Enabling efficient ample-level oxygen evolution on nickel-iron Prussian blue analogue/hydroxide via hierarchical mass transfer channel construction

Enhancing double-phase mass transfer capability and reducing overpotential at high currents are critical in the oxygen evolution reaction (OER) catalyst design. In this work, nickel-iron layered double hydroxide (NiFe-LDH) loaded on nickel foam (NF) was used as a self-sacrificing template for subsequent growth of nickel-iron Prussian blue (NiFe-PBA) hollow nanocubes on its sheet arrays. The triple-scale porous structure is therefore in-situ constructed in the produced NiFe-PBA@LDH/NF catalyst, where NiFe-PBA nanocubes, NiFe-LDH sheets and NF skeletons provide pores at hundred-nanometers, microns and hundred-microns, respectively. Due to the successful construction of hierarchical mass transfer channels in the catalyst, the overpotential required to deliver 1000 mA cm^-2 OER is only 396 mV, which is 80 mV lower than that of NiFe-LDH/NF with a double-scale porous structure, manifesting the importance of the appropriate mass transfer channels, promoting the potential application of the NiFe-PBA@LDH/NF catalyst in industrial-scale electrolysers.