Porous carbon was synthesized by heating the precursor FA within the pores of MOF-5. The resultant carbon displayed a high specific surface area (BET, 2872 m2·g−1) and important hydrogen uptake (2.6 wt % at 760 Torr, −196 °C) as well as excellent electrochemical properties as an electrode material for electrochemical double-layered capacitor (EDLC).

Metal-organic framework as a template for porous carbon synthesis

CO2 conversion covers a wide range of possible application areas from fuels to bulk and commodity chemicals and even to specialty products with biological activity such as pharmaceuticals. In the present review, we discuss selected examples in these areas in a combined analysis of the state-of-the-art of synthetic methodologies and processes with their life cycle assessment. Thereby, we attempted to assess the potential to reduce the environmental footprint in these application fields relative to the current petrochemical value chain. This analysis and discussion differs significantly from a viewpoint on CO2 utilization as a measure for global CO2 mitigation. Whereas the latter focuses on reducing the end-of-pipe problem “CO2 emissions” from todays’ industries, the approach taken here tries to identify opportunities by exploiting a novel feedstock that avoids the utilization of fossil resource in transition toward more sustainable future production. Thus, the motivation to develop CO2-based chemistry does...

Sustainable Conversion of Carbon Dioxide: An Integrated Review of Catalysis and Life Cycle Assessment

Because solar energy is available in large excess relative to current rates of energy consumption,
effective conversion of this renewable yet intermittent resource into a transportable and
dispatchable chemical fuel may ensure the goal of a sustainable energy future. However, low
conversion efficiencies, particularly with CO_2 reduction, as well as utilization of precious
materials have limited the practical generation of solar fuels. By using a solar cavity-receiver
reactor, we combined the oxygen uptake and release capacity of cerium oxide and facile catalysis
at elevated temperatures to thermochemically dissociate CO_2 and H_2O, yielding CO and H_2,
respectively. Stable and rapid generation of fuel was demonstrated over 500 cycles. Solar-to-fuel
efficiencies of 0.7 to 0.8% were achieved and shown to be largely limited by the system scale
and design rather than by chemistry.

http://science.sciencemag.org/content/sci/330/6012/1797.full.pdf

High-flux solar-driven thermochemical dissociation of CO2 and H2O using nonstoichiometric ceria

Solar thermochemical production of hydrogen--a review

To improve the sustainability of transportation, a major goal is the replacement of conventional petroleum-based fuels with more sustainable fuels that can be used in the existing infrastructure (fuel distribution and vehicles). While fossil-derived synthetic fuels (e.g. coal derived liquid fuels) and biofuels have received the most attention, similar hydrocarbons can be produced without using fossil fuels or biomass. Using renewable and/or nuclear energy, carbon dioxide and water can be recycled into liquid hydrocarbon fuels in non-biological processes which remove oxygen from CO2 and H2O (the reverse of fuel combustion). Capture of CO2 from the atmosphere would enable a closed-loop carbon-neutral fuel cycle. This article critically reviews the many possible technological pathways for recycling CO2 into fuels using renewable or nuclear energy, considering three stages—CO2 capture, H2O and CO2 dissociation, and fuel synthesis. Dissociation methods include thermolysis, thermochemical cycles, electrolysis, and photoelectrolysis of CO2 and/or H2O. High temperature co-electrolysis of H2O and CO2 makes very efficient use of electricity and heat (near-100% electricity-to-syngas efficiency), provides high reaction rates, and directly produces syngas (CO/H2 mixture) for use in conventional catalytic fuel synthesis reactors. Capturing CO2 from the atmosphere using a solid sorbent, electrolyzing H2O and CO2 in solid oxide electrolysis cells to yield syngas, and converting the syngas to gasoline or diesel by Fischer–Tropsch synthesis is identified as one of the most promising, feasible routes. An analysis of the energy balance and economics of this CO2 recycling process is presented. We estimate that the full system can feasibly operate at 70% electricity-to-liquid fuel efficiency (higher heating value basis) and the price of electricity needed to produce synthetic gasoline at U.S.D$ 2/gal ($ 0.53/L) is 2–3 U.S. cents/kWh. For $ 3/gal ($ 0.78/L) gasoline, electricity at 4–5 cents/kWh is needed. In some regions that have inexpensive renewable electricity, such as Iceland, fuel production may already be economical. The dominant costs of the process are the electricity cost and the capital cost of the electrolyzer, and this capital cost is significantly increased when operating intermittently (on renewable power sources such as solar and wind). The potential of this CO2 recycling process is assessed, in terms of what technological progress is needed to achieve large-scale, economically competitive production of sustainable fuels by this method.

Sustainable hydrocarbon fuels by recycling CO2 and H2O with renewable or nuclear energy

The limitations of thermochemical energy storage devices are the limitations of Carnot devices. Entropy production entailed in product separation further limits the efficiency of thermochemical processes. Thus, high upper temperatures and few reaction steps are desirable. In this article, the one-step effusional separation of water into hydrogen and oxygen is considered. Membrane materials, design, and fabrication techniques are suggested. A parametric analysis of the process suggests that the idea is a tantalizing possibility.

https://science.sciencemag.org/content/sci/197/4308/1050.full.pdf

Hydrogen- and oxygen from water.

Research on solarthermal processing and the need for alternative energy sources have reached the point where efforts to develop some industrial processes and expand research to suggest others are at least desirable, if not imperative. This paper presents a rationale for such an effort, describes the underlying thermodynamics, and summarizes much of the research which has been conducted in the years since the end of World War II. Major emphasis is placed on the work that has been done since the imposition of the 1973 oil embargo and the present.

Solarthermal Processing: A Review

The production of Zn from ZnO in a high- temperature solar decomposition quench process—I. The scientific framework for the process

The advantages of using the high thermodynamic potential of sunlight for energy-intensive industrial solar thermochemical and thermoelectrochemical processing and the concomitant need for high-temperature separation methods are discussed. Example applications are introduced. The production of zinc from zinc oxide is used as an explicit illustrative example to show some opportunities and problems that solar energy presents. The use of quasi-electrolysis, which takes advantage of the high-temperature process heat available from sunlight, is introduced as a separation technique. Suggestions are made for additional kinds of opportunities which might be profitably explored.

Edward A. Fletcher

Papers

Hydrogen- and oxygen from water.

Solarthermal Processing: A Review

The production of Zn from ZnO in a high- temperature solar decomposition quench process—I. The scientific framework for the process

Solarthermal and Solar Quasi-Electrolytic Processing and Separations: Zinc from Zinc Oxide as an Example

Reaction of steam with cellulose in a fluidized bed using concentrated sunlight