burnable fuel (Science, July 29) > > Please correct me if I'm wrong, but isn't this catalyzed electrolysis, > where the solution in question produces hydrogen and carbon monoxide (as > opposed to the more familiar hydrogen and oxygen from the electrolysis of > water)? Does the PV solar cell participate in any capacity other than > providing electrical current? > > I understand why the idea of artificial photosynthesis is exciting, and > why this system could claim to achieve that. But if the PV cells are just > providing electricity, then this (in my personal opinion) is actually MORE > exciting than just artificial photosynthesis, because it suggests that it > is a CDR technology with the potential to be driven by any power source. > That means all electricity-producing renewables (wind, geothermal, wave, > etc.) plus nuclear energy could be used to drive this CDR method. > > The only catch is that with PV solar driving it, one can somewhat get away > with ignoring the energy efficiency of the process - since the power source > is "free" in the sense that the electricity isn't coming from a wall socket > at a direct opportunity cost to other uses. > > I am unable to access the actual paper yet, but the news article doesn't > mention energy or material throughput, so it isn't yet possible to evaluate > the technology's efficiency. (They do claim a 1000x greater "speed" and 20x > lower cost compared to other catalysts, but these figures aren't meaningful > without accompanying energy consumption and gas output data). > > Potential downsides/concerns include the toxicity of the compounds > involved (not sure about ethyl-methyl-imidazolium tetrafluoroborate, but > cobalt oxides can be nasty beyond minute amounts), and the durability of > the catalyst (i.e. number of cycles it can sustain, given than its efficacy > depends on nanostructure). > > > Adam > > > -- > Adam Dorr > University of California Los Angeles School of Public Affairs > Urban Planning PhD Candidate > adamd...@ucla.edu > adamd...@gmail.com > > On Fri, Jul 29, 2016 at 9:02 AM, Fred Zimmerman < > geoengineerin...@gmail.com> wrote: > > > > Thoughts? I'm having a difficult time evaluating significance of this. > > > https://news.uic.edu/breakthrough-solar-cell-captures-co2-and-sunlight-produces-burnable-fuel > > Researchers at the University of Illinois at Chicago have engineered a > potentially game-changing solar cell that cheaply and efficiently converts > atmospheric carbon dioxide directly into usable hydrocarbon fuel, using > only sunlight for energy. > The finding is reported in the July 29 issue of *Science* and was funded > by the National Science Foundation and the U.S. Department of Energy. A > provisional patent application has been filed. > Unlike conventional solar cells, which convert sunlight into electricity > that must be stored in heavy batteries, the new device essentially does the > work of plants, converting atmospheric carbon dioxide into fuel, solving > two crucial problems at once. A solar farm of such “artificial leaves” > could remove significant amounts of carbon from the atmosphere and produce > energy-dense fuel efficiently. > “The new solar cell is not photovoltaic — it’s photosynthetic,” says Amin > Salehi-Khojin, assistant professor of mechanical and industrial engineering > at UIC and senior author on the study. > “Instead of producing energy in an unsustainable one-way route from fossil > fuels to greenhouse gas, we can now reverse the process and recycle > atmospheric carbon into fuel using sunlight,” he said. > While plants produce fuel in the form of sugar, the artificial leaf > delivers syngas, or synthesis gas, a mixture of hydrogen gas and carbon > monoxide. Syngas can be burned directly, or converted into diesel or other > hydrocarbon fuels. > The ability to turn CO2 into fuel at a cost comparable to a gallon of > gasoline would render fossil fuels obsolete. > Chemical reactions that convert CO2 into burnable forms of carbon are > called reduction reactions, the opposite of oxidation or combustion. > Engineers have been exploring different catalysts to drive CO2 reduction, > but so far such reactions have been inefficient and rely on expensive > precious metals such as silver, Salehi-Khojin said. > “What we needed was a new family of chemicals with extraordinary > properties,” he said. > [image: Amin Salehi-Khojin & Mohammad Asadi] > Amin Salehi-Khojin (left), UIC assistant professor of mechanical and > industrial engineering, and postdoctoral researcher Mohammad Asadi with > their breakthrough solar cell that converts atmospheric carbon dioxide > directly into syngas. > Salehi-Khojin and his coworkers focused on a family of nano-structured > compounds called transition metal dichalcogenides — or TMDCs — as > catalysts, pairing them with an unconventional ionic liquid as the > electrolyte inside a two-compartment, three-electrode electrochemical cell. > The best of several catalysts they studied turned out to be nanoflake > tungsten diselenide. > “The new catalyst is more active; more able to