Comparative Study on the Electrocatalytic Performance of ABO₃-Based Hexagonal Perovskite Oxides with Different [AO₃] Layers

To systematically investigate the influence of the number of [AO₃] layers in the unit cell of hexagonal perovskite oxide on the oxygen evolution reaction performance, we successfully synthesized the three new hexagonal perovskite oxides 2H-BaCo_0.9Ru_0.1O_3-δ, 6H-BaCo_0.9Ru_0.1O_3-δ, and 10H-BaCo_0.9Ru_0.1O_3-δ with the same element composition but different [BaO₃] layers via the sol-gel method. Here, 2H, 6H, and 10H refer to the number of [BaO₃] layers contained in the unit cell of the BaCo_0.9Ru_0.1O_3-δ system. Experimentally, 10H-BaCo_0.9Ru_0.1O_3-δ, featuring ten layers of [BaO₃], exhibits optimal electrochemical activity among the three oxide catalysts, and in situ Raman results under various bias voltages confirm its ability to maintain a high surface crystal structural stability. Notably, as the number of [BaO₃] layers increases, the effective magnetic moments and the valence state of surface Co ions in these three catalysts also increase, with the spin configuration of the surface Co ions being in a high-spin state. More importantly, DFT calculations provide the evolution rules of the p-band center (ε_p) with the number of [BaO₃] layers, predicting the electrochemical performance of the BaCo_0.9Ru_0.1O_3-δ system with different [BaO₃] layers. Our experimental results offer a distinctive perspective for the future design, synthesis, and application of hexagonal perovskite oxides in electrocatalysis.