Simultaneous energy harvesting and storage via solar-driven regenerative electrochemical cycles

Solar energy is regarded as the most promising source of electricity considering its large magnitude on earth every day. The effective use of such an intermittent energy source relies on development of affordable, inexhaustible and clean solar energy conversion and storage technologies. Here, we design a novel solar-driven regenerative electrochemical system for simultaneous photoelectric energy harvesting and storage. With rational screening of redox species and comprehensive electrochemical study, a high Seebeck coefficient of -1.8 mV K-1 is achieved by solely exploiting earth-abundant materials based on the thermogalvanic effect. A high energy conversion efficiency (1.23%, and 11.9% versus the Carnot efficiency) is achieved under a low temperature gradient of 35 degrees C. Moreover, the durability of the proof-of-concept device has been examined under solar irradiation employing the bifunctional current collector/solar absorber with good electrical conductivity, efficient solar absorption and photothermal transduction. This innovative cell design integrating simultaneous energy conversion and storage represents an alternative approach towards cost-effective harnessing of solar energy and even more broad thermal energy in ambient environments.