Patent Application: US-201515539074-A

Abstract:
the present invention provides a method for making materials and electrocatalytic materials comprising amorphous metals or metal oxides . this method provides a scalable preparative approach for accessing state - of - the - art electrocatalyst films , as demonstrated herein for the electrolysis of water , and extends the scope of usable substrates to include those that are non - conducting and / or three - dimensional electrodes .

Description:
the present disclosure relates to a new process for generating thin films of amorphous metals and metal oxides through the exposure of transition metal precursors ( e . g ., a metal salt or a metal coordination complex ) to near - infrared ( nir ) radiation under inert and aerobic environments , respectively . fig1 is a schematic representation of the nir - driven decomposition ( nirdd ) of a metal precursor on a substrate leading to the formation of amorphous metal oxide ( α - mo x ) and reduced metal ( α - m ) films under air and nitrogen , respectively . not only does this nirdd process furnish amorphous metal oxide films that display properties commensurate with films prepared by more complex methods and precursors , it is compatible with curing techniques widely used in large - scale manufacturing processes , including roll - to - roll processing ( 22 , 23 ). the nirdd method therefore provides unprecedented access to amorphous phases of reduced metals and alloys using moderate experimental conditions . the finding that amorphous metal or metal oxide films can be prepared by merely exposing metal precursors ( e . g ., a metal salt or a metal coordination complex ) coated on a substrate to nir radiation represents an important breakthrough for the scalable manufacture of state - of - the - art electrocatalysts and other thin - film applications . the nirdd process of the present invention provides easy access to complex compositions of alloys and metal oxide films in the amorphous phases , on a much broader substrate scope than is available to other commonly used methods . in embodiments of the invention , the amorphous metal - containing film is an amorphous metal oxide , an amorphous mixed metal oxide , an amorphous metal , or an amorphous mixed metal . in accordance with the present invention , the amorphous metal - containing film comprises a metal which is selected from any transition metal . in preferred embodiments of the present invention , the metal is selected from iron , iridium , manganese , nickel , copper , ruthenium , cobalt , tungsten , indium , tin , molybdenum or any combination thereof . also suitable for use in the present invention are metals from groups 1 to 12 , rows 2 to 6 , and any element from groups 13 to 16 , rows 2 to 6 . in one embodiment , the metal precursor solution is a solution of a metal salt . nonlimiting examples of suitable metal salts include mcl x or m ( no 3 ) x , where m is a metal selected from iron , iridium , manganese , nickel , copper , ruthenium , cobalt , tungsten , indium , tin , molybdenum or any combination thereof , and x is an integer from 1 to 6 . accordingly , nonlimiting examples of suitable metal precursors include fecl 3 , fe ( no 3 ) 3 , ircl 3 , nicl 2 , ni ( no 3 ) 2 , fe 2 ni 3 cl , cocl 2 , rucl 3 , cucl 2 , and wcl 6 . in one embodiment , the metal precursor solution is a solution of a metal coordination complex . nonlimiting examples of ligands suitable for use in the metal coordination complexes are 2 - ethylhexanoate ligands [ eh ] or acetylactonate [ acac ] ligands . accordingly , nonlimiting examples of suitable metal precursors include fe ( eh ) 3 , cu ( eh ) 2 , ir ( acac ) 3 , ni ( eh ) 2 , mn ( eh ) 3 , co ( eh ) 2 , mo ( eh ) 2 , sn ( eh ) 2 , in ( acac ) 3 , and fe 2 ni 3 ( eh ) 3 . in one embodiment , the process is carried out in an inert atmosphere such as nitrogen , or any other inert , non - oxidizing gas , which favorably allows for the formation of amorphous metal or amorphous mixed metal ( or metal alloy ) films . accordingly , non - limiting examples of amorphous metal - containing films which can be obtained using the process of the present invention include α - fe , α - cu , α - fe 2 ni 3 , α - ni , and α - mn . in one embodiment , the process is carried out in an oxidizing ( i . e ., oxygen containing ) atmosphere ( e . g ., air ), which favorably allows for the formation of amorphous metal oxide or mixed metal oxide films . accordingly , nonlimiting examples of amorphous metal oxide or mixed metal oxide films which can be obtained using the process of the present invention include α - feo x , α - iro x , α - nio x , α - mno x , α - fe 2 ni 3 o x , α - cuo x , α - coo x , α - moo x , α - sno x , α - ino x , α - ruo x , and α - wo x . the process of the present invention allows for the formation of amorphous metal - containing