Ethanol oxidation occurs at the anode in the presence of Platinum catalyst. Positively charged Hydrogen ions and negatively charged electrons result.
Electrochemistry
A porous Platinum ANODE will provide the many chemical sites for alcohol oxidation to occur.
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Liquid electrolyte is in intimate contact with the Platinum and provides ion transfer at the many sites.
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An alcohol molecule adsorbs to the Platinum catalyst at a site, and…if the site has no imperfections to prevent a catalyzed reaction…
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The reaction occurs! Oxygen is consumed. Ions are created.
By-products are created.
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By-products may include aldehydes, organic acids, and carbon dioxide. By-products may dissipate.
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As long as alcohol molecules and active sites are available at the anode, multiple reactions will continue simultaneously and an electric current will be formed.
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Similarly, at the CATHODE, where excess ions have collected, oxygen molecules will adsorb and…
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will complete the electric circuit by reacting with the ions and producing water as a by-product that will dissipate.
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Not only do the electrodes provide the Platinum catalyst for the chemical reactions required in the fuel cell, but both the anode and the cathode act as electrical conductors to carry electrons to and from the external circuit.
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Fuel Cell Theory
Ethanol Oxidation
Charged Ions
Electrons travel from the anode to the cathode through metallic conductors and an external circuit. The circuit measures the electrons but does not consume them. Hydrogen ions travel from the anode to the cathode through the electrolytic solution in the porous substrate.
Porous Substrate
A porous substrate exists between the anode and cathode. It contains an acidic solution allowing the free movement of ions. The solution already contains large numbers of positively charged Hydrogen ions before any ethanol oxidation ever occurs.
Oxygen Reduction
Oxygen reduction occurs at the cathode in the presence of Platinum catalyst. The Oxygen combines with free electrons and positively charged Hydrogen ions to produce water.
Pioneers
Sir Humphry Davy
“In the present state of our knowledge, it would be useless to attempt to speculate on remote cause of the electrial energy…it’s relation to chemical affinity is, however, sufficiently evident. May it not be identical with it, and an essential property of matter?”
– H. Davy postulates whether chemical and electrical forces are identical, 1806
Johann Wolfgang Döbereiner
“The platinum sub-oxide moreover, does not undergo any change during this transformation of the alcohol and can immediately be used again to acidify fresh, perhaps limitless, quantities of alcohol…a circumstance that permits its use for the large scale preparation of acetic acid.”
– Döbereiner discovers the catalytic property of platinum, 1821
Christian Friedrich Schönbein
“…currents can only be generated if hydrogen, water and platinum are in contact with each other and connected in such a manner that each of them forms a continuous conducting line or chain.”
– C.F. Schönbein proposes the triple phase boundary in 1842
Sir William Robert Grove
“I have never thought of the gas battery as a practical means of generating voltaic power,…; there is, however a form of gas battery which I may here describe, … which, independently of any practical result, is,… not without interest.”
– W.R. Grove discusses his recent invention of what is now generally regarded as the first working fuel cell, 1845
Ludwig Mond
“All attempts to attain this with various constructions of the gas battery involving the use of a liquid electrolyte failed. We have only succeeded by using an electrolyte in a quasi-solid form, viz., soaked up by a porous non-conducting material, in a similar way as has been done in the so-called dry piles and batteries.”
–Mond describing attempts to build a practical version of Grove’s gas battery using coal gas as fuel, 1889
Anatomy of a Gas Measurement
First Sample
A single cubic centimeter of gas is captured and contains 1,000 molecules of alcohol.
The fuel cell is exposed to the gas sample, and begins breaking down the alcohol chemically and producing electrons.
The electrons pass through the external circuit and are counted.
When all the alcohol has been consumed, the fuel cell quits producing electrons; the circuit has counted a total of 3,000 electrons.
Second Sample
A single cubic centimeter of gas is captured and contains 2,000 molecules of alcohol.
The fuel cell is exposed to the gas sample, and begins breaking down the alcohol chemically and producing electrons.
The electrons pass through the external circuit and are counted.
When all the alcohol has been consumed, the fuel cell quits producing electrons; the circuit has counted a total of 6,000 electrons.
