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Hydrogen peroxide (H2O2)is an important chemical with multiple uses across domestic and industrial settings. With a global need for wider adoption of green synthetic methods, there has been a growing interest in the electrochemical synthesis of H2O2 from oxygen reduction or water oxidation. State-of-the-art catalyst and reactor developments are beginning to advance to a stage where electrochemical synthesis is discussed as a viable alternative to current industrial methods. In this review, we highlight some of the most promising candidates for H2O2 electrosynthesis technologies and what further advancements are needed before the electrochemical route could challenge the ubiquitous anthraquinone process.

Transient studies of electrochemical systems at microelectrodes allow analysis under rapid mass transport conditions. The small active area allows rapid resolution of charging currents, giving access to meaningful information even at short times. Sampled current voltammetry at microelectrodes (MSCV) is a multistep technique whereby data is collected from a series of potential step experiments along the redox wave of interest. Varying the sampling time allows comparison of how a reaction proceeds at varying timescales, whilst simultaneously showing the potential dependence. Selection of an appropriate sampling time tunes the rate of mass transport to give quasireversible conditions, allowing facile kinetic analysis using quasireversible models. Application to the oxygen reduction reaction (ORR) revealed unreasonably large currents at short times. This work suggests that pre-adsorbed oxygen at the electrode surface is responsible. The presence of the pre-adsorbed oxygen was confirmed by its direct reduction in argon purged solution, and its strong dependence on the metal substrate. The resultant peak potentials were used to calculate the binding energies of varying metals towards oxygen (?G?), which are in excellent agreement with the literature. This is useful, as ?G? is a popular descriptor for oxygen reduction activity. Once the pre-adsorbed oxygen is consumed, MSCVs for the ORR can be used for standard kinetic analysis using Tafel or Koutecky-Levich analyses, with the advantage of the electrode being oxide free before each data point is recorded.