Iron and cobalt molecular complexes for the selective electrochemical reduction of co2 into co, with flow cells

Abstract

The present invention concerns a flow cell electrolyzer (1) to electrochemically reduce reagent gas CO2 into gaseous CO, with an anodic compartment comprising an anode (2) with a current collector, and on the current collector, at least a catalyst to electrochemically oxidize H2O to O2, an anodic electrolyte solution (3) at a controlled flow rate Qa, comprising: a solvent, and an anodic electrolyte, the solvent being water at neutral or basic pH; a cathodic compartment comprising a cathodic electrolyte solution (6), at a controlled flow rate Qc, comprising: the solvent, and a cathodic electrolyte, the solvent being water at neutral or basic pH, a gas diffusion porous cathode (9) which comprises, on a gas diffusion porous current cathode collector which is electrochemically inert, at least a molecular catalyst on a surface S to electrochemically reduce CO2 into CO, with a by-production of H2, the molecular catalyst being chosen between the list with the metal chosen among: Iron, Cobalt: metal porphyrin with one or several +N(C1-C4 alkyl)3 groups, metal phthalocyanine, metal phthalocyanine with one or several +N(C1-C4 alkyl)3 groups, or cobalt quarter pyridine.

1 . A flow cell electrolyzer to electrochemically reduce CO 2  in a CO 2 -containing reagent gas, passing onto or through a gas diffusion electrode (GDE), into gaseous CO, the flow cell electrolyzer comprising:
 an anodic compartment comprising:
 an anode with a current collector, 
 an anodic electrolyte solution, at a controlled flow rate Q a , comprising: a first solvent, and an anodic electrolyte, the first solvent being water, 
 an anodic electrolyte solution inlet and an anodic electrolyte solution outlet connected to the anodic compartment, adapted to circulate the anodic electrolyte solution; 
   a cathodic compartment comprising:
 a cathodic electrolyte solution, at a controlled flow rate Q c , comprising: a second solvent, and a cathodic electrolyte, the second solvent being H 2 O, 
 a cathodic electrolyte solution inlet and a cathodic electrolyte solution outlet connected to the cathodic compartment, adapted to circulate the cathodic electrolyte solution, as well as the CO 2 -containing reagent gas and CO product gas, 
 a gas diffusion electrode comprising, on an electrochemically inert gas diffusion porous current collector having a surface S, a molecular catalyst to electrochemically reduce the CO 2  in the CO 2 -containing reagent gas into said CO product gas in the cathodic electrolyte solution, with by-production of gaseous H 2 ; 
   the molecular catalyst being selected from the group consisting of:
 metal tetra phenyl porphyrin substituted with at least one  + N(C 1 -C 4  alkyl) 3  group and having other groups independently selected from the groups consisting of H, OH, F, C(CH 3 ) 3 , wherein the metal is chosen from among: iron and cobalt, 
 metal phthalocyanine, with the metal chosen among: iron and cobalt, 
 metal phthalocyanine, substituted with at least one group among:  + N(C 1 -C 4  alkyl) 3 , F, C(CH 3 ) 3  wherein the metal is chosen among: iron and cobalt, and 
 cobalt quarter pyridine; 
   an anion exchange membrane, impermeable at least to CO 2 , CO and H 2 , between the anodic compartment and the cathodic compartment;   a channel for passing flow of the CO 2 -containing reagent gas, at a controlled flow rate Q g , through the porous current collector surface S of the gas diffusion electrode of the cathodic compartment on which there is the molecular catalyst, while the cathodic electrolyte solution circulates in between the gas diffusion electrode and the anion exchange membrane;   pumping means adapted to:
 circulate by pumping the anodic electrolyte solution in the anodic compartment and the cathodic electrolyte solution in the cathodic compartment between the respective inlets and outlets thereof, 
 control flow by pumping the CO 2 -containing reagent gas in the channel, passing through the porous current collector surface of the gas diffusion electrode, 
   the pumping means being configured to control all flow rates of the cathodic and anodic electrolyte solutions as well as the CO 2 -containing reagent gas passing through the porous current collector surface S of the gas diffusion electrode;   a power supply providing energy necessary to trigger the electrochemical reactions involving the CO 2  reagent gas.   
     
     
         2 . The flow cell electrolyzer according to  claim 1 , wherein the anodic and/or cathodic electrolyte solution has a neutral or basic pH. 
     
     
         3 . The flow cell electrolyzer according to  claim 1 , wherein the anodic electrolyte solution and/or the cathodic electrolyte solution has a pH from 9 to 14. 
     
     
         4 . (canceled) 
     
     
         5 . The flow cell electrolyzer according to  claim 1 , wherein the CO 2 -containing reagent gas flow is at atmospheric pressure. 
     
