Clean Water Generation Research Articles

Perylene diimide-derived supramolecules-modified graphene sponge as a high-efficiency solar steam generator

Generating steam using solar energy appears to be an effective approach to obtaining clean water, especially from salty water and wastewater, since the sun is a natural and constant source. Compared to many methods, studies in solar steam generation have accelerated due to being highly efficient, sustainable, and low-cost. Graphene sponges (GrSs), possessing structural flexibility and effective photothermal activity, are widely used for this purpose. However, the hydrophobic character of these materials limits their effectiveness in solar steam generators. At this point, we prepared perylene diimide-derived supramolecules (PDI) modified three-dimensional (3D) gradient hydrophobic GrS (PDI/GGrS) as the highly efficient solar thermal converter for the generation of clean water. PDI allowed us to achieve perfect absorption of broad-band sunlight and GGrS facilitated water transport through channels of sponge structure. As a result, PDI/GGrS has achieved a high water evaporation rate of 3.5 kg h−1 m−2 with a superior solar thermal conversion efficiency of up to 90 %. This study can provide new possibilities for harvesting solar energy by producing clean water from seawater, wastewater, and even acidic/alkali solutions.

Design plasmonic nanostructure of silicon dioxide and titanium dioxide loaded on a nano surface for clean water production through photocatalysis and electrochemical techniques

The work is targeted to rebuild the framework of a nanocatalyst (NCat) that depends on the n/p-type heterojunction through the plasmonic structure of reduced graphene oxide (rGO), silicon oxide nanoparticles (SiO2 NPs), polyvinyl alcohol (PVA NPs), and titanium dioxide (TiO2 NPs). The removal of medical and organic contaminants occurs via photocatalysis operation which follows through the electrochemical technique and UV-spectrophotometer under visible light with nanocatalyst (rGO@SiO2@PVA@TiO2) for clean water and a safe medical environment. The Z-Scheme mechanism explains the development of electron maps in fabricated nanocatalyst engineering to increase the efficiency of the photocatalytic activity. The high activity of the NCat appeared, after 160 min, and the photocatalytic efficiency for methylene blue (MB), methyl orange (MO), rhodamine B (RhB), moxifloxacin (MFX), and colchicine, was 90 %, 76 %, 88 %, 84 %, and 91 % respectively. The stability of NCat was confirmed via the recyclability process, with the efficiency at 58 % after the fifth cycle. The high stability of NCat was proved by the electrochemical technique performed after 100 cycles. The safety of the NCat for the generation of clean water was highlighted by the cytotoxicity test using normal mouse liver cells. It is suggested to use the new NCat design because of its distinctive optical characteristics, which make it a viable candidate for use as a revolutionary nanomaterial with high efficiency and safety for clean water and removal of medical contaminants.