films on a wide variety of substrates . nonlimiting examples of suitable substrates include glass , fluorine - doped tin oxide - coated glass ( fto ), synthetic polymers ( e . g ., nafion ®), metallic substrates ( e . g ., nickel , platinum , gold , silver , copper or titanium ), plastic , glassy carbon and stainless steel . in one embodiment , the process for forming an amorphous metal - containing film for use in electrocatalysis further comprises a step of tuning the properties of the electrocatalyst . in one embodiment , the tuning step comprises annealing the metal oxide film . the nirdd process of the present invention is also easy to scale on the basis that the infrastructure requirements are similar to curing processes currently used in industry ( 22 , 23 ). in addition , the nirdd fabrication process is also compatible with substrates that are non - conducting , three - dimensional , and sensitive to temperature and uv radiation , for example , nafion ®. in accordance with the present invention , the process allows the formation of an amorphous metal - containing film on a substrate , thereby providing a material suitable for use in electrocatalysis . the nirdd process of the present invention can be used for the formation of amorphous ( oxide ) films containing metals of relevance to the oer reaction [ e . g ., iron ( 7 , 8 ), iridium ( 18 , 24 ), manganese ( 6 , 25 ), nickel ( 7 , 8 , 26 ), copper ( 27 , 28 )]. novel synthesis of metal oxides ( mo x ) using ir irradiation the formation of amorphous metal oxide films upon exposure of metal salts to nir radiation was confirmed by placing fecl 3 spin - cast on fto , fecl 3 / fto , under a 175 - w nir lamp for 120 min in an aerobic environment . the color change from yellow to light brown upon irradiation supported the formation of iron oxide ( uv - vis spectra are provided in fig6 ), while the absence of reflections in the powder xrd patterns indicated the amorphous nature of the material ( fig7 ). fig7 illustrates powder xrd patterns required on as - prepared and annealed ( t anneal = 500 ° c .) α - feo x and α - fe films prepared by applying the nirdd process to ( a ) fecl 3 and ( b ) fe ( eh ) 3 deposited on fto under air and nitrogen , respectively . data recorded on a bare fto substrate is also provided . inset : expanded view highlighting the region where the reflection associated with the maghemite and hematite form of fe 2 o 3 at 35 . 5 ° is observed . this reflection is observed only for the films annealed at 500 ° c . under air , denoted feo x - annealed . ( a signature bragg reflection of hematite is apparent at 2θ = 35 . 9 ° only after annealing the same film in air for 1 h at 500 ° c .) fig6 illustrates uv - vis absorption spectra , before and after being subjected to the nirdd process , of : ( a ) metal halide precursor complexes on glass , fecl 3 / glass ( 1 ), nicl 2 / glass ( 2 ), and fe 2 ni 3 cl / glass ( 3 ); and ( b ) coordination complexes on glass , fe ( eh ) 3 / glass ( 1 ), ni ( eh ) 3 / glass ( 2 ), fe 2 ni 3 ( eh ) 3 / glass ( 3 ), ir ( acac ) 3 / glass ( 4 ) and mn ( eh ) 3 / glass ( 5 ). data for fecl 3 / glass and fe ( eh ) 3 / glass following the nirdd process in a nitrogen environment is indicated by “ 1 / n 2 ”, respectively . the glass background is also shown . note that glass was used rather than fto to avoid interference at longer wavelengths . the film fe 2 ni 3 cl / glass was prepared from a solution of 2 g of deionized water containing nicl 2 ( 0 . 088 g ) and fecl 3 ( 0 . 039 g ) that was spin - cast onto a glass substrate . fig2 is an sem image of feo x prepared according to this process . the electrochemical behavior of this amorphous film , α - feo x , in aqueous media was also consistent with previous accounts of amorphous iron oxide ( fig2 , table 1 ). fig2 illustrates cyclic voltammograms for thin films of α - feo x ( fig2 a ) and α - fe ( fig2 b ) on fto . values indicate the sequence of the cycles that were recorded ( experimental conditions : counter - electrode = pt mesh ; reference electrode = ag / agcl , kcl ( sat &# 39 ; d ); scan rate = 10 mv s 31 1 ; electrolyte = 0 . 1 m koh ( aq )). importantly , an extensive electrochemical analysis indicated that α - feo x could be readily produced from other iron compounds [ e . g ., fe ( no 3 ) 3 , fe ( eh 3 ; eh = 2 - ethylhexanoate ] ( fig8 ), and that the nirdd method translated effectively to other metals : films of α - iro x , α - nio x , and α - mno x were also formed when the corresponding metal compounds were subjected to nir radiation ( fig9 and 10 ). the electrocatalytic properties of α - iro x in 1 m h 2 so 4 ( fig1 ), a rare acid - stable oer catalyst , are consistent with literature values , as are those for α - nio x and α - mno x , oer electrocatalysts pervasive in the contemporary literature owing to their high activities and high natural abundances , in alkaline conditions ( table 1 ). fig8 illustrates cyclic voltammograms for thin films of α - feo x , prepared by the nirdd process in air , and the respective precursor films from which they were derived from ; fe ( no 3 ) 3 , fecl 3 and fe ( eh ) 3 precursors . all data is collected on films deposited on fto , and thus the slight differences in the response of the α - feo x films are attributed to minor differences in film roughness or film densities . electrochemistry conditions : counterelectrode = pt mesh ; reference electrode = ag / agcl , kcl ( sat &# 39 ; d ); scan rate = 10 mv s − 1 ; electrolyte = 0 . 