Towards H2 production from water and ethanol interactions on hydrated TiO2(101): Insights from ReaxFF molecular dynamics

ReaxFF molecular dynamics is employed to investigate interactions between water, ethanol, their mixture, and hydrated TiO2(101) surfaces. Water maintains hydration, while exchanging both hydrogen and oxygen atoms with the surface. Ethanol dissociates, leading to the formation of ethoxy radicals (CH3CH2O) permanently attached to the surface, water molecules, and acetic acid (CH3CO2) species. Ethoxy reduces the number of hydroxyl groups and hinders hydrogen migration across the surface. The mixture of water, ethanol, and TiO2(101) results in a reduction of ethoxy coverage, inhibits CH3CO2 formation, and increases hydroxyl coverage, indicating the dominant role of water. Potential of mean force analysis shows that hydroxyl formation follows exothermic paths, with activation energy lower than 0.45 eV. A narrower pathway for ethanol access to its adsorbed site is a key factor in the dominance of water. The formation of H2 molecules exhibits a prohibitive energy barrier (4 eV), suggesting that catalytic pathways, rather than purely surface reactions, could be favored.