By replacing catalysts made of expensive noble metals like platinum with cheaper, earth-abundant materials, researchers have taken a step toward enabling the large-scale production of hydrogen from sunlight and water. In a recent study, the researchers have demonstrated that catalysts made of molecular clusters based on molybdenum and sulphur can generate hydrogen from sunlight at rates comparable to those of platinum.
The researchers, led by Professor Ib Chorkendorff from the Technical University of Denmark, with coauthors from institutions in Denmark and the US, have published their study in a recent issue of Nature Materials.
As the researchers explain in their study, producing fuels from sunlight could lead to the development of a sustainable energy system, without the need for fossil fuels. Sunlight can be used to produce a variety of carbon-based solar fuels such as methanol and methane, but the simplest solar fuel to produce is hydrogen. In a typical solar hydrogen system, photovoltaic panels turn sunlight into electricity that is then used to extract hydrogen from water.
One type of solar hydrogen system is a chemical solar cell, which can harvest a large part of the solar spectrum and use it to generate hydrogen from water. Chemical solar cells consist of many pillars, with the top half of each pillar made of a photoanode that absorbs the blue part of the solar spectrum, and the bottom half made of a photocathode that absorbs the red part. When blue light is absorbed, it oxidizes water into oxygen and protons. The protons migrate through a membrane in which the pillars are embedded, ending up at the photocathode. As red light is absorbed, catalysts attached to the sides of the pillars reduce the protons to hydrogen.