In the electrochemical conversion of carbon dioxide, high currents need to be employed to obtain large production rates, thus implying that mass transport of reactants and products is of crucial importance.This aspect...In the electrochemical conversion of carbon dioxide, high currents need to be employed to obtain large production rates, thus implying that mass transport of reactants and products is of crucial importance.This aspect can be investigated by employing a model that depicts the local environment for the reduction reactions. Simultaneously, electrochemical impedance spectroscopy, despite being a versatile technique, has rarely been adopted for studying the mass transport features during the carbon dioxide(CO_(2))electroreduction. In this work, this aspect is deeply analyzed by correlating the results of impedance spectroscopy characterization with those obtained by a bubble-induced mass transport modeling under controlled diffusion conditions on a gold rotating disk electrode. The effects of potential and rotation rate on the local environment are also clarified. In particular, it has been found that CO_(2) depletion occurs at high kinetics when the rotation is absent, giving rise to an increment of the competing hydrogen evolution reaction. This feature reflects in an enlargement of the diffusion resistance, which overcomes the charge transport one.展开更多
In many optical applications,there is an increasing need for dynamically tunable optical elements that are able to shape the wavefront of light‘on demand’.In this work,an elastomeric easy-to-fabricate optical elemen...In many optical applications,there is an increasing need for dynamically tunable optical elements that are able to shape the wavefront of light‘on demand’.In this work,an elastomeric easy-to-fabricate optical element whose transmission functions can be reversibly phase configured by visible light is demonstrated.The light responsivity of proper azopolymers incorporated within an elastomeric matrix is exploited to induce a light-controlled graded refractive index(GRIN)distribution within the bulk compound.The induced refractive index distribution is continuous and conformal to the intensity profile of the illumination at moderate power.A 100mW doubled-frequency Nd:YAG Gaussian beam focused to a 650μm waist is shown to induce a maximum relative refractive index change of~0.4%in the elastomeric matrix,with an approximately parabolic profile.The restoring characteristics of the elastomeric matrix enable full recovery of the initial homogeneous refractive index distribution within a few seconds when the incident laser is switched off.As an exemplary application,the configurable GRIN element is used in a microscope-based imaging system for light control of the effective focal length.展开更多
文摘In the electrochemical conversion of carbon dioxide, high currents need to be employed to obtain large production rates, thus implying that mass transport of reactants and products is of crucial importance.This aspect can be investigated by employing a model that depicts the local environment for the reduction reactions. Simultaneously, electrochemical impedance spectroscopy, despite being a versatile technique, has rarely been adopted for studying the mass transport features during the carbon dioxide(CO_(2))electroreduction. In this work, this aspect is deeply analyzed by correlating the results of impedance spectroscopy characterization with those obtained by a bubble-induced mass transport modeling under controlled diffusion conditions on a gold rotating disk electrode. The effects of potential and rotation rate on the local environment are also clarified. In particular, it has been found that CO_(2) depletion occurs at high kinetics when the rotation is absent, giving rise to an increment of the competing hydrogen evolution reaction. This feature reflects in an enlargement of the diffusion resistance, which overcomes the charge transport one.
基金from the Italian Flagship Project NANOMAX(Progetto Bandiera MIUR PNR 2011–2013).
文摘In many optical applications,there is an increasing need for dynamically tunable optical elements that are able to shape the wavefront of light‘on demand’.In this work,an elastomeric easy-to-fabricate optical element whose transmission functions can be reversibly phase configured by visible light is demonstrated.The light responsivity of proper azopolymers incorporated within an elastomeric matrix is exploited to induce a light-controlled graded refractive index(GRIN)distribution within the bulk compound.The induced refractive index distribution is continuous and conformal to the intensity profile of the illumination at moderate power.A 100mW doubled-frequency Nd:YAG Gaussian beam focused to a 650μm waist is shown to induce a maximum relative refractive index change of~0.4%in the elastomeric matrix,with an approximately parabolic profile.The restoring characteristics of the elastomeric matrix enable full recovery of the initial homogeneous refractive index distribution within a few seconds when the incident laser is switched off.As an exemplary application,the configurable GRIN element is used in a microscope-based imaging system for light control of the effective focal length.
