Insight into the amorphous nickel-iron (oxy)hydroxide catalyst for efficient oxygen evolution reaction

Abstract

The specific roles of Ni and Fe in nickel-iron (oxy)hydroxide catalyst (NiFeOx(OH)y) are extensively discussed during oxygen evolution reaction (OER). However, there still remains controversy about whether Ni or Fe species as the dominate active site. In this work, we reported the NiFeOx(OH)y catalysts with varied atomic ratio of nickel and iron for OER to explore the dominate active site during OER processes. From the electrochemical performances, the similar Tafel slopes of catalysts with Fe species can achieve at a level of 40 mV dec−1, outperforming the Tafel slopes of catalysts without Fe species. Thus, it can be concluded that the present Fe site can serve as the dominant active site in NiFeOx(OH)y for OER. Meanwhile, the Ni species is proved as the OH– adsorption site, which is beneficial to the Fe site to deliver a better OER performance. As a result, the catalyst with an optimal Ni/Fe interface (atomic ratio of 1 : 1.18) displays outstanding OER performances. It only requires a low overpotential of 250 mV to deliver current density of 10 mA cm−2 and exhibits a small Tafel slope of 39 mV dec−1. This catalyst also shows remarkable stability with negligible potential decay after 50 h at a current density of 50 mA cm−2. This work offers a new sight into the specific roles of Ni and Fe in NiFeOx(OH)y for OER.