Interfacial electric fields catalyze Ullmann coupling reactions on gold surfaces.

The electric fields created at solid-liquid interfaces are important in heterogeneous catalysis. Here we describe the Ullmann coupling of aryl iodides on rough gold surfaces, which we monitor using the scanning tunneling microscope-based break junction (STM-BJ) and using mass spectrometry and fluorescence spectroscopy. We find that this Ullmann coupling reaction occurs only on rough gold surfaces in polar solvents, the latter of which implicates interfacial electric fields.