The Preparation Of Transition Metal Compounds And Their Application In Electrocatalytic Water Splitting

Hydrogen is studied as clean renewable energy in recent years due to the characteristics as high combustion value,easy prepared methods,and common raw materials,facilitating storage and transportation technology.In the process of electrolyzed water,there are two important reactions as hydrogen evolution reaction(HER)and oxygen evolution reaction(OER).However,in the electrolyzed water process,there are serious electrode polarization problem which will lead to high energy consumption.Because the transition metal is earth abundant and low cost,catalysts based on the transition metal(Fe,Co,Ni)are well researched for HER and OER in recent years.In this paper,a series of Ni-Fe bimetallic sulphides(Ni-Fe-S/NSC)were prepared by solution deposition and followed by high-temperature calcination.The microstructure and morphologies of the sulfides was explored by the by the XRD,SEM,TEM,Raman,BET,XPS and other methods.The HER and OER properties of the Ni-Fe-S/NSC were measured in alkaline electrolyte and they showed the excellent HER/OER bifunctional catalytic performance.In the Ni-Fe-S/NSC,the OER performance was firstly increased and then decreased with the increase of the Ni/Fe input molar ratio.Among them,the Ni60Fe40-S/NSC-550 showed the best OER catalytic performance and the current density in 10 mA·cm-2(η10)was only 32m mV while the Tafea slope is 66 mV·dec-1.In addition,the Ni60Fe40-S/NSC-550 also showed an excellent HER activity and the η10 was 351 mV while the Tafel slope was 228 mV·dec-1.A series of Co-PPPh3 phosphides were also prepared by solution deposition and followed by high-temperature calcination.Among them,the HER and OER performance of the Co-OPPh3 were improved with the increase of the calcination temperature.Ther η10 of the Co-OPPh3-800 of HER and OER was 354 and 440 mV,respectively,and the Tafel slope was 190 and 119 mV·dec-1,respectively.In addition,the Co+OPPh3 were prepared by firstly mixed the raw material and then calcining.The HER performance of the Co+OPPh3 were increased with the increase of the calcination temperature.The η10 of the Co-OPPh3-800 was 334 mV for HER and the Tafel slope was 115 mV·dec-1.The OER performance of the Co+OPPh3 were firstly increased and then decreased with the increase of the calcination temperature.The η10 of the Co-OPPh3-600 was 414 mV for OER and the Tafel slope was 84 mV·dec-1.Further investigation of the Co/P input molar ratio showed that a higher input of P content means a greater influence on the HER performance for Co+OPPh3 catalysts while there was an optimum input ratio for OER.The η10 of the Co-OPPh3-1:8-600 was 357 mV for HER while the Co-OPPh3-1:2-600 showed the best OER activity.Furthermore,a series of ZIF-67@Co-OPPh3 composite material with different ZIF-67/OPPh3 mass ratio was prepared first by solution deposition and followed by 600 ℃ calcination.The HER and OER performance of the ZIF-67@Co-OPPh3 was firstly increased and then decreased with the increase of the OPPh3 input mass.When the input of OPPh3 is 0.4 g,ZIF-67@Co-OPPh3-0.4-600 showed the best HER activity,the η10 was 388 mV and the Tafel slope was 237 mV·dec-1.The ZIF-67@Co-OPPh3-0.2-600 showed the best OER activity,the η10 was 380 mV and the Tafel slope was 130 mV·dec-1.Among the ZIF-67@Co-OPPh3 with different calcination temperature,the catalytic activity of HER was increased with the increase of calcination temperature.The HER performance of the ZIF-67@Co-OPPh3-0.2-800 and ZIF-67＠Co-OPPh3-0.4-800 were the best,and the η10 was 349 and 324 mV,respectively.The ZIF-67@Co-OPPh3-0.2-800 and ZIF-67@Co-OPPh3-0.4-800 showed the best catalytic activity of OER,and the η10 were 380 and 421 mV,respectively,...