Low-Temperature Wastewater Electrolysis for H2 and Clean Water Generation

Water electrolysis represents a sustainable approach to produce green hydrogen (H2); however, the high energy cost (H2O → 2H+ + 2e- + ½O2, ∆H° = 275 kJ/mol H2, E° = −1.18 V) associated with water electrolysis and electricity cost (>$50/MWh) results in a minimum H2 selling price ≈$4/kg H2. Hence, we need to find alternative process to generate H2 to meet the current U.S. Department of Energy's (DOE's) Energy Earthshots of $1/kg H2 in one decade.Wastewater electrolysis represents an alternative approach to generate H2 with renewable sources by electrochemically oxidizing organic molecules to generate H2 (e.g., CH3COOH + 2H2O → 2CO2 + 8e- + 8H+, ∆H° = 53 kJ/mol, E° = −0.02 V,) which has up to 5 times lower energy requirement than water electrolysis. As opposed to water electrolysis that requires clean water streams, wastewater electrolysis uses readily available waste streams that need cleanup anyway to generate H2; hence, integrating a second application in addition to H2 generation.1-3 In this work, we compare the performance of heterogeneous electrocatalysts for the electrocatalytic oxidation (ECO) of organic molecules present in wastewater as well as electrocatalysts for the H2 evolution reaction (HER) at room temperature. ECO electrocatalysts were developed and tested using real wastewaters derived from several sources including the hydrothermal liquefaction (HTL) of food waste. We synthesized the ECO electrocatalysts using both platinum-group metals (PGM) as well as base-group metals (BGM) with equimolar loadings and tested them as a function of half-cell potential. Our results show that both PGM- and BGM-based bimetallics improve the activity and stability compared to the baseline RuO2-based catalysts4-6. We performed a preliminary techno-economic analysis and showed that the levelized costs of using this technology to process the wastewater alone is equivalent to that of traditional wastewater processing. The sale of the produced H2 co-product will decrease the levelized processing cost below that of current wastewater processing. References Andrews, E.; Lopez-Ruiz, J. A.; Egbert, J. D.; Koh, K.; Sanyal, U.; Song, M.; Li, D.; Karkamkar, A. J.; Derewinski, M. A.; Holladay, J.; Gutiérrez, O. Y.; Holladay, J. D., Performance of Base and Noble Metals for Electrocatalytic Hydrogenation of Bio-Oil-Derived Oxygenated Compounds. ACS Sustainable Chemistry & Engineering 2020, 8 (11), 4407-4418.Lopez-Ruiz, J. A.; Qiu, Y.; Andrews, E.; Gutiérrez, O. Y.; Holladay, J. D., Electrocatalytic valorization into H2 and hydrocarbons of an aqueous stream derived from hydrothermal liquefaction. Journal of Applied Electrochemistry 2021, 51 (1), 107-118.Lopez-Ruiz, J. A.; Andrews, E.; Akhade, S. A.; Lee, M.-S.; Koh, K.; Sanyal, U.; Yuk, S. F.; Karkamkar, A. J.; Derewinski, M. A.; Holladay, J.; Glezakou, V.-A.; Rousseau, R.; Gutiérrez, O. Y.; Holladay, J. D., Understanding the Role of Metal and Molecular Structure on the Electrocatalytic Hydrogenation of Oxygenated Organic Compounds. ACS Catalysis 2019, 9 (11), 9964-9972.Qiu, Y.; Lopez-Ruiz, J. A.; Zhu, G.; Engelhard, M. H.; Gutiérrez, O. Y.; Holladay, J. D., Electrocatalytic decarboxylation of carboxylic acids over RuO2 and Pt nanoparticles. Appl. Catal. B-Environ. 2022, 305, 121060.Lopez-Ruiz, J. A.; Qiu, Y.; Andrews, E.; Gutiérrez, O. Y.; Holladay, J. D., Electrocatalytic valorization into H2 and hydrocarbons of an aqueous stream derived from hydrothermal liquefaction. J. Appl. Electrochem. 2021, 51 (1), 107-118.Qiu, Y.; Lopez-Ruiz, J. A.; Sanyal, U.; Andrews, E.; Gutiérrez, O. Y.; Holladay, J. D., Anodic electrocatalytic conversion of carboxylic acids on thin films of RuO2, IrO2, and Pt. Appl. Catal. B-Environ. 2020, 277, 119277. Figure 1

Carbonized sawdust based solar absorber in a solar still for seawater desalination

AbstractCurrent industrial technologies for seawater desalination involve high cost and energy consumption, that is, distillation and reverse osmosis, where these technologies are difficult to implement especially in developing countries. A cost‐effective, environmental‐friendly, and sustainable technology is essential in providing alternative methods for generation of clean water. Solar vapor generation is one of the potential green technologies in generating clean water, where the production and collection of clean water is made possible by using a solar absorber in a solar still. The practicality and performance of the carbonized sawdust based solar absorber in a solar still for the seawater desalination towards clean water generation was conducted outdoors with gradual enhancement on the solar still setup. The enhanced solar still with reflective surface and external thermal insulator improved the solar absorber performance, in contrast to the evaporation of the bulk seawater only and using solar absorber in the solar still without any enhancement. The average efficiency and evaporation rate of the solar absorber in the enhanced solar still was recorded at 61.5% and 0.98 kg m−2 h−1, respectively. The pH (7.52) and salinity (10 ppm) of the collected clean water meets the standard of safe water by the World Health Organization.

