This paper reports a comparative study on the tribological characteristics of base oils in four groups, synthetic esters, mineral oils, polymerized alpha olefins (PAOs), and poly alkylene glycols (PAGs), by means of viscosity, friction, and wear measurements. Friction coefficients for the lubricants in each group, measured with a pin-on-disk tribometer, are summarized in the form of Stribeck curves. Wear of the disk specimens due to rubbing in the interfaces lubricated with the tested oils is evaluated by surface topographic changes. The results indicate that for surfaces of similar roughness, viscosity has the predominant influences on the friction and wear-protection properties of these lubricants.

Production of clean water from seawater and wastewater is significant through photothermal evaporation using unlimited solar energy. Here, we constructed a double-layer-structure evaporator (DLSE) consisting of nickel foam@reduced graphene oxide–carbon nanotube (NF@RGO–CNT) as a solar absorber and an expanded polyethylene foam (EPE)/thermoelectric (TE) module as a heat insulator, which was used in various water purification processes and simultaneous electricity generation. The reduced graphene oxide covered on the surface of nickel foam increases broad-band absorption of sunlight and weakens the thermal emittance, and its coarse surface decreases the reflectance of light, which ensures the largest photo-to-heat conversion efficiency. Compared with the pristine nickel foam, NF@RGO–CNT has a low thermal conductivity to achieve localized high temperatures, which favors the evaporation of water on the interfacial surface. As such, a high water evaporation rate of 1.37 kg m–2 h–1 together with a photothermal conversion efficiency of 96.4% was achieved over the NF@RGO–CNT under 1 kW/m2. Meanwhile, the thermoelectricity during solar evaporation is generated by utilizing the TE module instead of EPE, in which a maximum output power of 0.251 W m–2 was achieved under 1 kW/m2. In addition, clean water can be produced using DLSE equipment from various water sources such as brine water, organic wastewater, seawater, and lake water, in which the quality of the evaporated water is better than drinkable water standard, and the evaporation performance is comparable to that of pure water.

This work reported the coupling reaction of lactic acid (LA) to produce pyruvic acid (PyA) and propionic acid (PA) simultaneously over defect-rich MoS 2 nanosheets. The process intensification linked to dehydrogenation of LA and hydrodeoxygenation of LA brings about the advantage that is not supplied additionally with oxygen and hydrogen, achieving a green and safe route. The defected structure is characterized by highresolution transmission electron microscopy (HRTEM) and positron annihilation lifetime spectroscopy (PALS), which promotes the catalytic performance for the coupling reaction of LA. To fully understand the importance of the defected structure, the catalytic performance of defect-free MoS 2 is also evaluated. It is found that the PyA/PA ratio is less than 1 and acetaldehyde selectivity is relatively high, suggesting that the produced hydrogen from the dehydrogenation of LA is insufficient for hydrodeoxygenation of LA over defect-free MoS 2 , and the difference of hydrogen comes from the side reactions of decarbonylation and decarboxylation of LA. Unlike the defect-free MoS 2 , the dehydrogenation of LA over the defect-rich MoS 2 can provide sufficient hydrogen for hydrodeoxygenation of LA, so that the side reactions are drastically weakened. The widened interplanar spacing can fully expose the defect and the LA reactant molecule is more accessible to defective sites, which can endow a better catalytic activity. Surface hydrophilicity can improve adsorption and transfer, and better activity is observed over the defect-rich MoS 2 and widened defect-rich MoS 2 . At 300 °C and a LA LHSV of 2.6 h −1 under an inert atmosphere, the catalyst offers a satisfactory total selectivity to pyruvic acid and propionic acid of about 85%, and the molar ratio of pyruvic acid/propionic acid is 1.1.

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