Synthesis Of Transition Metal Phosphides And Their Performances For Electrocatalytic Water Splitting

Today, the energy shortage and environmental pollution limit the development of human society. Hydrogen is considered as the one of the most potential energy for our future to overcome above probloms, due to its high efficiency, cleanness and renewability. Among all the technologies for producing hydrogen, water electrolysis is the most mature industrial technology with the advantages of abandunt raw materials, renewability and possible combination with fuel cell. This dissertation primarily studied the preparation and performances of electrode materials for electrocatalytic water splitting. The main results are as follow:1. The Co3O4/Ti nanorods bundle array precursor was obtained through a simple low temperature hydrothermal reaction and annealing treatment. After low temperature phosphating reaction, the self-supported three-dimensional(3D) porous CoP/Ti nanorods bundle array was finally fabricated. The porous CoP/Ti nanorods bundles array can be directly used as an active cathode for electrocatalytic water splitting. In 0.5 M H2SO4 electrolyte, the onset potential is 155 m V, and the Tafel slope value is 40 mV dec-1. In different pH electrolyte, it also exhibited good stability and excellent performance for electrocatalytic hydrogen evolution.2. The Co3O4/carbon cloth(CC) precursor was prepared by using similar method. Through second hydrothermal reaction and low temperature phosphating treatment, the self-supported hierarchical structure CoP@FeP/CC was obtained. It exhibited superior activity and stability for electrocatalytic hydrogen evolution reaction(HER) in 0.5 M H2SO4 electrolyte, compared with CoP/CC, FeP/CC, and TiO2@FeP/CC, suggesting structure and composition of eletrocatalyst have great effect on electrocatalytic performance. The electrochemical test test show that CoP@FeP/CC can yeild current density of 10 mA cm-2 at overpotential of 30 mV and Tafel slope is 42 mV dec-1.3. We prepared self-supported 3D CoP/Ti nanorods arrays by directly phosphating the Co(OH)0.11(CO3)0.5H2O/Ti at low temperature. The optimal amount of sodium hypophosphite and phosphating temperature were studied. On the basis of optimal experiments, in-depth study on the optimal CoP/Ti was carried out, which presented bifunctional performances for hydrogen evolution reaction(HER) and oxygen evolution reaction(OER) in alkaline electrolyte. In three electrode system, this catalyst offords low overpotential for both HER and OER(68 mV of overpotential for HER and 313 mV for OER at 10 mA cm-2) and small value of Tafel slop(31 mV dec-1 for HER and 58 mV dec-1 for OER). In two electrode system, CoP/Ti uesed as both anode and cathode to drive the overall water splitting to produce hydrogen and oxygen by one 1.5 V AAA battery. The observed activity after 24 h of water electrolysis was nearly unchanged, indicating its good stability for water splitting.4. We prepared amorphous Fe-Co-P alloy on nickel foam(Fe-Co-P/NF) by a simple and green electrodeposition method under ambient temperature. This electrode also had bifunctional performances for HER and OER in alkaline electrolyte. The optimal results revealed best catalyst activity is achieved when the molar ratio of Fe:Co is 3:7. Similarly, the Fe-Co-P/NF is a highly efficient and stable electrocatalyst for overall water splitting, which can be drived by a 1.5 V AAA battery to split water to produce hydrogen and oxygen.