Catalysis plays a central role in clean energy conversion, enabling a number of sustainable processes for future technologies. Today’s catalysts, however, are inadequate. The grand challenge is to develop advanced catalysts with the enhanced performance needed to enable widespread penetration of clean energy technologies.
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There are generally two strategies to improve the catalytic activity:
- Increasing the number of active sites, e.g., through increased loading or improved catalyst structuring to expose more active sites per gram
- Increasing the intrinsic activity of each active site
These two strategies are not mutually exclusive and can ideally be addressed simultaneously, leading to the greatest improvements in activity.
The methodology we use in our work is based on an interdisciplinary feedback loop between:
- Model catalyst synthesis
- Testing of catalytic activity and selectivity
Hydrogen evolution reaction
Hydrogen (H2) is one of the world’s most important chemicals and is e.g. used for synthesizing ammonia-based fertilizers. Electrochemical water splitting coupled to renewable energy sources, e.g., wind or solar, is a potential sustainable source of H2. Platinum is the most effective hydrogen evolution reaction (HER) catalyst, but high cost and scarcity may inhibit its wide spread use. We have investigated several non-precious metal HER catalysts, and transition metal sulfide and phosphides have been found to exhibit good HER activity.
Oxygen evolution reaction
Oxygen evolution reaction (OER) is the complementary half-reaction to the HER in electrochemical water splitting. Unfortunately, there are significant kinetic limitations for the OER.
Oxygen reduction reaction
Oxygen electrochemistry also plays a key role in fuel cells. Here the oxygen reduction reaction (ORR) is a major source of efficiency limitations due to sluggish kinetics. Improving both the activity and stability of the cathode catalyst in platinum-based polymer electrolyte fuel cells is a key technical challenge for next generation sustainable-energy conversion technologies.
Hydrogen peroxide (H2O2) is produced in the anthraquinone oxidation batch process that requires multiple energy-intensive reaction steps and is not economical for small-scale operations. A direct electrochemical route to H2O2 from O2 would be advantageous for decentralized small-scale continuous production.
Reducing CO2 into chemical feedstocks and liquid energy carriers with high energy density in either an electrochemical or a thermochemical process holds a vast and untapped potential. Fossil fuels in the current energy system could be replaced with sustainably produced synthetic fuels cycle in a closed carbon cycle with no net CO2 emission.
The production of ammonia from its elements through the Haber–Bosch process has been suggested to be the most important scientific discovery in the twentieth century. Without the fertilizers produced from this single catalytic process, the worldwide food production would only be able to sustain half of the current global population. The Haber-Bosch process requires high temperature and pressure and consequently, ammonia is produced in large, centralized plants. Electrochemical ammonia synthesis provides an attractive alternative, enabling the use of renewable electricity and decentralized production.
Single site catalysis
Traditional catalyst design based on nanoparticles is subject to fundamental limitations and for a number of reactions we have no viable catalyst today. The quantum regime of single atoms will significantly change their catalytic properties as compared to their nanoparticle counterparts. Furthermore, reducing the catalyst to a single active site motif may offer the possibility to tailor the selectivity to a desired product.