Cathodes for microbial electrolysis cells and microbial fuel cells

Abstract

An apparatus is provided according to embodiments of the present invention which includes a reaction chamber having a wall defining an interior of the reaction chamber and an exterior of the reaction chamber; exoelectrogenic bacteria disposed in the interior of the reaction chamber; an aqueous medium having a pH in the range of 3-9, inclusive, the aqueous medium including an organic substrate oxidizable by exoelectrogenic bacteria and the medium disposed in the interior of the reaction chamber. An inventive apparatus further includes an anode at least partially contained within the interior of the reaction chamber; and a brush or mesh cathode including stainless steel, nickel or titanium, the cathode at least partially contained within the interior of the reaction chamber.

1 . An apparatus, comprising:
 a reaction chamber having a wall defining an interior of the reaction chamber and an exterior of the reaction chamber;   exoelectrogenic bacteria disposed in the interior of the reaction chamber;   an aqueous medium having a pH in the range of 3-9, inclusive, the aqueous medium comprising an organic substrate oxidizable by exoelectrogenic bacteria, the aqueous medium disposed in the interior of the reaction chamber;   an anode at least partially contained within the interior of the reaction chamber; and   a brush or mesh cathode comprising stainless steel, nickel or titanium, the cathode at least partially contained within the interior of the reaction chamber.   
     
     
         2 . The apparatus of  claim 1 , wherein the cathode has, in operation, a solution facing portion and a gas facing portion, and further wherein PTFE is excluded from the gas facing portion. 
     
     
         3 . The apparatus of  claim 1 , wherein microbes are substantially excluded from contact with the cathode. 
     
     
         4 . The apparatus of  claim 1 , wherein no exogenous noble metal catalyst is in contact with the cathode. 
     
     
         5 . The apparatus of  claim 1 , wherein the cathode further comprises a catalyst. 
     
     
         6 . The apparatus of  claim 5 , wherein the catalyst is a nickel or platinum catalyst. 
     
     
         7 . The apparatus of  claim 6 , wherein the nickel catalyst is a nickel oxide catalyst. 
     
     
         8 . The apparatus of  claim 5 , wherein the catalyst is an electrodeposited catalyst. 
     
     
         9 . The apparatus of  claim 1 , wherein the cathode is generally tubular in shape, having a wall defining an interior space, an interior wall surface, an exterior, and an exterior wall surface, wherein the wall comprises a stainless steel, nickel or titanium mesh, the mesh having a first mesh surface disposed towards the interior space and a second mesh surface disposed towards the exterior. 
     
     
         10 . The apparatus of  claim 1 , wherein the mesh has a first mesh surface and a second mesh surface and wherein a coating is present on the first mesh surface, the second mesh surface or both the first mesh surface and the second mesh surface. 
     
     
         11 . The apparatus of  claim 9 , wherein the coating on the second mesh surface is a water impermeable coating. 
     
     
         12 . The apparatus of  claim 9 , wherein the coating on the second mesh surface is an oxygen impermeable coating. 
     
     
         13 . The apparatus of  claim 10 , wherein the coating on the second mesh surface is an oxygen permeable coating. 
     
     
         14 . The apparatus of  claim 10 , wherein the coating on the first mesh surface, second mesh surface or both the first mesh surface and second mesh surface comprises an electron conductive binder. 
     
     
         15 . The apparatus of  claim 10 , wherein the coating on the first mesh surface, second mesh surface or both the first mesh surface and second mesh surface comprises a catalyst. 
     
     
         16 . The apparatus of  claim 9 , wherein the generally tubular cathode has a cross section selected from the group consisting of: circular, oval, oblong, square and rectangular. 
     
     
         17 . The apparatus of  claim 1 , further comprising a power source operably connected to add voltage to enhance an electrical potential between the anode and cathode. 
     
     
         18 . A biological process for producing hydrogen or electric current, comprising:
 providing an apparatus according to  claim 1 ;   maintaining oxidizing reaction conditions such that electrons are produced by oxidation of the organic substrate by the electrogenic bacteria and the electrons are transferred to an anode.   
     
     
         19 . The biological process of  claim 18 , further comprising application of a voltage in the range of 25-1000 millivolts, enhancing an electrical potential between the anode and cathode. 
     
     
         20 . A method for fabricating a cathode comprising:
 coating a stainless steel, nickel or titanium mesh, the mesh having wires defining pores, with an oxygen permeable layer comprising a viscoelastic polymer, the coating adherent to the mesh and present in the pores, forming a continuous coating on one or both sides of the mesh, wherein the mesh and coating are not exposed to a temperature above 100° C. or a pressure above ambient pressure.