The Faraday-efficiency effect refers to the potential for misinterpretation of data from experiments in

electrochemistry Electrochemistry is the branch of physical chemistry concerned with the relationship between electrical potential difference, as a measurable and quantitative phenomenon, and identifiable chemical change, with the potential difference as an outco ...

through failure to take into account a

Faraday efficiency Faraday efficiency (also called ''faradaic efficiency'', ''faradaic yield'', ''coulombic efficiency'' or ''current efficiency'') describes the efficiency with which charge (electrons) is transferred in a system facilitating an electrochemical reacti ...

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

electrolysis In chemistry and manufacturing, electrolysis is a technique that uses direct electric current (DC) to drive an otherwise non-spontaneous chemical reaction. Electrolysis is commercially important as a stage in the separation of elements from n ...

of water always has a Faraday efficiency of 100%. Pons and Fleischmann, and other investigators who reported the finding of anomalous excess heat in electrolytic cells, all relied on this popular assumption. No one bothered to measure the Faraday efficiency in their cells during the experiments. 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 A tacit assumption or implicit assumption is an assumption that underlies a logical argument, course of action, decision, or judgment that is not explicitly voiced nor necessarily understood by the decision maker or judge. These assumptions may be ...

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

Pons The pons (from Latin , "bridge") is part of the brainstem that in humans and other bipeds lies inferior to the midbrain, superior to the medulla oblongata and anterior to the cerebellum. The pons is also called the pons Varolii ("bridge of Va ...

and

Fleischmann Fleischman or Fleischmann may refer to: * Fleischmann (surname), including a list of people with the name * Fleischmann (model railroads), a German company that produces model railroad models and equipment * Fleischmann (band), was a band from Ge ...

cold fusion Cold fusion is a hypothesized type of nuclear reaction that would occur at, or near, room temperature. It would contrast starkly with the "hot" fusion that is known to take place naturally within stars and artificially in hydrogen bombs and p ...

. 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.

Measurement

From 1991-1993 a group of investigators, headed by Zvi Shkedi, in the state of Massachusetts, USA, built well-insulated cells and

calorimeter A calorimeter is an object used for calorimetry, or the process of measuring the heat of chemical reactions or physical changes as well as heat capacity. Differential scanning calorimeters, isothermal micro calorimeters, titration calorimete ...

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 K₂CO₃ 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 with the following word of advice:

"All reports claiming the observation of excess heat should be accompanied by simultaneous measurements of the actual Faraday efficiency."

Jones et al.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 have confirmed the Shkedi et al. findings with the same conclusion:

"Faradaic efficiencies less than 100% during electrolysis of water can account for reports of excess heat in 'cold fusion' cells."Calorimetry, Excess Heat, and Faraday Efficiency in Ni-H₂O 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

References

{{Michael Faraday Electrochemistry