View source for Chemistry:Faraday-efficiency effect

The '''Faraday-efficiency effect''' refers to the potential for misinterpretation of data from experiments in [[Chemistry:Electrochemistry|electrochemistry]] through failure to take into account a [[Chemistry:Faraday efficiency|Faraday efficiency]] of less than 100 percent.
==Assumption about efficiency==
Until recent decades it was common to assume that the release of hydrogen and oxygen gas during [[Chemistry:Electrolysis|electrolysis]] of water always has a Faraday efficiency of 100%. Pons and Fleischmann, and other investigators who reported the finding of [[Physics:Cold fusion|anomalous excess heat]] in electrolytic cells,<ref>{{Cite web |url=http://www.chem.au.dk/~db/fusion/Papers |title=Archived copy |access-date=2008-02-15 |archive-url=https://web.archive.org/web/20080223203010/http://www.chem.au.dk/~db/fusion/Papers |archive-date=2008-02-23 |url-status=dead }}</ref> all relied on this popular assumption. No one bothered to measure the Faraday efficiency in their cells during the experiments.{{Dubious|date=April 2008}} Many publications reporting the finding of excess heat included an explicit statement like: "The Faraday efficiency is assumed to be unity." Even if not explicitly stated so, these publications included this implicit assumption in the formulas used to calculate the cells' energy balance.

==Relevance to cold fusion==
Lacking any other plausible explanation, the anomalous excess heat produced during such electrolysis was attributed by [[Biography:Stanley Pons|Pons]] and [[Biography:Martin Fleischmann|Fleischmann]] to [[Physics:Cold fusion|cold fusion]]. Later, it was discovered that such excess heat can easily be the product of conventional chemistry, i.e. internal recombination of hydrogen and oxygen. Such recombination leads to a reduction in the Faraday efficiency of the electrolysis. The Faraday-efficiency effect is the observation of anomalous excess heat due to a reduction in the Faraday efficiency.{{citation needed|date=February 2014}}

==Measurement==
From 1991-1993 a group of investigators,<ref name="s" /><ref>Response to "Comments on 'Calorimetry, Excess Heat, and Faraday Efficiency in Ni-H<sub>2</sub>O Electrolytic Cells' ". Shkedi Z., Fusion Technology Vol.30 (1996) p.133</ref> headed by Zvi Shkedi, in the state of Massachusetts, USA, built well-insulated cells and [[Physics:Calorimeter|calorimeter]]s which included the capability to measure the actual Faraday efficiency in real-time during the experiments. The cells were of the light-water type; with a fine-wire nickel cathode; a platinum anode; and K<sub>2</sub>CO<sub>3</sub> electrolyte.

The calorimeters were calibrated to an accuracy of 0.02% of input power. The long-term stability of the calorimeters was verified over a period of 9 months of continuous operation. In their publication, the investigators show details of their calorimeters' design and teach the technology of achieving high calorimetric accuracy.

===Experiments===
A total of 64 experiments were performed in which the actual Faraday efficiency was measured. The results were analyzed twice; once with the popular assumption that the Faraday efficiency is 100%, and, again, taking into account the measured Faraday efficiency in each experiment. The average Faraday efficiency measured in these experiments was 78%.

===First analysis===
The first analysis, assuming a Faraday efficiency of 100%, yielded an average apparent excess heat of 21% of input power. The term "apparent excess heat" was coined by the investigators to indicate that the actual Faraday efficiency was ignored in the analysis.

===Second analysis===
The second analysis, taking into account the measured Faraday efficiency, yielded an actual excess heat of 0.13% +/- 0.48%. In other words, when the actual Faraday efficiency was measured and taken into account, the energy balance of the cells was zero, with no excess heat.

===Conclusion===
This investigation has shown how conventional chemistry, i.e. internal recombination of hydrogen and oxygen, accounted for the entire amount of apparent excess heat. The investigators concluded their publication<ref name="s" /> with the following word of advice:<blockquote>
"All reports claiming the observation of excess heat should be accompanied by simultaneous measurements of the actual Faraday efficiency."
</blockquote>
Jones et al.<ref>Faradaic efficiencies less than 100% during electrolysis of water can account for reports of excess heat in 'cold fusion' cells. J.E. Jones et al., J. Physical Chem. 99 (May 1995) p.6973-6979</ref> have confirmed the Shkedi et al. findings with the same conclusion:
<blockquote>"Faradaic efficiencies less than 100% during electrolysis of water can account for reports of excess heat in 'cold fusion' cells."<ref name="s">Calorimetry, Excess Heat, and Faraday Efficiency in Ni-H<sub>2</sub>O Electrolytic Cells. Z. Shkedi, R.C. McDonald, J.J. Breen, S.J. Maguire, and J. Veranth, Fusion Technology Vol.28 No.4 (1995) p.1720-1731</ref>
</blockquote>

==References==
{{reflist}}

{{Michael Faraday}}

[[Category:Electrochemistry]]

{{Sourceattribution|Faraday-efficiency effect|1}}