AbstractExposing active sites and optimizing their binding strength to reaction intermediates are two essential strategies to significantly improve the catalytic performance of 2D materials. However, pursuing an efficient way to achieve these goals simultaneously remains a considerable challenge. Here, using 2D PtTe₂ van der Waals material with a well‐defined crystal structure and atomically thin thickness as a model catalyst, it is observed that a moderate calcination strategy can promote the structural transformation of 2D crystal PtTe₂ nanosheets (c‐PtTe₂ NSs) into oxygen‐doped 2D amorphous PtTe₂ NSs (a‐PtTe₂ NSs). The experimental and theoretical investigations cooperatively reveal that oxygen dopants can break the inherent Pt‐Te covalent bond in c‐PtTe₂ NSs, thereby triggering the reconfiguration of interlayer Pt atoms and exposing them thoroughly. Meanwhile, the structural transformation can effectively tailor the electronic properties (e.g., the density of state near the Fermi level, d‐band center, and conductivity) of Pt active sites via the hybridization of Pt 5d orbitals and O 2p orbitals. As a result, a‐PtTe₂ NSs with large amounts of exposed Pt active sites and optimized binding strength to hydrogen intermediates exhibit excellent activity and stability in hydrogen evolution reaction.