5.9275
g
92.79
%
18,000
C
16,701.84
C
1,298.16
C
1.1
g/(A·h)
5.9275
g
92.79
%
18,000
C
16,701.84
C
1,298.16
C
1.1
g/(A·h)
The Current Efficiency Calculator determines what percentage of the total electric charge was used for the desired electrochemical reaction versus side reactions. In real electrolysis, not all the current goes toward depositing the target substance — some is consumed by competing reactions such as hydrogen evolution, oxygen evolution, or metal dissolution. Current efficiency (also called Faradaic efficiency or coulombic efficiency) is the ratio of the actual mass deposited to the theoretical mass predicted by Faraday's law. This metric is essential for electroplating quality control, industrial process optimization, battery performance evaluation, and electrolysis cost analysis. Higher current efficiency means less energy is wasted on unproductive side reactions.
The theoretical mass from Faraday's law is:
$$m_{theoretical} = \frac{M \cdot I \cdot t}{n \cdot F}$$
The current (Faradaic) efficiency is:
$$\eta = \frac{m_{actual}}{m_{theoretical}} \times 100\%$$
Equivalently, in terms of charge:
$$\eta = \frac{Q_{useful}}{Q_{total}} \times 100\%$$
where the useful charge is back-calculated from the actual mass:
$$Q_{useful} = \frac{m_{actual} \cdot n \cdot F}{M}$$
The wasted charge is:
$$Q_{wasted} = Q_{total} - Q_{useful}$$
An efficiency of 100% means all charge goes to the desired product. In practice, efficiencies range from 60% (chromium plating) to 99%+ (copper refining). Side reactions consume the wasted charge, producing undesired byproducts and generating heat.
An efficiency above 95% is considered excellent for most electroplating operations. Efficiencies between 80–95% are typical for many industrial processes. Below 80% indicates significant side reactions that should be investigated. The wasted charge shows how much electricity is lost to parasitic reactions. In aqueous electrolysis, the main side reaction is usually hydrogen evolution at the cathode (consuming H⁺/H₂O) or oxygen evolution at the anode. Monitoring current efficiency over time helps detect bath contamination, pH drift, or electrode degradation.
Inputs
Results
Theoretical mass = (63.546 × 18000)/(2 × 96485) = 5.93 g. Actual = 5.50 g. Efficiency = 5.50/5.93 × 100 = 92.8%. About 1296 C (7.2%) was wasted on side reactions, likely hydrogen evolution.
Inputs
Results
Theoretical = (51.996 × 36000)/(6 × 96485) = 3.24 g. Actual = 1.80 g. Efficiency = 55.6%. Chromium plating from chromic acid baths has notoriously low efficiency (10–30% typical) due to massive hydrogen evolution.
Current efficiency (Faradaic efficiency) is the ratio of the actual mass deposited to the theoretical mass predicted by Faraday's law, expressed as a percentage. It measures how effectively the electric charge is used for the desired electrochemical reaction.
Side reactions are the main cause: hydrogen evolution, oxygen evolution, dissolution of deposited metal, reduction of other metal ions, or decomposition of bath additives. Poor bath chemistry, wrong pH, or excessive current density can worsen efficiency.
In principle, no — you cannot deposit more than Faraday's law predicts. However, apparent efficiencies above 100% can occur if the weighed deposit includes co-deposited impurities, occluded electrolyte, or oxides, giving a falsely high actual mass.
Acid copper sulfate baths typically achieve 95–100% current efficiency. Copper cyanide baths range 60–90% depending on free cyanide concentration. Copper pyrophosphate baths achieve 90–100%.
Chromium plating from chromic acid (CrO₃) baths has only 10–30% efficiency because the hexavalent chromium is reduced through multiple intermediates, and massive hydrogen evolution occurs simultaneously. Trivalent chromium baths have better efficiency (15–40%).
There is usually an optimal current density range. Too low current density may allow chemical dissolution to compete. Too high current density causes hydrogen evolution (exceeding the limiting current for metal deposition), lowering efficiency and deposit quality.
In rechargeable batteries, coulombic efficiency is the ratio of charge extracted during discharge to charge put in during charging. High coulombic efficiency (>99.5%) is critical for long cycle life — lost charge represents irreversible side reactions degrading the battery.
Weigh the electrode before and after electrolysis using an analytical balance (±0.1 mg). The electrode must be thoroughly rinsed, dried, and cooled to room temperature. Subtract any corrosion or dissolution that occurred independently.
Optimize pH and temperature, maintain proper additive concentrations, use the correct current density range, minimize impurities in the bath, ensure good agitation for mass transport, and select appropriate electrolyte composition.
Current efficiency measures charge utilization (mass deposited vs. theoretical). Energy efficiency also accounts for voltage losses (overpotential, IR drop). Energy efficiency = current efficiency × voltage efficiency, and is always lower than current efficiency alone.
Roboculator Team
The Roboculator Team explains calculations, planning tools, and practical formulas in clear language for real-life situations.
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