1 m koh ( aq ) ; current densities were corrected for uncompensated resistance . fig9 illustrates powder xrd patterns acquired on as - prepared films of ( a ) α - iro x , ( b ) α - nio x and ( c ) α - mno x on fto . no reflections are observed other than those associated with fto . fig1 illustrates cyclic voltammograms recorded on thin films of α - iro x , α - nio x , α - mno x and α - fe 2 ni 3 o x on fto . data recorded on bare fto is also shown . electrochemistry conditions : counterelectrode = pt mesh ; reference electrode = ag / agcl , kcl ( sat &# 39 ; d ); scan rate = 10 mv s − 1 ; electrolyte = 1 m h 2 so 4 ( aq ) for α - iro x , or 0 . 1 m koh ( aq ) for α - nio x , α - mno x , α - fe 2 ni 3 o x and bare fto . current densities were corrected for uncompensated resistance . the discovery that nirdd could drive α - mo x formation was not expected given the low absorptivity of the films at λ & gt ; 600 nm ( fig6 ). it is therefore contended that the efficacy of the process is due to localized heating of the film rather than a photochemical effect . this assessment is validated by the observations that : ( i ) substrates do not exceed 200 ° c . under the present experimental conditions ( fig5 ); ( ii ) bulk samples of fecl 3 do not decompose to a mass corresponding to fe 2 o 3 until & gt ; 300 ° c . ( fig1 and 12 ); ( iii ) samples of precursors on fto exposed to 1 h of constant irradiation yielded complete decomposition , while six successive 10 - min segments of exposure separated by 5 - min periods in the dark did not ; and ( iv ) films of precursors on fto did not show the same rates of decomposition when placed in an oven set at 200 ° c . ( fig1 ). fig5 illustrates temperature profiles of fecl 3 / fto , fe ( eh ) 3 / fto and bare fto . additional control measurements were also collected on a sample where fe ( eh ) 3 deposited directly on the copper wire of the thermocouple by the nirdd process , denoted fe ( eh ) 3 / thermocouple , as well as the bare wire of the thermocouple . temperature readings were recorded with a thermocouple in 5 - min increments , and indicated a rise in temperature that plateaus at a value no greater than 175 ° c . these collective results confirm that a substrate temperature of 200 ° c . is not reached during a constant 1 h exposure to nir radiation under the present experimental conditions . fig1 illustrates tga and dsc profiles for ( a ) fecl 3 and ( b ) fe ( eh ) 3 under air and n 2 at a ramp rate of 10 ° c . min − 1 . the bottom plots overlay the respective percent - mass - loss profiles in air and n 2 to highlight the effect of the atmospheric environment . both fecl 3 and fe ( eh ) 3 appear to lose ligands in a stepwise fashion ; our tentative assignments indicate that the first ligand is excluded at ˜ 200 ° c . and the last ligand is liberated at ˜ 400 ° c . the ligands are excluded from fecl 3 in three distinct steps in both air and n 2 , while data recorded on fe ( eh ) 3 in air shows the loss of two ligands in quick succession followed by the loss of the third ligand at higher temperatures ; this pattern is reversed under nitrogen . complete decomposition is not complete until t & gt ; 400 ° c . for any of the data shown , which is much higher than the surface temperatures reached during the nirdd process . fig1 illustrates tga and dsc profiles for ( a ) fecl 3 and ( b ) fe ( eh ) 3 brought to 200 ° c . and then held for 60 min . the fecl 3 and fe ( eh ) 3 precursor complexes do not decompose fully to a final mass of fe 2 o 3 during this period . both measurements were recorded in an aerobic environment . fig1 illustrates ftir spectra of independent samples of fe ( eh ) 3 / fto before and after ( a ) exposure to nir radiation for 30 min , ( b ) heating at 200 ° c . in a furnace for 30 min , ( c ) heating at 250 ° c . in a furnace for 30 min . the temporal resolution of the nirdd process was evaluated by tracking the formation of α - feo x during the nir - irradiation of fe ( eh ) 3 , which contains ligands that can be tracked by ftir spectroscopy ( 17 , 29 ), and indicated complete ligand loss within 1 h in both air and n 2 ( fig3 ). fig3 illustrates ftir spectra for thin films of fe ( eh ) 3 on fto upon exposure to nir radiation for ( a ) 0 , 4 , 16 , 32 and 64 min in air , and ( b ) 0 and 60 min under nitrogen . arrows indicate trends in the intensities of the c — h and c — o vibrational modes of 2 - ethylhexanoate . ( 8 ). [ the absorption spectra ( fig6 ), lack of powder xrd reflections ( fig7 ), and electrochemical data ( table 1 ) collectively support the assignment of the resultant films as α - feo x .] films of α - mo x ( m = ir , ni , mn ) derived from ir ( acac ) 3 ( acac = acetylacetonate ), ni ( eh ) 2 , and mn ( eh ) 2 , respectively , were formed quantitatively within four hours of irradiation ( fig1 ). fig1 illustrates ftir spectra of thin films of ir ( acac ) 3 / fto , ni ( eh ) 2 / fto , and mn ( eh ) 3 / fto for 0 , 4 , 16 , 64 , 128 , and 256 min subjected to the nirdd process showing the progressive loss of ligands in & lt ; 2 h . absorption bands are associated with the symmetric and asymmetric vibrations of the c — o groups of the 2 - ethylhexanoate ligand and free acid . novel synthesis of metals ( m ) using ir irradiation under inert atmosphere the formation of α - feo x from fecl 3 signaled that oxygen in the films was sourced from the aerobic environment , thus raising the possibility that more reduced forms of amorphous films could be accessed by carrying out nirdd in an inert atmosphere . this hypothesis was tested by irradiating a film of fecl 3 on fto under nitrogen , which yielded a light grey film , denoted α - fe , that did not produce any bragg reflections ( fig7 ). moreover , the electrochemistry of α - fe on fto in 0 . 1 m koh ( aq ) was consistent with a lower average iron valency than that of α - feo x ( fig2 ). as oxidative sweep of α - feo x leads to a sharp rise in current at 1 . 55 v coincident with catalytic oer ( fig2 a ), and subsequent cycles over the 1 . 0 - 1 . 8 v range led to superimposable traces . the oxidative sweep for α - fe featured a markedly different current profile ( fig2 b ); however , subsequent cycles indicated α - fe was converted to α - feo x upon oxidation in aqueous media on the basis of the superimposable scans . the differences in the reductive behavior were more stark , as the cathodic peak at − 0 . 25 v for α - feo x was not detected for α - fe prior to her catalysis at ca . − 0 . 50 v . the two films could be interconverted : holding α - feo x at − 0 . 68 v for 10 min yields a color change that matches that of α - fe ( grey ), white maintaining α - fe at 1 . 92 v for 10 min drives a color change towards that of α - feo x ( brown ). evidence for the oxidized and reduced forms of the films being formed under oxygen and nitrogen environments , respectively , is further supported by the different absorption ( fig6 ) and x - ray photoelectron spectroscopy ( xps ; fig1 and 16 ) data . fig1 illustrates x - ray photoelectron spectra for α - feo x and α - fe on fto . the ( a ) survey scan , and spectral regions corresponding to the ( b ) iron 2p and ( c ) carbon 1s regions , are shown . fig1 illustrates x - ray photoelectron spectra detailing the fe 2p 3 / 2 region . sums of the fitting components for ( a ) α - feo x and ( b ) α - fe are shown . curve fitting in a used gupta sen parameters based on fe 2 o 3 along with a surface peak and an fe 3 + satellite peak . curve fitting in b used centre - of - gravity peaks for fe 2 + and fe 3 + ; a surface peak and a fe 2 − satellite peak are also shown . the fe 3 + satellite peak is not shown , as it is likely superimposed with the fe 2p 1 / 2 peak . the xps data for α - feo x contains a signature iron ( iii ) satellite signal at 719 ev that is not observed for α - fe , and an iron 2p 3 / 2 envelope that could be accurately modeled using peak parameters corresponding to fe 2 o 3 ( 30 ). the 2p 3 / 2 envelope of α - fe was fit to a combination of iron ( iii ), iron ( ii ), and iron ( 0 ), where the zero valency was unequivocally implicated by the low - energy shoulder . while these results confirm that α - fe exists in a more reduced form , the high susceptibility of the films to areal oxidation prevented confirmation that elemental iron was being formed is exclusivity during the nirdd process . surrogate films of α - cuo x and α - cu prepared by applying the nirdd process to cu ( eh ) 2 on fto under air and nitrogen were analyzed , respectively , in view of elemental copper oxidizing less readily to cu 2 o and , in turn , cuo ( 31 ). xps data recorded on these samples did indeed yield different spectroscopic signatures ( fig4 and 17 ): the copper 2p 3 / 2 envelope for α - cuo x showed a mixture of cuo and cu ( oh ) 2 , while the same envelope for α - cu shows a single peak corresponding to zero - or mono - valent copper sites . fig4 illustrates the fitting of the copper 2p 3 / 2 region of x - ray photoelectron spectra recorded on thin films of cu ( eh ) 2 on fto after being subjected to the nirdd process under ( a ) air and ( b ) nitrogen , respectively ; sum of the fitting components are indicated . fitting of the data used centre - of - gravity peaks for ( a ) cu ( o ) and cu ( oh ) 2 , and ( b ) cu ( 1 )/ cu ( 0 ). signature copper ( ii ) satellite peaks present in ( a ) but not ( b ) confirm a more reduced form of the film when prepared under nitrogen . the computed baselines are indicated . fig1 illustrates xps data for α - cuo x and α - cu on fto . the ( a ) survey scan , along with the rough fitting of the cu lmm regions denoting ( b ) cuo and ( c ) cu 2 o , are shown . visible inspection of the samples prepared by nirdd in an inert atmosphere indicated a color consistent with elemental copper ( fig1 ), with xrd measurements ruling out formation of crystalline domains ( fig1 ), lending credence to the samples existing in a reduced form when prepared under nitrogen . fig1 illustrates images of solid samples of ( a ) cu ( eh ) 2 , ( b ) cu ( eh ) 2 subjected to nirdd under nitrogen , and ( c ) cu ( eh ) 2 subjected to nirdd under air . the colors of the samples in ( b ) and ( c ) indicate elemental copper and copper oxide , respectively . fig1 illustrates powder xrd patterns acquired on as - prepared and annealed ( t anneal = 500 ° c .) α - cuo x and α - cu films prepared from cu ( eh ) 3 under ( a ) air and ( b ) nitrogen . data recorded on bare fto substrate is also included . inset : expanded view highlighting the region where the reflection associated with the crystalline form of cuo at 35 . 5 ° is observed . this signal is observed only for the films annealed at 500 ° c . under air and n 2 , cuo x - annealed and cu - annealed . mixed - metal oxides are known to exhibit superior electrocatalytic behavior in basic media , which prompted the synthesis of the binary solid , α - fe 2 ni 3 o x , by subjecting a mixture of iron precursors [ e . g ., fe ( eh ) 3 , fecl 3 or fe ( no 3 ) 3 ] and nickel precursors [ ni ( eh ) 2 , nicl 2 or ni ( no 3 ) 2 ] ( mol fe / mol ni 2 : 3 ) spin - cast on fto to the nirdd process ( fig2 ). fig2 a illustrates ftir spectra of fe 2 ni 3 ( eh ) 3 / fto subjected to nirdd for the times indicated under air to highlight the progressive loss in intensity of the bands associated with the ligand . in the spectra depicted in fig2 a , no peaks are present at 32 minutes . the resultant films were amorphous according to powder xrd measurements ( fig2 a ), and the edx measurements recorded on different regions of the films confirmed uniform metal distributions across the substrates ( fig3 and table 2 ). fig2 a illustrates powder xrd patterns acquired on as - prepared films of α - fe 2 ni 3 o x on fto recorded under air . no reflections were observed other than those associated with fto . the electrochemical behavior , including oer catalytic activity , also matches films of similar compositions prepared by other methods ( fig2 a and table 1 ), including the absence of an oxidative peak at e p ˜ 1 . 45 v that is present in pure phases of nio x . fig2 a illustrates cyclic voltammograms for thin films of α - fe 2 ni 3 o x prepared by nirdd under air . electrochemistry conditions : counterelectrode = pt mesh ; reference electrode = ag / agcl , kcl ( sat &# 39 ; d ); scan rate = 10 mv s − 1 ; electrolyte = 0 . 1 m koh ( aq ) ; current densities were corrected for uncompensated resistance . * based on the relative molar ratios of metal nitrate films deposited on fto glass ; error bars represent the standard deviation between the three different areas of measurement on the surface novel synthesis of mixed - metal ( mm ) using ir irradiation under inert atmosphere the binary film , α - fe 2 ni 3 , was prepared in the same manner as α - fe 2 ni 3 o x , but under nitrogen . alloy formation was corroborated by the electrocatalytic behavior of the films indicating a more reduced phase compared to that of α - fe 2 ni 3 o x ( fig2 b ). fig2 b illustrates ftir spectra of fe 2 ni 3 ( eh ) 3 / fto subjected to nirdd for the times indicated under nitrogen to highlight the progressive loss in intensity of the bands associated with the ligand . the resultant films were amorphous according to powder xrd measurements ( fig2 b ), and the edx measurements recorded on different regions of the films confirmed uniform metal distributions across the substrates ( fig3 ). fig2 b illustrates powder xrd patterns acquired on as - prepared films of α - fe 2 ni 3 on fto recorded under nitrogen . no reflections were observed other than those associated with fto . fig2 b illustrates cyclic voltammograms for thin films of ( b ) α - fe 2 ni 3 prepared by nirdd under n 2 . electrochemistry conditions : counterelectrode = pt mesh ; reference electrode = ag / agcl , kcl ( sat &# 39 ; d ); scan rate = 10 mv s − 1 ; electrolyte = 0 . 