β-Na 2 TeO 4 : Phase Transition from an Orthorhombic to a Monoclinic Form. Reversible CO 2 Capture

Abstract : The present work concerns the tellurate Na2TeO4 which has a 1D structure and could then present a CO2 capture ability. It has been synthesized in a powder form via a solid-state reaction and structurally characterized by thermal X-ray diffraction experiments, Raman spectroscopy, and differential scanning calorimetry. The room temperature structure corresponds to the β-Na2TeO4 orthorhombic form, and we show that it undergoes a reversible structural transition near 420 °C toward a monoclinic system. Ab initio computations were also performed on the room temperature structure, the Raman vibration modes calculated, and a normal mode attribution proposed. In agreement with our expectations, this sodium oxide is able to trap CO2 by a two-step mechanism: Na+/H+ exchange and carbonation of the released sodium as NaHCO3. This capture is reversible since CO2 can be released upon heating by recombination of the mother phase.