1D/2D NiFeP/NiFe-OH heterostructure: roles of the unique nanostructure in stabilizing highly efficient oxygen evolution reaction

The oxygen evolution reaction (OER) catalysts of transition-metal-based (oxy)hydroxides are usually faced with poor stability due to the dissolution of the active center and/or the adsorbed bubbles. Herein, we address the issues by constructing a 1D/2D heterostructure of NiFeP/NiFe-OH. The heterostructure exhibits a promising overpotential of 190 mV at 10 mA cm-2, a state-of-the-art value for OER catalysts. More importantly, after 220 h operation at a near-industrial potential, there is only a 10% decrease in current density. The great stability could be attributed in part to the superaerophobic surface for repelling bubbles. On the other hand, although the unstable Fe active sites in the 2D layer dissolve rapidly during OER operation, the 2D layer could inhibit the Fe dissolution from the 1D NTs. The final NiFeP/NiOOH heterostructure endows the catalyst with excellent catalytic activity and stability. DFT calculations suggest that the synergistic effect between NiFeP and NiOOH could still efficiently catalyze the OER. The 1D/2D NiFeP/NiFe-OH catalyst could not only rapidly release O2 bubbles during OER operation, but also suppress Fe dissolution from the 1D NTs by the 2D outer shells, tending to form stable NiFeP/NiOOH heterostructures eventually.