Enhanced electrolytic oxygen evolution by the synergistic effects of trimetallic FeCoNi boride oxides immobilized on polypyrrole/reduced graphene oxide

Multi-metallic electrocatalysts based on Fe, Co and Ni usually exhibit enhanced electrocatalytic activity towards the oxygen evolution reaction (OER); however, the contribution of each metal in trimetallic electrocatalysts to the OER activity and their synergistic effects are still unclear. In order to reveal the specific role of each metal for OER in trimetallic electrocatalysts based on Fe, Co, and Ni and further improve their OER activity, a series of electrocatalysts containing unitary, binary and ternary metal boride oxides of Fe, Co, and Ni with different permutations and combinations immobilized on polypyrrole/reduced graphene oxide (PPy/rGO) nanosheets have been synthesized by one-step reduction. Regardless of which two metals are combined, the OER activities of the bimetallic electrocatalysts are generally higher than those of the monometallic electrocatalysts; also, the trimetallic FeCoNiBOx/PPy/rGO nanocomposites exhibit optimal OER activity due to the synergistic effects of each component, where Fe can significantly accelerate the OER kinetics by decreasing the Tafel slope and Co can effectively reduce the overpotential, while Ni can further simultaneously and significantly improve the electrocatalytic performance of both Fe and Co for OER. Additionally, PPy/rGO not only provides a large specific surface area for the immobilization of FeCoNiBOx, but also efficiently improves the OER activity of the obtained electrocatalysts due to its good conductivity. This work may provide some insights into the design and synthesis of multicomponent materials with compelling performance for electrochemical water splitting in further practical applications.