the exemplary embodiments will be described in detail with reference to the accompanying drawings , wherein like reference numerals refer to like elements throughout . hereinafter , an electrochromic device according to exemplary embodiments will be described in detail with reference to the annexed drawings . the electrochromic device has an active layer that includes a catalyst to facilitate charge transfer and thereby provide superior chromic effects . first , a basic configuration of the electrochromic device will be described with reference to fig1 and an operation principle of the electrochromic device will be described with reference to fig2 . as illustrated in fig1 , the electrochromic device has a laminate structure including an active layer m 1 and an ion storage layer m 2 and light reflectivity of the active layer m 1 is changed in response to an external stimuli . the active layer m 1 includes a light control material which changes optical properties according to concentration of a certain element . the light control material may be a mg alloy where the mg alloy is interconverted between a reflective state and a transmission state according to hydrogen ion ( h + ) concentration . a mg alloy having a low hydrogen ion ( h + ) concentration reflects incident light to render a metal color and a mg alloy having a high hydrogen ion ( h + ) concentration due to hydrogen ions bonded thereto provides a transparent state due to superior transmittancy . the ion storage layer m 2 includes a material containing a certain element such as hydrogen ( hereinafter , referred to as a “ conversion material ”). the conversion material releases or absorbs the certain element ( for example , hydrogen ) in response to external stimuli such as an injection and release of electric charges ( electrons or holes ) or light radiation . hereinafter , a principle of the movement of hydrogen ion ( h + ) from the ion storage layer m 2 to the active layer m 1 , or from the active layer m 1 to the ion storage layer m 2 by injection and release of electric charges , will be described with reference to fig2 . in this process , ions of the certain element ( hydrogen ) changing optical properties of the active layer m 1 are moved based on transfer of electric charges , rather than electrochemical reaction . both the active layer m 1 and the ion storage layer m 2 are capable of absorbing and releasing hydrogen and have electrical conductivity capable of moving electric charges ( electrons or holes ) and ions . referring to fig2 ( a ), fig2 ( a ) illustrates an initial state of the active layer m 1 and the ion storage layer m 2 shown in fig1 . in the initial state of the active layer m 1 and the ion storage layer m 2 , balance ( equilibrium ) between the active layer m 1 , which does not substantially store hydrogen , and the ion storage layer m 2 , which previously stores hydrogen , is kept . the active layer m 1 reflects light and renders an inherent metal luster because a sufficient concentration of hydrogen is not present in the active layer m 1 . next , as illustrated in fig2 ( b ), electrons are injected into the active layer m 1 and the active layer m 1 is rich in electrons when a negative voltage is applied to the active layer m 1 and a positive voltage is applied to the ion storage layer m 2 . meanwhile , electrons are released from the ion storage layer m 2 and at the same time , holes are injected thereto . the holes injected into the ion storage layer m 2 are moved from the ion storage layer m 2 to the active layer m 1 . as a result , hydrogen ions ( h + ) are readily released from the ion storage layer m 2 , while a large amount of hydrogen ions ( h + ) injected from the ion storage layer m 2 is stored in the active layer m 1 . for this reason , hydrogen ion ( h + ) balance between the active layer m 1 and the ion storage layer m 2 is not kept . the active layer m 1 tends to retain hydrogen , and hydrogen ions ( h + ) released from the ion storage layer m 2 are moved to the active layer m 1 . as a result , as illustrated in fig2 ( c ), a new balance state is created . in this state , hydrogen ions ( h + ) moved to the active layer m 1 bond to the light control material , thus making the active layer m 1 transparent . in brief , the reaction described above is represented by m 1 + m 2 ( h )→ m 1 ( h )+ m 2 . m 1 ( h ) and m 2 ( h ) represent a state in which hydrogen is adhered to the active layer m 1 and a state in which hydrogen is adhered to the ion storage layer m 2 , respectively . as such , exchange of only hydrogen ions ( h + ) occurs between the active layer m 1 and the ion storage layer m 2 , and reactions associated with other ions do not occur therebetween . next , reverse reaction occurs when a polarity