Method of forming a pd-au layer on a substrate

Abstract

A method for preparing a palladium-gold alloy layer on a substrate by electrodepositing said coating surface with an aqueous electroplating solution comprising of an aqueous solution of a soluble palladium compound and a soluble gold complex, wherein the ratio of gold to palladium to in the solution is from 5 to 40 w/w %. Also taught is a substrate such as a vanadium or vanadium alloy gas separation membrane coated with a palladium-gold alloy layer.

1 - 41  (canceled) 
     
     
         42 . A method for preparing a palladium-gold alloy layer on a vanadium or vanadium alloy gas separation membrane, comprising:
 providing a vanadium or vanadium alloy gas separation membrane having a coating surface; and   electrodepositing said coating surface with an aqueous electroplating solution comprising a soluble palladium compound and a soluble gold complex, wherein the ratio of gold to palladium in the solution is from 5 to 40%, and wherein said electrodepositing is conducted for a period of time sufficient to deposit a layer of palladium-gold alloy on the coating surface.   
     
     
         43 . A method according to  claim 42 , wherein the ratio of gold to palladium in the solution is the w/w % ratio of gold to palladium in the solution and is from 5 to 40%. 
     
     
         44 . A method according to  claim 42 , wherein the palladium compound is palladium diamino dinitrite, palladium sulfate, palladium phosphate, a palladium organo sulfonate or a palladium organo phosphonate, and wherein the gold complex comprises potassium gold cyanide or sodium gold cyanide. 
     
     
         45 . A method according to  claim 42 , wherein the electrodepositing step is conducted at at least one of:
 a plating temperature of from 10 and 60° C.;   a pH of between 8 and 9; or   a current density of from 1 to 10×10 −2  A/cm 2 .   
     
     
         46 . A method according to  claim 42 , wherein the palladium-gold alloy forms a coated layer having a lightness of less than 50 measured using a Konica Minolta CR-400 Chroma Meter or a HunterLab MiniScan EZ. 
     
     
         47 . A method according to  claim 42 , wherein the deposited palladium-gold alloy has a purity of at least 99.9%. 
     
     
         48 . A method according to  claim 42 , wherein the palladium-gold alloy layer has at least one of a bulbous and/or cauliflower shaped morphology, or a microstructure which comprises dendrites. 
     
     
         49 . A method according to  claim 42 , wherein the palladium-gold alloy has a thickness of between 100 nm and 5 microns on the coating surface of the vanadium or vanadium alloy gas separation membrane. 
     
     
         50 . A method according to  claim 42 , wherein the palladium-gold alloy layer has a composition of from Pd 60 Au 40  to Pd 95 Au 5 . 
     
     
         51 . A method according to  claim 42 , wherein the coated gas separation membrane has a hydrogen permeability of 1 to 5×10 −7  mol/m/s/Pa 0.5  at temperatures between 325 to 350° C. 
     
     
         52 . A method according to  claim 42 , wherein the method further comprises, prior to the electrodeposition step, a cleaning procedure in which the coating surface undergoes at least one of a washing treatment using a solvent, mechanical cleaning, or chemical etching. 
     
     
         53 . A method according to  claim 52 , wherein mechanical cleaning comprises abrading said coating surface with an abrasion media to increase the surface roughness to a mean surface roughness (Sa) from above 0.8 micron up to 2.5 microns. 
     
     
         54 . A palladium-gold alloy-coated vanadium or vanadium alloy gas separation membrane, comprising a palladium-gold alloy coating layer having a thickness of between 100 nm and 5 microns, and having a composition of from Pd 60 Au 40  to Pd 95 Au 5 . 
     
     
         55 . A palladium-gold alloy-coated vanadium or vanadium alloy gas separation membrane according to  claim 54 , wherein the palladium-gold alloy coating layer has a lightness of less than 50 measured using a Konica Minolta CR-400 Chroma Meter or a HunterLab MiniScan EZ. 
     
     
         56 . A palladium-gold alloy-coated vanadium or vanadium alloy gas separation membrane according to  claim 54 , wherein the palladium-gold alloy of the palladium-gold alloy coating layer has a purity of at least 99.9%. 
     
     
         57 . A palladium-gold alloy-coated vanadium or vanadium alloy gas separation membrane according to  claim 54 , wherein the palladium-gold alloy coating layer has a bulbous and/or cauliflower shaped morphology. 
     
     
         58 . A palladium-gold alloy-coated vanadium or vanadium alloy gas separation membrane according to  claim 54 , wherein the palladium-gold alloy coating layer has a microstructure which comprises dendrites. 
     
     
         59 . A palladium-gold alloy-coated vanadium or vanadium alloy gas separation membrane according to  claim 54 , wherein the palladium-gold alloy coating has a composition of from Pd 70 Au 30  to Pd 90 Au 10 . 
     
     
         60 . A palladium-gold alloy-coated vanadium or vanadium alloy gas separation membrane according to  claim 54 , having a hydrogen permeability of 1 to 5×10 −7  mol/m/s/Pa 0.5  at temperatures between 325 to 350° C. 
     
     
         61 . A palladium-gold alloy-coated vanadium or vanadium alloy gas separation membrane according to  claim 54 , comprising a tubular gas separation membrane.