Confined Water for Catalysis: Thermodynamic Properties and Reaction Kinetics

Water is a salient component in catalytic systems and acts as a reactant, product and/or spectator species in the reaction. Confined water in distinct local environments can display significantly different behaviors from that of bulk water. Therefore, the wide-ranging chemistry of confined water can provide tremendous opportunities to tune the reaction kinetics. In this review, we focus on drawing the connection between confined water properties and reaction kinetics for heterogeneous (electro)catalysis. First, the properties of confined water are presented, where the enthalpy, entropy, and dielectric properties of water can be regulated by tuning the geometry and hydrophobicity of the cavities. Second, experimental and computational studies that investigate the interactions between water and inorganic materials, such as carbon nanotubes (1D confinement), charged metal or metal oxide surfaces (2D), zeolites and metal-organic frameworks (3D) and ions/solvent molecules (0D), are reviewed to demonstrate the opportunity to create confined water structures with unique H-bonding network properties. Third, the role of H-bonding structure and dynamics in governing the activation free energy, reorganization energy and pre-exponential factor for (electro)catalysis are discussed. We highlight emerging opportunities to enhance proton-coupled electron transfer by optimizing interfacial H-bond networks to regulate reaction kinetics for the decarbonization of chemicals and fuels.