Surface-dependent generation of reactive oxygen species at pyrite–water interface

The generation of reactive oxygen species (ROS) at the pyrite–water interface is an important discovery for both early Earth’s and present environments in the past two decades. In these revealed reactions, pyrite can oxidize water to ROS and reduce O2 and ROS to water. However, the two types of reactions are controversial. The underlying physical theory responsible for the reactions has yet to be elucidated. In this study, we established a surface structure-dependent model of oxidation and reduction potentials (ORP) for semiconductors. Surface atomic structure-dependent electronic structures were adopted to estimate the ORP of pyrite. We apply this model to gain insights into the generation of ROS at the pyrite–water interface. The results demonstrate that the surface structure of pyrite controls its ORP, and ROS production can only occur on certain pyrite facets. The {210} and {111} facets with certain defects (e.g., 210-2S′ and 111-3S, respectively) could oxidize either H2O or OH− to O2, and ROS form during the oxidation of pyrite surfaces by O2. This suggests that surface effects play a crucial role in governing the ORP of semiconducting minerals. Accurately calculating surface ORP could potentially be used to better understand redox reactions and develop more efficient catalysts.