Global ammonia production reached 175 million metric tons in 2016, 90% of which is produced from high purity N2 and H2 gases at high temperatures and pressures via the Haber–Bosch process. Reliance on natural gas for H2 production results in large energy consumption and CO2 emissions. Concerns of human-induced climate change are spurring an international scientific effort to explore new approaches to ammonia production and reduce its carbon footprint. Electrocatalytic N2 reduction to ammonia is an attractive alternative that can potentially enable ammonia synthesis under milder conditions in small-scale, distributed, and on-site electrolysis cells powered by renewable electricity generated from solar or wind sources. This review provides a comprehensive account of theoretical and experimental studies on electrochemical nitrogen fixation with a focus on the low selectivity for reduction of N2 to ammonia versus protons to H2. A detailed introduction to ammonia detection methods and the execution of control experiments is given as they are crucial to the accurate reporting of experimental findings. The main part of this review focuses on theoretical and experimental progress that has been achieved under a range of conditions. Finally, comments on current challenges and potential opportunities in this field are provided.

We introduce an asymmetric supercapacitor composed of graphene wrapped yolk-double shell NiGa2S4 as a cathode, and graphene wrapped FeS2–FeSe2 core–shell as an anode.

Demanding more reliable power sources causes a huge development of modern electronic and optoelectronic devices with a high energy density (ENDE) and exceptional durability. Accordingly, designing modern electrode materials with outstanding structures can improve the construction of a new generation of electronic devices. Transition metal oxides hollow structures (TMOHS) have received considerable attention as appropriate materials for supercapacitors due to their structural properties and electrochemical performances. As a fascinating TMOHS, we make a new highly porous triple-shelled cobalt gallium oxide (CoGa2O4) hollow spheres (HTS-CGOHS) with triple narrow shells, and pseudocapacitive graphene wrapped CuFeS2 hollow spheres (GW@CFSHS) as developed positive and negative electrodes, respectively, in an energy storage device. The HTS-CGOHS electrode shows specific capacitance (SpCa) of 1724.30 F g–1 (239.5 mAh g–1) at 1 A g–1 which maintains as high as 1198.40 F g–1 (166.44 mAh g–1) at 24 A g–1, and reasonable durableness (96.80% capacity retention at 12 A g–1) owing to the low internal resistance, fast kinetics, reversibility, high surface area (104.30 m2 g–1), and numerous active sites. Moreover, the GW@CFSHS advanced negative electrode reveals electrochemical performance comprising a SpCa of 621.20 F g–1 (172.6 mAh g–1), rate performance of 58% and excellent durableness, which are superior to that of CuFeS2 hollow sphere (CFSHS) electrode. According to the electrochemical nature of the as-obtained pseudocapacitive electrode materials, an energy storage device (ESD) based on the HTS-CGOHS as a cathode and GW@CFSHS as an anode was studied. The HTS-CGOHS//GW@CFSHS device shows SpCa of 376.40 F g–1 (153.1 mAh g–1), high ENDE of 114.8 W h kg–1, and notable durableness (only 6.3% decrease after 5000 cycles at 6 A g–1).

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