Li 4 SiO 4 sorbent attracts wide attention due to its high and stable CO 2 adsorption. However, the process of CO 2 capture is significantly affected by various impurities under the circumstance of industrial applications, and water vapor is one such impurity that needs to be well studied. Herein, we aim to evaluate the effect of water vapor on physicochemical characteristics of Li 4 SiO 4 -based sorbents during cyclic CO 2 adsorption and desorption and to understand the action mechanism of H 2 O molecules on CO 2 adsorption by Li 4 SiO 4 . Reaction tests show that water vapor can significantly enhance CO 2 adsorption performance of sorbents, but the promotion effect varies with the different presence of water vapor during reactions. Material characterization and DFT calculation reveal that although the presence of water vapor leads to deterioration of internal pore structure of the sorbent, H 2 O molecule will form OH – on the surface of Li 4 SiO 4 and further react with CO 2 to generate HCO 3 – , thus the adsorption energy with water vapor presenting is increased with an observation of promoted CO 2 adsorption.
Yuying Zhao,Fengming Zhou,Qiuyue Liang,Bo Zhang,Peng Wang,Qingliang Lv,Caixia Li,Zhenyu Xiao,Lei Wang
Although the intrinsic layer structure of layered double hydroxide (LDH) is beneficial for more accessible active centers and faster electrolyte ions diffusion rate than closed-packed atom arrangement for achieving higher capacitance, the narrow interlaminar spacing results in inevitable “death volume” during the rapid charging-discharging process. Herein, an electrochemical assistant MOF etching strategy is developed to construct hierarchical porous LDH with pre-embed OH − ions and filled H 2 O molecule in inter-layer space (E-MOF-0.5 V) for unsealing theoretical capacity. According to the valence equilibrium theory, the increased valence of the metal center during electrochemical polarization can accelerate the filling of OH − ions and H 2 O molecules in the LDH inter-layer space. The involved OH − and water molecules can achieve rapid mass transfer processes through ‘‘Newton’s Cradle’’ and the rich pore and ultra-thin layer structure may make sure the active centers are almost completely accessible. Therefore, the optimized E-MOF-0.5 V delivers an outstanding specific capacity of 8547.2 mF cm −2 (2670.9 F g −1 ) at 4 mA cm −2 and maintains an excellent cycling performance of 88 % after 7200 cycles at 20 mA cm −2 . Besides, an E-MOF-0.5 V//rGO-Zn hybrid supercapacitor device is assembled, which presents an energy density of 7.97 mWh cm −2 and a power density of 6.63 mW cm −2 .
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