The Preparation Of Graphene-Ni-Fe-Co Composite Coating And Its Electrocatalytic Performance

Electrolysis of water for hydrogen evolution is a most widely used method in the industrial production.Therefore,it is of great significance to find a kind of electrode material with large reserves and high catalytic performance.In this paper,the coating of Ni-Fe-Co alloy and the compound coating of Graphene-Ni-Fe-Co(G-Ni-Fe-Co)are synthesized respectively by electrochemical deposition.And the effects of electrodeposition conditions and stirring methods on the electrocatalytic hydrogen evolution activity of the two coatings were investigated by means of single factorexperiment.Firstly,the electrodeposition solution of the coating of Ni-Fe-Co alloy was determined on the basis of orthogonal experiment with the porosity as reference.And then according to single factor experiment,the conditions of electrodeposition,(including the current density,bath temperature and bath pH),and different stirring approaches in the synthesis process were studied respectively to investigate the effects on the microstructure and the efficiency for hydrogen evolution of the Ni-Fe-Co alloy.Based on these experiments,the optimum conditions were obtained as following:the optimum current density is 60 mA/cm2;the optimum bath temperature is 50 ? and the optimum pH value of the solution is 3.8;Moreover,magnetic stirring is the best stirring method.Secondly,adding different graphene concentration in the basis plating bath of Ni-Fe-Co alloy,it is found that the composite coating of G-Ni-Fe-Co,prepared with 0.2 g/L graphene concentration,had the largest real surface area and the highest electrocatalytic hydrogen evolution activity.And then according to single factor experiment,the conditions of electrodeposition and different stirring approaches in the synthesis process were studied respectively to investigate the effects on the microstructure and the efficiency for hydrogen evolution of the G-Ni-Fe-Co alloy.Based on these experiments,the optimum conditions were obtained as following:the optimum current density is 60 mA/cm2;the optimum bath temperature is 60 ? and the optimum pH value of the solution is 3.8;Moreover,magnetic stirring is the best stirring method among different stirring approaches and the optimum stirring rate is 120 r/min.Finally,combined with the potentiodynamic polarization curve,electrochemical impedance spectroscopy and electrolytic water potential stability test in alkaline condition,the electrocatalytic hydrogen evolution properties of G-Ni-Fe-Co composite coating and Ni-Fe-Co alloy coating prepared under optimum conditions were characterized.The addition of graphene increased the true specific surface area of G-Ni-Fe-Co composite coating,and further improved the electrocatalytic hydrogen evolution activity of the coating electrode.The exchange current density of G-Ni-Fe-Co composite coating is 173.3 ?A/cm2,which is 3.7 times of that of Ni-Fe-Co alloy coating.When the current density of hydrogen evolution is 200 mA/cm2,the hydrogen evolution overpotential ?200 of G-Ni-Fe-Co composite coating is 0.373 V,which is 103 mV lower than that of Ni-Fe-Co alloy coating.