The self-supported Zn-doped CoNiP microsphere/thorn hierarchical structures as efficient bifunctional catalysts for water splitting

Abstract

The hierarchical electrocatalysts with the superaerophobic property are in favor of removal of gas bubbles and supply of numerous active sites to improve the electrochemical catalytic activity for water splitting. In this work, the self-supported Zn-doped CoNiP (Zn–CoNiP/NF) hierarchical structure that consisted of nanothorns and radial microspheres were prepared with via a facile precursor phosphorization method. Zn-doping could tailor the initial electronic state of CoNiP to improve the hydrogen or oxygen atom binding, which effectively promoted the catalytic kinetics of water splitting. The hierarchical structure not only offered more catalytic active sites for water splitting, but also facilitated gas releasing due to the superaerophobic interface. The hierarchical Zn–CoNiP structure showed a high hydrogen evolution reaction (HER) efficiency in electrolytes with pH 0–14, which yielded low overpotentials of 73 mV in acidic solution and 34 mV in alkaline media at current density of 10 mA cm−2. Furthermore, it also had evidenced by an overpotential of 310 mV for oxygen evolution reaction (OER) at the current density of 50 mA cm−2. Note that the required cell initial voltage was 1.51 V for overall water splitting. These results were comparable or even better than many non-noble catalysts.