Materials for evaporation‐driven hydrovoltaic technology

Abstract

Water constitutes the largest energy carrier on earth, absorbing more than 70% of the solar energy received by the earth's surface, yet its low exploitation has been a constant concern. The hydrovoltaic effect is an emerging technology that generates electricity through the direct interaction between nanomaterials and water of various forms (raindrops, waves, flows, moisture, and natural evaporation). Especially, the evaporation-driven hydrovoltaic effect is a spontaneous and ubiquitous process that can directly convert thermal energy from the surrounding environment into electricity without the demand for additional mechanical work, which shows unique advantages compared with other hydrovoltaic effects. A variety of nanostructured materials have been steadily developed for evaporation-driven hydrovoltaic devices (EHDs) in recent years. However, there has been a lack of a clear specification on the selection and design of materials for improving device performance. Herein, we first analyze the mechanisms of EHDs followed by a summarization of the recent advances in materials, including carbon materials, biomass-based materials, metal oxides, composite materials, and others. We then discuss the strategies for improving the energy conversion efficiency and the output power in terms of structural design, surface modification, and interface treatment. Finally, we provide an outlook on the potential applications of electricity generation, sensors, and desalination technology, as well as the challenges and prospects for the development of this emerging technology in the future.

3D Tea-Residue Microcrystalline Cellulose Aerogel with Aligned Channels for Solar-Driven Interfacial Evaporation Co-generation

“…The TPPA-5 shows the best evaporation-generation level, reaching a maximum output voltage of 58.436 mV under a light intensity of 1 kW m –2 . It is worth noting that the output voltage tends to decrease after reaching the peak, which, we hypothesize, is due to the reduction of the TPPA’s Debye length, which weakens the EDL effect ,,− (Figure S7).…”

Electricity Generation from Phase Transitions between Liquid and Gaseous Water

“…[2] Furthermore, since the water delivery is inversely proportional to the channel length, shortening the channel is also beneficial for the enhancement of output power density and enhancing the zeta potential of the materials are also beneficial for the enhancement of output power density attributed to the elevated ionic selectivity. [31,77] However, a few issues require to be considered, such as how is the direct interaction between water molecules and the surface charges, how the ionic movement within the channel coverts into the electronic current, and whether chemical reactions and charge transfer at the water/solid interface contributes the power generation. [12] Recently, the evaporation of ethanol out of a porous matrix composed of carbon nanoparticles was also demonstrated to yield a constant volt-level potential at ambient conditions, with negligible contribution from the streaming potential.…”

Phase Transformation Strategies for the Construction of Heterojunction TiO2 Photocatalysts

“…[5] Among numerous photocatalysts, titanium dioxide (TiO 2 ) based materials have attracted extensive attention due to its abundance, low cost, non-toxicity, high photo corrosion resistance and superior photocatalytic activity. [6] It is known that TiO 2 usually exists in three structures of crystal phase: anatase, rutile and brookite. [7][8] Although the chemical composition is same, different chemical bonds and coordination modes lead to the formation of different crystal and energy band structures, and thus showing different light efficiency and selectivity.…”