Design of an artificial photosynthetic system for production of alcohols in high concentration from CO₂

Abstract

Artificial photosynthesis of liquid fuels is a potential source for clean energy. Of particular interest is the formation of alcohols because Alcohols are particularly attractive products because of their high energy density and market value per amount of energy input. The major challenges in photo/electrochemical synthesis of alcohols from sunlight, water and CO2 are low product selectivity, high membrane fuel crossover losses, and high cost of product separation from the electrolyte. Here we propose an artificial photosynthesis scheme for direct synthesis and separation to almost pure ethanol with minimum product crossover using saturated salt electrolytes. The ethanol produced in the saturated salt electrolytes can be readily phase separated into a microemulsion, which can be collected as pure products in a liquid-liquid extractor. A novel design of an integrated artificial photosynthetic system is proposed that continuously produces >90 wt% pure ethanol using a polycrystalline copper anode and an IrO2 cathode at a current density of 0.85 mA cm -2 . The annual production rate of > 90 wt% ethanol using such a photosynthesis system operating at 10 mA cm -2 (12% solar-to-fuel (STF) efficiency) can be 15.27 million gallons per year per square kilometer, which corresponds to 7% of the industrial ethanol production capacity of California.

110th Anniversary: Theory of Activity Coefficients for Lithium Salts in Aqueous and Nonaqueous Solvents and in Solvent Mixtures

“…A has molar concentration c. Assuming complete dissociation, anion and cation concentrations c -= c + = c. Following thermodynamic convention, we define the chemical potential of a 1-1 salt as the sum of three parts: the reference chemical potential of A, the ideal mixing chemical potential of the fully dissociated electrolyte, and the excess chemical potential due to nonideality caused by ion-ion interactions including ion-pair formation(18) (2) where R is the gas constant and T is the temperature. The first term on the right side of eq 2, μ A θ , is the reference chemical potential of salt A in a hypothetical, ideal, fully dissociated solution of salt concentration c θ in the same solvent and at the same temperature and pressure as those of the system.…”

Si photocathode with Ag-supported dendritic Cu catalyst for CO2reduction

“…4 Of these, systems which replicate the functions of photosynthesis, 5,6 which synthetically converts CO2 to more reduced forms (Photosystem I and Calvin cycle) and oxidize water to oxygen (Photosystem II), are both intellectually and technologically interesting. [7][8][9] There is an analogy between the Z-scheme configuration of photosystems I and II and a tandem solar cell, as both generate chemical potential differences in their sub-components that add together to produce electricity or drive a chemical reaction. In the case of photosynthesis, the generated chemical potential difference enables the requisite carbon dioxide reduction and oxygen evolution reactions (CO2R and OER, respectively) to occur.…”

Transport of Neutral and Charged Solutes in Imidazolium-Functionalized Poly(phenylene oxide) Membranes for Artificial Photosynthesis

“…[1][2][3][4] Artificial photosynthesis devices typically consist of an anode and a cathode separated by an ion exchange membrane and liquid electrolyte. [5][6][7][8] As CO2 (introduced as a humidified gas or dissolved in the liquid electrolyte) is reduced to gaseous or liquid products at the cathode, water is oxidized to oxygen at the anode. 5,6 Near-neutral or alkaline electrolyte conditions usually favor CO2 reduction (CO2R) to C2+ products over the competing hydrogen evolution reaction.…”

“…[5][6][7][8] As CO2 (introduced as a humidified gas or dissolved in the liquid electrolyte) is reduced to gaseous or liquid products at the cathode, water is oxidized to oxygen at the anode. 5,6 Near-neutral or alkaline electrolyte conditions usually favor CO2 reduction (CO2R) to C2+ products over the competing hydrogen evolution reaction. 6,[9][10][11] The electrolyte charge carrier between the anode and cathode in the liquid electrolyte is commonly bicarbonate or carbonate, although supplemental electrolyte charge carriers are sometimes employed.…”

“…6,16 While the range of potential CO2R products is large, products of specific interest are alcohol fuels (e.g., methanol and ethanol) due to their high energy density and market value relative to energy input. 3,5,17 Crossover of products from the cathode to the anode lowers overall device efficiency because these reduced species may undergo oxidation at the anode, which leads to product loss and wasted energy. [18][19][20][21] Therefore, a membrane that transports carbonate/bicarbonate ions while minimizing the transport of small product alcohols is expected to enable high efficiency artificial photosynthesis devices.…”