One-step electroreductively deposited iron-cobalt composite films as efficient bifunctional electrocatalysts for overall water splitting

Due to the large overpotentials on both cathodic hydrogen evolution reaction (HER) and anodic oxygen evolution reaction (OER) during the process of water splitting, the large-scale production of hydrogen is limited. Therefore, it is crucial to find earth-abundant, low-cost and efficient bifunctional catalysts for such process. In this paper, we report one-step electroreductive deposition of Fe-Co composite films on carbon fiber papers (CFPs) in a solution containing Fe(III) and Co(II) ions without and with N2 bubbling, and the prepared composite films show highly efficient electrocatalytic performances and good durabilities for both OER and HER in 1.0 M KOH. To reach a current density of 10 mA cm−2, the overpotentials are only 283 mV for OER and −163 mV for HER with small Tafel slopes of 34 and 51 mV dec−1, respectively. Moreover, the Fe-Co composite films can be used as bifunctional catalysts for water splitting with the current density of 10 mA cm−2 at 1.68 V, which is comparable with most of the Ni-based films reported. This proves that the Ni-free derivatives of 3d transition metals can also show high catalytic performance.