1 m hoh ( aq ) ; current densities were corrected for uncompensated resistance . the alloy , which contains a uniform distribution of metals within the solid ( fig3 and table 3 ), is not a state - of - the - art her electrocatalyst but is superior to pure phases of α - fe and α - ni , thus highlighting that metal cooperativity with other metal combinations may unearth superior catalysts in future studies ( 7 , 17 , 32 ). * based on the relative molar ratios of metal nitrate films deposited on fto glass ; error bars represent she standard deviation between the three different areas of measurement on the surface the viability of the nirdd method for situations where the substrate is non - conducting , or sensitive to high temperatures ( e . g ., interfacial layers in solar cells , carbon - based substrates , etc .) was tested . proof - of - principle experiments of relevance to electrolysis was designed where an 180 - μm thick film of nafion ® was saturated with ircl 3 or ir ( acac ) 3 , and subjected to the nirdd process . the exclusive formation of amorphous iro x within the nafion was found within 60 min of irradiation , with no damage to the membrane , according to electrochemical and ftir data ( fig2 and 24 ). fig2 a illustrates cyclic voltammograms for thin films of α - iro 3 / membrane , ircl 3 / membrane , and the membrane , where the membrane is nafion ®. these results show that nirdd may have the potential to efficiently coat three - dimensional electrodes , which is particularly important in contemporary electrolyzers . fig2 b illustrates the membrane electrode assembly prepared by mechanically pressing a platinum mesh counter electrode , the prepared nafion membrane , and a toray carbon paper gas diffusion layer between two ti plate electrodes . the catalytic current with the blank membrane is due to the titanium plates mediating the oer reaction . chronoamperometric measurements were done by holding the potential at 1 . 8 v for 3600 s . electrochemistry conditions : counterelectrode = pt mesh ; reference electrode = ag / agcl , kcl ( sat &# 39 ; d ); scan rate = 10 mv s − 1 ; electrolyte = 0 . 5 m h 2 so 4 ( aq ) ; current densities were corrected for uncompensated resistance . fig2 illustrates ( a ) full and ( b ) expanded ftir spectra of ir ( acac ) 3 / membrane subjected to nir radiation for 0 and 60 min . a trace for untreated nafion membrane is also shown . the magnified spectrum in ( b ) is included to feature the loss in intensities of the bands associated with the ligand vibrational modes . iron ( iii ) 2 - ethylhexanoate ( fe ( eh ) 3 , 50 % w / w in mineral spirits ,), iridium ( iii ) acetylacetonate ( ir ( acac ) 3 ), nickel ( ii ) 2 - ethylhexanoate ( ni ( eh ) 2 , 78 % w / w in 2 - ethylhexanoic acid ,) manganese ( iii ) 2 - ethylhexanoate ( mn ( eh ) 3 , 40 % w / w in 2 - ethylhexanoic acid ), and copper ( ii ) 2 - ethylhexanoate ( cu ( eh ) 2 ) were purchased from strem chemicals . nafion ® n117 proton exchange membranes ( 177 . 8 μm thick ) were purchased from ion power , ferric chloride ( 98 %) anhydrous ( fecl 3 ) was purchased from aldrich , iron ( iii ) nitrate nonahydrate ( fe ( no 3 ) 3 9h 2 o ), nickel nitrate hexahydrate ( ni ( no 3 ) 2 6h 2 o ) and nickel chloride hexahydrate ( nicl 2 6h 2 o ) were purchased from fischer scientific . all reagents were used without further purification . to a 20 - ml beaker containing 0 . 58 g of fe ( eh ) 3 ( 0 . 66 mmol ) was added to 1 . 07 g hexanes ( 12 . 4 mmol ). the solutions were then spin - cast onto fto ( or glass ) at 3000 rpm for 1 min . the resultant film , fe ( eh ) 3 fto ( or fe ( eh ) 3 / glass ), was left under a nir lamp for 30 min . the following conditions for this “ nirdd ” process were used for each experiment unless otherwise stated : the samples were placed underneath a phillips 175 w nir lamp , where the bottom of the lamp was positioned 2 cm above the substrate that was set on an aluminum foil surface to help dissipate the heat ; the face of the active film was positioned towards the lamp for this process . films were also prepared from fecl 3 ( 0 . 24 g ) or fe ( no 3 ) 3 ( 0 . 11 g ) in deionized water ( 2 g ), that were spin - cast on fto to form fecl 3 / fto and fe ( no 3 ) 3 / fto , respectively , and subject to the nirdd process described above to form α - feo x . samples prepared on glass were prepared using the same protocol as those prepared on fto . fig2 is an sem image of feo x prepared according to this process . the films were prepared following the same protocol as α - feo x , except the subsequent photolysis step being carried out in an mbraun labmaster 310 glove box filled with nitrogen . films of α - feo x on fto were annealed in a furnace at 500 ° c . for 60 min . films of α - fe on fto were annealed for 60 min on a hot plate set at 500 ° c . inside the glove box . the temperature of the hot plate was confirmed with a fluke 52 thermocouple . to a 20 - ml beaker containing 0 . 09 g of ir ( acac ) 3 ( 0 . 3 mmol ) was added 1 . 