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 (PBA@MnO2) 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 PBA@MnO2-150/30 (where 150 and 30 represent the hydrothermal temperature (degrees 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.

Automated summary

The study presents a novel design strategy for PBA catalysts that can efficiently achieve high-performance hydrogen and oxygen evolution reactions for water splitting. By assembling hierarchical PBA structures and controlling the temperature and precursor concentration during hydrothermal reactions, catalysts with outstanding catalytic performance, such as PBA@MnO2 and N-FeMnNi materials, were obtained.