Heterometallic Cluster-Based Organic Frameworks As Highly Active Electrocatalysts for Oxygen Reduction and Oxygen Evolution Reaction: a Density Functional Theory Study

Recently, metal-organic frameworks are one of the potential catalytic materials for electrocatalytic applications. The oxygen reduction reaction and oxygen evolution reaction catalytic activities of heterometallic cluster-based organic frameworks are investigated using density functional theory. Firstly, the catalytic activities of heterometallic clusters are investigated. Among all heterometallic clusters, Fe2Mn-Mn has a minimum overpotential of 0.35 V for oxygen reduction reaction, and Fe2Co-Co possesses the smallest overpotential of 0.32 V for oxygen evolution reaction, respectively 100 and 50 mV lower than those of Pt(111) and RuO2(110) catalysts. The analysis of the potential gap of Fe2M clusters indicates that Fe2Mn, Fe2Co, and Fe2Ni clusters possess good bifunctional catalytic activity. Additionally, the catalytic activity of Fe2Mn and Fe2Co connected through 3,3′,5,5′-azobenzen-etetracarboxylate linker to form Fe2M-PCN-Fe2M is explored. Compared with Fe2Mn-PCN-Fe2Mn, Fe2Co-PCN-Fe2Co, and isolated Fe2M clusters, the mixed-metal Fe2Co-PCN-Fe2Mn possesses excellent bifunctional catalytic activity, and the values of potential gap on the Mn and Co sites of Fe2Co-PCN-Fe2Mn are 0.69 and 0.70 V, respectively. Furthermore, the analysis of the electron structure indicates that constructing a mixed-metal cluster can efficiently enhance the electronic properties of the catalyst. In conclusion, the mixed-metal cluster strategy provides a new approach to further design and synthesize high-efficiency bifunctional electrocatalysts.