Transition metal-doped nickel oxyhydroxide catalyst, preparation method thereof, and use thereof

Abstract

Provided is a transition metal-doped nickel oxyhydroxide catalyst, its preparation method, and its application in seawater electrolysis for hydrogen production. The method includes: (1) constructing a three-electrode system and using a chronoamperometry or chronopotentiometry method to electrodeposit a precatalyst onto a conductive substrate from a mixed metal salt solution containing nickel, iron, and at least one other transition metal salt such as cobalt or chromium; and (2) using the precatalyst-loaded substrate as a working electrode in an alkaline solution and applying a constant current to perform an in-situ conversion, thereby forming the final transition metal-doped nickel oxyhydroxide catalyst. The resulting catalyst exhibits high catalytic activity, high selectivity for oxygen evolution, and exceptional long-term stability under high current densities, making it highly suitable for direct seawater electrolysis systems,

What is claimed is: 
     
         1 . A method for preparing a transition metal-doped nickel oxyhydroxide catalyst, the method comprising:
 (a) preparing a mixed metal salt solution, and performing electrodeposition in a three-electrode system comprising a conductive substrate as a working electrode, a counter electrode, and a reference electrode, with the mixed metal salt solution as an electrolyte, to obtain the conductive substrate loaded with a precatalyst; and   (b) performing an in-situ conversion of the precatalyst to form the transition metal-doped nickel oxyhydroxide catalyst by applying a constant current in a three-electrode system comprising the precatalyst-loaded conductive substrate as a working electrode, a counter electrode, and a reference electrode, with an alkaline solution as an electrolyte;   wherein the mixed metal salt solution comprises a first metal salt, a second metal salt, and a third metal salt, wherein the first metal salt is a nickel salt, the second metal salt is an iron salt, and the third metal salt is one or both of cobalt salt, chromium salt, manganese salt and molybdenum salt;   wherein a molar ratio of the first metal salt to the second metal salt to the third metal salt in the mixed metal salt solution is 1-4:0.5-2:1; and   wherein the in-situ conversion in step (b) is performed at a current density of 20-200 mA/cm 2 , a temperature of 20-40° C., and for a duration of 6-24 hours.   
     
     
         2 . The method of  claim 1 , wherein the first metal salt is nickel nitrate, the second metal salt is iron nitrate, and the third metal salt is one or both of cobalt nitrate, chromium nitrate, manganese nitrate and molybdenum nitrate. 
     
     
         3 . The method of  claim 1 , wherein a molar concentration of the first metal salt in the mixed metal salt solution is 15-20 mM. 
     
     
         4 . The method of  claim 1 , wherein the conductive substrate is selected from the group consisting of carbon paper, carbon cloth, and nickel foam. 
     
     
         5 . The method of  claim 1 , wherein the electrodeposition in step (a) is performed by a chronoamperometry method at a voltage of −1 V to −0.9 V, a temperature of 20-30° C., and for a duration of 50-70 minutes. 
     
     
         6 . The method of  claim 1 , wherein the electrodeposition in step (a) is performed by a chronopotentiometry method at a current of −5 mA to −10 mA, a temperature of 20-30° C., and for a duration of 50-70 minutes. 
     
     
         7 . The method of  claim 1 , wherein the alkaline solution comprises potassium hydroxide or sodium hydroxide at a concentration of 0.1-3 M. 
     
     
         8 . A transition metal-doped nickel oxyhydroxide catalyst prepared by the method of  claim 1 . 
     
     
         9 . A method for producing hydrogen from seawater, the method comprising the step of:
 performing electrolysis using the transition metal-doped nickel oxyhydroxide catalyst of claim  8  as an anode catalyst in an electrolyte comprising seawater.