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The strain effect on oxygen reduction reaction (ORR) activity and stability of FeNC electrocatalysts has been studied using density functional theory in this work. Based on the reaction free energy results, the rate-determining step (RDS) of ORR on FeNC is *OH → H2O, and the reaction proceeds with the pathway O2 → *OOH → *O → *OH → H2O on the Fe site. Tensile stress is favorable to enhance the ORR activity, and the highest ORR activity is obtained on the 6%-FeNC electrocatalyst. On the other hand, when the whole oxygen reduction process needs synergy between Fe and adjacent C atoms and proceeds with the pathway O2 → *OOH → *TS → *O & #OH → *O → *OH → H2O, the applied stress will decrease the ORR activity of the FeNC electrocatalyst. We further constructed a Cu@FeNC core–shell model to simulate strained FeNC. However, the adsorption energy of ORR intermediates on Cu@FeNC (1.9%-FeNC) is much weaker than on the corresponding 2%-FeNC, mainly due to the coordination between the Cu substrate and Fe atom. In addition, the formation energy and binding energy indicate that neither tensile nor compressive stress is conducive to the stability of the FeNC electrocatalyst. In summary, tensile stress could enhance the ORR activity of FeNC electrocatalysts when ORR occurs on the Fe atom only. What's more, we should pay more attention to the influence of interface interaction if utilizing a M@FeNC model to achieve strained FeNC. [ABSTRACT FROM AUTHOR]

[Display omitted] • The effect of structure evolution under working condition of MNC electrocatalysts on the OER activity and stability has been studied with the DFT method. • This work conducted a comprehensive evaluation method for MNC electrocatalysts by taking ΔG *OH as the screening criterion for OER activity and ΔE b of electrocatalysts under working conditions as the stability descriptor. • The stability of MNC electrocatalysts under working conditions, including high temperature, dynamic condition, local electric field and strong specific adsorption has been studied in detail. 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 (MN 4 C 8 , MN 4 C 10 , MN 4 C 12) 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 (PdN 4 C 8 , PdN 4 C 10 , PdN 4 C 12), ΔG *OH < 1.23 eV (RuN 4 C 8 , RuN 4 C 10 , RuN 4 C 12 , CoN 4 C 8 , CoN 4 C 10) and 1.23 eV < ΔG *OH < 1.53 eV (RhN 4 C 8 , RhN 4 C 10 , RhN 4 C 12 , IrN 4 C 8 , IrN 4 C 10 , IrN 4 C 12 , CoN 4 C 12), 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 M N C 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. [ABSTRACT FROM AUTHOR]

[Display omitted] • Study of crystal plane, strain and ligand effects on the intrinsic stability of Pt alloy electrocatalysts. • Study of specific adsorption and local electric field on the stability of Pt alloy electrocatalysts. • Highlighting the importance of intrinsic stability and working environment on the durability of Pt alloy electrocatalysts. Electrocatalyst stability is a key parameter for commercializing high-temperature polymer electrolyte membrane fuel cells (HT-PEMFCs). Here, we used density functional theory (DFT) to investigate the stability of Pt-based electrocatalysts by calculating the binding energy (ΔE b) of surface Pt atoms under working conditions. Our results show that Pt(1 1 1) is more stable than Pt(1 0 0) and Pt(1 1 0) under vacuum conditions. Stress hurts the stability of Pt(1 1 1), regardless of compressive or tensile stress. Most of the transition metals alloyed with Pt improve the stability of Pt(1 1 1), especially PtV, PtY, and PtTa, which increase the ΔE b by 0.60–0.70 eV (ΔΔE b). However, the stability of Pt is significantly destroyed under the working conditions of oxygen reduction reaction (ORR). The specific adsorption of ORR intermediates and electrolyte ions decreases the ΔE b of Pt(1 1 1) by 0.35–0.95 eV, and the effect of PO 4 3-* is more significant. Furthermore, when the electric field of the electrochemical double layer is coupled with PO 4 3-* specific adsorption, ΔΔE b further increases to 1.12 eV. Our results highlight the importance of the intrinsic ΔE b and the working conditions for the stability of Pt-based electrocatalysts. This work provides important guidelines for the design of stable ORR electrocatalysts for HT-PEMFCs. [ABSTRACT FROM AUTHOR]