Harnessing microscopically opposite wettability in Janus nanofiber film for solar steam generation and photodegradation

Amphiphilic Janus nanofibers film composed of microscopically assembled hydrophilic and hydrophobic nanofibers is fabricated as a base film for the solar steam generator possessing functions of solar steam generation and photodegradation. The amphiphilic Janus nanofibers film integrates many advantageous properties including water pumping, thermal resisting, self floating, salt resisting, and high stability, which make it an excellent base film for solar steam generators. The mixture comprising carbon nanotubes, black TiO2 nanoparticles and poly(dopamine) is synthesized as a dual-functional photothermal layer on the solar steam generator for realizing photothermal conversion and photocatalysis. The fabricated solar steam generator can achieve a superior water evaporation rate (2.491 kg m−2 h−1, 1 sun) and synchronously degrade organic pollutants. Furthermore, it is delighted to find that the water evaporation rate can be boosted while treating organic-contaminated water. The synergistic property of solar steam generation and photodegradation offers an inspiration in the fields of wastewater elimination and clean water generation.

Biomimetic solar evaporator for continuous clean water production with synergistic organic dye wastewater remediation

Solar-driven water evaporation is recognized as an environment-friendly technology for sustainable clean water generation, serving the needs of both desalination and wastewater purification. However, its practical application is constrained by challenges such as single functionality and significant salt accumulation. Inspired by the transpiration of vascular plant, this work introduces a scalable and cost-effective biomimetic evaporator (PyCOF/Tri-Layers), consisting of a biomimetic hierarchical fibrous membrane (Tri-Layers) and a composite photothermal layer (PyCOF). Furthermore, the PyCOF composite, featuring an aloe-like flower structure, enhances the light trapping (95.1 %) through multiple scattering, realizing simultaneous desalination and azo dye degradation. Based on the PyCOF/Tri-Layers evaporator, we demonstrate a suspended multi-section hanging evaporation structure sustaining a consistent evaporation rate of approximately 1.41 kg m−2 h−1 over 15 days without salt accumulation, achieving above 99.3 % removal of dye pollutants within 120 min under one sun irradiation. Moreover, in outdoor experiments, the improved evaporator realizes a daily clean water yield rate of 8.73 kg m−2 d−1, and the collected water is suitable for supporting crop cultivation within an integrated solar desalination-cultivation system. This work not only provides a one-stone-two-birds approach for generating clean water from polluted seawater, but also presents promising possibilities for offshore self-sustainable agriculture production.

All-weather-available down carbon fiber hydrogel with enhanced mechanical properties for simultaneous efficient clean water generation and dye adsorption from dye wastewater

Solar-driven photothermal conversion can produce clean water from dye wastewater while leaving the dye in the evaporation medium. Herein, a biomass-based composite hydrogel via down-fiber carbon (DFC) aerogel modified with chitosan-polyvinyl alcohol (CS-PVA) hydrogel was designed to address the aforementioned problem. The CS-PVA@DFC hydrogel integrated the capacity of simultaneous clean water production/dye adsorption during the day and continuous dye adsorption during the night. Furthermore, the modification of the CS-PVA hydrogel endowed the composite hydrogel with enhanced compression stress of 190.07 kPa (76.03 times that of DFC aerogel of 2.50 kPa) and impressive resilient recovery. Moreover, the CS-PVA@DFC hydrogel possessed solar light absorption of 99.56 % and strengthened water replenishment capacity due to the high porosity and CS-PVA hydrophilic network structure. The CS-PVA@DFC hydrogel demonstrated a stable, high evaporation rate of 2.34 kg·m−2·h−1 and simultaneous dye adsorption capacity of 70.39 % for treating methyl orange dye solution within 5 h. Additionally, the 24-h outdoor test showed that the CS-PVA@DFC hydrogel possessed excellent clean water production capacity during the daytime (reaching 4.17 kg·m−2·h−1 at 1:00p.m.) and continuous satisfactory dye adsorption capacity all day (89.68 %). These findings will inspire researchers seeking opportunities to improve the mechanical properties of aerogel and its application for treating wastewater, especially wastewater with harmful dyes.