of applied voltage is reversed , as illustrated in fig2 ( d ). for this reason , the present state returns to the original balance state illustrated in fig2 ( a ). more specifically , electrons are injected into the ion storage layer m 2 and the ion storage layer m 2 is rich in electrons when a negative voltage is applied to the ion storage layer m 2 , and a positive voltage is applied to the active layer m 1 . meanwhile , electrons are released from the active layer m 1 , and at the same time , holes are injected thereto . the holes injected into the active layer m 1 are moved from the active layer m 1 to the ion storage layer m 2 . as a result , hydrogen ions ( h + ) are readily released from the active layer m 1 , while a large amount of hydrogen ions ( h + ) injected from the active layer m 1 is stored in the ion storage layer m 2 . for this reason , the new hydrogen ion ( h + ) balance between the active layer m 1 and the ion storage layer m 2 is not kept , the ion storage layer m 2 readily retains hydrogen , and hydrogen ions ( h + ) released from the active layer m 1 are moved to the ion storage layer m 2 . as a result , as illustrated in fig2 ( d ), the present state returns to the original balance state . in this state , the active layer m 1 renders an inherent metal luster because a sufficient concentration of hydrogen is not present in the active layer m 1 . hereinafter , a more detailed configuration of the electrochromic device according to an exemplary embodiment will be described . the electrochromic device according to an exemplary embodiment includes a catalyst material to facilitate oxidation - reduction reaction rate . in a related art electrochromic device , the catalyst material is dispersed as a layer around the active layer m 1 . in this case , there are problems in that light transmittance is deteriorated in a transmission mode and reaction rate is not uniform in the active layer m 1 . accordingly , an exemplary embodiment provides an electrochromic device including an active layer m 1 in which a catalyst material is uniformly dispersed in the form of a powder , a particle or an island . fig3 is a diagram illustrating an electrochromic device 10 a according to an exemplary embodiment , including an active layer m 1 in which a catalyst is dispersed in the form of a powder . referring to fig3 , the electrochromic device 10 a according to an exemplary embodiment includes a substrate m 5 , a transparent electrode m 4 provided on the substrate m 5 , an ion storage layer m 2 provided on the transparent electrode m 4 , an electrolyte layer m 3 provided on the ion storage layer m 2 , and an active layer m 1 containing a catalyst , provided on the electrolyte layer m 3 . furthermore , the electrochromic device 10 a according to an exemplary embodiment may further include a buffer layer to prevent oxidization of the metal contained in the active layer m 1 and the buffer layer may be provided between the active layer m 1 and the electrolyte layer m 3 . the substrate m 5 is provided to support the transparent electrode m 4 , the ion storage layer m 2 , the electrolyte layer m 3 and the active layer m 1 and may be composed of a transparent material . the ion storage layer m 2 includes a conversion material containing hydrogen . the conversion material includes transition metal oxide capable of transmitting and absorbing light . the transition metal oxide may include at least one selected from the group consisting of hydrogen ( h ), lithium ( li ), sodium ( na ), titanium ( ti ), molybdenum ( mo ) and niobium ( nb ). more specifically , the transition metal oxide may include at least one selected from the group consisting of tungsten oxides with hydrogen ( h x wo 3 ), titanium oxide ( tio 2 ), molybdenum oxide ( moo 3 ) and niobium ( nb 2 o 5 ). the ion storage layer m 2 receives electrons from the electrode using the conversion material and releases or absorbs hydrogen ions ( h + ). the ion storage layer m 2 may include an electrically conductive material , in addition to the conversion material . when the electrically conductive material is present in the ion storage layer m 2 , ion exchange between the active layer m 1 and the ion storage layer m 2 is facilitated . the electrically conductive material may be an ion - conducing material such as a liquid or solid electrolyte , a conductive polymer capable of conducting electric charges ( electrons or holes ), or the like . furthermore , the ion storage layer m 2 may further include a bonding material such as a binder resin , in addition to the conversion material or the electrically conductive material . the electrolyte layer m 3 is provided to facilitate ion exchange between the ion storage layer m 2 and the active layer m 1 . more specifically , the electrolyte layer m 3 may be provided between the ion storage layer m 2 and the active layer m 1 to exchange electric charges or ions between the ion storage layer m 2 and the active layer m 1 . when the electrolyte layer m 3 is disposed , hydrogen ions ( h + ) are readily moved via the electrolyte . the electrolyte layer m 3 may be provided in a liquid , gel or solid state and include tantalum oxide ( ta 2 o 5 ). furthermore , the electrochromic device 10 a according to an exemplary embodiment may be provided with a film containing a conductive polymer material , instead of the electrolyte layer m 3 . the conductive polymer material may serve as the electrolyte layer m 3 because it is doped with ions providing conductivity . the active layer m 1 includes a light control material which changes optical properties according to hydrogen ion ( h + ) concentration and the entirety or part of the active layer m 1 is formed with a light control material of a single layer or multiple layers . more specifically , the active layer m 1 may include an mg alloy material , and the mg alloy may exemplarily include magnesium ( mg ) and an alloy material at an atomic ratio of magnesium ( mg ) and an alloy material , i . e ., mg / alloy material , of 2 to 8 . the electrochromic device 10 a according to an exemplary embodiment has a structure in which a catalyst having a powdery form is uniformly dispersed in the active layer m 1 . the catalyst functions to facilitate oxidation - reduction reaction in the active layer m 1 and improve the overall conversion rate of the electrochromic device 10 a . the catalyst may include at least one selected from the group consisting of platinum ( pt ), palladium ( pd ), silver ( ag ) and gold ( au ). fig4 is a view illustrating a comparison in catalyst dispersion between a related art electrochromic device 10 a ′ and the electrochromic device 10 a according to an exemplary embodiment . as illustrated in fig4 ( a ), in the case of a related art electrochromic device 10 a ′, the catalyst is formed in the form of a layer between the active layer m 1 ′ and the electrolyte layer m 3 ′. thus , a conversion rate at the interface a 1 between the catalyst layer c ′ and the active layer m 1 is high , but a conversion rate in an opposite part a 2 is relatively low . as a result , the overall conversion rate of the electrochromic device 10 a ′ is not advantageous . on the other hand , in the case of the electrochromic device 10 a according to an exemplary embodiment , a catalyst c - 1 having a powdery form is uniformly dispersed in the active layer m 1 , as illustrated in fig4 ( b ), thereby resulting in uniform and rapid oxidation - reduction reactions over the entire region of the active layer m 1 . in addition , in the case of a related art electrochromic device 10 a ′, the catalyst is formed in the form of a layer , thus causing a problem of deterioration in light transmittance in a transmission mode ( see fig4 ( a )). however , in the case of the electrochromic device 10 a according to an exemplary embodiment , a catalyst c - 1 having a powdery form is uniformly dispersed in the active layer m 1 , thereby improving transmittance in a transmission mode ( see fig4 ( b )). furthermore , in the electrochromic device 10 a according to an exemplary embodiment , the catalyst c - 1 having a powdery form is added to the active layer m 1 , thereby making a crystal structure of mg alloy loose , increasing mobility of hydrogen ions ( h + ) and improving the overall conversion rate . hereinafter , an operation of the electrochromic device 10 a shown in fig4 will be described with reference to fig5 a to 5d . fig5 a to 5d are diagrams illustrating the operation of the electrochromic device 10 a shown in fig4 . fig5 exemplifies a case in which the active layer m 1 is provided as an alloy of magnesium and nickel ( mg 2 ni ), the electrolyte layer m 3 is provided as a solid , the ion storage layer m 2 is provided as h x wo 3 and the transparent electrode m 4 is provided as an ito material . referring to fig5 a , in the electrochromic device 10 a according to an exemplary embodiment , a negatively charged electrode of a power supply 20 is connected to the active layer m 1 and a positive power is connected to a transparent electrode m 4 . in the electrochromic device 10 a according to an exemplary embodiment , a negative power may be directly connected to the active layer m 1 without providing an additional electrode around the active layer m 1 because the active layer m 1 is composed of a metal material . furthermore , hydrogen is not substantially stored in the active layer m 1 . hydrogen is substantially stored in the ion storage layer m 2 and a balance is kept between the layers . thus , the active layer m 1 is present in the form of mg 2 ni and renders an inherent metal luster while the surface thereof reflects light . power is supplied to the electrochromic device 10 a keeping the balance via the power supply 20 . as illustrated in fig5 b , electrons are injected into the active layer m 1 when a negative voltage is applied to the active layer m 1 and a positive voltage is applied to an ito electrode . thus , the active layer m 1 is rich in electrons and the ion storage layer m 2 is rich in hydrogen ions ( h + ). for this reason , the hydrogen ion ( h + ) balance between the active layer m 1 and the ion storage layer m 2 is not kept , the active layer m 1 tends to retain hydrogen ions ( h + ), and hydrogen ions ( h + ) released from the ion storage layer m 2 are moved to the active layer m 1 via the electrolyte layer m 3 . in conclusion , the ion storage layer m 2 performs an oxidization reaction ( represented by the following reaction scheme 1 ) and the active layer m 1 performs a reduction reaction ( represented by the following reaction scheme 2 ). h x wo 3 → wo 3 + x h + + xe − reaction scheme 1 mg 2 ni + 4h + + 4 e − → mg 2 nih 4 reaction scheme 2 as a result , the magnesium - nickel alloy ( mg 2 ni ) of the active layer m 1 is bonded to hydrogen ions ( h + ) and optical property is changed to a transmission mode , as illustrated in fig5 c . next , power is supplied via the power supply 20 so that the electrochromic device 10 a , keeping the balance after the optical property is changed , implements a metal appearance again . as illustrated in fig5 d , electrons are injected into the ion storage layer m 2 through an ito electrode , when a positive voltage is applied to the active layer m 1 and a negative voltage is applied to the ito electrode . as a result , electrons are rich in the ion storage layer m 2 and hydrogen ions h + are relatively rich in the active layer m 1 . for this reason , the balance in hydrogen ion ( h + ) between the active layer m 1 and the ion storage layer m 2 is not kept , the ion storage layer m 2 tends to retain hydrogen ions ( h + ) and hydrogen ions ( h + ) released from the active layer m 1 are moved to the ion storage layer m 2 via the electrolyte layer m 3 . in conclusion , the ion storage layer m 2 performs a reduction reaction ( represented by the following reaction scheme 3 ) and the active layer m 1 performs an oxidization reaction ( represented by the following reaction scheme 4 ). wo 3 + x h + + xe − → h x wo 3 reaction scheme 3 mg 2 nih 4 → mg 2 ni + 4h + + 4 e − reaction scheme 4 as a result , the magnesium - nickel alloy of the active layer m 1 lacks hydrogen ions ( h + ) and the present state is returned back to a reflective state as shown in fig5 a . hereinafter , several aspects of the exemplary embodiments will be described in detail . fig6 is a diagram illustrating a structure of an electrochromic device 10 b according to another exemplary embodiment , including an active layer m 1 containing a catalyst c - 2 dispersed in the form of a particle therein . referring to fig6 , the electrochromic device 10 b according to another exemplary embodiment includes a substrate m 5 , a transparent electrode m 4 provided on the substrate m 5 , an ion storage layer m 2 provided on the transparent electrode m 4 , an electrolyte layer m 3 provided on the ion storage layer m 2 , and an active layer m 1 containing a catalyst c - 2 disposed in the form of a particle , provided on the electrolyte layer m 3 . furthermore , the electrochromic device 10 b according to an exemplary embodiment may further include a buffer layer to prevent oxidization of the metal contained in the active layer m 1 and the buffer layer may be provided between the active layer m 1 and the electrolyte layer m 3 . configurations of the substrate m 5 , the transparent electrode m 4 , the ion storage layer m 2 and the electrolyte layer m 3 are the same as those shown in fig3 and a repeated explanation thereof is omitted and only differences associated with the active layer m 1 are described . the electrochromic device 10 b according to another exemplary embodiment has a structure in which a catalyst c - 2 having a particle form is homogeneously dispersed in the active layer m 1 . the catalyst c - 2 functions to facilitate oxidation - reduction reaction in the active layer m 1 and to improve the overall conversion rate of the electrochromic device 10 b as compared to the case in which the catalyst layer c ′ is formed in the form of a layer . the catalyst may include at least one selected from the group consisting of platinum ( pt ), palladium ( pd ), silver ( ag ) and gold ( au ). fig7 is a diagram illustrating a structure of an electrochromic device 10 c according