Concentration-Dependent Solar Thermochemical CO ₂ /H ₂ O Splitting Performance by Vanadia–Ceria Multiphase Metal Oxide Systems

Abstract

<jats:p>The effects of V and Ce concentrations (each varying in the 0–100% range) in vanadia–ceria multiphase systems are investigated for synthesis gas production <jats:italic>via</jats:italic> thermochemical redox cycles of CO<jats:sub>2</jats:sub> and H<jats:sub>2</jats:sub>O splitting coupled to methane partial oxidation reactions. The oxidation of prepared oxygen carriers is performed by separate and sequential CO<jats:sub>2</jats:sub> and H<jats:sub>2</jats:sub>O splitting reactions. Structural and chemical analyses of the mixed-metal oxides revealed important information about the Ce and V interactions affecting their crystal phases and redox characteristics. Pure CeO<jats:sub>2</jats:sub> and pure V<jats:sub>2</jats:sub>O<jats:sub>5</jats:sub> are found to offer the lowest and highest oxygen exchange capacities and syngas production performance, respectively. The mixed-oxide systems provide a balanced performance: their oxygen exchange capacity is up to 5 times higher than that of pure CeO<jats:sub>2</jats:sub> while decreasing the extent of methane cracking. The addition of 25% V to CeO<jats:sub>2</jats:sub> results in an optimum mixture of CeO<jats:sub>2</jats:sub> and CeVO<jats:sub>4</jats:sub> for enhanced CO<jats:sub>2</jats:sub> and H<jats:sub>2</jats:sub>O splitting. At higher V concentrations, cyclic carbide formation and oxidation result in a syngas yield higher than that for pure CeO<jats:sub>2</jats:sub>.</jats:p>

Effect of specific surface area on syngas production performance of pure ceria in high-temperature thermochemical redox cycling coupled to methane partial oxidation

“…4a, the SSA value slightly decreased from $8.0 to $6.5 cm 2 g À1 even at t ¼ 1 min and T ¼ 1173 K, and was almost constant during t ¼ 1-30 min. The average SSA value during t ¼ 1-30 min was 6.82 AE 0.24 cm 2 g À1 , and was used as an initial SSA value (SSA(0)) expressed in the eqn (6) and (7). The nal SSA values at t ¼ 50 h were 4.25 AE 0.15 cm 2 g À1 ($50% SSA of the asreceived samples) at T ¼ 1173 K, 2.30 AE 0.10 cm 2 g À1 ($25%) at T ¼ 1273 K and 1.31 AE 0.08 cm 2 g À1 ($12.5%) at T ¼ 1373 K, respectively.…”

“…1, which includes a vertical-tube reactor (alumina tube) placed inside an electric IR furnace (P4C-VHT, Advance Riko Ltd.). [4][5][6][7]21 Commercial pure ceria powders with a typical diameter of 5 mm (REacton®, 99.9% (REO), 11 328, LOT: T16A086, Alfa Aesar Ltd.) are used as the sample material in both heating experiments and cycling experiments. The initial SSA for the as-received samples is obtained by calculating an average SSA for nine as-received samples, and is 8.02 AE 0.80 cm 2 g À1 .…”

“…The cycle (1)- (2) has been demonstrated with different oxygen exchange materials under temperature-swing and isothermal conditions. [3][4][5][6][7] Typical temperatures for the reduction and oxidation steps are above 1700 K and below 1400 K, respectively. The temperature swing between the reduction and oxidation steps necessitates application of heat recovery strategies to maximize process efficiency, and leads to considerable thermal stresses.…”

“…10,14 In order to lower the cycle temperature below 1273 K, the metaloxide reduction reaction can be coupled to MPO as given by eqn (4). [3][4][5][6][7]12 Gao et al synthesized three types of ceria morphologies with different SSA and porosities. The materials were comparatively investigated for their initial and long-term syngas production performances during the isothermal redox cycling coupled to MPO at the reduction step and carbon dioxide splitting (CDS) at the oxidation step.…”

Stereoassembled V 2 O 5 @FeOOH Hollow Architectures with Lithiation Volumetric Strain Self-Reconstruction for Lithium-Ion Storage

“…Therefore, TMOs have been widely explored and designed with expected structures, compositions, and size [6][7][8][9]. Particularly, vanadium oxides can intercalate more lithium ions owing to the distinct feature of multiple oxidation states (V 2+ to V 5+ ) [10][11][12][13][14]. In practice, despite the high theoretic capacity as both anode and cathode mate-rials for LIBs, low electrical conductivity and large volumetric strains of V 2 O 5 inevitably render poor rate capability and cycling stability [15][16][17].…”