Visible Light Locking in Mineral-Based Composite Phase Change Materials Enabling High Photothermal Conversion and Storage

Hierarchical Porous Silicon-Carbon Encapsulated Phase Change Materials for Efficient Photothermoelectric Conversion

Scale-up applications in solar energy storage of phase change materials (PCMs) are hindered by the limitation of solid-liquid leakage and the lack of light absorption ability. Porous silicon-carbon (PSC) with a high specific surface area was prepared from a phytolith (Phy) silicon-carbon ore by the alkali-melting method, taking advantage of the natural mineral rich in light-trapping carbon structures in Phy. Stearic acid (SA) was impregnated into the PSC to produce integrated photothermal composite phase change materials (SA/PSC). The performance analysis of the form-stable PCMs (FSPCMs) shows that SA/PSC800 has good shape stability and excellent photothermal conversion efficiency and storage capacity, with a high photothermal conversion efficiency of 98.87%. The enthalpy change of the phase change was weak after 200 cycles, indicating good cycle regeneration. A solar thermoelectric generator (STEG) system for light-heat-electric energy conversion and storage was constructed using SA/PSC800 as a hot-side material integrated with a thermoelectric generator. Under a simulated solar light intensity of 200 mW/cm2, the output power generated by the STEG system through the Seeback effect can keep the small bulb and LED glowing for 21 and 18 s, respectively. Therefore, the prepared composite FSPCMs have promising applications in battery-coupled photovoltaic power generation.

Salt-resistant continuous solar evaporation composites based on nonwovens with synergistic photothermal effect of graphene oxide/copper sulphide

Solar interfacial evaporation is an innovative and environmentally friendly technology for producing freshwater from seawater. However, current interfacial evaporators are costly to manufacture, have poor tolerance to environmental conditions, exhibit instability in evaporation efficiency in highly saline solutions, and fail to prevent salt crystallization. The production of user-friendly, durable and salt-resistant interfacial evaporators remains a significant challenge. By spraying graphene oxide on a nonwoven material using PVA as a binder and adding biphasic Cu x S by an in situ growth method, we designed 2D/3D micro- and nanostructured graphene oxide nanosheets/copper sulfide nanowires (GO/Cu x S) with synergistic photo-thermal effects in the full spectral range. The evaporation efficiency in pure water was 94.61% with an evaporation rate of 1.5622 kg m-2 h-1. In addition, we enhanced convection by employing a vertically aligned water-guide rod structure design, where the concentration difference drives salt dissolution thereby reducing the formation of salt crystals. The evaporation efficiency in 20% salt water was 80.41% with an evaporation rate of 1.3228 kg m-2 h-1 and long-term stability of brine evaporation was demonstrated under continuous sunlight. This solar steam generator expands the potential application areas of desalination and wastewater purification.

BiVO4 Film Coupling with CoAl2O4 Nanoparticles for Photoelectrochemical Water Splitting Utilizing Broad Solar Spectrum through p-n Heterojunction, Photothermal, and Cocatalytic Synergism

Water oxidation is an endothermic and kinetics-sluggish reaction; the research of photoanodes with photothermal and cocatalytic properties is of great significance. Herein, BiVO4/CoAl2O4 film photoanodes were studied for solar water splitting through coupling spinel p-type CoAl2O4 nanoparticles on n-type BiVO4 films. Compared to the BiVO4 photoanode, better performance was observed on the BiVO4/CoAl2O4 photoanode during water oxidation. A photocurrent of 3.47 mA/cm2 was produced on the BiVO4/CoAl2O4 photoanode at 1.23 V vs RHE, which is two-fold to the BiVO4 photoanode (1.70 mA/cm2). Additionally, the BiVO4/CoAl2O4 photoanodes showed an acceptable stability for water oxidation. The BiVO4/CoAl2O4 photoanode being of higher water oxidation performance could be attributed to the presence of p-n heterojunction, cocatalytic, and photothermal effects. In specific, under the excitation of λ < 520 nm light, the holes produced in/on BiVO4 can be transferred to CoAl2O4 owing to the p-n heterojunctions of BiVO4/CoAl2O4. Meanwhile, the temperature on the BiVO4/CoAl2O4 photoanode rises quickly up to ∼53 °C under AM 1.5 G irradiation due to the photothermal property of CoAl2O4 through capturing the 520 < λ < 720 nm light. The temperature rising on the BiVO4/CoAl2O4 photoanode improves the cocatalytic activity of CoAl2O4 and modifies the wettability of BiVO4/CoAl2O4 for effective water oxidation.

