Sponge‐Supported Reduced Graphene Oxides Enable Synergetic Photothermal and Electrothermal Conversion for Water Purification Coupling Hydrogen Peroxide Production

Abstract

To address the freshwater scarcity issue and the environmental impact of wastewater disposal, herein a novel efficient strategy to enhance the performance of solar‐driven interfacial evaporation technique is developed to purify salt‐containing wastewater and seawater for sustainable clean water production. This strategy enables photovoltaic electricity to power photothermal conversion for rapidly vaporizing brine using commercial melamine sponge (MS)‐supported reduced graphene oxides (MS@rGO). The record‐high performance with an evaporation rate of 9.02 kg m−2 h−1 along with a solar‐to‐vapor efficiency of 287.4% in 7 wt% salt brine is achieved under 1 sun and optimized voltage applied. During evaporating brine, MS@rGO can also efficiently catalyze oxygen reduction for the sustainable production of H2O2 to serve as the broad‐acting disinfecting agent in the condensed water. Because applying voltages can facilitate the movement of salt ions in brine, the presented system is endowed with excellent salt‐resistance and superior ability of extracting photogenerated electrons, significantly improving the energy utilization efficiency. Therefore, this design provides a new way for highly efficiently applying solar energy in saline wastewater purification and seawater desalination with low cost.

Recent Advances in High‐Rate Solar‐Driven Interfacial Evaporation

“…[58] Diffusion and dilution through rapid water transport has been the main method to manage the salt accumulation the high evaporation designs evaluated above. [52,53,55] Wang et al tested the salt rejection through a constant extended operation of 8 h and a salt reflux test where the deposited salt was fully dissolved in 120 min for the C-1200 design. [52] Similarly, Guo et al deposited 2.5 g of sodium chloride crystals on the surface and was dissolved within 15 min.…”

“…Evaporators have been constructed using affordable commercial melamine sponge and incorporated well‐dispersed graphene oxide (GO) to evenly wrap the sponge substrate framework (Figure 4F ). [ 55 ] The GO layer on the framework was subsequently reduced using hydrogen iodide (HI) to prevent the reaggregation of the reduced GO. This resulted in the creation of the MS@rGO (melamine sponge wrapped with reduced graphene oxide), which exhibited conductive properties suitable for electrothermal processes, combined with photothermal heating, to achieve ultra‐high evaporation rate.…”

“…The evaporation achieved 1.9 kg m −2 h −1 under 1 Sun, and 9.02 kg m −2 h −1 under combined 1 Sun and 10 V of electricity. [ 55 ] Applying 5 V of electricity would result in an evaporation rate of ≈3–3.5 kg m −2 h −1 . The effect of salinity on the rate of evaporation relies on a specific concentration of salt that is necessary to facilitate the transfer of electrons within the bulk water.…”

Solar Interfacial Evaporation at the Water–Energy Nexus: Bottlenecks, Approaches, and Opportunities

“…In today's scarcity of freshwater resources, SIE technology is becoming attractive extremely. [21][22][23][24] In the last decade, along with the rapid boom of new nanomaterials such as graphene oxide (GO), [25][26][27][28] reduced graphene oxide (rGO), [29][30][31][32][33] carbon nanotube (CNT), [34][35][36] and various efficient photothermal structure designs, the efficiency of SIE can still reach 90% even at low solar concentration. New photothermal nanomaterials can achieve excellent broad-spectrum absorption and can convert solar energy into heat efficiently, making a qualitative leap in the traditional thermal distillation process and becoming a green and environmentally clean water production technology.…”

Engineering High‐Tortuosity 3D Gradient Structure and CFD‐Assisted Multifield Analysis for Solar Interfacial Evaporation

“…[31][32][33] While many 3D structures have been developed to improve transmission efficiency, few studies have explored the role of structures in promoting transmission efficiency beyond porosity. [28,[34][35][36][37] The high tortuosity structure can make the incident sunlight reflect a lot inside the structure, which effectively enhances the light absorption ability of the structure and creates a thermal field environment with higher temperature inside the structure. Moreover, unlike the low tortuosity structure, the high tortuosity structure can change the pressure distribution inside the structure through the change of porosity, which in turn affects the overflow of water vapor and the rapid supply of water to the evaporating surface.…”