Highly salt-resistant and all-weather solar-driven interfacial evaporators with photothermal and electrothermal effects based on Janus graphene@silicone sponges

Lingxiao Li,Junping Zhang

doi:10.1016/j.nanoen.2020.105682

Abstract

Abstract Solar-driven interfacial evaporators are very promising for obtaining clean water, but suffer from serious performance degradation due to salt-fouling, low evaporation rate under weak illumination and low clean water collection rate. Here, we report highly salt-resistant and all-weather evaporators with photothermal and electrothermal effects based on the Janus graphene@silicone sponges with opposing wettability. The evaporators achieve a remarkable high evaporation rate of 6.53 kg m−2 h−1 for 3.5 wt% NaCl solution under 1 sun illumination with a 5 V solar cell as compensation owing to their high solar absorption, low thermal conductivity, unique Janus structure and synergetic photothermal and electrothermal effects. Even in gloomy and dark environments, the evaporators could still generate vapor (1.51 kg m−2 h−1). Moreover, the evaporators feature long-term excellent salt-resistance, e.g., > 10 d continuous evaporation in 10 wt% NaCl solution without performance degradation and salt precipitation, because of ultrafast water supply and salt diffusion in the macroporous superhydrophilic shell. Furthermore, the evaporators show high clean water collection rates of 21.92 kg m−2 d−1 (1 sun-9 h/0 sun-15 h + 5 V, indoor) and 9.65 kg m−2 d−1 (natural sun light + 5 V, outdoor). This study offers a new approach for efficiently obtaining clean water via solar desalination.

Highlights

Clean water scarcity is an enormous challenge to human survival and development.[1]
The silicone sponges were fabricated by hydrolytic condensation of methyltrimethoxysilane (MTMS) and dimethyldimethoxysilane (DMDMS) in the presence of traces of HAc, Na2CO3 and dihexadecyldimethyl ammonium bromide (DHDAB).[18]
Highly salt-resistant and all-weather Solar-driven interfacial (SI) evaporators with photothermal and electrothermal effects were developed by coating the superelastic silicone sponges with graphene followed by activation with O2-plasma

Summary

Introduction

Clean water scarcity is an enormous challenge to human survival and development.[1]. Water purification by efficiently harvesting solar energy has always been an attractive area in academia and industry.[1,2,3,4] Solar-driven interfacial (SI) evaporation has recently been emerging as a very promising approach to purify water by localizing heat at the water-vapor interface.[4,5] High evaporation rate and solar-vapor efficiency have been achieved by developing advanced SI evaporators via the combination of new photothermal materials (e.g., semiconductors,[6] carbonaceous materials[7] and metal oxides8), structural optimization and thermal management.[3, 9,10] the main bottleneck hindering SI evaporators from practical solar desalination is serious salt-fouling due to insufficient water supply, strong solar flux and high salt concentration, etc.[11]. The p-GS sponges achieve a remarkable evaporation rate of 6.53 kg m-2 h-1 for 3.5 wt% NaCl solution under 1 sun illumination with the aid of a 5 V solar cell, benefiting from high solar absorption (~99%), low thermal conductivity (0.043 W m-1 K-1), unique wettability, and synergetic photothermal and electrothermal effects.

Results

Conclusion