Surface in situ self-reconstructing hierarchical structures derived from ferrous carbonate as efficient bifunctional iron-based catalysts for oxygen and hydrogen evolution reactions

Abstract

Exploring the relationships between the composition or morphology of a catalyst and its performance is important in the design of efficient catalysts. Herein, a unique FeCO₃@IF electrode, comprising FeCO₃ cubes grown on iron foam (IF), is prepared via the regulation of the iron source. During oxygen and hydrogen evolution reactions (OER and HER), the FeCO₃ compounds on FeCO₃@IF can transform in situ into efficient active sites for the OER (iron oxo/hydroxide nanosheet arrays) and HER (zero-valent iron nanorod arrays coated with FeO_x). Meanwhile, the in situ formed vertically aligned arrays improve electron transport and the diffusion of bubbles, compared with accumulated nanoparticles and interlaced nanowires on Fe₃O₄@IF and Fe–O–M@IF, respectively. Therefore, FeCO₃@IF shows high catalytic activity and robust stability for the OER and HER. Furthermore, the transformation of the surface morphology of ferrous carbonate during the catalytic process was observed. Importantly, this work provides a new method to prepare efficient catalytic materials with hierarchical structures via surface in situ self-reconstruction induced by carbonate leaching.