Marine biomass-derived PDMS-based composite sponge for sustainably sourced solar-driven interfacial evaporation

Solar-driven interface evaporation has emerged as an attractive technology for addressing the pressing issue of water scarcity. Herein, from the perspective of utilizing and managing ocean resources, we have developed a comprehensive evaporator based on ocean biomass for efficient solar-driven interfacial evaporation, aiming to sustainably harness marine resources. The construction of a biomass-based evaporator was achieved using three-dimensional melanin nanoparticles (MNPs)@carboxymethyl chitosan (CMCS)/polydimethylsiloxane (PDMS) porous sponge, which exhibits highly hydrophilic and porous properties. In this study, MNPs functioned as the photothermal material and the CMCS-hydrophilic modified PDMS sponge was utilized as the supportive material. Owing to its outstanding photothermal conversion capability and ingeniously designed columnar shape with cold evaporation surface, the MCP sponge-based evaporator achieves a water evaporation rate of 2.04 kg·m−2·h−1 and an evaporation efficiency of 85% under 1sun illumination. In addition, the MCP sponge-based evaporator exhibits an outstanding desalination performance (93% salt rejection) and purification efficiency for dyes with natural sunlight. This groundbreaking study presents an innovative method by utilizing marine biomass-derived CMCS and MNPs as raw materials to construct a high-performance solar-driven interface evaporator, thereby tackling clean water generation and promoting the sustainability of marine ecosystems.

Simultaneous solar steam and electricity generation from biochar based photothermal membranes

Clean water and energy are essential for reducing poverty, fostering economic growth and sustainable development while mitigating CO2 emissions. Considering that, solar-powered interfacial vapor or steam generation is sustainable and promising environmental technology for both water purification and energy generation while being CO2-free. Despite continuous research progress, most of the solar absorbers to capture sunlight following heat conversion for steam generation are generally made from expensive nanostructures, which in part prevents their widespread manufacturing for useful applications. Herein, we experimentally demonstrate a biomass-derived carbon composite membrane that nearly covers the entire sunlight spectrum as a solar absorber with an estimated absorptivity of 90%. As a result, the light absorbed yields a surface temperature of 55 °C at the surface of the B700 and 33 °C for water. Evaporation rates up to 1.26 and 1.16 kg/(m2 h) and solar-to-vapor efficiencies of 80 and 74% were recorded in presence of sodium chloride with two different types of biochar B700 and B300 based photothermal membranes, respectively, under 1 sun illumination. The water evaporation in presence of mixed sodium chloride/magnesium chloride reached up to 1.21 and 1.05 kg/(m2 h) with 77 and 69% efficiency with B700 and B300; due to different solar absorber geometry. Furthermore, by merging the thermoelectric technology, we exploit the concept of hybrid clean water and energy generation. At a relative humidity of 60%, the thermoelectric device may generate approximately 0.9 W/m2 power density. These results highlight the interactive effects of biochar and polyvinylidene fluoride with porous hierarchies and enhanced absorption of sunlight, thus enabling a considerable elevation of temperature with great potential for clean water and energy. Overall biochar photothermal membrane represents a significant advancement as low-cost sustainable technology, addressing both water and energy challenges by providing efficient, environmentally friendly solution for freshwater production and clean power generation.

Trapping waste metal ions in a hydrogel/coal powder composite for boosting sewage purification via solar-driven interfacial water evaporation with long-term durability

The improper disposal of effluents contaminated with waste metal ions poses significant threats to clean water resources. Recently, solar-driven interfacial water evaporation has gained increasing interests for sustainable water purification, nevertheless, the presence of various hydrated metal ions from industrial effluents makes it challenging for conventional distillers to achieve efficient purification performances. Herein, a waste metal ion trapping strategy based on a novel solar vapor generator (SVG) toward highly efficient solar-driven sewage purification with prolonged durability is reported. This SVG is constructed based on a polyion complex (PIC) hydrogel/coal powder composite (PCC), where the PIC skeleton provides metal ion entrapment capabilities, and the low-cost coal powders act as solar absorbents. PCC enables improved solar-driven sewage purification from two aspects: first, the entrapped multivalent ions help to activate the water molecules inside PCC and lower water evaporation enthalpy, leading to enlarged evaporation rate; second, the strong interactions between the multivalent metal ions and polyelectrolyte chains aid in stabilizing their porous structure and maintaining continuous water transport capabilities. The resultant PCC-based SVG demonstrated high evaporation rate up to 3.6 kg · m−2· h−1 in simulated industrial sewage under one sun illumination, as well as stable and efficient clean water generation in actual coal washery wastewater even for three weeks. We envision that the rational design of SVG with ions trapping capabilities and cost-effective solar absorbers should broaden the practical applications of SVG for harsh wastewater treatment.

