Current efficiency and energy efficiency used in electrolysis
Answers
current efficiency versus acid and base product concentration of a bipolar stack containing anionand cation membranes. As can be seen, current efficiency is highly dependent on the product concentration (about 85% for 1 N product, and decreasing with increasing product concentration to 70% for 2 N product). The loss in efficiency with concentration is due mainly to increasing leakage of hydroxide and hydrogen ions through the monopolar membranes into the salt stream. Hydrogen leakage through the anion membrane is typically higher than hydroxide through the cation. Depending on the membrane, this can result in a slightly lower acid current efficiency than base.
ENERGY EFFICIENCY
Researchers have boosted the efficiency of water electrolysis. They applied a layer of copper atoms in a conventional platinum electrode. Thus, reaction intermediates could desorb a bit more easily from the catalyst surface. The modified system generated twice the amount of hydrogen than a platinum electrode without a copper layer. The team from the Ruhr-Universität Bochum, Technical University in Munich and Universiteit Leiden published these results in the journal Nature Communications.
Answer:
Conventional alkaline electrolysis has an efficiency of about 70%. Accounting for the accepted use of the higher heat value (because inefficiency via heat can be redirected back into the system to create the steam required by the catalyst), average working efficiencies for PEM electrolysis are around 80%.