48 g chloroform . the solution was spin - cast onto the substrates ( glass or fto ) at 3000 rpm for 1 min . the resultant film , ir ( acac ) 3 / fto , was subject to the nirdd process for 2 h to ensure the reaction was completed . fig2 is an sem image of iro x prepared according to this process . to a 20 - ml beaker containing 0 . 27 g of ni ( eh ) 2 ( 0 . 61 mmol ) was added to 1 . 26 g hexanes ( 14 . 6 mmol ). the solutions were then spin - cast onto the substrates ( glass or fto ) at 3000 rpm for 1 min . the resultant film , ni ( eh ) 2 / fto , was subject to the nirdd process until the reaction was complete (˜ 60 min ). fig2 is an sem image of nio x prepared according to this process . films were also prepared from nicl 2 ( 0 . 17 g ) or ni ( no 3 ) 2 ( 0 . 14 g ) in deionized water ( 2 g ), that were spin - cast on fto to form nicl 2 / fto and ni ( no 3 ) 3 / fto , respectively , and then subject to the nirdd process to form α - nio x on fto (˜ 30 min ). to a 20 - ml beaker containing 0 . 55 g of mn ( eh ) 3 ( 0 . 64 mmol ) was added to 1 . 06 g of hexanes ( 12 . 3 mmol ). the solutions were then spin - cast onto fto at 3000 rpm for 1 min . the resultant film , mn ( eh ) 3 / fto , was then subject to the nirdd process to form α - mno x on fto (˜ 30 min ). to a 20 ml beaker containing 0 . 21 g cu ( eh ) 2 ( 0 . 65 mmol ) was added to 1 . 62 g ethanol ( 35 . 2 mmol ). the solutions were then spin - cast onto fto at 3000 rpm for 1 min . the resultant film , cu ( eh ) 2 / fto , was then subject to the nirdd process to form α - cuo x on fto (˜ 30 min ). fig3 is an sem image of cuo x prepared according to this process films were also prepared from a 0 . 3 m solution of cucl 2 in methanol spin - cast on fto and subject to the nirdd process as described above to form α - cuo x . a 0 . 3 m solution of co ( eh ) 2 was prepared in hexanes . the solution was then spin - cast onto fto at 3000 rpm for 1 min . the resultant film , co ( eh ) 2 / fto , was then subject to the nirdd process to form α - coo x on fto (˜ 30 min to 2 h ). fig2 is an sem image of coo x prepared according to this process . films wore also prepared from a 0 . 3 m solution of cocl 2 in methanol spin - cast on fto and subject to the nirdd process as described above to form coo x . a 0 . 3 m solution of mo ( eh ) 2 was prepared in hexanes . the solution was then spin - cast onto fto at 3000 rpm for 1 min . the resultant film , mo ( eh ) 2 / fto , was then subject to the nirdd process to form α - moo x on fto (˜ 30 min to 2 h ). a 0 . 3 m solution of sn ( eh ) 2 was prepared in methanol . the solution was then spin - cast onto fto at 3000 rpm for 1 min . the resultant film , sn ( eh ) 2 / fto , was then subject to the nirdd process to form α - sno x on fto (˜ 30 min to 2 h ). a 0 . 3 m solution of in ( acac ) 3 was prepared in methanol . the solution was then spin - cast onto fto at 3000 rpm for 1 min . the resultant film , in ( acac ) 3 / fto , was then subject to the nirdd process to form α - ino x on fto (˜ 30 min to 2 h ). a 0 . 3 m solution of rucl 3 was prepared in methanol . the solution was then spin - cast onto fto at 3000 rpm for 1 min . the resultant film , rucl 3 / fto , was then subject to the nirdd process to form α - ruo x on fto (˜ 30 min to 2 h ). fig3 is an sem image of ruo x prepared according to this process . a 0 . 3 m solution of wcl 6 was prepared in methanol . the solution was then spin - cast onto fto at 3000 rpm for 1 min . the resultant film , wcl 6 / fto , was then subject to the nirdd process to form α - wo x on fto (˜ 30 min to 2 h ). α - fe 2 ni 3 o x on fto ( or glass ) to a 20 - ml beaker containing 0 . 23 g of fe ( eh ) 3 ( 0 . 24 mmol ) and 0 . 16 g of ni ( eh ) 2 ( 0 . 36 mmol ) was added 1 . 28 g of hexanes ( 14 . 9 mmol ). the mixture was spin - cast onto fto at 3000 rpm for 1 min . the resultant film , feni ( eh )/ fto , was then subject to the nirdd process to form α - fe 2 ni 3 o x on fto (˜ 30 min ). films were also prepared from a solution of nicl 2 ( 0 . 088 g ) [ or ni ( no 3 ) 2 ( 0 . 105 g )] and fecl 3 ( 0 . 039 g ) [ or fe ( no 3 ) 3 ( 0 . 097 g )] in deionized water ( 2 g ) spin - cast on fto and subject to the nirdd process as described above to form α - fe 2 ni 3 o x . films of α - fe 2 ni 3 on fto were prepared in the same fashion as α - fe 2 ni 3 o x , but the photolysis step was carried out in a glove box . nafion membranes were cut into squares with geometric surface areas of 6 . 25 cm 2 and then submerged in a bath of 3 % w / w h 2 o 2 stirring at 800 rpm for ˜ 5 min . the membranes were then left to stand in a bath of stirring 0 . 5 m h 2 so 4 at 150 ° c . for 60 min . the membranes were dehydrated in a vacuum oven ( room temperature , 0 . 8 atm ) for at least 5 h . excess acid was removed before dehydration with compressed nitrogen . a solution containing 0 . 016 g of ir ( acac ) 3 ( 0 . 