Nanostructured nickel thin films on porous nickel foam for electrocatalytic oxygen evolution

Abstract

An electrocatalyst including a nickel foam (NF) substrate and a layer of metallic nickel particles on the nickel foam substrate. The metallic nickel particles are spherical and have an average diameter of 100-500 nanometers (nm). Further, the metallic nickel particles are aggregated with aggregates having an average size of 0.5 to 5 micrometers (μm).

1 . An electrocatalyst, comprising:
 a nickel foam substrate; and   a layer of metallic nickel particles on the nickel foam substrate,   wherein the metallic nickel particles are spherical and have an average diameter of 100-500 nanometers (nm), and   wherein the metallic nickel particles are aggregated with aggregates having an average size of 0.5 to 5 micrometers (μm).   
     
     
         2 . The electrocatalyst of  claim 1 , wherein the aggregates of the metallic nickel particles have a popcorn shape. 
     
     
         3 . The electrocatalyst of  claim 1 , wherein the metallic nickel particles have a cubic crystal structure. 
     
     
         4 . The electrocatalyst of  claim 1 , wherein the metallic nickel particles comprise Ni. 
     
     
         5 . The electrocatalyst of  claim 1 , wherein at least 90% of an outer surface area of the nickel foam substrate is covered with the layer of metallic nickel particles. 
     
     
         6 . The electrocatalyst of  claim 1 , wherein the metallic nickel particles form a continuous layer on the nickel foam substrate. 
     
     
         7 . The electrocatalyst of  claim 1 , wherein the layer of the metallic nickel particles on the nickel foam substrate has a thickness of 0.01 μm to 50 μm. 
     
     
         8 . The electrocatalyst of  claim 1 , wherein the nickel foam substrate is porous and has an average pore size of 50 to 500 μm. 
     
     
         9 . The electrocatalyst of  claim 8 , wherein the pores have a spherical shape. 
     
     
         10 . A method of oxidizing water, comprising:
 contacting the electrocatalyst of  claim 1  and a counter electrode with the water; and   applying a potential to the electrocatalyst,   wherein the electrocatalyst and the counter electrode are at least partially submerged in the water and are not in physical contact with each other.   
     
     
         11 . The method of  claim 10 , wherein the water is an aqueous electrolyte solution with a base selected from the group consisting of an alkaline earth metal hydroxide and an alkali metal hydroxide. 
     
     
         12 . The method of  claim 11 , wherein the base is potassium hydroxide. 
     
     
         13 . The method of  claim 10 , wherein the counter electrode is made from a material selected from the group consisting of platinum, gold, and carbon. 
     
     
         14 . The method of  claim 10 , wherein the electrocatalyst has a water oxidation overpotential of 280-305 millivolts (mV) at 10 milliampere per square centimeter (mA cm −2 ). 
     
     
         15 . The method of  claim 14 , wherein the water oxidation overpotential does not vary by more than 5% after the potential is applied for 10-50 hours. 
     
     
         16 . The method of  claim 10 , wherein the electrocatalyst has an electrochemically active surface area (ECSA) of 250-300-centimeter square (cm −2 ). 
     
     
         17 . The method of  claim 10 , wherein the electrocatalyst has a current density of at least 1,000 mA cm −2  at 1.6 V.