Diamond formation in an electric field under deep Earth conditions

Electric Field Effects in Flash Joule Heating Synthesis

Flash Joule heating has emerged as an ultrafast, scalable, and versatile synthesis method for nanomaterials, such as graphene. Here, we experimentally and theoretically deconvolute the contributions of thermal and electrical processes to the synthesis of graphene by flash Joule heating. While traditional methods of graphene synthesis involve purely chemical or thermal driving forces, our results show that the presence of charge and the resulting electric field in a graphene precursor catalyze the formation of graphene. Furthermore, modulation of the current or the pulse width affords the ability to control the three-step phase transition of the material from amorphous carbon to turbostratic graphene and finally to ordered (AB and ABC-stacked) graphene and graphite. Finally, density functional theory simulations reveal that the presence of a charge- and current-induced electric field inside the graphene precursor facilitates phase transition by lowering the activation energy of the reaction. These results demonstrate that the passage of electrical current through a solid sample can directly drive nanocrystal nucleation in flash Joule heating, an insight that may inform future Joule heating or other electrical synthesis strategies.

Formation and growth characteristics of nanostructured carbon films on nascent Ag clusters during room-temperature electrochemical CO2 reduction

Synthesis of carbon nanostructures at room temperature and under atmospheric pressure is challenging but it can provide significant impact on the development of many future advanced technologies. Here, the formation and growth characteristics of nanostructured carbon films on nascent Ag clusters during room-temperature electrochemical CO2 reduction reactions (CO2RR) are demonstrated. Under a ternary electrolyte system containing [BMIm]+[BF4]-, propylene carbonate, and water, a mixture of sp2/sp3 carbon allotropes were grown on the facets of Ag nanocrystals as building blocks. We show that (i) upon sufficient energy supplied by an electric field, (ii) the presence of negatively charged nascent Ag clusters, and (iii) as a function of how far the C-C coupling reaction of CO2RR (10-390 min) has advanced, the growth of nanostructured carbon can be divided into three stages: Stage 1: sp3-rich carbon and diamond seed formation; stage 2: diamond growth and diamond-graphite transformation; and stage 3: amorphous carbon formation. The conversion of CO2 and high selectivity for the solid carbon products (>95%) were maintained during the full CO2RR reaction length of 390 min. The results enable further design of the room-temperature production of nanostructured carbon allotropes and/or the corresponding metal-composites by a viable negative CO2 emission technology.