32 mmol ) in 3 . 2 ml ethanol was then spray - coated on the surface of the dehydrated nafion to form ir ( acac ) 3 / membrane . the resultant film was then subjected to the nirdd process to form α - iro 3 / membrane (˜ 120 min ). similar substrates could be prepared by immersing the nafion into a 2 - ml solution prepared from a bulk solution of 1 . 0 g of ircl 3 h 2 o ( 2 . 8 mmol ) in 28 ml h 2 o . electrochemical measurements were performed on a c — h instruments workstation 660d potentiostat . the ag / agcl ( sat . kcl ) reference electrode ( e ref ) was calibrated regularly against a 1 - mm aqueous k 3 [ fe ( cn ) 6 ] solution . cyclic voltammograms were acquired at a 10 mv s − 1 scan rate unless otherwise indicated . all potentials were corrected for uncompensated resistance ( r u ) and are reported relative to the reversible hydrogen electrode ( vs rhe ), e rhe = e + e ref = 0 . 059 ( ph )− ir u . tafel plots were acquired through staircase voltammetry ( 10 mv steps , 50 s intervals for the final 25 s sampled ). for the metal oxide and metal films on fto , all experiments were carried out using 0 . 1 m koh as an electrolyte , unless otherwise noted , in a standard three - compartment electrochemical cell . a luggin capillary connects the reference and working electrodes while a porous glass frit connects the working electrode to the platinum mesh counter electrode . all experiments involving nafion were carried out in 0 . 5 m h 2 so 4 . membranes were hydrated in 0 . 2 m h 2 so 4 prior to electrochemical experiments . measurements were performed in a customized three - electrode test cell using the above ag / agcl reference electrode . all potentials were corrected for r u . the membrane electrode assembly ( mea ) was prepared by mechanically pressing a platinum mesh counter electrode ( aldrich ), the prepared nafion membrane , and a toray carbon paper gas diffusion layer ( ion power ) between two ti plate electrodes ( mcmaster carr ). no aggregation was induced on the test cell besides that from evolved gaseous products . powder x - ray diffraction ( xrd ) data was recorded with a bruker d8 advance diffractometer using cu ka radiation . data was collected between 2θ angles of 5 ° and 90 ° with a step size of 0 . 04 °. the step time was 0 . 6 s unless otherwise indicated . thermogravimetric analysis and differential scanning calorimetry ( tga / dsc ) measurements were collected simultaneously with a perkinelmer simultaneous thermal analyzer ( sta ) 6600 . these measurements were carried out under both air and n 2 at a 20 - ml min − 1 flow rate . starting from a temperature of 50 ° c ., the temperature was ramped up ( 10 ° c . min − 1 ) until 100 ° c . where it was held for one minute . it was then ramped at 10 ° c . min − 1 until a final temperature of 500 ° c . was reached and held for an additional minute . for constant temperature measurements , the temperature was ramped up ( 10 ° c . min − 1 ) until 200 ° c . where it was held for 60 minutes . uv - vis absorption spectroscopy on fresh and on metal oxide films was performed using a perkin elmer lambda 35 uv - vis spectrometer with a solid sample holder accessory . baseline scans were performed with clean glass . x - ray photoelectron spectroscopy ( xps ) measurements were collected on a leybold max200 spectrometer using al k - alpha radiation . the pass energy used for the survey scan was 192 ev while for the narrow scan it was 48 ev . scanning electron microscopy ( sem ) and energy dispersive x - ray spectroscopy ( edx ) measurements were carried out on a fei helios nanolab 650 dual beam scanning electron microscope with an edax pegasus system with eds detector . the magnification was set to 2000 ×, the accelerating voltage was set to 2 . 0 kev , the current was set to 51 na and the working distance was 9 mm . the temperature of the substrates was tracked with a fluke 52 thermocouple attached to a multimeter . for the fto measurements , constant contact of the tip of the defector was maintained throughout the experiment . for the thermocouple measurements , the tip of the detector was dipped in fe ( eh ) 3 . the substrate & amp ; thermocouple was placed 2 cm from the lamp . temperature values were recorded every 5 mm . all amorphous film examples could also be fabricated on different substrates including fluorine doped tin oxide ( fto ), glass , copper , titanium , nafion membrane , plastic and glassy carbon using the same protocols as described in the examples above . it will be understood by those of skill in the art that the scope of the claims should not be limited by the preferred embodiments set forth in the examples , but should be given the broadest interpretation consistent with the description as a whole . 1 . k . nomura , h . ohta , a . takagi , t . kamiya , m . hirano , h . hesono , room - 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