In 2D TMCs, the top and bottom basal planes have full coordination between the transition metal and sulfur, which are usually chemically inert. The prismatic edges, however, can exhibit various �facets� (the so?called S? or Mo? edge) and low?coordination sites similar to those on the surface of 0D nanoparticles, such as steps, kinds and corners. In addition, chalcogen vacancies appear when the lateral size of TMC sheets is reduced to the nanoscale, which associates with the formation of metallic edge sites. These features have been examined on single?crystal Au(111) supported MoS2 nanosheets prepared by CVD, with the atomic structures revealed by scanning tunneling microscopy (STM). These low?coordinated sites in 2D TMCs could be catalytically active sites, which has been demonstrated in cases such as hydrodesulfurization (HDS) and hydrogen evolution reactions (HER).Our group has recently developed an organic solution approach towards the synthesis of 2D TMCs with robust control over the size and composition. This was achieved via a two-step method, in which transition metal or transition metal oxide nanoparticles were first synthesized, and then applied as seeds for chalcogenation to form TMC nanoparticles; 2D TMCs were produced either by in situ solvothermal exfoliation, or by post-synthesis liquid exfoliation. For electrocatalytic applications these 2D TMCs were supported on ultrahigh?surface?area carbon black and the organic surfactants were removed by mild thermal or chemical treatment. Electrocatalytic studies show that, for example, MoS2 is highly active for the HER. The HER catalytic activity was further found to be improved by tailoring the composition of bimetallic 2D TMCs, through manipulation of the binding energy of hydrogen to Mo at the edges. Certain 2D TMCs have further been shown to be active for the oxygen reduction reaction (ORR). Our work indicate that 2D TMCs as earth?abundant and cost?effective materials hold great potentials for replacement of noble metals in (electro)catalytic applications.

2D transition metal chalcogenides for electrocatalytic applications

247th National Meeting (2014)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.