Solar photochemistry with 2D materials

Ultrathin two-dimensional (2D) semiconductors such as monolayer (ML) MoS₂ or WS₂ are fascinating photocatalyst candidates for solar fuels production because photo-excited charge carriers need only traverse three atoms to reach and react with molecules at the interface, maximizing the possibility of carrier extraction before recombination. However, like with electrochemical energy storage materials heterogeneity is also a major problem in the 2D materials community. The electronic structure depends on the number of layers and chemical reactivity depends on the number of exposed basal plane or edge sites, which is not straightforward to synthetically control or characterize.

To tackle the heterogeneity issue, my laboratory has developed spatially resolved measurements to overcome the 2D materials heterogeneity challenge. The driving force behind our early discoveries was the development of a correlated laser reflection/photocurrent mapping technique that spatially resolved light-induced electrochemical reactions from single nanosheets. This single-nanosheet photoelectrochemical approach revealed critical structural/property relationships that remain hidden in ensemble-averaging measurements.

We published nine key research articles in the field of 2D semiconductor photoelectrochemistry, including the first reports on the photoelectrochemical properties of pristine, isolated monolayers (MoS₂, MoSe₂, WS₂, WSe₂) and monolayer heterojunctions (MoS₂/WS₂ and MoSe₂/WSe₂). We have extensive expertise in preparing and characterizing 2D semiconductor electrodes and are well-positioned to make breakthrough discoveries in 2D semiconductor (photo)electrochemistry.