     
         6 . The flow cell electrolyzer according to  claim 1 , wherein the anodic and the cathodic electrolyte solutions are at ambient temperature. 
     
     
         7 . The flow cell electrolyzer according to  claim 1 , wherein the molecular catalyst is a tetra-phenyl iron porphyrin with the formula: 
       
         
           
           
               
               
           
         
         wherein:
 at least 1 and at most 8 groups among R 1  to R 10  and R 1′  to R 10′  being independently  + N(C 1 -C 4  alkyl) 3  group, 
 the others of groups R 1  to R 10  and R 1′  to R 10′  are independently selected from the groups consisting of H, OH, F, C(CH 3 ) 3 . 
 
       
     
     
         8 . The flow cell electrolyzer according to  claim 7 , wherein:
 the others of groups among R 1  to R 10  and R 1′  to R 10′  are H, or   the others of groups among R 1  to R 10  and R 1′  to R 10′  are independently selected from the groups H and F.   
     
     
         9 . The flow cell electrolyzer according to  claim 7 , comprising  + N(C 1 -C 4  alkyl) 3  groups in the para or ortho position. 
     
     
         10 . The flow cell electrolyzer according to  claim 1 , wherein the molecular catalyst presents the formula: 
       
         
           
           
               
               
           
         
         wherein R 1  to R 16  are independently selected from the groups consisting of H, F, C(CH 3 ) 3  and  + N(C 1 -C 4  alkyl) 3 . 
       
     
     
         11 . The flow cell electrolyzer according to  claim 10 , wherein R 1  to R 16  are H. 
     
     
         12 . The flow cell electrolyzer according to any  claim 10 , at least 1 and at most 8 groups among R 1  to R 16  being independently  + N(C 1 -C 4  alkyl) 3 . 
     
     
         13 . The flow cell electrolyzer according to  claim 12 , wherein at least one or several of the specific groups R 1 , R 4 , R 5 , R 8 , R 9 , R 12 , R 13  and R 16  groups, comprises a  + N(C 1 -C 4  alkyl) 3  substituent. 
     
     
         14 . The flow cell electrolyzer according to  claim 1 , wherein the cathodic electrolyte solution comprises a phosphate buffer or potassium hydroxide, and the anodic electrolyte solution comprises a phosphate buffer or potassium hydroxide. 
     
     
         15 . The flow cell electrolyzer according to  claim 1 , wherein the cathodic electrolyte solution comprises sodium hydroxide or cesium hydroxide and/or the anodic electrolyte solution comprises sodium hydroxide or cesium hydroxide. 
     
     
         16 . The flow cell electrolyzer according to  claim 1 , wherein the molecular catalyst is tetra-phenyl iron porphyrin, wherein:
 the pH of the anodic electrolyte solution and/or the cathodic electrolyte solution is between from 11.5 to 14,   the CO 2 -containing reagent gas flow passes at atmospheric pressure through the porous current collector surface S of the gas diffusion electrode, and   the anodic and the cathodic electrolyte solutions are at ambient temperature.   
     
     
         17 . The flow cell electrolyzer according to  claim 10 , wherein:
 the pH of the anodic electrolyte solution and/or the cathodic electrolyte solution is between from 11.5 to 14,   the CO 2 -containing reagent gas flow passes at atmospheric pressure through the porous current collector surface S of the gas diffusion electrode, and   the anodic and the cathodic electrolyte solutions are at ambient temperature.   
     
     
         18 . The flow cell electrolyzer according to  claim 10 , wherein R 1  to R 16  comprise at least one  + N(C 1 -C 4  alkyl) 3  group, wherein:
 the pH of the anodic electrolyte solution and/or the cathodic electrolyte solution is between from 11.5 to 14,   the CO 2 -containing reagent gas flow passes at atmospheric pressure through the porous current collector surface S of the gas diffusion electrode (GDE), and   the anodic and the cathodic electrolyte solutions are at ambient temperature.   
     
     
         19 . The flow cell electrolyzer according to  claim 1 , wherein the molecular catalyst is cobalt quarter pyridine, wherein:
 the pH of the anodic electrolyte solution and/or the cathodic electrolyte solution is between from 11.5 to 14,   the CO 2 -containing reagent gas flow passes at atmospheric pressure through the porous current collector surface S of the gas diffusion electrode, and   the anodic and the cathodic electrolyte solutions are at ambient temperature.   
     
     
         20 . The flow cell electrolyzer according to  claim 1 , wherein the gas diffusion electrode in the cathodic compartment comprises, on the current collector, an electrode film which contains polymers with the molecular catalysts and wherein the electrode film is deposited or grafted on the current collector. 
     
     
         21 . The flow cell electrolyzer according to  claim 1 , wherein pumping means are configured to recirculate the anodic electrolyte solution and the cathodic electrolyte solution. 
     
     
         22 - 31 . (canceled)