No abstract

Efficient heat removal and recovery are two conflicting processes that are difficult to achieve simultaneously. Here, in this work, we pave a new way to achieve this through the use of a smart thermogalvanic hydrogel film, in which the ions and water undergo two separate thermodynamic cycles: thermogalvanic reaction and water-to-vapor phase transition. When the hydrogel is attached to a heat source, it can achieve efficient evaporative cooling while simultaneously converting a portion of the waste heat into electricity. Moreover, the hydrogel can absorb water from the surrounding air to regenerate its water content later on. This reversibility can be finely designed. As an applicative demonstration, the hydrogel film with a thickness of 2 mm was attached to a cell phone battery while operating. It successfully decreased the temperature of the battery by 20 °C and retrieved electricity of 5 μW at the discharging rate of 2.2 C.

No abstract

Ammonia (NH3) is mainly produced through the traditional Haber-Bosch process under harsh conditions with huge energy consumption and massive carbon dioxide (CO2) emission. The nitrogen electroreduction reaction (NERR), as an energy-efficient and environment-friendly process of converting nitrogen (N2) to NH3 under ambient conditions, has been regarded as a promising alternative to the Haber-Bosch process and has received enormous interest in recent years. Although some exciting progress has been made, considerable scientific and technical challenges still exist in improving the NH3 yield rate and Faradic efficiency, understanding the mechanism of the reaction and promoting the wide commercialization of NERR. Single-atom catalysts (SACs) have emerged as promising catalysts because of its atomically dispersed activity sites and maximized atom efficiency, unsaturated coordination environment, and its unique electronic structure, which could significantly improve the rate of reaction and yield rate of NH3. In this review we briefly introduce the unique structural and electronic features of SACs, which contributes to comprehensively understand the reaction mechanism owing to their structural simplicity and diversity, and in turn expedite the rational design of fantastic catalysts at the atomic scale. Then, we summarize the most recent experimental and computational efforts on developing novel SACs with excellent NERR performance, including precious metal-, nonprecious metal-and nonmetal-based SACs. Finally, we present challenges and perspectives of SACs on NERR, as well as some potential means for advanced NERR catalyst.

No abstract