Taking advantage of the self-assembling function of amino acids, cobaltalanine complexes are synthesized by straightforward process of chemical precipitation. Through a controllable calcination of the cobalt-alanine complexes, N-doped Co 3 O 4 nanostructures (N-Co 3 O 4 ) and N-doped CoO composites with amorphous carbon (N-CoO/C) are obtained. These N-doped cobalt oxide materials with novel porous nanostructures and minimal oxygen vacancies show a high and stable activity for the oxygen evolution reaction. Moreover, the influence of calcination temperature, electrolyte concentration, and electrode substrate to the reaction are compared and analyzed. The results of experiments and density functional theory calculations demonstrate that N-doping promotes the catalytic activity through improving electronic conductivity, increasing OH − adsorption strength, and accelerating reaction kinetics. Using a simple synthetic strategy, N-Co 3 O 4 reserves the structural advantages of micro/nanostructured complexes, showing exciting potential as a catalyst for the oxygen evolution reaction with good stability.

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Sodium-ion batteries (NIBs), due to the advantages of low cost and relatively high safety, have attracted widespread attention all over the world, making them a promising candidate for large-scale energy storage systems. However, the inherent lower energy density to lithium-ion batteries is the issue that should be further investigated and optimized. Toward the grid-level energy storage applications, designing and discovering appropriate anode materials for NIBs are of great concern. Although many efforts on the improvements and innovations are achieved, several challenges still limit the current requirements of the large-scale application, including low energy/power densities, moderate cycle performance, and the low initial Coulombic efficiency. Advanced nanostructured strategies for anode materials can significantly improve ion or electron transport kinetic performance enhancing the electrochemical properties of battery systems. Herein, this Review intends to provide a comprehensive summary on the progress of nanostructured anode materials for NIBs, where representative examples and corresponding storage mechanisms are discussed. Meanwhile, the potential directions to obtain high-performance anode materials of NIBs are also proposed, which provide references for the further development of advanced anode materials for NIBs.

We report a density functional theory (DFT) study of microscopic detailed effects of the bonding configuration of nitrogen-doped graphene (N-graphene) within the carbon lattice (including pyridinic, pyrrolic, and graphitic N) on the reactivity and mechanistic processes of H2O2 reduction reaction. We simulated the adsorption process of H2O2, analyzed the mechanistic processes, and calculated the reversible potential of each reaction step of the H2O2 reduction reaction on N-graphene. The results indicate that the adsorption of H2O2 on the pristine and N-doped graphene surfaces occurs via physisorption without the formation of a chemical bond. When H(+) is introduced into the system, a series of reactions can occur, including the breakage of the O-O bond, the formation of an O-C chemical bond between oxygen and graphene, and the creation of water molecules. The results also indicate a decrease in the energy of the system and a positive reversible potential for each reaction step. The calculations of the relative energy of each reaction step and the value of the onset potential for H2O2 reduction reaction suggest that the reactivity of pristine and N-doped graphene has the following order: pyridinic N-graphene > pyrrolic N-graphene > graphitic N-graphene > pristine graphene. We also proposed an explanation based on electrostatic potential calculations for this dependence of the reactivity order on the bond configuration of the doping in N-graphene. The results of this study should help in the atomic-scale understanding of the dependence of the reactivity of N-graphene on its microstructure, inspire the study of various types of heteroatom-doped graphenes to improve their catalytic efficiency, and provide a theoretical framework to analyze their reactivities.

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