Impact of Reversible Proton Insertion on the Electrochemistry of Electrode Materials Operating in Mild Aqueous Electrolytes: A Case Study with TiO ₂

Near-neutral aqueous electrolytes are to be preferred for the development of sustainable electrochemical energy conversion and storage devices. Protons inherent these their reactivity toward electrode material extends beyond own reduction, especially when reversible proton insertion takes place in bulk from acidic or buffered electrolytes. However, a still burning question is regarding whether persists working unbuffered mild electrolytes, if so, with which consequences on functioning material. Here this issue addressed by examining TiO2 as model range Through combination experiments, modelling multiphysics simulations, it demonstrated that KCl-based electrolyte, water acts donor support protons TiO2, while NH4Cl-based NH4+. Moreover, established strong pH gradients develop at interface during insertion/disinsertion, highlighting dependence donor/acceptor rationalizing impact voltage. Overall, work provides comprehensive framework proton-insertion coupled electron transfer can easily generalized other materials.