Crystal-field-driven redox reactions: How common minerals split H2O and CO2 into reduced H2 and C plus oxygen

It is difficult to prove the presence of molecular H2 and reduced C in minerals containing dissolved H2 and CO2. A technique was developed which unambiguously shows that minerals grown in viciously reducing environments contain peroxy in their crystal structures. The peroxy represent interstitial oxygen atoms left behind when the solute H2O and/or CO2 split off H2 and C as a result of internal redox reactions, driven by the crystal field. The observation of peroxy affirms the presence of H2 and reduced C. It shows that the solid state is indeed an unusual reaction medium

O

MgO and CaO are catalytically active for the oxidative dimerization of methane. The basic step involves a transfer of charge between adsorbed CH4 molecules and the catalyst surface. The catalytic activity has been ascribed to O- states. A new technique, Charge Distribution Analysis has been used to study undoped, NaOH- and La2O3 - promoted CaO catalysts and CaO single crystals. CDA allows to obtain information about mobile charge carriers. CDA utilizes the fact that a dielectric, when placed in an electric field gradient, experiences a force. This force depends on the dielectric polarization which contains contributions from the ideal crystal, from local defects that rotate, from charges that diffuse, and from surface charges. In combination with magnetic susceptibility data CDA allows to unambiguously determine that the mobile charge carriers that appear in the CaO-based catalysts above 550-600 °C are O' states. Their precursors are preoxy anions, O22-