Noble-metal-free bi-functional electrocatalyst design approach to prompt synergistic properties with incorporating high-valence Zr metal for overall water splitting

The development of noble-metal-free electrocatalysts for oxygen evaluation reaction (OER) and hydrogen evaluation reaction (HER) in water splitting is required to reduce the preparation cost and enhance catalytic activity. Here, we report a 3D core-shell structure electrocatalyst (ZrFe@Fe3O4@NiFeLDH/IF) with synergistic properties that can benefit the HER and OER catalytic activity of overall water splitting for long-term operation. In particular, due to the incorporation of high-valance Zr, the electrocatalysts exhibit exceptional low charge transfer resistance and lower overpotential. Moreover, the electrocatalyst achieved HER and OER long-term stability for more than 100 h at a large current density of 500 mA cm−2. Furthermore, ZrFe@Fe3O4@NiFeLDH/IF reveals superior overall water-splitting cell voltage of 1.53 V, long-term stability for 400 h at 10 mA cm−2 and around 300 h at 500 mA cm−2, respectively. Therefore, these noble-metal-free and high-valence Zr-based electrocatalysts may offer a feasible and green design approach for proficient overall water-splitting performance over the long-term.