Optimum dynamic dispatch of clean water, methane, electricity and heat considering carbon capture

This paper suggests a novel clean water, natural gas, heat and power generation system using wind turbine generators, PVT panels, bioenergy power plants, micro-hydro power plants, micro-cogeneration units (MCUs), battery energy storage system, thermal energy storage system and plug-in electric vehicles (PEVs). In this system, a power to gas technology consisting of a carbon capture unit, an electrolyzer, a hydrogen storage unit, and a methanation process, is used to supply the natural gas demand using CO2 captured from the MCUs and the hydrogen generated by the clean water electrolyzer. Furthermore, the electricity is consumed by a desalination unit to procure the clean water demand, carbon captured unit (CCU), electrolyzer water inflow, and fill up the water storage tank. At peak clean water demand periods, the excess water is pumped from the storage tank to the consumption side. Demand response program (DRP) is used for levelling the demand. Here, total cost for water-gas-heat-power nexus model throughout the day with and without DRP for three different scenarios is minimized by using quasi-oppositional fast convergence evolutionary programming, fast convergence evolutionary programming, self-organizing hierarchical particle swarm optimizer with time-varying acceleration coefficients and differential evolution. It is seen from numerical results that cost attained with DRP is less than the cost attained without DRP.

Efficient solar-driven freshwater generation through an inner hierarchical porous metal-carbon layer bridging synergistic photothermal evaporation and adsorption photodegradation.

Solar-driven interfacial evaporation has emerged as a promising avenue for clean water production, leveraging solar energy to extract water vapor from salty and polluted water sources. However, a critical challenge remains, during the photothermal evaporation process, organic pollutants and small water-soluble molecules can transfer into distilled steam, degrading the purity of the collected water. Herein, we develop a multifunctional clean water generation system that integrates photothermal conversion, adsorptive filtration and subsequent photocatalytic purification within a unified platform. This system features an inner hierarchical porous metal-carbon layer derived from ZIF-67 carbonization, seamlessly bridging a wood carbon scaffold and BiOBr nanosheets (BiOBr@ZCW) to smoothly facilitate synergistic actions between photothermal evaporation and adsorption-photodegradation processes. This BiOBr@ZCW configuration not only minimizes thermal dissipation, facilitating a high evaporation rate of 1.67 kg m-2 h-1 and an efficiency of 85% under standard solar irradiation but also enhances the photocatalytic degradation of the rhodamine B organic pollutant with a remarkable 98.43% degradation rate within just 20 minutes. This integrated system offers a robust solution to the challenges of water purification by ensuring both high efficiency in solar steam generation and effective pollutant degradation.

Reusable Floating Spherical Hydrogel Evaporator for Solar Desalination with Salt Mitigation and Contaminant Elimination.

The generation of clean and drinkable fresh water from seawater and contaminated water holds great potential to mitigate water scarcity. Herein, a floating spherical hydrogel evaporator (SHE) is designed to achieve sunlight-driven desalination, self-salt cleaning, and removal of environmental contaminants. The spherical lightweight polystyrene is coated with a porous carbon-embedded sodium alginate/PVA/CMC photothermal hydrogel to generate a spherical hydrogel evaporator (SHE) that floats naturally. The SHE is very sensitive to the weight imbalance (500 mg) and can respond quickly to the accumulation of salt by rotation to the fresh evaporation surface, realizing excellent antisalt fouling performance. Remarkably, with energy localization by porous carbon, the spherical floating evaporator achieved a high evaporation rate of 2.65 kg m-2 h-1 with an evaporation efficiency of 98%. At the same time, SHE is also capable of adsorbing both organic contaminants and heavy metal ions through functional groups of the hydrogel, attaining 99% removal efficiency. Overall, this low-cost spherical floating evaporator may offer solution for eco-friendly and sustainable production of fresh water on a large scale.

