Carbon-based Materials For High Efficient Solar-driven Interfacial Desalination

In the framework of the"two-carbon"strategic,solar-driven interfacial desalination（SDID）is widely regarded as one of the most promising alternative technologies for conventional desalination due to its high efficiency,sustainability,and low cost.However,SDID has been afflicted by the low evaporation rate and poor durability caused by thermal dissipation and the rapid salt accumulation.Based on this background,using carbon-based materials with wide-spectrum light absorption and strong solar-heat conversion as matrix materials,and the self-salt-discharge theory of back diffusion and convection as the salt-resistant principle,this paper solves these problems by regulating light absorption and water transport,limiting thermal loss,expanding energy input channel and reducing evaporation enthalpy,resulting in high rate,stable and salt-resistant SDID.Moreover,it is also innovatively proposed to harvest low-grade waste heat for synergetic coupling of SDID and thermoelectric power generation.The main contents of this thesis are concluded as follows:1.We propose a low-cost and sustainable way of repurposing discarded pomelo peel that converts it into 3D porous carbon foam（CPP）with multi-channel waterways for synergetic coupling of SDID and low-grade heat-to-electricity generation.The super-hydrophilic 3D porous CPP with multi-channel waterways utilizes its powerful water supply capability to avoid salt accumulation during continuous seawater desalination.By cautiously weighing the water transport and thermal management of CPP-based evaporator,CPP with three-channel waterways（CPP3）can achieve efficient solar-driven evaporation on the premise of salt resistance through its superior light absorption and the ultrafast solar-thermal response.Besides,by introducing a thermoelectric（TE）module into the CPP3 evaporator,the Seebeck effect triggered by the temperature difference between the evaporation site and the underlying bulk water is used for synchronous generation of solar steam and thermoelectricity.Such an integrated device can simultaneously achieve an evaporation rate of 1.39 kg m^-2 h^-1and a power output of 0.5 W m^-2 under one-sun illumination.2.In order to further improve the evaporation rate,a carbon nanotubes（CNTs）-based 3D wavy evaporator was designd and demonstrated not only beneficial to the double-surface evaporation,but also can effectively diffuse the suspended vapor assisted by the convective flow,so as to reverse the heat loss and continuously harvest additional energy for efficient evaporation.An evaporation rate as high as5.55 kg m^-2 h^-1 is achieved under one sun illumination coupled with convective flow of 5 m s^-1,well beyond 278%of the input solar energy limit,presuming 100%solar-to-vapor energy conversion.More importantly,the 3D wavy evaporator can consistently evaporate for 24 h in the natural environment,with the outdoor evaporation up to 53.72 kg m^-2 and no salt deposition.Furthermore,theoretical simulations of convective flow velocity and distribution,as well as relative humidity distribution,are remarkably compatible with experimental results.3.A 3D hydrogel evaporator with vertical radiant vessels is prepared for the first time to surmount the long-standing trade-off,thereby achieving high-rate and stable solar desalination of high-salinity.Experiments and numerical simulations reveal that the unique hierarchical structure,which consists of a large vertical vessel channel,radiant vessels and porous vessel walls,facilitates strong self-salt-discharge and low longitudinal thermal conductivity.With the structure employed,a groundbreaking comprehensive performance,under one sun illumination,of evaporation rate as high as 3.53 kg m^-2 h^-1,salinity of 20 wt%,and a continuous 8 h evaporation is achieved,which to our knowledge is the best reported result from a salt-free system.