Sustainable systems for generating solar fuels

September 2, 2022, Thabassum Ahammad

I am a first-year Graduate Student working in the lab of Prof. Stephen Bradforth at the Department of Chemistry at USC. The central project towards my PhD focuses on designing systems for generating solar fuels.

student wearing a blue lab coat, blue gloves, and protective goggles pouring a neon yellow liquid into a glass container.
Preparation of sample to probe with ultrafast laser techniques.

The energy demand of humankind is accelerating day by day. The scarce abundance and detrimental environmental impacts of fossil fuels demand continuing the search for new eco-friendly and sustainable alternatives. The substantial energy punch of sunlight can be further utilized to solve the energy puzzle. Prototypical solar fuels such as hydrogen, ammonia, and methanol are produced from water, carbon dioxide and the sunlight. As we can see, capturing and storing of sunlight energy is a holy grail in chemical sciences. Solar fuels stand apart from other liquid fuels due to their renewable nature and environmental benefits and complement stored electricity solutions. Photocatalysis is a method inspired by natural photosynthesis that uses sunlight to split water and produce hydrogen, an efficient solar fuel.

As part of my research, I am investigating the molecular architecture of photocatalytic systems and contributing to designing the most affordable, efficient, and sustainable solar fuels. Implementation of sustainable photocatalytic systems made from earth-abundant components facilitates the generation of solar fuels with reduced capital and operational expenditure.

student in blue gloves and protective eye goggles holding a piece of paper in front of a laser
Aligning the optics in the ultrafast laser lab.

We know that renewable energy can be generated from solar panels and wind turbine farms. Electric vehicles are already a reality on our roads. However, batteries are cumbersome and expensive, and so heavy trucks, ships and airplanes will not run on batteries any time soon. So, to facilitate the transition of the energy infrastructure away from fossil fuels, humankind still needs to implement sustainable methods to power the world’s ever-increasing needs which will replace traditional fossil fuels. Solar fuels generated on a large scale are such a solution.

A photocatalytic system employed in solar fuel generation consists of three components: a photosensitizer, a catalyst, and a sacrificial charge donor. A photosensitizer absorbs sunlight, drives the charge generation process, and transfers the charge to the electrocatalyst. The electrocatalyst part of the system is well studied and quite well optimized. In this project, we will be focusing on the photosensitizer. We are designing and testing photosensitizers made of earth-abundant elements capable of achieving efficient charge transfer to electrocatalysts. We interrogate the systems with laser spectroscopy to elucidate the fundamental molecular behavior. The project is in collaboration with Prof. Mark Thompson lab from USC.

student pointing to red and blue graphs on a computer
Completing data analysis of ultrafast time-correlated single photon counting studies.

I thank Wrigley Institute for Environmental Studies, Prof. Stephen Bradforth, Prof. Mark Thompson and my colleagues for facilitating this exciting research.