Researchers at Rice University have created a new catalyst on which light could make the main process of hydrogen production entirely emission-free. Currently, over half of the world’s hydrogen supply comes from SMR; it produces substantial greenhouse gases. With this new catalyst and its innovative approach to the use of light, the future of hydrogen production in the industry could look vastly different-with much higher purity and sustainability.
The catalyst is based on the design of an antenna-reactor copper-rhodium photocatalyst that breaks down methane and water vapor into hydrogen and carbon monoxide when exposed to light of a certain wavelength, without the need for heating from the outside. Such a feedstock has the added advantage of being an industrially useful product that does not contribute to greenhouse gases, unlike carbon dioxide. The pioneering approach by Rice Professors Peter Nordlander and Naomi Halas opens new pathways compared to SMR production with less negative impacts on the environment and towards hydrogen production.
Such a light-driven pathway to reaction is only possible because in 2011, labs by Halas and Nordlander demonstrated plasmons: collective oscillations of electrons in metallic nanoparticles, exposed to light to be an energetic way to produce high-energy “hot carriers”. Such energetic electrons and holes will be able to drive chemical reaction with much higher efficiency compared to conventional thermocatalysis where generation of such reactions is reliant on heat.
In the design of the new catalyst, copper nanoparticles capture and harvest energy, mimicking the antennae. Rhodium atoms and clusters perform a role of reactors in capturing methane and water molecules to the surface. It permits the efficient use of hot carriers produced by light in the overall process of driving the SMR reaction. The surface deposition of rhodium onto the nanoparticles also enhances catalyst stability, less susceptible to debilitation due to oxidation and coking, typical causes of deactivation in industrially used catalysts. Under illumination, these hot carriers facilitate cleaning processes against oxygen species and carbon deposits thus, acting as regenerators of the catalyst.
Besides this, the proposed photodriven SMR technology allows for the on-site production of hydrogen in mobile fueling stations or even directly at the vehicles with the environmentally benign source of energy for transportation. In this effort, we are supported by the Robert A. Welch Foundation and the Air Force Office of Scientific Research, and the promise of new photochemistry to bring toward a more sustainable future is highlighted in this research. Thus, the new research marks a giant leap in cleaning energy solutions by removing hydrogen production emissions.