Polypyrrole-modified natural eggplant aerogel with high shape recovery for simultaneous efficient clean water generation and heavy metal ion adsorption from wastewater

Solar water evaporation has proven to be one of the most effective approaches to generate clean water. However, simultaneous clean water generation and heavy metal ion removal is challenging and urgent for the treatment of wastewater containing heavy metal ions. Herein, polypyrrole (PPy)-modified natural eggplant (PPy@eggplant) aerogel was developed to effectively address the aforementioned problems. The resultant PPy@eggplant aerogel possessed impressive shape recovery capacity after absorbing water regardless of multiple squeezing and twisting, which contributed to usage stability in long-term applications. Moreover, the PPy@eggplant aerogel achieved solar light absorption of 98.48 % due to PPy uniform distribution and multiple light diffraction/scattering in the porous structure (porosity of 92.16 %), excellent water replenishment capacity (water droplet fully spread within 118 ms), and extremely low thermal conductivity (0.039 W·m−1·K−1). Thus, the PPy@eggplant aerogel demonstrated a high evaporation rate of 2.05 kg·m−2·h−1 and a simultaneous Cr6+ adsorption capacity of 27.83 mg·g−1 for treating dye water with Cr6+ ions. Additionally, the PPy@eggplant aerogel preserved the evaporation rate after a 10-h test, indicating long-term stability in practical applications. In conclusion, the impressive shape recovery capacity, high evaporation performance, and satisfactory Cr6+ adsorption ability make the PPy@eggplant aerogel a good alternative for treating wastewater, especially wastewater with heavy metal ions.

Synergistic solar-powered water-electricity generation: An integrated floating system on water

The global pursuit of sustainable development faces two critical challenges: the scarcity of clean water and the growing energy crisis. The integration of solar-powered hybrid systems that harness the photovoltaic effect and passive steam generation has emerged as a crucial strategy. While several thermally-localized multi-stage solar stills have been developed, they predominantly rely on ground-mounted designs. Herein, we present a groundbreaking integration concept that combines a floating solar panel with a five-stage membrane distillation (MD) device, enabling simultaneous clean water and electricity generation on water surfaces. Positioned on the reverse side of the photovoltaic (PV) cell, the Janus membrane-involved multi-stage architecture of the MD device passively cools the PV cell, captures and repurposes the waste heat and manages vaporization enthalpy recycling. Our research highlights the importance of optimizing heat and mass transport within each stage, boosting the photoelectronic and photothermal conversion of the whole system. As a result, the integrated system achieves an impressive water production rate of 4.14 kg m−2 h−1 while simultaneously maintaining a high electricity generation efficiency of 16.4 % under 1 sun, therefore maximizing the total solar energy conversion. The clean water production rate of 11.6 kg m−2 day−1 places our system among the best-performing solar stills operating under natural sunlight. This integrated system sets a pioneering example of clean water and electricity co-generation with minimized carbon footprint, extending the applicability of ground-mounted solar conversion systems to water bodies.

Bio‐Inspired Sandwich‐Structured All‐Day‐Round Solar Evaporator for Synergistic Clean Water and Electricity Generation

AbstractThe integration of solar‐driven interfacial evaporation and electricity co‐generation is considered a promising approach to simultaneously alleviate freshwater scarcity and the energy crisis. However, affected by intermittent solar irradiation/uncontrollable weather, the overall performance of solar‐driven evaporation in the real world is greatly reduced. Herein, inspired by antifreeze proteins in beetles that survive in extreme climates, all‐weather solar‐driven interfacial evaporators with a sandwich structure are designed. The top and bottom layers composed of MnO2‐modified cotton cloth are used for photothermal conversion and water transport, meanwhile, the middle layer made of a phase change microcapsule/hydrogel composite serves for heat storage and release. Under 1 kW m−2 irradiation, the evaporator exhibits a high evaporation rate of 2.67 kg m−2 h−1 and an efficiency of 89.5%. In the dark, the heat released from the phase change layer supports an evaporation rate of 0.43 kg m−2 h−1, 3.6 times that of pure water. Additionally, assembled with a thermoelectric module, the hybrid device achieves a stable output electricity power of 0.42 W m−2 under 1‐sun illumination and a prolonged output for 30 min in the dark. This work provides a novel approach for full‐time solar‐powered steam‐electricity co‐generation and a proof of concept for biomimetic steam generation/heat management integration.

Achieving Solar-Thermal-Electro Integration Evaporator Nine-Grid Array with Asymmetric Strategy for Simultaneous Harvesting Clean Water and Electricity.

