Heterojunction of the CoMn metal-organic framework with lanthanum for enhanced oxygen evolution reaction

Surface and interfacial electron transfer tends to be the rate-limiting step in multiple electron electrocatalytic reactions such as oxygen evolution reaction (OER). Constructing a heterojunction structure is an effective approach to strengthen the processes. Here, CoMnLax-MOF/CF has been synthesized via a one-pot solvothermal pathway to integrate the charge transport advantage of the heterojunction and the mass-transfer superiority of high porosity of the metal-organic framework (MOF), wherein the heterojunction is formed by introducing La in preparing the CoMn-MOF process. The results demonstrate that the as-prepared CoMnLax-MOF/CF possesses flower-like/flower-bud microstructures with a CoMn-MOF/La-MOF heterojunction topology, resulting in superior OER performance. The enhanced OER property originates from reduced charge-transfer resistance and an enlarged activated surface area. At a molar ratio of nLa:nCo:nMn= 0.2:1:1, the CoMnLa0.2-MOF/CF presents optimal performance. In 1 M KOH, the overpotential is only 201 mV to reach 10 mA cm-2current density. There appears no significant current density degeneration in the 25 h stability test. This work demonstrates one facile pathway for directly building the heterojunction in CoMn-MOF to achieve superb OER activity.