Tao Wang,Xishan Zhou,Zhao Liu,Jiawei Wang,Yongsheng Zhang,Wei-Ping Pan
As an inorganic phase change material (PCM), CaCl 2 ·6H 2 O is an effective energy storage material because its energy can be transformed around 30 °C through the melting and crystallization. The different compositions of PCM were prepared in order to decrease the phase transition temperature to 20–25 °C and to improve its capability of heat storage and release. MgCl 2 ·6H 2 O was added as a nucleating agent and the composite PCMs (CPCMs) of CaCl 2 ·6H 2 O/MgCl 2 ·6H 2 O binary salt system was prepared. At the same time, SrCl 2 ·6H 2 O was added to reduce the supercooling degree of inorganic PCM. As a thickener, hydroxyethyl cellulose (HEC) was also included to improve the recycling ability. With the application of thermogravimetric analysis and differential scanning calorimeter, the phase transition temperature, thermal properties of CPCMs, supercooling degree and thermal cycle performance were studied by changing the content of each component in the CPCMs. The results demonstrated that the phase transition temperature of PCM with 35% MgCl 2 ·6H 2 O, 5% SrCl 2 ·6H 2 O, 0.5% HEC balanced by CaCl 2 ·6H 2 O was reached to 23 °C. The phase change latent heat of PCM was kept at 130 J/g. The degree of supercooling was kept within 0.7 °C and the recyclability was greatly improved after 100 cycles.
Ion leaching from pure-phase oxygen-evolving electrocatalysts generally exists, leading to the collapse and loss of catalyst crystalline matrix. Here, different from previous design methodologies of pure-phase perovskites, we introduce soluble BaCl 2 and SrCl 2 into perovskites through a self-assembly process aimed at simultaneously tuning dual cation/anion leaching effects and optimizing ion match in perovskites to protect the crystalline matrix. As a proof-of-concept, self-assembled hybrid Ba 0.35 Sr 0.65 Co 0.8 Fe 0.2 O 3- δ (BSCF) nanocomposite (with BaCl 2 and SrCl 2 ) exhibits the low overpotential of 260 mV at 10 mA cm -2 in 0.1 M KOH. Multiple operando spectroscopic techniques reveal that the pre-leaching of soluble compounds lowers the difference of interfacial ion concentrations and thus endows the host phase in hybrid BSCF with abundant time and space to form stable edge/face-sharing surface structures. These self-optimized crystalline structures show stable lattice oxygen active sites and short reaction pathways between Co–Co/Fe metal active sites to trigger favorable adsorption of OH − species.
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