How widespread is the problem?

To check whether this was a niche quirk, the researchers surveyed more than 600 papers on organic electrosynthesis published since 2010. About 89% of those studies involved reactions at electrodes where both electrons and protons are transferred — exactly the conditions that disturb local acidity.

That figure suggests the hidden factor could influence a broad range of electrochemical reactions, not a few special cases.

How did they boost selectivity from 16% to 97%?

The team demonstrated their approach on a classic reaction called Baeyer-Villiger oxidation, which inserts an oxygen atom into a ketone to produce an ester or lactone. Conventionally, this requires highly reactive peroxyacids that raise handling, waste, and byproduct problems.

The Seoul group instead used electricity to activate oxygen gas at the electrodes, generating reactive oxygen species. Isotope-tracing experiments confirmed the oxygen in the products came from oxygen gas, not water. The two electrodes even cooperate: hydrogen peroxide formed at the cathode gets converted back into reactive species at the anode, sustaining the supply.

The fix for local pH was a reactor redesign, guided by computer simulations and electrochemical measurements:

• Closer electrodes. Reducing the gap from 20 mm to 4 mm raised the production rate about 2.2 times.
• Flowing electrolyte. The conductive liquid carrying the reactants circulates between electrodes, counterbalancing the acidic anode zone against the alkaline cathode zone. Across the tested flow rates, output per unit time increased roughly 14-fold from lowest to highest.
• Selectivity jump. Without local pH control, about 16% of the relevant products were the desired compound. With the redesigned reactor, that figure reached about 97%.

The most telling result came when the researchers let the liquid sit still. With identical voltage and solution composition, they obtained almost none of the desired product — proof that the microscopic environment, not just the ingredients, decides the outcome.

What can the method actually make?

Using their optimized conditions, the team synthesized lactones from 18 different ketones, including ε-caprolactone at an 82% yield — a building block for polycaprolactone, a biodegradable polymer used in surgical sutures and drug-delivery systems. They also produced epoxides from six alkene starting materials; epoxides feed into adhesives, coatings, epoxy resins in electronics, and pharmaceutical intermediates.

Because the reactions run on electricity, the approach could eventually pair with renewable energy for more sustainable manufacturing. Pharmaceutical and other high-value specialty chemicals, which demand tight reaction control and strict safety measures, look especially promising.

The researchers caution that the technology is not yet ready for industrial deployment. Larger-scale testing will be needed to confirm the lab results can be reproduced economically and reliably.

A new way to think about reactors

Beyond specific applications, the study reframes how electrochemical reactions should be designed. "This study transforms 'local pH' near the electrode from a hidden variable into a controllable design principle," Professor Ryu said.

He added: "To improve the efficiency of organic electrosynthesis, we need to design not only the reaction substrates and catalysts, but also the environment in which the molecules actually react."

The study's co-first authors, Seonghyeon Min and Junghoon Lee (both M.S. students), along with co-author Hanju Kim, plan to extend the approach to a wider range of reactions. The research was supported by Seoul National University, the National Research Foundation of Korea, and the Institute for Basic Science.