Electronic Surface Properties of the Co(101̅15) Crystal

Ammonia plays a central role in global fertilizer production and is increasingly recognized as a versatile energy carrier within emerging sustainable energy systems. The La/Co system is an example of an ammonia production catalyst with efficiency greater than that of current commercial catalysts. A spin-mediated promotion mechanism has been proposed as the mechanism behind the catalytic activity. While the resulting catalytic promotion is clearly observed, the change in spin has not yet been directly demonstrated experimentally. In the present study, scanning tunneling microscopy (STM) and scanning tunneling spectroscopy (STS) measurements were performed on a Co(101̅15) crystal and compared with density functional theory (DFT) calculations. The purpose was to obtain an understanding of the properties of the Co(101̅15) crystal surface as a first step to verify the electronic structure changes behind spin promotion. The STM results revealed a stepped surface as expected. A comparison between the STS measurements and DFT calculations indicated that the spin of the Co atoms changes across the surface. This could potentially be caused by adsorbates on the crystal surface or by an interaction between the STM tip and the sample surface.