Metal and nitrogen co-doped carbons (M-N/Cs) are promising alternatives to platinum-based catalysts for the oxygen reduction reaction (ORR). Here, density functional theory calculations are used to compare the ORR activity of Co single and double sites embedded in N-doped carbon. Two different models of a Co double site are investigated, one in which two single sites are stacked on top of each other and one which has two Co atoms next to each other in a single graphene sheet. For both it is found that the ORR can proceed via a dissociative mechanism that splits the ∗OOH intermediate into ∗O and ∗OH, but only for the double site in the graphene sheet does it result in a significant deviation from the scaling relations. The adsorption energies of the ORR intermediates are investigated using different implicit and explicit solvent models, showing some variation in the results. In particular, the addition of explicit water on the same side of the catalyst as the ORR intermediate can result in stabilisation due to hydrogen bonding, while an explicit water molecule adsorbed on the opposite side of the Co atom can have an effect due to the change in coordination which affects the splitting of the Co d orbitals.

金属和氮共掺杂碳（MN / Cs）是用于氧还原反应（ORR）的铂基催化剂的有前途的替代品。在这里，使用密度泛函理论计算来比较嵌入N掺杂碳中的Co单和双位点的ORR活性。研究了Co双位点的两种不同模型，其中两个单位点彼此堆叠，一个在一个石墨烯片中彼此相邻的两个Co原子。两者都发现，ORR可以通过将＊ OOH中间体分为＊ O和＊ OH的解离机理进行，但仅对于石墨烯片中的双位点，它才会导致显着偏离比例关系。使用不同的隐式和显式溶剂模型研究了ORR中间体的吸附能，显示结果有些变化。特别地，在催化剂的与ORR中间体相同的一侧添加明显的水可由于氢键而导致稳定，而吸附在Co原子另一侧的明显的水分子可因该变化而产生作用。在协调中影响公司的分裂d轨道。