Water evaporation is a ubiquitous and spontaneous phase transition process. The utilization of solar-driven interface water evaporation that simultaneously obtains clean water and power generation can effectively alleviate people's concerns about fresh water and energy shortages. However, it remains a great challenge to efficiently integrate the required functions into the same device to reduce the complexity of the system and alleviate its dependence on solar energy to achieve full-time operation. In this work, a multifunctional device based on reduced graphene oxide (RGO)/Mn3 O4 /Al2 O3 composite nanomaterials is realized by an asymmetric strategy for effective solar-thermal-electro integration that can induce power generation by water evaporation in the presence/absence of light. Under one sun irradiation, the solar-driven evaporation rate and output voltage are 1.74kgm-2 h-1 and 0.778V, respectively. More strikingly, the nine-grid evaporation/power generation array integrated with multiple devices in series has the advantages of small volume, large evaporation area, and high power generation, and can light up light-emitting diodes (LEDs), providing the possibility for large-scale production and application. Based on the high photothermal conversion efficiency and power production capacity of the RGO/Mn3 O4 /Al2 O3 composite evaporation/generator, it will be a promising energy conversion device for future sustainable energy development and applications.

Low-Temperature Wastewater Electrolysis for H2 and Clean Water Generation

Water electrolysis represents a sustainable approach to produce green hydrogen (H2); however, the high energy cost (H2O → 2H+ + 2e- + ½O2, ∆H° = 275 kJ/mol H2, E° = −1.18 V) associated with water electrolysis and electricity cost (>$50/MWh) results in a minimum H2 selling price ≈$5/kWh. Hence, we need to find alternative process to generate H2 to meet the current U.S. Department of Energy's (DOE's) Energy Earthshots of $1/kg H2 in one decade.Wastewater electrolysis represents an alternative approach to generate H2 with renewable sources by electrochemically oxidizing organic molecules to generate H2 (e.g., CH3COOH + 2H2O → 2CO2 + 8e- + 8H+, ∆H° = 53 kJ/mol, E° = −0.02 V,) which has up to 5 times lower energy requirement than water electrolysis. As opposed to water electrolysis that requires clean water streams, wastewater electrolysis uses readily available waste streams that need cleanup anyway to generate H2; hence, integrating a second application in addition to H2 generation.1-3 In this work, we compare the performance of heterogeneous electrocatalysts for the electrocatalytic oxidation (ECO) of organic molecules present in wastewater as well as electrocatalysts for the H2 evolution reaction (HER) at room temperature. ECO and HER electrocatalysts were developed and tested using real wastewaters derived from the hydrothermal liquefaction (HTL) of food waste. We synthesized the electrocatalysts using both platinum-group metals (PGM) as well as base-group metals (BGM) with equimolar loadings and tested them as a function of potential. Our results show that while PGM-based electrocatalysts were required to perform ECO of HTL-derived wastewater4-6, BGM-based electrocatalysts were able to perform HER similarly to PGM electrocatalysts in HTL-derived wastewater. We performed a preliminary techno-economic analysis to outline a path towards $1/kg H2 via wastewater electrolysis and identified the next research and development areas. References Andrews, E.; Lopez-Ruiz, J. A.; Egbert, J. D.; Koh, K.; Sanyal, U.; Song, M.; Li, D.; Karkamkar, A. J.; Derewinski, M. A.; Holladay, J.; Gutiérrez, O. Y.; Holladay, J. D., Performance of Base and Noble Metals for Electrocatalytic Hydrogenation of Bio-Oil-Derived Oxygenated Compounds. ACS Sustainable Chem. Eng. 2020, 8 (11), 4407-4418.Lopez-Ruiz, J. A.; Qiu, Y.; Andrews, E.; Gutiérrez, O. Y.; Holladay, J. D., Electrocatalytic valorization into H2 and hydrocarbons of an aqueous stream derived from hydrothermal liquefaction. J. Appl. Electrochem. 2021, 51 (1), 107-118.Lopez-Ruiz, J. A.; Andrews, E.; Akhade, S. A.; Lee, M.-S.; Koh, K.; Sanyal, U.; Yuk, S. F.; Karkamkar, A. J.; Derewinski, M. A.; Holladay, J.; Glezakou, V.-A.; Rousseau, R.; Gutiérrez, O. Y.; Holladay, J. D., Understanding the Role of Metal and Molecular Structure on the Electrocatalytic Hydrogenation of Oxygenated Organic Compounds. ACS Catalysis 2019, 9 (11), 9964-9972.Qiu, Y.; Lopez-Ruiz, J. A.; Zhu, G.; Engelhard, M. H.; Gutiérrez, O. Y.; Holladay, J. D., Electrocatalytic decarboxylation of carboxylic acids over RuO2 and Pt nanoparticles. Appl. Catal. B-Environ. 2022, 305, 121060.Lopez-Ruiz, J. A.; Qiu, Y.; Andrews, E.; Gutiérrez, O. Y.; Holladay, J. D., Electrocatalytic valorization into H2 and hydrocarbons of an aqueous stream derived from hydrothermal liquefaction. J. Appl. Electrochem. 2021, 51 (1), 107-118.Qiu, Y.; Lopez-Ruiz, J. A.; Sanyal, U.; Andrews, E.; Gutiérrez, O. Y.; Holladay, J. D., Anodic electrocatalytic conversion of carboxylic acids on thin films of RuO2, IrO2, and Pt. Appl. Catal. B-Environ. 2020, 277, 119277. Figure 1

