Effect of Wetting on the Ability of Nanomaterials to Act as Effective Catalysts

Michael W Cross,Walter J Varhue,M Ryan Mcdevitt,Darren L Hitt

doi:10.4236/aces.2016.65047

Abstract

The ability of some nanostructured materials to perform as effective heterogeneous catalysts is potentially hindered by the failure of the liquid reactant to effectively wet the solid catalyst surface. In this work, two different chemical reactions, each involving a change of phase from liquid to gas on a solid catalyst surface, are investigated. The first reaction is the catalyzed decomposition of a H2O2 monopropellant within a micro-chemical reactor chamber, decorated with RuO2 nanorods (NRs). The second reaction involves the electrolysis of dilute aqueous solutions of H2SO4 performed with the cathode electrode coated with different densities and sizes of RuO2 NRs. In the catalyzed H2O2 decomposition, the reaction rate is observed to decrease with increasing catalyst surface density because of a failure of the liquid to wet on the catalyst surface. In the electrolysis experiment, however, the reaction rate increased in proportion to the surface density of RuO2 NRs. In this case, the electrical bias applied to drive the electrolysis reaction also causes an electrostatic force of attraction between the fluid and the NR coated surface, and thus assures effective wetting.

Highlights

A properly functioning catalyst acts to lower the activation energy required to transform chemical reactant species into chemical reaction products
The reaction rate increased in proportion to the surface density of RuO2 NRs
Decomposition of H2O2 Monopropellant The image shown in Figure 2 is the catalyzed decomposition of a 30% aqueous solution of H2O2 monopropellant flowing in a microchannel coated with RuO2 NRs

Summary

Introduction

A properly functioning catalyst acts to lower the activation energy required to transform chemical reactant species into chemical reaction products. An electrocatalyst promotes this transition with the accompanying transfer of electrical charge. 2) An electrode coated with nanomaterials may contain abrupt geometric features which produces a high electric field region near the electrode/catalyst surface. In this investigation, the same RuO2 NR coating was used to enhance the reactivity of two different chemical reaction systems. The experimental results in both cases were analyzed in light of the relative degree of wetting that occurs on the nanomaterial catalyst surface and was found to be a significant factor in the coating’s ability to function as a catalyst [4]-[13]

Methods

Results

Conclusion