Method for syngas production using a silver-doped zeolitic imidazolate framework (ag@zif-8)-based electrocatalyst

Abstract

A method for syngas production includes contacting an electrocatalytic working electrode with a gaseous electrolytic solution including carbon dioxide in a cell with a reference electrode and a counter electrode, applying a potential to the cell during the contacting, and forming a gaseous syngas product by electrocatalytically reducing the carbon dioxide in the gaseous electrolytic solution without forming any liquid syngas product. The electrocatalytic working electrode includes an electrocatalytic material on a conductive carbon paper. The electrocatalytic material includes a zeolitic imidazolate framework-8 (ZIF-8) and silver in an amount of 5 to 10 percent by weight of the electrocatalytic material. The ZIF-8 and silver are in a layer of particles. The particles are in the form of one or more polyhedrons and the one or more polyhedrons have a longest dimension with an average length of 0.1 to 20 μm. The electrocatalytic working electrode, the reference electrode, and the counter electrode are in connection with a potentiostat workstation.

1 : A method for syngas production, comprising:
 contacting an electrocatalytic working electrode with a gaseous electrolytic solution comprising carbon dioxide in a cell having a reference electrode and a counter electrode,   wherein the electrocatalytic working electrode comprises an electrocatalytic material on a conductive carbon paper,   wherein the electrocatalytic material comprises a zeolitic imidazolate framework-8 (ZIF-8) and silver in an amount of 5 to 10 percent by weight of the electrocatalytic material,   wherein the ZIF-8 and silver are in a layer of particles,   wherein the particles are in the form of one or more polyhedrons,   wherein the one or more polyhedrons have a longest dimension with an average length of 0.1 to 20 μm,   wherein the electrocatalytic working electrode, the reference electrode, and the counter electrode are in connection with a potentiostat workstation;   applying a potential to the cell during the contacting; and   forming a gaseous syngas product by electrocatalytically reducing the carbon dioxide in the gaseous electrolytic solution without forming any liquid syngas product.   
     
     
         2 : The method of  claim 1 , wherein the electrocatalytic material was made by a process comprising:
 forming a first mixture by mixing a silver salt with a first organic solvent,   adding the ZIF-8 to the first mixture, then   sonicating and mixing the first mixture to form a solid,   washing the solid,   suspending the solid in a second organic solvent and an acid to form a second solution,   filtering the second solution to obtain the solid, and   drying the solid to form the electrocatalytic material.   
     
     
         3 : The method of  claim 1 , wherein the electrocatalytic working electrode was made by a process comprising:
 dispersing the electrocatalytic material in an organic solvent, water, and a polymer to form a suspension,   sonicating the suspension,   drop-casting the suspension onto the conductive carbon paper, and   drying the suspension-covered conductive carbon paper to form the electrocatalytic working electrode.   
     
     
         4 : The method of  claim 1 , wherein the electrocatalytic material is in the form of dodecahedron crystals. 
     
     
         5 : The method of  claim 4 , wherein the dodecahedron crystals have an average length of 100 to 10000 nanometers (nm). 
     
     
         6 : The method of  claim 1 , wherein the electrocatalytic material has a surface area of 1000 to 1300 meter square per gram (m 2  g −1 ). 
     
     
         7 : The method of  claim 1 , wherein the electrocatalytic material has a Tafel value of 150 to 230 millivolts per decade (mV dec −1 ). 
     
     
         8 : The method of  claim 1 , wherein the electrocatalytic material has a double layer capacitance of 1.0 to 1.3 millifarads (mF). 
     
     
         9 : The method of  claim 1 , wherein the electrocatalytic material has a charge transfer resistance of 130 to 150 ohms (Ω). 
     
     
         10 : The method of  claim 1 , wherein the electrocatalytic material has a chronoamperometry stability for 15 to 20 hours in a CO 2 -saturated 0.1 molar (M) KHCO 3  solution. 
     
     
         11 : The method of  claim 1 , wherein the syngas product comprises carbon monoxide and hydrogen in a weight ratio of carbon monoxide to hydrogen from 15:85 to 80:20 at a potential of −0.5 to −1.5 V vs. RHE. 
     
     
         12 : The method of  claim 1 , wherein the cell is a flow cell, the electrocatalytic material comprises silver in the amount of 10 percent by weight of the electrocatalytic material, the potential is −0.7 V vs. RHE, and the syngas product comprises 70% by weight carbon monoxide and 30% by weight hydrogen. 
     
     
         13 : The method of  claim 1 , wherein the cell is a flow cell, the electrocatalytic material comprises silver in the amount of 10 percent by weight of the electrocatalytic material, the potential is −0.9 V vs. RHE, and the syngas product comprises 80% by weight carbon monoxide and 20% by weight hydrogen. 
     
     
         14 : The method of  claim 13 , wherein the electrocatalytic material has a current density of 25 to 30 milliamperes per square centimeter (mA cm −2 ). 
     
     
         15 : The method of  claim 1 , wherein the cell is a flow cell, the electrocatalytic material comprises silver in the amount of 10 percent by weight of the electrocatalytic material, the potential is −1.1 V vs. RHE, and the syngas product comprises 65% by weight carbon monoxide and 35% by weight hydrogen. 
     
     
         16 : The method of  claim 1 , wherein the cell is a flow cell, the electrocatalytic material comprises silver in the amount of 10 percent by weight of the electrocatalytic material, the potential is −1.3 V vs. RHE, and the syngas product comprises 40% by weight carbon monoxide and 60% by weight hydrogen. 
     
     
         17 : The method of  claim 1 , wherein the cell is an H-cell, the potential is −1.1 V vs. RHE, the syngas product comprises 70% by weight carbon monoxide and 30% by weight hydrogen, and the electrocatalytic material has a current density of 2 to 3 mA cm −2 . 
     
     
         18 : The method of  claim 1 , wherein the reference electrode is a silver/silver chloride (Ag/AgCl) electrode. 
     
     
         19 : The method of  claim 1 , wherein the counter electrode is a platinum mesh electrode. 
     
     
         20 : The method of  claim 1 , wherein the gaseous electrolytic solution further comprises a potassium salt.