Bimetallic iron-vanadium oxide electrocatalyst for oxygen evolution reaction

Abstract

An electrocatalyst including a first layer, including a porous nickel foam, and a second layer, including an iron-vanadium oxide (FeVO x ). The iron-vanadium oxide includes an iron oxide and a vanadium oxide. The iron-vanadium oxide contains 10 to 30 atomic percent (at. %) iron and 15 to 30 at. % vanadium based on the total number of atoms in the iron-vanadium oxide. The second layer includes iron-vanadium oxide particles having the longest dimension of 0.5 to 5 micrometers (μm). The electrocatalyst of the present disclosure may be used in oxygen evolution reactions.

1 : An electrocatalyst, including:
 a first layer including a porous nickel foam,   a second layer including an iron-vanadium oxide,   wherein the iron-vanadium oxide includes an iron oxide and a vanadium oxide,   wherein the iron-vanadium oxide contains 10 to 30 at. % iron and 15 to 30 at. % vanadium based on a total number of atoms in the iron-vanadium oxide,   wherein the second layer includes iron-vanadium oxide particles having a longest dimension of 0.5 to 5 micrometers (μm).   
     
     
         2 : The electrocatalyst of  claim 1 , wherein the electrocatalyst is made by a process including:
 dissolving an iron salt and a vanadium salt in a polar organic solvent to form a solution; and   depositing the solution as an aerosol mist via an aerosol-assisted chemical vapor deposition process on the porous nickel foam to form the electrocatalyst,   wherein the depositing occurs at a temperature of 450 to 500° C.,   wherein the depositing occurs for 30 to 150 mins.   
     
     
         3 : The electrocatalyst of  claim 2 , wherein a weight ratio of the iron salt to the vanadium salt is from 2:1 to 1:2. 
     
     
         4 : The electrocatalyst of  claim 1 , wherein the particles of iron-vanadium oxide in the second layer include nanocrystallites having a longest dimension of 30 to 90 nm. 
     
     
         5 : The electrocatalyst of  claim 4 , wherein a plurality of the nanocrystallites are stacked. 
     
     
         6 : The electrocatalyst of  claim 1 , wherein the iron oxide forms hematite (Fe 2 O 3 ) crystals in a trigonal phase. 
     
     
         7 : The electrocatalyst of  claim 1 , wherein the vanadium oxide is a vanadium(II) oxide (VO). 
     
     
         8 : The electrocatalyst of  claim 1 , wherein the iron-vanadium oxide does not contain V 2 O 3  phases, V 2 O 5  phases, and Fe 3 O 4  phases. 
     
     
         9 : The electrocatalyst of  claim 1 , wherein the second layer is a continuous particle layer formed of the iron-vanadium oxide particles with active sites on an exposed surface. 
     
     
         10 : The electrocatalyst of  claim 1 , wherein the electrocatalyst has an onset potential of 1.4 to 1.6 V vs. RHE. 
     
     
         11 : The electrocatalyst of  claim 1 , wherein the electrocatalyst has an overpotential of 270 to 280 mV at a current density of 10 mA/cm 2 . 
     
     
         12 :  claim 4 : The electrocatalyst of  claim 1 , wherein the electrocatalyst has a Tafel slope of 48 to 52 mV/dec. 
     
     
         13 : The electrocatalyst of  claim 1 , wherein the electrocatalyst has a mass activity of 13,000 to 13,500 mA/mg at an overpotential of 350 mV. 
     
     
         14 : The electrocatalyst of  claim 1 , wherein the electrocatalyst has an electrochemically active surface area of 80 to 90 cm 2 . 
     
     
         15 : The electrocatalyst of  claim 1 , wherein the electrocatalyst has a specific activity of 10 to 15 mA/cm 2 . 
     
     
         16 : The electrocatalyst of  claim 1 , wherein the electrocatalyst has a charge transfer resistance of 0.8 to 0.9 Ω. 
     
     
         17 : The electrocatalyst of  claim 1 , wherein the electrocatalyst has a turnover frequency of 1.5 to 2.5 s −1  at an overpotential of 350 mV. 
     
     
         18 : The electrocatalyst of  claim 1 , wherein the electrocatalyst has a stability of 90 to 110 hours at a current density of 10 mA/cm 2  and 50 mA/cm 2 . 
     
     
         19 : The electrocatalyst of  claim 1 , wherein the electrocatalyst has 0.05 to 0.10 mg of iron-vanadium oxide in the second layer. 
     
     
         20 : A method of oxygen evolution, including:
 connecting a working electrode, a reference electrode, and a counter electrode with a potentiostat,   wherein the working electrode is the electrocatalyst of  claim 1 ,   wherein the reference electrode is a mercury/mercurous oxide (Hg/HgO) electrode,   wherein the counter electrode is a platinum electrode,   contacting the working electrode, the reference electrode, and the counter electrode with an aqueous solution,   wherein the aqueous solution is an alkali metal salt and water,   applying a potential; and   generating oxygen at the working electrode.