Heterogeneous catalysis is one of the areas where colloidal nanocrystals can be most useful. Nanocatalysts that have been used to make chemical reactions more efficient are increasingly in demand for clean and sustainable chemical processes in recent years as humanity undergoes global warming and drastic climate change. Among the catalytic reactions for sustainable chemical processes, there are relatively simple reactions such as hydrogen evolution reaction (HER), oxygen evolution reaction (OER), and oxygen reduction reaction (ORR), in which the reactants and products consist only of hydrogen, oxygen, and water. On the other hand, in the case of catalytic reactions that produce value-added chemicals using biomass or atmospheric CO₂ as a reactant, the reaction pathway is complex, and multiple products are generated during catalysis. Therefore, it is essential to construct the proper active sites in nanocatalysts that can facilitate or suppress the specific reaction pathway for increasing the selectivity of desired products.
In Chapter 1, the cutting-edge strategies for regulating the active sites in nanocrystals and applications in selective conversion, including furfural hydrogenation and electrochemical CO₂ reduction, are introduced. After the comprehensive introduction of background, Chapter 2 describes the synthesis of Pd₃Pb alloy nanosponges and their applications for selective conversion of furfural to furfuryl alcohol. Numerous active sites of nanosponge structure and optimized surface energy improved the conversion rate and product selectivity of sponge-like Pd₃Pb nanocatalysts simultaneously. Chapter 3 contains the synthesis of hierarchical Cu₂O nanocrystals via a microfluidic system and their catalytic performance for the selective production of C2+ products during the electrochemical CO₂ reduction reaction. The mosaic-like structure consisting of Cu and Cu₂O phases generated on the surface of hierarchical Cu₂O nanocrystal derived from surface reconstruction during the CO₂ reduction increase the catalytic selectivity for C2+ products by promoting C-C coupling.