Current Research Topics

Ammonia synthesis and decomposition

(collaboration with Dr. S.-Y. Chen (AIST), Prof. H.-Y. Chen (NTHU), and Prof. H.-H. Chou (NTHU))

Ammonia (NH3) is essential for agriculture and energy. Industrially, NH3 is mainly synthesized by the Haber-Bosch process using iron-based catalysts at high pressure (20-40 MPa) and temperature (400-600°C), a process consuming >1% of the world's energy and contributing to ~1% of greenhouse gas emission every year. Obviously, a more sustainable process is needed. On the other hand, NH3 is envisioned as a carbon-free energy storage vector, or a H2 carrier, in a sustainable energy system for the future. Energy storage in NH3, in form of chemical bonds, would enable much greater uptake of intermittent renewable power sources (e.g., solar, tidal and wind), and the stored energy can be delivered by on-demand production of H2 from the decomposition of NH3 in combination with fuel cells. To realize such a prospect, it is pivotal to develop highly efficient catalysts for ammonia synthesis and decomposition. We are developing ruthenium-based and nitride-based nanocomposite catalysts for the reactions, aiming to gain more insights into the reaction mechanisms and to rationally design more efficient catalysts for low-temperature processes.

Hydrogenation of carbon dioxide

Reducing carbon dioxide (CO2) emission is an extensive and long-term task. In principle, there are three strategies with this regard: reduction of the amount of CO2 produced, capture and storage of CO2, and transformation and usage of CO2. As an economical and renewable carbon source, CO2 turns out to be an attractive C1 building block for making chemicals. Currently, the use of CO2 as feedstock in limited to a few industrial processes, a fact that is primarily due to the thermodynamic stability of CO2. Hydrogen (H2) is a high-energy molecule and can be used as a reagent for CO2transformation. We focus on the development of various types of nickel-based catalysts for CO2 hydrogenation to produce molecules including methane and methanol  at ambient pressure.

Selective oxidation of light alkanes

(collaboration with Dr. S.-F. Yu (IoC, AS))

Methane is an abundant feedstock on earth. Methane is burned for heating and electrical power generation, and it can be transformed into value-added chemicals through the energy-intensive production of syngas. It remains attractive but challenging to directly convert methane to valuable chemicals. Methanol, a liquid under standard conditions, is an important chemical in industry and is a suitable energy carrier for future society. The direct oxidation of methane to methanol under moderate conditions is a highly desirable reaction and is considered to be one of the holy grail reactions of chemical and catalysis research. We aim to design copper-based and other nanocomposite catalysts and to access different strategies for the selective oxidation of methane and light alkanes under mild conditions.

Photocatalytic water splitting & carbon dioxide reduction

Direct photocatalytic conversion of water and CO2 into solar fuels (e.g., H2, CO and CH3OH ) is an attractive prospect, serving to provide an alternative energy source on a renewable basis. Photocatalytic reactions involve the utilization of semiconductor materials to absorb light and generate electrons and holes for reduction and oxidation reactions, respectively. In most cases, cocatalysts composed of noble metals with proper Fermi level or metal oxides with suitable band positions are necessary to suppress charge recombination and enhance photocatalytic activity. For the overall water splitting, the oxidation half reaction involves the transfer of four electrons to produce O2 and is more difficult to proceed. Photocatalytic CO2 reduction with water as a reductant is even more challenging. In our group, we focus on developing the tantalum-based pyrochlore nanocrystals and their nanocomposites and exploring their activity for both photocatalytic reactions.