Quasimetallic Molybdenum Carbide-Based Flexible Polyvinyl Alcohol Hydrogels for Enhancing Solar Water Evaporation

Solar interfacial water evaporation has been regarded as a promising technique for large-scale water purification by utilizing sustainable solar energy. However, fresh water production, especially in resource limited areas, still remains challenging and needs to be addressed. Here, molybdenum carbide (MoCx)- based polyvinyl alcohol hydrogels (MoCxPH) are strategically designed as flexible and highly efficient solar evaporators for producing clean water from different water-bearing media. Through adjusting the calcination temperatures, the phase transition of MoCx from eta-MoC to beta-Mo2C makes the product to be a quasimetal from a semiconductor, leading to a strong broadband adsorption over the full solar spectrum together with excellent photothermal conversion capability. The hydrogel-based solar evaporator exhibits an average water evaporation rate of 1.59 kg m(-2) h(-1) with superb solar thermal efficiency up to 83.6% under one sun illumination. This scalable solar evaporator can be used to generate clean water from contaminated water with rejections close to 100% for organic dyes and metal ions. The solar water evaporator has potential applications for the remote areas to deal with the drinkable water shortage problem.