Developing better electrode materials has attracted significant interest in recent years due to the utilization of electrochemical devices for energy conversion and storage. Specifically, iron (III) oxide (Fe2O3) has been widely considered as an anode material for water oxidation. Recently, major advances were made in improving Fe2O3 catalysis through surface coverage with material overlayers. In order to understand how material overlayers improve performance, we perform Density Functional Theory + U (DFT + U) calculations to model water oxidation catalysis on Fe2O3 partially covered with Ga2O3. We find that Ga2O3 overlayer shows no improvement in the calculated overpotential required for water oxidation on Fe2O3. This result suggests that Ga2O3 overlayer does not alter the catalytic reaction steps directly, but may be involved in other mechanisms related to charge transport and recombination that improve overall performance. [GRAPHICS] .