Boiling effect on oxygen evolution reaction-Theoretical analysis of its mass transfer enhancement mechanism

Abstract

In water electrolysis experiments on hydrogen production, boiling effectively decreases the overpotential of the oxygen evolution reaction (OER) [Li et al. Int. J. Hydrog. Energy. 2022, 47(61):25499–510]. This study constructed a theoretical model to quantitatively explore the mechanism by which boiling reduces the OER overpotential. The model considers dissolved oxygen, liquid water, gaseous oxygen, and water vapor flowing through the porous transfer layer (PTL). The results showed that boiling increases the molar flux of gaseous oxygen and reduces the dissolved oxygen concentration. The PTL embedded in the catalyst layer (CL) increased the mass transfer resistance of dissolved oxygen and increased the dissolved oxygen concentration in the CL. Once boiling is superimposed on the OER, it attracts more dissolved oxygen to the water vapor bubbles and significantly decreases the dissolved oxygen concentration at the CL, thereby reducing the Nernst loss of the OER.