Utilizing the broad‐band solar spectrum for sea water desalination is a promising method that can provide fresh water without sophisticated infrastructures. However, the solar‐to‐vapour efficiency has been limited due to the lack of a proper design for the evaporator to deal with either a large amount of heat loss or salt accumulation. Here, these issues are addressed via two cost‐effective approaches: I) a rational design of a concave shaped supporter by 3D‐printing that can promote the light harvesting capacity via multiple reflections on the surface; II) the use of a double layered photoabsorber composed of a hydrophilic bottom layer of a polydopamine (PDA) coated glass fiber (GF/C) and a hydrophobic upper layer of a carbonized poly(vinyl alcohol)/polyvinylpyrrolidone (PVA/PVP) hydrogel on the supporter, which provides competitive benefit for preventing deposition of salt while quickly pumping the water. The 3D‐printed solar evaporator can efficiently utilize solar energy (99%) with an evaporation rate of 1.60 kg m–2 h–1 and efficiency of 89% under 1 sun irradiation. The underlying reason for the high efficiency obtained is supported by the heat transfer mechanism. The 3D‐printed solar evaporator could provide cheap drinking water in remote areas, while maintaining stable performance for a long term.

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An efficient reduction method to obtain high-quality graphene sheets from mass-producible graphene oxide is highly desirable for practical applications. Here, we report an in situ deoxidation and graphitization mechanism for graphene oxide that allows for high-quality reduced graphene oxide sheets under the low temperature condition (<300 °C) by utilizing a well-known Fischer–Tropsch reaction catalyst (CuFeO2). By applying modified FTR conditions, where graphene oxide was reduced on the catalyst surface under the hydrogen-poor condition, deoxidation with much suppressed carbon loss was possible, resulting in high-quality graphene sheets. Our experimental data and density functional theory calculations proved that reduction which occurred on the CuFeO2 surface preferentially removed adsorbed oxygen atoms in graphene oxide sheets, leaving dissociated carbon structures to be restored to a near-perfect few-layer graphene sheet. TGA-mass data revealed that GO with catalysts released 92.8% less carbon-containing gases than GO without catalysts during the reduction process, which suggests that this process suppressed carbon loss in graphene oxide sheets, leading to near-perfect graphene. The amount of oxygen related to the epoxide group in the basal plane of GO significantly decreased to near zero (from 43.84 to 0.48 at. %) in catalyst-assisted reduced graphene oxide (CA-rGO). The average domain size and the density of defects of CA-rGO were 4 times larger and 0.1 times lower than those for thermally reduced graphene oxide (TrGO), respectively. As a result, CA-rGO had a 246 and 8 times lower electrical resistance than TrGO and CVD-graphene. With these performances, CA-rGO coated paper connected to a coin-cell battery successfully lit an LED bulb, and CA-rGO itself acted as an efficient catalyst for both the hydrogen evolution reaction and the oxygen evolution reaction.

We have discovered a carbonized polymer film to be a reliable and durable carbon-based substrate for carbon enhanced Raman scattering (CERS). Commercially available SU8 was spin coated and carbonized (c-SU8) to yield a film optimized to have a favorable Fermi level position for efficient charge transfer, which results in a significant Raman scattering enhancement under mild measurement conditions. A highly sensitive CERS (detection limit of 10 M) that was uniform over a large area was achieved on a patterned c-SU8 film and the Raman signal intensity has remained constant for 2 years. This approach works not only for the CMOS-compatible c-SU8 film but for any carbonized film with the correct composition and Fermi level, as demonstrated with carbonized-PVA (poly(vinyl alcohol)) and carbonized-PVP (polyvinylpyrollidone) films. Our study certainly expands the rather narrow range of Raman-active material platforms to include robust carbon-based films readily obtained from polymer precursors. As it uses broadly applicable and cheap polymers, it could offer great advantages in the development of practical devices for chemical/bio analysis and sensors.

We report a three-dimensional graphene network decorated with nickel nanoparticles as a current collector to achieve outstanding performance in Ni(OH)2-based supercapacitors with excellent energy density.

Solar Evaporators In article number 2102649, Ji‐Hyun Jang and co‐workers present a 3D‐printed solar evaporator that can efficiently utilize solar energy (99%) with an evaporation rate of 1.60 kg m−2 h−1 and efficiency of 89% under 1 sun irradiation, which promotes light‐harvesting capacity via multiple reflections on the surface and provides competitive benefits for preventing deposition of salt while quickly pumping the water, for long‐term provision of drinking water in remote locations.

Aqueous zinc-ion batteries (ZIBs) are promising next-generation battery system which can mitigate the prevailing issues on the conventional lithium-ion batteries. However, insufficient energy density with low operating voltage prevents the practical utilization of the aqueous system. Notably, aqueous ZIBs suffer from electrolyte decomposition due to its narrow electrochemical stability window (ESW) for 1.23 V. Also, studies on cathode active materials that store charge at an elevated voltage region is still in the initial stage. In this perspective, we cover the recent strategies for developing high-voltage aqueous ZIBs. First, electrolyte designs for expanding the ESW of an aqueous electrolyte are introduced based on their characterization, materials, and working mechanisms. Next, we propose the cathode active materials with high-working voltage. Furthermore, studies on zinc anodes are also briefly presented. Lastly, we summarize the as-reported strategies and provide insight for developing future ZIBs.

Reduced graphene oxide (rGO) composites for energy-related applications have attracted increasing attention. However, previous studies on rGOs still showed limitations because of unresolved several issues including π−π stacking between the graphene sheets, low wettability, and relatively high electrical resistance. Here, we report a fabrication method for a stacking-free porous graphene network (PGN) based on the intercalation of oxidized multiwall carbon nanotubes and graphitic carbon nitrides into partially exfoliated GO sheets with covalent sulfate bonding between each layer, followed by hydrothermal reduction to rGO. The three-dimensional PGN with high wettability and low electrical resistance provided a high capacitance of 338 F/g at 1 A/g, an outstanding energy density of 36.0 W h/kg at a power density of 1496.1 W/kg, and nearly 100% capacitance retention after 10,000 cycles. Our strategy overcomes the previous limitations of rGO and presents remarkable potential of 3D stacking-free rGO composites for practical energy-storage systems.