On the concept of metal-hydrogen peroxide batteries: improvement over metal-air batteries?

While metal-air batteries (MABs) are considered to outperform lithium-ion batteries for energy-storage applications, the sluggish bifunctional oxygen electrocatalysis at the cathode of MABs still represents a major bottleneck that severely limits efficiency. Recently, it was motivated by means of electronic structure calculations to replace the oxygen redox chemistry at the cathode of MABs by the redox chemistry of peroxide, considering that the latter is governed by kinetically facile two-electron processes. Herein, two different concepts of rechargeable metal-hydrogen peroxide batteries are investigated, consisting of either the peroxide reduction (PRR) and peroxide formation (PFR) reactions or the two-electron oxygen reduction (ORR) and two-electron oxygen evolution (OER) reactions at the cathode. Applying a dedicated thermodynamic framework in the spirit of the descriptor Gmax(U), a potential-dependent activity measure that factors overpotential and kinetic effects into the evaluation of adsorption free energies, generalized volcano plots for the PRR, PFR, two-electron ORR, and two-electron OER as well as their competing side reactions are derived. It is illustrated that for the PFR/PRR, selectivity can be steered toward the desired product without loss in activity whereas for the two-electron ORR/OER, a trade-off between activity and selectivity is encountered. The derived volcano models in this contribution may aid the search for potential material motifs for the PFR/PRR and the two-electron ORR/OER by calculations in the framework of electronic structure theory. While peroxide formation can be steered toward the desired product without loss in activity, a trade-off between activity and selectivity is encountered for the 2-electron oxygen reduction reaction at the cathode in metal-hydrogen peroxide batteries.