break carbon dioxide’s > chemical bonds,” said UIC postdoctoral researcher Mohammad Asadi, first > author on the *Science* paper. > In fact, he said, the new catalyst is 1,000 times faster than noble-metal > catalysts — and about 20 times cheaper. > Other researchers have used TMDC catalysts to produce hydrogen by other > means, but not by reduction of CO2. The catalyst couldn’t survive the > reaction. > “The active sites of the catalyst get poisoned and oxidized,” > Salehi-Khojin said. The breakthrough, he said, was to use an ionic fluid > called ethyl-methyl-imidazolium tetrafluoroborate, mixed 50-50 with water. > “The combination of water and the ionic liquid makes a co-catalyst that > preserves the catalyst’s active sites under the harsh reduction reaction > conditions,” Salehi-Khojin said. > The UIC artificial leaf consists of two silicon triple-junction > photovoltaic cells of 18 square centimeters to harvest light; the tungsten > diselenide and ionic liquid co-catalyst system on the cathode side; and > cobalt oxide in potassium phosphate electrolyte on the anode side. > When light of 100 watts per square meter – about the average intensity > reaching the Earth’s surface – energizes the cell, hydrogen and carbon > monoxide gas bubble up from the cathode, while free oxygen and hydrogen > ions are produced at the anode. > “The hydrogen ions diffuse through a membrane to the cathode side, to > participate in the carbon dioxide reduction reaction,” said Asadi. > The technology should be adaptable not only to large-scale use, like solar > farms, but also to small-scale applications, Salehi-Khojin said. In the > future, he said, it may prove useful on Mars, whose atmosphere is mostly > carbon dioxide, if the planet is also found to have water. > “This work has benefitted from the significant history of NSF support for > basic research that feeds directly into valuable technologies and > engineering achievements,” said NSF program director Robert McCabe. > “The results nicely meld experimental and computational studies to obtain > new insight into the unique electronic properties of transition metal > dichalcogenides,” McCabe said. “The research team has combined this > mechanistic insight with some clever electrochemical engineering to make > significant progress in one of the grand-challenge areas of catalysis as > related to energy conversion and the environment.” > “Nanostructured transition metal dichalcogenide electrocatalysts for CO2 > reduction in ionic liquid” is online at > http://www.eurekalert.org/jrnls/sci/ or by contacting sci...@aaas.org. > Co-authors with Asadi and Salehi-Khojin are Kibum Kim, Aditya Venkata > Addepalli, Pedram Abbasi, Poya Yasaei, Amirhossein Behranginia, Bijandra > Kumar and Jeremiah Abiade of UIC’s mechanical and industrial engineering > department, who performed the electrochemical experiments and prepared the > catalyst under NSF contract CBET-1512647; Robert F. Klie and Patrick > Phillips of UIC’s physics department, who performed electron microscopy and > spectroscopy experiments; Larry A. Curtiss, Cong Liu and Peter Zapol of > Argonne National Laboratory, who did Density Functional Theory calculations > under DOE contract DE-ACO206CH11357; Richard Haasch of the University of > Illinois at Urbana-Champaign, who did ultraviolet photoelectron > spectroscopy; and José M. Cerrato of the University of New Mexico, who did > elemental analysis. > > -- > You received this message because you are subscribed to the Google Groups > "geoengineering" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to geoengineering+unsubscr...@googlegroups.com. > To post to this group, send email to geoengineering@googlegroups.com. > Visit this group at https://groups.google.com/group/geoengineering. > For more options, visit https://groups.google.com/d/optout. > > > -- > You received this message because you are subscribed to the Google Groups > "geoengineering" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to geoengineering+unsubscr...@googlegroups.com. > To post to this group, send email to geoengineering@googlegroups.com. > Visit this group at https://groups.google.com/group/geoengineering. > For more options, visit https://groups.google.com/d/optout. > > > -- > You received this message because you are subscribed to the Google Groups > "geoengineering" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to geoengineering+unsubscr...@googlegroups.com. > To post to this group, send email to geoengineering@googlegroups.com. > Visit this group at https://groups.google.com/group/geoengineering. > For more options, visit https://groups.google.com/d/optout. > -- You received this message because you are subscribed to the Google Groups "geoengineering" group. To unsubscribe from this group and stop receiving emails from it, send an email to geoengineering+unsubscr...@googlegroups.com. To post to this group, send email to geoengineering@googlegroups.com. Visit this group at https://groups.google.com/group/geoengineering. For more options, visit https://groups.google.com/d/optout.
