(A) The multistep process in pothole-free WO₃. (B) Calculated Gibbs free energy diagram of reaction transformation process over pothole-free WO₃. (C) DFT calculation results indicated the strong chemisorption behavior of N₂ and the obvious charge transfer behavior on the pothole-rich surface with dangling bonds. (D) The specific Gibbs free energy diagram of the stepwise of activation and cleavage of N≡N bonds of N₂. Adapted with permission from Ref. [94], copyright 2019 Wiley-VCH.