Electrocatalysis with Atomically Precise Metal Nanoclusters

Colloidal nanoparticles have been extensively studied during the past decades due to their versatile applications in energy, pharmacy, catalysis, and optics etc. With the rapid development of chemical synthesis, nanoparticles with well controlled size, morphology and composition have been achieved. However, the precise structure of nanoparticles is still challenging to be resolved due to their polydispersity. Such uncertain structure of nanoparticles has limited the study of the structure-property relationship in various applications. In this context, it is of paramount importance to develop atomically precise nanoparticle system.

Atomically precise gold NCs (NCs) have emerged in recent nanoscience research, and this new class of nanomaterials has attracted wide interest in many applications owning to their intriguing properties and well-defined structures. Within the ultrasmall size regime (1-3 nm), Au NCs exhibit molecule-like quantized electronic structure because of the quantum confinement effect. The breakthrough in the synthesis and single-crystal X-ray diffraction analysis has led to the discovery of a large family of NCs with various unprecedented structures that were not observed in conventional nanoparticles. The special size regime of 1-3 nm and unique electronic properties of ultrasmall NCs provide new opportunities for diverse applications, including sensing, optical and catalysis. Unlike the polydisperse nanoparticles, the atomically precise NCs allow in-depth analysis on the underlying fundamentals. Especially, the computational simulation based on real structures of NCs is more convincing than the hypothetical models for nanoparticles (e.g., icosahedral 13-atom Au13 to represent larger nano-catalysts). These features make atomically precise NCs an ideal system to investigate the underlying structure-property relationship in electrochemical catalysis. In this thesis, we explored the electrochemical catalysis of atomically precise metal NCs. Various critical effects including size effect, doping effect, surface morphology effect and isomer effect have been studied with well-designed NCs system. The center-doping effects of Au and Ag NCs as active catalysts for oxygen reduction (ORR) reaction and CO2 reduction reaction (CO2RR) were discussed in Chapter 2 and 3. The surface morphology effect of Au NCs in CO2RR was discussed in Chapter 4, where a unique reaction pathway has been observed. In Chapter 5, the ligand effect in CO2RR has been investigated with three unique Au NCs comprising identical inner kernel but different surface ligands. We also introduced the size effect and isomer effect in Chapter 6.