Structure evolution and durability of Metal-Nitrogen-Carbon (M = Co, Ru, Rh, Pd, Ir) based oxygen evolution reaction...

Developing low-cost, high activity and stability oxygen evolution reaction (OER) catalysts is significantly important but still challenging for water electrolyzers. In this work, we calculated the OER activity and stability of Metal-Nitrogen-Carbon (MNC, M = Co, Ru, Rh, Pd, Ir) based electrocatalyst with different structures (MN₄C₈, MN₄C₁₀, MN₄C₁₂) using density functional theory (DFT) method. These electrocatalysts were divided into three groups based on the value of ΔG_*OH, that is ΔG_*OH > 1.53 eV (PdN₄C₈, PdN₄C₁₀, PdN₄C₁₂), ΔG_*OH < 1.23 eV (RuN₄C₈, RuN₄C₁₀, RuN₄C₁₂, CoN₄C₈, CoN₄C₁₀) and 1.23 eV < ΔG_*OH < 1.53 eV (RhN₄C₈, RhN₄C₁₀, RhN₄C₁₂, IrN₄C₈, IrN₄C₁₀, IrN₄C₁₂, CoN₄C₁₂), and ΔG_*OH determine whether the structure evolution will appear. The results proved that MNC (M = Rh, Ir) with 1.23 eV < ΔG_*OH < 1.53 eV shows higher OER activity due to moderate binding energy between reaction intermediates and MNC. Furthermore, these catalysts could maintain MNC structure without further oxidation and structural evolution under working conditions (high temperature, dynamic condition, local electric field and strong specific adsorption), therefore show excellent stability. However, MNC electrocatalyst with ΔG_*OH > 1.53 eV or ΔG_*OH < 1.23 eV revealed less stability under working conditions, due to their low intrinsic stability or structural evolution under working conditions, respectively. In conclusion, we proposed a comprehensive evaluation method for MNC electrocatalysts by taking ΔG_*OH as the screening criterion for OER activity and stability, as well as ΔE_b under working condition as descriptor of stability. This is of great significance for the design and screening of ORR, OER and HER electrocatalysts under working conditions.