Efficient solar-driven interfacial water evaporation: Construction of facilely PVA/TA/GO gel copper foam evaporator

Solar-driven interfacial water evaporation (SDIWE) technology is crucial to alleviating the freshwater and energy crisis problems. However, most of the current evaporators have complex synthesis processes and some of the materials used are not biologically and environmentally friendly. Therefore, it is crucial to develop green, simple and efficient solar evaporators. Hence, photothermal interfacial gel copper foam (PTG@CF) solar evaporator was prepared by using a simple chemical cross-linking and "dip-coating" technique. The bio-friendly polyvinyl alcohol (PVA) and tannic acid (TA) were selected as the gel materials, and the in situ re-crosslinking of the copper foam (CF) surface to form a gel was realized by adjusting the hydrogen bonding cross-linking through waterethanol solution. In addition, graphene oxide (GO) was introduced to improve the photothermal conversion performance, which was combined with CF to further enhance the thermal conductivity. Furthermore, the effects of the number of pores per inch (ppi) and thickness of CF on its performance in SDIWE were deeply explored. When comparing different ppi values and thicknesses, it was found that the PTG@CF evaporator with a thickness of 2 mm and a ppi of 80 exhibited excellent performance. The evaporation rate and solar-to-vapor conversion efficiency reached 1.88 kg m- 2 h- 1 and 88.47 %, respectively, under one solar irradiation. The PTG@CF evaporator demonstrated excellent photothermal conversion and evaporation performances, which is expected to provide a new idea for the SDIWE technology.