Enhanced electronic interaction in hemin@Ni(OH)2 composite for efficient electrocatalytic oxygen evolution

Abstract

Ni(OH)2 has been acknowledged as a promising oxygen evolution reaction (OER) electrocatalyst owing to its good electrochemical activity and low cost. However, application of the pristine Ni(OH)2 is limited by the poor conductivity and low exposure of the active sites. Herein, a hemin@Ni(OH)2 composite is prepared through a hydrothermal reaction. Heat treatment temperature proves to have a great influence on the electrocatalytic activity. In 0.1 M KOH electrolyte, the composite treated at 175 °C shows an overpotential of only 287 mV to reach the current density of 10 mA·cm−2. Besides, the low Tafel slope (42 mV·dec−1) and superior stability (15 h at 10 mA·cm−2) also confirm the composite as an excellent OER electrocatalyst. The brilliant activity and stability toward OER can be attributed to the promoted coupling between Ni and Fe centers and the improved conductivity due to the 2D 18 p-electrons ring conjugate structure of hemin. Besides, effective hydrogen bonds between Ni(OH)2 and hemin hinder the aggregation of Ni(OH)2, which ensures the catalyst enormous accessible active sites. This work offers a new method for the modification of Ni(OH)2 as OER electrocatalysts. And the application of hemin also serves as a successful case for the use of biomass materials in OER electrocatalysis.