Microstructure and electrochemical properties of nanocrystalline diamond and graphene hybridized films

Abstract

We have successfully grown a series of nanocrystalline diamond and graphene hybridized (NCD-G) films with various morphologies and compositions of grain boundaries by adjusting the growth pressure by hot-filament chemical vapor deposition and extensively investigated their electrochemical performances. In the case of low growth pressure, such as 1.0 and 1.3 kPa, there is a large amount of graphene in the NCD-G films, and graphene exhibits better crystallinity and a bigger size. These produce quicker electron exchange, rising background current, and reduced potential window. As the growth pressure increases to above 1.6 kPa, the grain boundaries are reduced, so that the NCD-G films possess fewer graphene components. As the growth pressure is 1.6 kPa, the “bridge”-like graphene stands on the neighboring nanocrystalline diamond grains, providing degraded electrochemical properties of smaller redox current. With the growth pressure further increasing to 1.9 kPa, the least trans-polyacetylene wrapped diamond grains produce slightly rising redox current, wider potential windows, and smaller background current. Graphene exists as a small slice and is distributed parallel with the grains with the growth pressure increasing to 2.2 kPa, exhibiting a significant rising redox current accompanied with wider potential windows and lower background current. It is concluded that the high diamond content is beneficial to enlarge the potential windows and decrease the background current, and the graphene components take advantage of improving the redox current. Moreover, the ordered and small graphene surrounding the diamond grains is positive to improve the electrochemical response without the rising background current. Thus, we prepare an electrochemical electrode material with excellent performance by adjusting the state and the content of each component in the NCD-G films.