to another exemplary embodiment , including an active layer m 1 containing a catalyst c - 3 dispersed in the form of an island therein . referring to fig7 , the electrochromic device 10 c according to another exemplary embodiment includes a substrate m 5 , a transparent electrode m 4 provided on the substrate m 5 , an ion storage layer m 2 provided on the transparent electrode m 4 , an electrolyte layer m 3 provided on the ion storage layer m 2 , and an active layer m 1 containing a catalyst c - 3 disposed in the form of an island , provided on the electrolyte layer m 3 . furthermore , the electrochromic device 10 c according to an exemplary embodiment may further include a buffer layer to prevent oxidization of the metal contained in the active layer m 1 and the buffer layer may be provided between the active layer m 1 and the electrolyte layer m 3 . configurations of the substrate m 5 , the transparent electrode m 4 , the ion storage layer m 2 and the electrolyte layer m 3 are the same as those shown in fig3 and repeated explanation thereof is omitted and only the difference associated with the active layer m 1 is described . the electrochromic device 10 c according to an exemplary embodiment may include a catalyst c - 3 at the interface between the active layer m 1 and the electrolyte layer m 3 . the island form may be a semispherical shape as shown in fig7 , but it is not limited thereto . it is understood that the island form may include shapes that fall into any scope that is easily conceived by those skilled in the art . the catalyst c - 3 provided in the form of an island performs an inherent function of the catalyst of boosting an oxidation - reduction reaction rate and improving light transmittance in a transmission mode as compared to the case in which the catalyst layer c ′ is formed in the form of a layer . fig8 is a view illustrating a structure of an electrochromic device 10 d according to another exemplary embodiment , including an active layer m 1 of a multilayer film containing a catalyst dispersed in the form of an island . referring to fig8 , the electrochromic device 10 d according to an exemplary embodiment may include active layers m 1 a and m 1 b provided as a multilayer film and a catalyst c - 4 a and c - 4 b may be provided at the interface between the layers . the multilayer film may be provided as an mg alloy and concentrations of the magnesium and the alloy metal may be different . furthermore , the electrochromic device 10 d according to an exemplary embodiment may further include a buffer layer to prevent oxidization of the metal contained in the active layer m 1 and the buffer layer may be provided between the active layer m 1 and the electrolyte layer m 3 . the electrochromic device capable of improving reaction rate and improving light transmission in a transmission mode due to a catalyst disposed in the active layer m 1 has been described . herein , a case in which the active layer m 1 exhibits reversibly light transmission and reflection properties via movement of hydrogen ions h + is described as an example , but in addition to hydrogen ions ( h + ), lithium ions ( li + ) or sodium ions ( na + ) are moved between the active layer m 1 and the ion storage layer m 2 to cause conversion between transmission and reflection modes . in addition , the example in which the catalyst is dispersed in the active layer m 1 is not limited to the examples described above and it is understood that the aspects of the exemplary embodiments include other examples which may be apparent by those skilled in the art . as apparent from the foregoing , the electrochromic device according to embodiments described above has the following effects . first , a catalyst component is uniformly disposed in the form of a powder , particle or island , rather than in the form of a layer , in the active layer or at the interface between the active layer and the electrolyte layer or at the interface between the active layers , thereby improving light transmittance in a transmission mode . in addition , the catalyst may be homogeneously dispersed over the active layer , thereby improving reaction rate due to uniform reaction over the entire region of the active layer . in addition , the catalyst may be disposed over the active layer , thereby making a crystal structure of mg alloy looser , increasing mobility of protons and improving the overall conversion rate . although a few exemplary embodiments of the inventive concepts have been shown and described , it would be appreciated by those skilled in the art that changes may be made to these exemplary embodiments without departing from the principles and spirit of the invention , the scope of which is defined in the claims and their equivalents .