[en] Catalytic conversion of CO₂ to CO (reverse water-gas shift reaction, RWGS) is one of the most promising technologies for CO₂ resource utilization. In this work, a sulfur-containing zirconia supported nickel catalyst (Ni/ZrO₂) was prepared to improve the CO₂ conversion while adjusting the CO₂ hydrogenation selectivity from CH₄ to CO. The effect of support size (80 nm, 120 nm, 200 nm and 320 nm) on the catalytic performance of RWGS was investigated. The results showed that the Ni/ZrO₂-80 sample with a smaller support size of 80 nm exhibited higher Ni dispersion and oxygen vacancy concentration, which not only exposed more active sites but also enhanced the adsorption and activation capacity of CO₂. For these reasons, the CO₂ conversion of 27.6% with 100% selectivity of CO was achieved over Ni/ZrO₂-80, and no catalyst deactivation was observed during the stability test for 50 h. This work provides a new idea for designing the RWGS catalyst with an outstanding CO₂ hydrogenation performance. (authors)

[en] A simple approach to fabricating smart actuators with large directional bending actuation and fast response has yet to be developed. Herein, a self-standing actuator is fabricated through layer-by-layer assembly of a graphene oxide (GO) film on a flexible commercial cellulose acetate (CA) polymer membrane. The GO/CA actuator responds to acetone vapor and the bending angle depends on the strip length and the thickness of GO film. Bending greater than 720° is achieved within 19 s in acetone vapor at a fixed strip length of 30 mm and a GO film thickness of 29 μm, and recovery within 38 s in air. A bending mechanism of GO/CA bilayer actuator is proposed based on the swelling effect of the CA polymer membrane in alcohol vapor. The GO film plays an important role as the barrier layer to avoid over-swelling of the CA polymer, induced by the organic vapor, and to create tension in the recovery process. The new driven system is used in example applications for designing various devices to demonstrate the dynamic process. (paper)

[en] Highlights: • Layered double hydroxides (LDHs) is firstly explored for natural water evaporation (NWE) driven generators. • A continuous NWE-driven flexible generator is fabricated by painting Ni-Al LDH on polyethylene terephthalate. • The NWE driven generator can bear deformation without sacrificing its output performance. • Integrated circuit device is continuously powered by NWE driven Ni-Al LDH generators. -- Abstract: Natural water evaporation (NWE) is spontaneous and ubiquitous process that absorbs ambient thermal energy. Scavenging ambient thermal energy into electricity by NWE provides a promising approach to supply power for self-powered and low-cost devices and systems. Suitable materials and techniques are required to use this ubiquitous natural process for electricity generation. Herein, a continuous NWE-driven flexible generator is fabricated by painting Ni-Al layered double hydroxide (LDH) on a polyethylene terephthalate substrate at room temperature. The generator operates through an NWE-driven gradient of water that flows across the naturally formed surface-charged nanochannels between Ni-Al LDH flakes; i.e., the streaming potential mechanism. The output electrical characteristics of the device can be controlled by adjusting the environmental moisture and wind velocity. Continuous electricity output with a comparatively high power density of 16.1 μW cm⁻³ is achieved from a generator. The generator can maintain a stable output power under deformation. The output power of the generator can be scaled up to continuously power integrated circuit devices such as a digital calculator. Given the easy fabrication process of this flexible NWE-driven generator using an environmentally friendly LDH and its continuous electricity output with relatively high power density, this generator represents an important step towards practical green ambient energy harvesting.

[en] Nitrogen-rich porous “green carbons” derived from abundant shrimp shell shows good performance for Li–S batteries. The strategy in this work is highlighted to selective removal of intrinsic CaCO_3 in shrimp shell followed by KOH activation to tune the pore sizes of the obtained carbons. On the basis of the different porous structures, the discharge capacity of the obtained carbons as Li–S cathodes follows the order of micro-mesoporous carbon>mesoporous carbon>microporous carbon. The high capacity of the micro-mesoporous carbon is attributed to its positive characters such as the coexistence of micro-mesoporous structure, the large pore volume and the high specific surface area. Furthermore, well-dispersed nitrogen in the porous carbons is naturally doped and inherited from shrimp shell, and can help to enhance cycle stability when used as cathodes. As a result, all carbon cathodes exhibit the good cycle stability (>78%) due to their nitrogen doping induced chemical adsorption of sulfur on the surface areas of the porous carbons. Among them, mesoporous carbon cathode shows the best cycle stability with 90% retention within 100 cycles, which is mainly attributed to the synergistic effects of its both large pore size (5.12 nm) and high nitrogen content (6.67 wt %). - Highlights: • Nitrogen-rich porous “green carbons” derived from abundant shrimp shell shows good performance for Li–S batteries. • Intrinsic CaCO_3 in shrimp shell as the natural template plays an important role on tailoring of the pore sizes of the porous carbons. • Nitrogen containing polysaccharide in shrimp shell benefits to produce nitrogen-rich carbons. • The effects of pore sizes on the electrochemical performance are investigated in detail. • The carbon-sulfur cathodes exhibit the good cycle stability because of nitrogen doping induced chemical adsorption of sulfur.