Silicon Oxide-Encapsulated Platinum Thin Films as Highly Active Electrocatalysts for Carbon Monoxide and Methanol Oxidation

Abstract

Direct alcohol fuel cells (DAFCs) have the potential to provide high power densities for transportation and portable applications. However, widespread use of DAFCs is greatly hindered by the lack of anode electrocatalysts that are inexpensive, stable, resistant to CO poisoning, and highly active toward alcohol oxidation. One promising approach to overcoming these challenges is to combine transition metal catalysts with oxide supports, such as SiO2, which are known to enhance alcohol oxidation by promoting CO oxidation at oxide|metal interfacial regions through the so-called bifunctional mechanism. Herein, we report on a membrane-coated electrocatalyst (MCEC) architecture for alcohol oxidation, in which a thin, permeable silicon oxide (SiO x ) nanomembrane encapsulates a well-defined Pt thin film (SiO x |Pt). A key advantage of the MCEC design compared to oxide-supported nanoparticles is that the oxide encapsulation maximizes the density of oxide|metal interfacial sites between the SiO x and Pt catalyst. A series of electroanalytical measurements indicates that the SiO x overlayers provide proximal hydroxyls, in the form of silanol groups, which can enhance alcohol oxidation by interacting with adsorbed intermediates at SiO x |Pt interfaces. Thanks to these interactions, the SiO x |Pt electrocatalysts exhibit significantly enhanced CO oxidation activity and roughly a 2-fold increase in the maximum methanol oxidation current density compared to bare Pt. Overall, these demonstrations highlight the potential of using SiO x -based MCECs for CO tolerant and highly active methanol oxidation electrocatalysts.

Controlling Metallic Nanoparticle Redox Properties for Improved Methanol Oxidation Reaction Electrocatalysis

“…At a current density of 0.05 mA cm −2 the potentials are 130 mV, 80 mV and 60 mV more positive than monometallic Pd nanocrystals for the Au−Pd nanocrystals with thin, medium and thick shell, respectively. This is due to the reactivation of the surface at more positive potentials for oxidation of freshly adsorbed methanol, caused by the PdO reduction happening at more positive potentials. This shift results in 8.5x, 3.4x and 2.6x higher charge densities in the cathodic scan (q cat ) compared to Pd nanocrystals for the Au−Pd nanocrystals with thin, medium and thick shell, respectively (Table ).…”

An Analysis of Research on Membrane-Coated Electrodes in the 2001–2019 Period: Potential Application to CO2 Capture and Utilization

“…The papers published in the most productive journals resulting from the bibliometric search deal with the surface modification of carbon-based electrodes aimed at improving chemical sensing properties in biomedical or environmental applications. There is a significant presence of journals regarding surface and interface science and technology, such as ACS Interface Applied Materials, ACS Catalysis, and ChemElectroChem, which are already focusing on the effect of the coated thin film on the electrocatalytic behavior of the electrode [28,32,33].…”

“…. ) [28,39,40] and metal oxide (mostly, SiO x ) matrices to metal catalyst nanoparticles [32,33,46] and Nafion as the principal solid polymer electrolyte membrane [36,47]. In fact, conductive poly(4-vinyl pyridine) (PVP) polymer and hydrophilic chitosan biopolymer were coated over Cu electrodes before the time range of this study in electrochemistry studies for electroreduction reaction [48] and enhancing Cu sensitivity in humidity sensors [49] and used again for the development of coated electrodes [28,50].…”

A Bibliometric Analysis of Research on Membrane Coated Electrodes in the 2001-2019 Period: Potential Application to CO2 Capture and Utilization

“…or H2 reduction in organic and aqueous media [20,57] This highlights the role of the membrane layer as a means of overcoming the trade-off between performance and stability, by focusing on the influence of the mass transfer through the nano -thick membrane coated layer on top of an electroactive surface to keep electrocatalytic performance. The embedding of metal ions into inorganic structures avoids the dissolution of metal nanoparticles and enhances the synergy of active sites for catalysis and transport [15,60] and facilitates the membrane film fabrication as a mixed matrix membrane containing metal ions [61]. This new electrode configuration invoke novel research regarding the study of how reaction and transport mechanisms influence the geometry of reactor configurations, in order to optimize the cathodic and anodic efficiencies, avoiding catalyst loss or deactivation, gas -phase flooding, and control product delivery [62].…”