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.

Transition metal dichalcogenides (TMDs) constitute a class of materials wherein transition metals coordinated by bridging chalcogenides form two-dimensional layers that stack via van der Waals (vdW) interactions along the crystallographic c axis. This lamellar structure enables a diverse range of species, including transition metals, to be intercalated into these vdW interfaces. With open-shell intercalants, local magnetic moments can be introduced into the lattice, thereby inducing long-range magnetic order. The versatility of potential intercalants and host lattices has long made this class of materials an appealing choice as tunable platforms for investigating the interplay among composition, structure, and magnetism. More recently, there has been a growing appreciation for the influence of defects and domain structures in these intercalated compounds on exchange interactions and magnetic correlations. This recognition has led to the acknowledgment of complex magnetic phase spaces, highlighting the intricate interplay between structural features and magnetic properties.We design a spin glass with strong spin frustration induced by magnetic disorder by exploiting the distinctive structure of Fe intercalated ZrSe2, where Fe(II) centers are shown to occupy both octahedral and tetrahedral interstitial sites and to distribute between ZrSe2 layers without long-range structural order. Notably, we observe behavior consistent with a magnetically frustrated and multidegenerate ground state in these FexZrSe2 single crystals, which persists above room temperature. Moreover, this magnetic frustration leads to a robust and tunable exchange bias up to 250 K. These results not only offer important insights into the effects of magnetic disorder and frustration in magnetic materials generally, but also highlight as design strategy the idea that a large exchange bias can arise from an inhomogeneous microscopic environment without discernible long-range magnetic order. In addition, these results show that intercalated TMDs like FexZrSe2 hold potential for spintronic technologies that can achieve room temperature applications. Since Fe intercalated ZrSe2 is semiconducting which provides us a knob to tune its physical and chemical properties electrochemically inserting a foreign species (Li+ ions) into their interlayer spacing. We discover substantial enhancement of light transmission and electrical conductivity in thin (∼30 nm) Fe intercalated ZrSe2 nanosheets after Li intercalation due to changes in band structure and the injection of large amounts of free carriers. We also capture the first in situ optical observations of Li intercalation FexZrSe2, shedding light on the dynamics of the intercalation process. The high reversibility of the intercalation process might be attributed to the enhanced stability of the structure induced by the intercalated Fe ion between the host lattice layers. The enhancement of electron transport upon the Li intercalation in the materials lays down a robust groundwork for electrostatic control over spin polarization. We also briefly explore the effect of semiconducting spin glass FexZrSe2 on generating and manipulating spin current in heavy metal, which highlights the potential application of the materials in spintronic technology. Together, we study the interplay among composition, structure, and magnetism of Fe intercalated ZrSe2, explore the impact of electrostatic and electrochemical strategies to manipulate the properties of FexZrSe2, lay down the robust cornerstone for the application of FexZrSe2 in spintronic technology, and inspire the research interest in expanding the knowledge of the magnetic ion intercalated TMDs to diverse 2D heterostructures and twist moiré patterns.