Coordination compound-derived Al-doped Fe3O4/C as an efficient electrocatalyst for oxygen evolution reaction

It was synthesized an Fe-coordination compound (CC) [FeCl 3 (Hbta) 2 ] (Hbta ​= ​benzotriazole) and an Al-doped Fe-CC via a facile one-step grinding method. Upon subsequent annealing, Fe 3 O 4 /C and Al-doped Fe 3 O 4 /C were obtained, respectively. In the two obtained calcined samples, Fe 3 O 4 nanopolyhedra are not only anchored on the in-situ generated carbon material, but also coated by graphene-like ultrathin nanosheets. The carbon materials not only provide conductive networks to enhance the electrical conductivity of the composite material, but also prevent the aggregation of Fe 3 O 4 nanopolyhedra. Al-doped Fe 3 O 4 /C shows outstanding long-term oxygen evolution reaction (OER) activity during 60 h-electrolysis at 20 ​mA ​cm −2 with overpotentials of only 215 and 359 ​mV at 10 and 100 ​mA ​cm −2 , respectively. Density functional theory (DFT) calculations reveal that the rate-determining steps (RDS) on the Fe 3 O 4 and Al-doped Fe 3 O 4 surfaces are both the formation of ∗OOH, and the doping of Al 3+ into Fe 3 O 4 can lower the Δ G (1.969 ​eV) and overpotential (0.739 ​V) of the RDS during the OER process, which is due to the fact that the d -band center of Al-doped Fe 3 O 4 is positively shifted in comparison with that of Fe 3 O 4 , thus improving the affinity of the catalytic surface toward ∗OOH. • Al-doped Fe 3 O 4 /C was synthesized by annealing an Al-doped Fe coordination compound. • Fe 3 O 4 polyhedra are coated by in-situ generated graphene-like ultrathin nanosheets. • Al-doped Fe 3 O 4 /C shows outstanding OER activity. • The doping of Al 3+ can change the electronic structure and the affinity toward ∗OOH.