Novel MoS2/montmorillonite hybrid aerogel encapsulated PEG as composite phase change materials with superior solar-thermal energy harvesting and storage

Phase change materials (PCMs) offer significant advantages in energy conversion and storage by facilitating the storage and release of thermal energy during phase transition processes. However, challenges such as leakage during PCM phase transitions and poor light absorption properties have constrained their application in the field of photothermal energy storage. In this study, Montmorillonite (Mt) and molybdenum disulfide (MoS2) has been used to design and synthesize hybrid aerogels (MoS2/Mt) boasting high mechanical strength and excellent photothermal conversion performance. These aerogels are then used to encapsulate polyethylene glycol (PEG) to prepare composite PCMs with outstanding solar-thermal conversion and storage performances. The results show that the synthesized MoS2/Mt-PEG composite PCMs exhibit high enthalpies of melting and solidification of 169.16 J/g and 170.78 J/g, respectively, while the aerogel supporting material has a high compressive modulus of 1.96 MPa. Moreover, the composite material displayed excellent thermal stability and leakage resistance after undergoing 30 melting-cooling cycles. Furthermore, the incorporation of MoS2 imparted outstanding light absorption properties to the MoS2/Mt-PEG composite, resulting in a high light absorption and photothermal conversion-storage efficiency of 93.4 % and 96.47 %, respectively. Synthesized composite PCMs also demonstrate outstanding performance in solar-thermal-electricity conversion, achieving a voltage output of 458 mV under illumination conditions and maintaining a sustainable voltage output even after removing the light source. Thus, the composite PCMs prepared in this work can meet the requirements of high enthalpy, effective leakage prevention, efficient solar-thermal conversion and solar-thermal-electricity conversion performance, thereby presenting potential applications in practical solar energy collection, conversion, and storage.

Flexible Polyolefin Elastomer/Paraffin Wax/Alumina/Graphene Nanoplatelets Phase Change Materials with Enhanced Thermal Conductivity and Mechanical Performance for Solar Conversion and Thermal Energy Storage Applications

In this study, electrically insulating polyolefin elastomer (POE)-based phase change materials (PCMs) comprising alumina (Al2O3) and graphene nanoplatelets (GNPs) are prepared using a conventional injection moulding technique, which exhibits promising applications for solar energy storage due to the reduced interfacial thermal resistance, excellent stability, and proficient photo-thermal conversion efficiency. A synergistic interplay between Al2O3 and GNPs is observed, which facilitates the establishment of thermally conductive pathways within the POE/paraffin wax (POE/PW) matrix. The in-plane thermal conductivity of POE/PW/GNPs 5 wt%/Al2O3 40 wt% composite reaches as high as 1.82 W m-1K-1, marking a remarkable increase of ≈269.5% when compared with that of its unfilled POE/PW counterpart. The composite exhibits exceptional heat dissipation capabilities, which is critical for thermal management applications in electronics. Moreover, POE/PW/GNPs/Al2O3 composites demonstrate outstanding electrical insulation, enhanced mechanical performance, and efficient solar energy conversion and transportation. Under 80 mW cm-2 NIR light irradiation, the temperature of the POE/PW/GNPs 5 wt%/Al2O3 40 wt% composite reaches approximately 65 °C, a notable 20 °C improvement when compared with the POE/PW blend. The pragmatic and uncomplicated preparation method, coupled with the stellar performance of the composites, opens a promising avenue and broader possibility for developing flexible PCMs for solar conversion and thermal storage applications.