Transformation of Biomass Precursor into Both High‐Efficiency Cathode Catalyst and Solid Electrolyte for Rechargeable Zn‐Air Batteries

Abstract Cattail grass biomass is used as the precursor for preparing both bi‐functional cathode catalyst and solid electrolyte in the construction of high‐performance Zn‐air battery (ZAB). First, cattail grass is transformed into porous carbon micron tubes (CMTs), which are immobilized by polyoxometalate clusters of (H ₂ bimb) ₃ {Cd(P ₄ Mo ₆ O ₃₁ H ₈ ) ₂ }·5.5H ₂ O (bimb = 4,4‐di(1H‐imidazole‐1‐yl)‐1,1‐biphenyl) (abbreviation: {Cd(P ₄ Mo ₆ ) ₂ }), and then calcinated in N ₂ to form Mo ₂ C‐MoO ₂ /CMTs. {Cd(P ₄ Mo ₆ ) ₂ } not only acts as the Mo source for the formation of Mo ₂ C‐MoO ₂ heterojunction but also provides the Mo species to in situ etch carbon tubes to generate the porous microstructures. In ZABs, the multi‐catalytic sites (Mo ₂ C and MoO ₂ ) can both facilitate the oxygen reduction / evolution reaction (ORR/OER) catalytic performance at the battery cathode, and inhibit the formation of zinc dendrites by forming a large number of nucleation sites on the battery anode. Density Functional Theory results have verified the synergistic effect between Mo ₂ C and MoO ₂ , indicating that multiple active sites with superior catalytic effect than the individual materials. The ZABs assembled with Mo ₂ C‐MoO ₂ /CMTs exhibit a peak power density of 264.09 mW cm ⁻² . Cattail grass is also used to prepare highly conductive gel electrolyte to assemble all‐solid coin cell ZABs with high capacity of 97.33 mW cm ⁻² and 100 h of charge–discharge stability.