The d-band center descriptor based on the adsorption strength of adsorbate has been widely used in understanding and predicting the catalytic activity in various metal catalysts. However, its applicability is unsure for the single-atom-anchored two-dimensional (2D) catalysts. Here, taking the hydrogen (H) adsorption on the single-atom-anchored 2D basal plane as example, we examine the influence of orbitals interaction on the bond strength of hydrogen adsorption. We find that the adsorption of H is formed mainly via the hybridization between the 1s orbital of H and the vertical d_z2 orbital of anchored atoms. The other four projected d orbitals (d_xy/d_x2−y2, d_xz/d_yz) have no contribution to the H chemical bond. There is an explicit linear relation between the d_z2-band center and the H bond strength. The d_z2-band center is proposed as an activity descriptor for hydrogen evolution reaction (HER). We demonstrate that the d_z2-band center is valid for the single-atom active sites on a single facet, such as the basal plane of 2D nanosheets. For the surface with multiple facets, such as the surface of three-dimensional (3D) polyhedral nanoparticles, the d-band center is more suitable.

基于被吸附物吸附强度的 d 带中心描述符已广泛用于理解和预测各种金属催化剂的催化活性。然而，它对单原子锚定二维 (2D) 催化剂的适用性尚不确定。在这里，以单原子锚定二维基面上的氢（H）吸附为例，我们研究了轨道相互作用对氢吸附键强度的影响。我们发现 H 的吸附主要是通过 H 的 1s 轨道和锚定原子的垂直 d _z2轨道之间的杂化形成的。其他四个投影的 d 轨道 (d _xy /d _x2−y2 , d _xz /d _yz) 对 H 化学键没有贡献。在 d _{z2 带}中心和 H 键强度之间存在明确的线性关系。d _{z2 带}中心被提议作为析氢反应（HER）的活性描述符。我们证明了 d _{z2 带}中心对单个面上的单原子活性位点有效，例如二维纳米片的基面。对于具有多个面的表面，例如三维 (3D) 多面体纳米粒子的表面，d 带中心更合适。