Fabrication of 2D/3D hierarchical PBA and derivative electrocatalysts for overall water splitting

Assembling a hierarchical well-defined Prussian blue analogues (PBA) construction is a useful way to take earth-abundant elements into application toward hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). Herein, we report a unique strategy for in-situ grafting three-dimensional (3D) MnFe-PBA cubes on the top of two-dimensional (2D) MnO2 nanosheet arrays ([email protected]2) via a facile two-step hydrothermal method with the participation of Ni foam (NF). After experiencing low-temperature pyrolysis in NH3/Ar atmosphere, the above catalysts are transformed into metal-nitride derivatives (N-FeMnNi). Remarkably, when operated in 1.0 M KOH aqueous solution, the as-obtained [email protected]2-150/30 (where 150 and 30 represent the hydrothermal temperature (°C) and the concentration of K3Fe(CN)6 (mM) for preparation, respectively) shows the most outstanding OER activity, with an overpotential of 238 mV at 10 mA cm−2. Moreover, N-FeMnNi-130/10 requires an overpotential of 101 mV to reach 10 mA cm−2 for HER. As a result, the two samples are organized to establish a two-electrode cell, with a voltage of only 1.60 V needed to reach 10 mA cm−2. Meanwhile, it can stably work for 30 h without obvious current attenuation. This work provides a brand new perspective for the design of PBA electrocatalysts towards high-efficiency overall water splitting.