Metal-nitrogen-carbon (M-N-C) single-atom catalysts exhibit desirable electrochemical catalytic properties. However, the replacement of N atoms by heteroatoms (B, P, S, etc.) has been regarded as a useful method for regulating the coordination environment. The structure engineered M-N-C sites via doping heteroatoms play an important role to the adsorption and activation of the oxygen intermediate. Herein, we develop an efficient strategy to construct dual atomic site catalysts via the formation of a Co₁-PN and Ni₁-PN planar configuration. The developed Co₁-PNC/Ni₁-PNC catalyst exhibits excellent bifunctional electrocatalytic performance in alkaline solution. Both experimental and theoretical results demonstrated that the N/P coordinated Co/Ni sites moderately reduced the binding interaction of oxygen intermediates. The Co₁-PNC/Ni₁-PNC endows a rechargeable Zn-air battery with excellent power density and cycling stability as an air-cathode, which is superior to that of the benchmark Pt/C+IrO₂. This work paves an avenue for design of dual single-atomic sites and regulation of the atomic configuration on carbon-based materials to achieve high-performance electrocatalysts.

ZnO hierarchical aggregates have been successfully synthesized by solvothermal methods through reaction of zinc acetate and potassium hydroxide in methanol solution. The shapes of the aggregates were controlled by varying the ratio of Zn²⁺ and OH^– ions in the reaction system, while the size can be tuned from 2 μm to 100 nm. Oriented attachment was found to be the main mechanism of the three-dimensional assembly of small ZnO nanocrystallites into large aggregates. The performance of these aggregates in dye-sensitized solar cells (DSCs) indicated that hierarchical structured photoelectrodes can increase energy conversion efficiency of DSCs effectively when the sizes of aggregates match the wavelengths of visible light.