A major action to reduce CO 2 emissions is replacing fossil fuels by renewable energy sources . Matching the energy supply and demand by the mostly intermittent renewable resources (wind, solar, wave) is hence a hot topic, and energy storage has become crucial. Thermo-chemical energy storage (TCES) has a higher energy density than sensible and latent heat storage , and allows energy to be stored in the reaction products for multiple reuse and even off-site application. Design parameters are the equilibrium temperature , the reaction heat and the reaction rate, as obtained from both thermodynamic and kinetic assessments. Equilibrium temperatures of the selected metal oxides , Mn 2 O 3 /Mn 3 O 4 and Co 3 O 4 /CoO are between 1115 K and 1179 K. The present research studies both redox reactions as examples. Commercial Mn 2 O 3 and Co 3 O 4 were previously investigated in detail, and suffer from incomplete reversibility . The present study investigates the use of self-made Mn 2 O 3 and Co 3 O 4 mesoporous particles, of micrometer or nanometer scale, respectively. The average particle size of self-made Mn 2 O 3 particles is < 5 μm, with a BET surface area of 239.7 m 2 /g, and T eq of 1177 K at ambient pressure . Self-made Co 3 O 4 was of nano size, with average size of about 100 nm, a BET surface area of 54.2 m 2 /g, and T eq of 1109 K at ambient pressure. The redox reactions of these ultrafine particles are fast and nearly fully reversible. The effect of adding inert Al 2 O 3 or Fe 2 O 3 was also studied, but proven to offer no kinetic benefit, while reducing the reaction heat due to their inert additive character. The findings were used in the design of a 10 kW TCES pilot plant that is currently being tested in a concentrated solar furnace .
Jianhui Zhao,Zhiwei Zhao,Ning Li,Jun Nan,Ruixin Yu,Jinying Du
Valence state heterostructure exhibits great potential for contaminants remediation from water and wastewater with effective charge separation and little energy loss. However, the preparation process commonly shows complex with uncontrolled manner, forming undesired valence states, which hinders the advancement of valence state heterostructure. Herein, an Oxone induced strategy is established to controllably design manganese-based valence state heterostructure for the first time. A superior Mn 2 O 3 /Mn 3 O 4 /MnO 2 (molar ratio of 3:1:2) photocatalyst with dual Ⅱ heterostructures was generated by Oxone (0.3 mM) induced Mn 2 O 3 (0.2 g/L) under visible light. The Mn 2 O 3 /Mn 3 O 4 /MnO 2 heterojunction achieved 95.6% removal and 63.9% mineralization of ciprofloxacin (cipro) under visible light irradiation for 40 min. The excellent catalytic performance was derived from the improved surface area, decreased isoelectric point, enhanced light absorption and efficient charge separation of the Mn 2 O 3 /Mn 3 O 4 /MnO 2 heterostructure. Moreover, the radicals trapping experiment and Electron paramagnetic resonance (EPR) measurement revealed the dominant roles of holes and superoxide radicals for cipro degradation. Furthermore, the reusable Mn 2 O 3 /Mn 3 O 4 /MnO 2 could remove cipro selectively with co-existing natural organic matters and inorganic ions, which exhibited high practicability in real waters. Impressively, this work provides an innovative approach for controllable design of valence state heterostructure and fabricates a promising photocatalyst towards antibiotics degradation.
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