There is an increasing demand for harvesting renewable and sustainable energy sources due to an accelerating global energy consumption. International Energy Outlook projected that renewables are expected to be fast-growing energy sources, increasing by an average of 2.3 percent per year between 2015 and 2040.^[1]  Hydrogen is an ideal renewable energy source that can be stored, is transportable, and can be converted to electricity using fuel cells in a clean manner, without producing CO_2.^[2] A key challenge, however, is to produce cost-effective and environmentally friendly renewable hydrogen on a large scale. Recently, sun-driven water splitting semiconductor materials (also known as photocatalysts) have drawn considerable attention because they require only sunlight and water as sustainable resources to produce hydrogen: semiconductor materials absorb energy from sunlight and facilitate the breakdown of water to hydrogen and oxygen as seen in Figure 1. Therefore, producing efficient, cost-effective water splitting semiconductors is the key to the advancement of solar-hydrogen production on a large scale. To do so, Dr. Wooesok Ki has initiated an exciting research project to develop simple, solution processable, template-assisted microporous semiconductor materials to improve water-splitting performance. One of the most critical steps in the construction of such semiconductors is to create a uniform monolayer of polystyrene microspheres (500 nanometers in size, roughly 200 times thinner than a human hair) on substrates.

Figure 2 shows a 6 µm x 6 µm  Atomic Force Microscope (Stockton's new AFM used in collaboration with Dr. Jason Shulman) image of a monolayer produced by students in Ki’s research group. In the parlance of crystallography, the spheres have been arranged in a close-packed hexagonal lattice. Interestingly, we have observed defects that are found in atomic crystals, most commonly grain boundaries and vacancies. These defects can be observed in Figures 3 and 4. 

Hydrogen is an ideal renewable energy source that can be stored, is transportable, and can be converted to electricity using fuel cells in a clean manner, without producing CO2.[2] 

Ultimately, our goal is to create nanoporous WS₂ and MoS₂ semiconductors by pouring molecular precursor solution into the template of a close-packed monolayer of polystyrene microspheres. Thermal processing will remove polystyrene microspheres, resulting in the formation of a two dimensional, ordered nanoporous structured semiconductor. Finally, the nanoporous MoS₂ and WS₂ semiconductor materials will be tested for efficiency of hydrogen evolution in collaboration with Rutgers University researchers.