On the STM imaging contrast of graphite: towards a “true’' atomic resolution

Different phenomena observed in the high-resolution images of graphite by scanning tunneling microscopy (STM) or atomic force microscopy (AFM) such as the asymmetry in the charge density of neighboring carbon atoms in a hexagon, the high corrugation amplitudes and the apparent absence of point defects has led to a controversial discussion since the first published STM images of graphite. Different theoretical concepts and hypotheses have been developed to explain these phenomena. Despite these efforts a generally accepted interpretation is still lacking. In this paper we discuss a possible imaging mechanism based on mechanical considerations. Forces acting between tip and sample are taken into account to explain the image contrast. We present for the first time a direct atomic resolution of the graphite hexagonal structure by transmission electron microscopy (HRTEM), revealing the expected hexagonal array of atoms and the existence of several types of defects. We discuss the possibility that the STM image of graphite is a result of convolution of the electronic properties and the atomic hardness of graphite

Chemical energy storage enables the transformation of fossil energy systems to sustainability

The quest for the sustainable energy transition requires replacing fossil fuels by renewable electricity (RE). Systems of energy supply consist of both electrons and molecules as energy carriers. It is thus essential to interconvert both types of carriers. Capitalizing on the intrinsic efficiency of using electrons it is desirable to electrify in the sustainable system more end energy applications than in the fossil system being fully based upon molecular carriers. This does not eliminate the need to retain molecules as energy carriers in a substantial fraction of a whole energy system. The application “energy storage” as example compensates the volatility of RE and is thus critical to any energy transition. Chemical energy conversion (CEC) is the critical science and technology to eliminate fossil fuels, to create circular energy economies and to enable global exchange of RE. This paper describes generic structural features and dimensions of CEC