Two Dimensional Metal-Organic Complexes on Surface as A Novel Catalytic System for Energy Conversion

GRUMELLI DORIS; WURSTER BENJAMIN; STEPANOW SEBASTIAN; KERN KLAUS

Praga

Congreso; The 63rd Annual Meeting of the International Society of Electrochemistry; 2012

International Society of Electrochemistry

The presented work employs strategies from supramolecular chemistry to design twodimensionalmetal-organic coordination networks (2D MOCNs) on electrode surfacesfor applications in energy conversion and fuel production. In this study we show firstresults on the electrochemical activity of 2D MOCNs prepared under vacuumconditions.2D MOCNs consist of arrays of organic ligands coordinated with metal atoms selfassembledon metal surfaces. The lateral metal–organic coordination bonds providehigh chemical stability to these networks compared to those stabilized by hydrogenbonds or van-der-Waals forces. A particular and unique feature of these 2D-MOCNs isthe presence of low-coordinated metal centers offering multiple functional propertiesthat can be tuned by the coordination environment. Due to the similarity withcatalytically active sites in biological systems these structures are considered to havepromising properties in electrocatalysis, i.e., for the conversion of electrical energy intochemical fuels and vice versa [1].In this work, we will present the first electrochemical results of 2D MOCNs preparedvia self-assembly of aromatic carboxylic acids and iron atoms on a Au(111) surfaceunder ultra-high vacuum (UHV) conditions. The composition and structure of thenetwork are controlled and characterized by scanning tunneling microscopy (STM) inUHV before and after the electrochemical measurements. The electrochemicalproperties are determined using an electrochemical-adapted UHV setup with acontrolled sample transfer between both environments to prevent contamination.Typical features for a Au(111) single crystal surface in both STM and electrochemicalmeasurements were observed. These results demonstrate an effective and clean transferprocess. The deposition of aromatic carboxylic acids onto Au(111) was conducted byevaporation of the molecules in UHV at adequate sublimation temperatures withcontrolled surface coverage. Depending on the specific aromatic carboxylic acids used,typical molecular networks were obtained according to previously published results.The electrochemical behavior of the molecular networks is very similar to thoseobtained from preparation from solution [2]. The metal-organic Fe-carboxylate networkswere investigated for the first time and show clear changes in the electrochemicalresponse. The results point out that surface-confined metal-organic complex ispromising candidates for the design of novel electrocatalysts.