By: Mimi Martinez
In the quest for alternative fuel sources, we have successfully harnessed solar energy for electricity generation, but we are yet to discover methods to efficiently convert solar energy into fuel sources. Artificial photosynthesis offers a promising avenue for the future development of solar to fuel processes. Aimed at mimicking natural photosynthesis, artificial photosynthesis aims to cyclically use water, carbon, and sunlight in the generation and utilization of fuels.
Current research is making significant strides toward the development of viable fuel-generating solutions. Processes such as using solar energy to split water and produce hydrogen as a fuel, employing solar energy to reduce carbon dioxide with hydrogen to produce alcohols like ethanol and methanol, and exploring unconventional fuels like ammonia and hydrazine through the reduction of nitrogen with hydrogen using solar energy, are offering exciting new avenues for fuel solutions[i]. Simplifying these and other fuel creation processes can help speed up the development, commercialization, and adoption of these technologies.
One of the primary challenges in advancing solar to fuel technology lies in identifying suitable redox mediators. Redox mediator molecules act as intermediate electron carriers in simulating the natural solar-to-fuel processes. Finding redox mediators with appropriate redox potential (the tendency of a chemical species to gain or lose electrons, indicating its capacity for reduction or oxidation) and pH buffering capabilities is crucial[ii].
A new strategy aimed at altering the material structure of redox mediators to design a soluble redox mediator that can efficiently transfer multiple electrons. This process could help improve energy conversion processes like those in solar fuel production, made possible by the designed redox mediator’s ability to construct a combined photocatalysis and electrolysis system to ungroup H2 and O2 in solar-driven water splitting[iii].
Current e-fuel processes rely heavily on electrolysis, a method where an electric current is passed through a liquid or solution containing ions to produce fuels. However, the development of a mediator that can support a dual system involving both electrolysis and photocatalysis—where a photocatalyst accelerates a photoreaction—helps encourage the exploration of new possibilities for exploring photocatalysis and nature-inspired mechanisms of fuel creation.
Having successfully developed a multi-electronic redox mediator with pH buffering capacity, an appropriate redox potential, and a fast electron exchange rate, the research team that has created this new strategy has built a photocatalysis-electrolysis relay water splitting system. The system has a high solar energy storage capacity through photocatalytic O2 evolution with a high efficiency of the electrochemical reaction, of about 98.5%[iv].
Through these developments, the continued development of redox mediators and the integration of photocatalysis with electrolysis systems represent a promising path toward efficient, sustainable solar-to-fuel technologies that could revolutionize the energy landscape.
