ABSTRACT
In recent years, with the development of solar seawater desalination technology, many solar evaporators are affected by precipitated salts during the evaporation process, which can reduce efficiency. In this work, flexible fabrics made of polypyrrole (PPy)/MXene are obtained by impregnating the prepared PPy ink onto waffle like fabrics. The combination of PPy and fabric greatly improves the water absorption and evaporation performance of the fabric. The average evaporation rate of this structure is 1.43 kg m-2 h-1, and the average evaporation efficiency under a single light source is 85.13%. After a 15-h testing cycle and a total of 8 cycles, lasting nearly 120 h, the performance of the device remained stable. The structural characteristics of waffle fabric, based on the Marangoni thermal effect, make it possible to suppress salt precipitation during evaporation, avoiding large salt particles covering the evaporation surface and reducing efficiency. This experiment successfully demonstrated long-term stable water evaporation, providing new ideas for the development of fabric evaporators.
ABSTRACT
Solar-driven interfacial steam generation (SDISG), as an emerging green and renewable approach to overcome water shortage, is very suitable for remote locations, developing countries, and disaster zones because it does not require an additional energy supply. However, the traditional metal-based and carbon-based absorbers always suffered from fragility (or rigidity) and the complex preparation process, which dramatically inhibited their transportation and installation in areas with poor infrastructure. Therefore, there is an urgent need to develop a universal method to fabricate flexible solar evaporators. Herein, a novel solar evaporator that integrates a flexible matrix (Cu mesh or textile) and a hierarchical Fe-MOF-74 photothermal absorber component is perfectly prepared for the rapid and efficient SDISG. Notably, the results show that Fe-MOF-74-based flexible textile matrix composites exhibit outstanding light absorption (83.81%), low thermal conductivity (0.1730 W/m K), super hydrophilic properties (within 50 ms, the contact angle is close to 0°), excellent salt resistance, high evaporation rate (1.35 kg/m2 h), and photothermal conversion efficiency (η is 81.5% under one sun, stable for 30 days). Owing to the flexibility, recyclability, and above-mentioned excellent performance, the prepared hierarchical Fe-MOF-74-based flexible composite systems are more practical for transportation, large-scale production, and stable and efficient applications. As a result, this work offers new insight into the future development of the combination of a MOF-based photothermal absorber and flexible substrates, as well as for the application of interfacial solar seawater desalination, and provides a new reference for other applications.
ABSTRACT
We present a direct observation of the transformation of dense amorphous carbon clusters into diamond nanocrystalline under electron beam irradiation by in situ transmission electron microscopy, where the surrounding carbon matrix did not significantly change. Our findings provide clear and convincing evidence for the diamond nanocrystalline evolving from energetic amorphous carbon sites. Furthermore, graphitization of amorphous carbons usually demands a high temperature combined with high pressure. Hence, graphitization of amorphous carbons at relatively low temperatures is highly desired. Here we offer a useful method for catalyst-free graphitization of amorphous carbons by employing moderate electron beam irradiation, without external heating being applied.