Geothermal energy prospect for decarbonization, EWF nexus and energy poverty mitigation in East Africa; the role of hydrogen production

The affordability and availability of water and energy have a huge impact on food production. Research has shown that there exists a direct and indirect link between power production and clean water generation. Hence the inclusion/importance given to the energy-water-food (EWF) nexus in the United Nations' sustainable development goals. Acknowledging the importance of decarbonization to the global future, there exists a gap in literature on the development of models that can enhance the EWF nexus, reduce energy poverty, and achieve 100% renewable energy in the electricity sector. Therefore, the technical and economic prospect of geothermal energy for bridging the aforementioned gaps in existing works of literature is presented in this study. The energy poverty/wealthy status of a country has been confirmed to have a significant impact on economic development, as economic development is largely reflected in the food-water availability. Ditto, this study is focused on the interconnectivity of the EWF nexus while incorporating global decarbonization targets. Geothermal energy is of the utmost significance in East Africa due to its abundant potential and distinctive geological features. Located in the Great Rift Valley, the region has an abundance of geothermal reservoirs, making it an ideal location for geothermal power generation. This study is novel as a comprehensive assessment framework for energy poverty is developed and innovative models utilizing primarily the geothermal resource in the East African region to mitigate this problem are proposed and analyzed. The role of hydrogen generation from critical excess electricity production is also analyzed. The East Africa region is considered the case study for implementing the models developed. A central renewable energy grid is proposed/modelled to meet the energy demand for seven East African countries namely; Ethiopia, Tanzania, Uganda, Djibouti, Comoros, Eritrea, and Rwanda. This study considers 2030, 2040, and 2050 as the timestamp for the implementation of the proposed models. The hybrid mix of the biomass power plant, solar photovoltaic (PV), pumped hydro storage system and onshore wind power is considered to furthermore show the potency of renewable energy resources in this region. Results showed that the use of geothermal energy to meet energy demands in the case study will mitigate energy poverty and enhance the region's EWF.

Enhancing Freshwater Production via Customizable and Highly Efficient Solar-Driven Seawater Desalination.

Solar-powered water generation is an appealing strategy for cost-effective and energy-sustainable seawater purification/desalination, where rational material selection and device design is crucial. Nevertheless, prevailing carbon-based photothermal materials in such systems still suffer from mediocre steam-to-water efficiency, failing to satisfy an adequate freshwater supply. Herein, we demonstrate a biomimetic corrugated evaporator (CE) affording carbon nanotube (CNT) encapsulated Fe nanocluster-decoration in the pursuit of high-efficiency seawater purification. The thus-customized CE demonstrates a maximum evaporation rate of 4.2 kg m-2 h-1 with a refraction angle of 60° and a water-lifting height of 5.5 cm, outperforming most state-of-the-art carbon-based counterparts. By employing a tailored architectural design and optimized condensing volume, the steam-to-water efficiency increases from 65.8 to 88.2% as the volume enlarges from 0.8 to 5.3 L, further harvesting a peak value of 91% under negative pressure. Light intensity simulation and experimental mechanistic investigation disclose the dual property-performance relationships between evaporator microstructure and evaporation rate, as well as between condensing device volume and steam-to-water efficiency. The universality of the theoretical guidance of this work will offer insight into the development of solar-driven evaporator construction toward simultaneous seawater desalination and clean water generation.