UC Berkeley

In this thesis, we explore the novel electronic properties and reactivity of twisted bilayer and trilayer graphene (tBLG and tTG), and twisted bilayer transition metal dichalcogenides (TMDs) through systematic theoretical and experimental studies. We demonstrate that rotational misalignment in these materials leads to significant changes in their electronic band structures, primarily through the formation of flat bands at certain 'magic' angles. These flat bands result in enhanced electron correlation effects and localized electronic states that significantly alter the materials' electrochemical and electronic properties. For graphene-based systems, we have found that the electron transfer kinetics at the electrode-electrolyte interface can be tuned by manipulating the twist angle between the layers. This effect is more pronounced in trilayer graphene, where we discovered that localization of electronic density of states plays a significant role in altering electron transfer kinetics. This finding aligns with the conventional understanding of how defects enhance electrochemical activity. However, in trilayer systems, we extend that understanding to consider the lateral proximity of electronic density of states, hinting at the importance of surface density of states in influencing reactivity. In the case of TMDs, our investigations suggest that twisting can similarly modulate electronic properties and potentially improve catalytic activities, particularly for hydrogen evolution reactions, a critical reaction for hydrogen production in clean energy technologies. We delve into novel methods to probe hydrogen evolution on moiré superlattices of TMDs, noting the limitations and challenges encountered. This thesis enriches our understanding of moiré materials and lays the groundwork for future innovations in the field of moiré catalysis.