High Performance Bifunctional Porous Non-Noble Metal Phosphide Catalyst for Overall Water Splitting

Abstract

An electrode and system for electrocatalytic water splitting. The electrode for overall water splitting comprises a conductive substrate, and a bifunctional electrocatalyst comprising primarily metallic phosphides disposed on a surface of the substrate. The system comprises an anode and a cathode. Each of the anode and the cathode comprises a uniform distribution of a bifunctional electrocatalyst comprising metallic phosphides on a conductive substrate. The metallic phosphides can comprise iron phosphide (FeP) and dinickel phosphide (Ni2P). The bifunctional electrocatalyst promotes hydrogen evolution reaction (HER) at the cathode, and oxygen evolution reaction (OER) at the anode.

What is claimed is: 
     
         1 . An electrode for overall water splitting, the electrode comprising:
 a substrate; and   a bifunctional electrocatalyst comprising primarily metallic phosphides disposed on a surface of the substrate.   
     
     
         2 . The electrode of  claim 1 , wherein the substrate comprises a three dimensional substrate. 
     
     
         3 . The electrode of  claim 1 , wherein the three dimensional substrate comprises a metal foam or carbon cloth paper. 
     
     
         4 . The electrode of  claim 3 , wherein the metal foam comprises nickel (Ni), copper (Cu), iron (Fe), cobalt (Co), titanium (Ti), or a combination thereof. 
     
     
         5 . The electrode of  claim 4 , wherein the three dimensional substrate comprises nickel (Ni) foam, wherein the metallic phosphides comprise primarily a combination of iron phosphide (FeP) and dinickel phosphide (Ni 2 P), and wherein the electrode comprises or consists essentially of FeP and Ni 2 P on Ni foam. 
     
     
         6 . The electrode of  claim 1 , wherein the metallic phosphides comprise primarily iron phosphide (FeP) and dinickel phosphide (Ni 2 P). 
     
     
         7 . The electrode of  claim 6 , wherein the metallic phosphides comprise a majority of iron phosphide (FeP) and a minority of dinickel phosphide (Ni 2 P). 
     
     
         8 . The electrode of  claim 6 , wherein a loading of the bifunctional electrocatalyst comprising primarily metallic phosphides is in the range of from 8 to 13.5 mg/cm 2 . 
     
     
         9 . The electrode of  claim 8 , wherein a loading of dinickel phosphide (Ni 2 P) is in the range of from 1 to about 2 mg/cm 2 ; wherein a loading of iron phosphide (FeP) is in the range of from 7 to 13 mg/cm 2 , or a combination thereof. 
     
     
         10 . The electrode of  claim 6 , a porosity of the FeP/Ni 2 P on the substrate that is greater than or equal to a porosity of the substrate. 
     
     
         11 . A system for electrocatalytic water splitting, the system comprising:
 an anode and a cathode, wherein each of the anode and the cathode comprises a uniform distribution of a bifunctional electrocatalyst comprising metallic phosphides on a conductive substrate, wherein the bifunctional electrocatalyst promotes hydrogen evolution reaction (HER) at the cathode, and oxygen evolution reaction (OER) at the anode.   
     
     
         12 . The system of  claim 11 , wherein the bifunctional catalyst of the anode has the same composition as the bifunctional catalyst of the cathode. 
     
     
         13 . The system of  claim 12 , wherein the metallic phosphides comprise primarily iron phosphide (FeP) and dinickel phosphide (Ni 2 P). 
     
     
         14 . The system of  claim 13 , wherein the metallic phosphides comprise a majority of iron phosphide (FeP) and a minority of dinickel phosphide (Ni 2 P). 
     
     
         15 . The system of  claim 13 , wherein a loading of the metallic phosphides on the conductive substrate is in the range of from 8 to 15 mg/cm 2 . 
     
     
         16 . The system of  claim 13 , wherein a loading of dinickel phosphide (Ni 2 P) on the conductive substrate is in the range of from 1 to 2 mg/cm 2 , wherein a loading of iron phosphide (FeP) on the conductive substrate is in the range of from 7 to 13 mg/cm 2 , or a combination thereof. 
     
     
         17 . The system of  claim 16 , wherein the conductive substrate comprises nickel foam, and wherein the anode and the cathode comprise an FeP/Ni 2 P/Ni foam. 
     
     
         18 . The system of  claim 17 , wherein, when operated in 1 M alkaline solution, the bifunctional electrocatalyst requires a low overpotential of less than 15 mV to deliver a current density of 10 mA/cm 2  for the HER and of less than 155 mV to deliver a current density of 10 mA/cm 2  for the OER, leading to an overall water-splitting activity at 10 mA/cm 2  with less than 1.5 V. 
     
     
         19 . The system of  claim 18 , wherein a porosity of the bifunctional electrocatalyst on the conductive substrate that is greater than a porosity of the conductive substrate. 
     
     
         20 . The system of  claim 18 , wherein, when operated in 1 M alkaline solution, the bifunctional electrocatalyst yields a current density of at least 100 mA/cm 2  at an overpotential of less than or equal to about 225 mV for the OER, exhibits durability for at least 5,000 cycles, is operable for at least 20 hours at 100 mA/cm 2 , or a combination thereof.