| Nowadays, the rapid development of social economy, the demand for energy is also growing, the traditional fossil energy can not meet the growing social needs, but also cause irreparable pollution to the environment, so looking for clean, sustainable development of green new energy become the focus of common concern. Hydrogen energy has attracted the attention of researchers because of its wide range of sources, renewable, clean and pollution-free, high energy density, high conversion efficiency and easy storage. At present the most widely used hydrogen production technology for electrolysis of water to hydrogen. The key to the efficiency of water splitting is the rational choice of electrode catalyst materials. At present, the most widely used electrolytic water electrode catalyst materials are: noble metals such as IrO2 and RuO2, which are used in alkaline reaction. They are used for the hydrogenation reaction of Pt/C under acidic conditions. However, it is particularly urgent to find expensive and inexpensive non-precious metal electrode catalysts to replace the use of precious metal catalysts because of the high price of precious metals and the lack of sources and poor cycle stability.In this paper, transition metal phosphides (flower-like CoP/CoP2/Al2O3 and podiform Co2P/C) with different morphologies were successfully prepared by using the hydrotalcite-like materials as precursors and later phosphating and intercalation. The performance of the catalyst as electrolytic water electrode was studied. The main research contents are as follows:1. We herein report a controllable preparation of CoP/CoP2 nanoparticles well-dispersed in flower-like Al2O3 scaffolds (f-CoP/CoP2/Al2O3) as a bi-functional electrocatalyst for HER and OER, via phosphorization of a flower-like CoAl-layered double hydroxide precursor. In-situ X-ray diffraction (XRD) characterization monitors the topotactic transformation underlying the controllable formation of CoP/CoP2 via tuning phosphorization time. Electrocatalytic tests show that the f-CoP/CoP2/Al2O3 electrode exhibits lower onset potential and higher electrocatalytic activities for HER and OER in the same alkaline electrolyte than the electrodes of flower-like and powdered CoP/Al2O3. The enhanced electrochemical performances are supported experimentally by measuring electrochemically active surface area.The f-CoP/CoP2/Al2O3 electrode is capable of requiring low over-potentials of 300 mV for OER and -138 mV for HER to deliver a current density of 10 mA cm-2 both in 1.0 M KOH solution. Furthermore, the f-CoP/CoP2/Al2O3 composite is capable of generating a current density of 10 mA cm-2 at 1.65 V,and also exhibit the good durability when used as a bi-functional catalyst for overall water splitting.2. According to the unique layered structure of the hydrotalcite-like material, the use of an anionic surfactant (SDP) intercalation of Co(OH)2 layered material as a precursor to prepare the podiform Co2P/C composite by the method of temperature programme. And its electrocatalytic performance is explored. The advantage of this preparation method is that the carbon source and the phosphorus source are introduced simultaneously by a simple one-step intercalation method, which avoids the use of organic phosphorus source and at the same time can improve the conductivity of the catalyst material and further improve its catalytic activity and its electrochemical stability. The podiform Co2P/C composite electrode is capable of requiring low over-potentials of 320 mV for OER and -140 mV for HER to deliver a current density of 10 mA cm-2 both in 1.0 M KOH solution. Furthermore, the podiform Co2P/C composite is capable of generating a current density of 10 mA cm-2 at 1.50 V, and also exhibit the good durability when used as a bi-functional catalyst for overall water splitting. |
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