Pressure-enhanced performance of metal oxides for thermochemical water and carbon dioxide splitting

The thermochemical dissociation of water and/or carbon dioxide over a reduced metal oxide has long been thought to be independent of total pressure, as the number of moles of gaseous reactants (i.e., H2O and/or CO2) and gaseous products (i.e., H2 and/or CO) is equal. In this study, however, through careful experimentation, we conclusively demonstrate that in an open system—where product gases are swept away from the reaction site—operating at elevated pressures improves both the equilibrium extent and rate of the aforementioned equimolar oxidation reaction. These findings have important implications for the viability of commercial systems, as the discovery of a temperature-independent technique for increasing reactant conversion not only enables the use of more earth-abundant materials but may also finally facilitate the development of a process for the production of green hydrogen (or syngas) that is both practical and efficient.