Prediction of Flatband Potentials at Semiconductor‐Electrolyte Interfaces from Atomic Electronegativities

The electron affinities of several metal oxide semiconductors that have been used as anodes in photoelectrochemical cells are calculated using the atomic electronegativities of the constituent atoms. These electron affinities are quantitatively related to the measured flatband potentials by considering the effects of specific adsorption of potential‐determining ions (for metal oxides used in photoelectrolysis, these are usually OH− and H+). Methods are discussed for determining the pH at which net adsorbed surface charge and thus potential across the Helmholtz layer is zero (point of zero zeta potential, pzzp). This pH value is shown to correlate with the electronegativity of the metal oxides. The application of these ideas to other semiconductor‐electrolyte systems is discussed.