Self-regulating and asymmetric evaporator for efficient solar water-electricity generation

Water evaporation is a ubiquitous natural process than can be applied to generate electricity through hydrovoltaic effect. However, it remains a great challenge to construct an evaporation system that can satisfy both high-efficiency evaporation and stable power output due to their differences in water managements. Herein, we demonstrate a sandwich membrane strategy to construct a three-dimensional (3D) asymmetric evaporator for efficient tandem solar water-electricity generation by coating two carbon black (CB)/polyvinyl alcohol (PVA) functional films with different channel structures and water uptake at two opposite sides of a wood chip. Owing to the smart self-regulating property of the thin PVA skin and the superior thermal utilization performance of the 3D structure, the fabricated device achieves high evaporation rate of 1.93 kg m−2 h−1. More importantly, the asymmetric water distribution of the evaporation unit and the confined nanochannels of the dense PVA network render the generator with stable and efficient power output, and the simple connections of several units in series and/or parallel can easily power a commercial calculator, electrolyze methylene blue solution, and light up light emitting diodes, which well proves the conception of combining solar water evaporation and electricity generation in an integrated device.