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In power storage technology, ion exchange is widely used to modify the electronic structures of electrode materials to stimulate their electrochemical properties. Here, we proposed a multistep ion exchange (cation exchange and anion exchange) strategy to synthesize amorphous Ni-Co-S and β-Co(OH)2 hybrid nanomaterials with a hollow polyhedron structures. The synergistic effects of different components and the remarkable superiorities of hollow structure endow Ni-Co-S/Co(OH)2 electrode with outstanding electrochemical performance, including ultra-high specific capacity (1440.0 C/g at 1 A/g), superior capacitance retention rate (79.1% retention at 20 A/g) and long operating lifespan (81.4% retention after 5000 cycles). Moreover, the corresponding hybrid supercapacitor enjoys a high energy density of 58.4 Wh/kg at the power density of 0.8 kW/kg, and a decent cyclability that the capacitances are maintained at 80.8% compared with the initial capacitance. This research presents a high-performance electrode material and provides a promising route for the construction of electrode materials for supercapacitors with both structural and component advantages.

Carbon nitride (CN) photocatalysts have attracted much attention due to their excellent photocatalytic properties. And hydrothermal fluorination is a common method to improve the photocatalytic effect of CN photocatalyst. Here, the influence of the band gap was first revealed of fluorination and hydroxylation of CN photocatalyst based on the first theoretical principle. Here, the effect of fluorination and hydroxylation on the CN band gap was discussed for the first time using the first theoretical principle. With F atoms and OH doping, the band gap of CN was significantly improved, conduction band and valence band moved up. Then, F CN photocatalyst with F atoms and OH was successfully synthesized by a hydrothermal fluorinated method. Next, the reasons why F CN photocatalyst was more effective than that of traditional CN photocatalyst were fully discussed. From the photocatalytic effect of photocatalyst (12,593.2 μmol g−1 h−1 to the morphology (super-small nanosheets), structure (homojunctions), composition (metal‐free), specific surface area (54.1 m2/g), visible light absorption response (AQE is 10.9% at 420 nm) and photo-induced carrier life (14.13 ns). Therefore, this work has a great guiding effect on the development of CN photocatalyst.

g-C3N4 have been widely used in the fields of photocatalytic hydrogen production, photocatalytic degradation of dyes and oxidative degradation of toxic gases due to their excellent performance. It has attracted extensive attention in recent years due to its highly efficient photocatalytic capacity of hydrogen generation, water oxidation, carbon dioxide reduction and degradation of organic pollutants. Because of the abundant carbon and nitrogen composition of the earth, large-scale production and industrial applications of this material are possible. The modification of this material makes its performance more excellent so that this new material can obtain a steady stream of vitality. These outstanding works have become important materials and milestones on the road to mankind’s photocatalytic hydrogen production. This review will begin with the basic idea of designing, synthesizing and improving g-C3N4 based photocatalytic materials, and introduce the latest development of g-C3N4 photocatalysts in hydrogen production from four aspects of controlling the carbon/nitrogen ratio, morphology, element doping and heterojunction structure of g-C3N4 materials.