Factors affecting the cathode/electrolyte interfacial pH change during water reduction: A simulation study

Abstract

Water reduction reaction to produce hydrogen has been extensively studied in electrochemical and photoelectrochemical water splitting. The cathode/electrolyte interfacial pH change (ΔpH) during water reduction has a non-negligible impact on the activity and stability. However, there are difficulties in experimentally detecting pH change of the localized solution close to the electrode. Herein, a one-dimensional finite element numerical computational model is proposed to simulate the water reduction process. Potential, bulk pH, temperature, and buffer species are considered as variable factors to investigate their effects on interfacial pH change. The interfacial ΔpH could decrease to a large extent as the bulk pH increases. The ΔpH in the whole diffusion layer would decrease when buffer species is introduced. Whereas, the impact of temperature is less significant. According to the simulation results, raising the bulk pH and introducing buffer species can keep the interfacial pH change within 1 unit, which is an efficient route to stabilize water electrolysis.