Janus transitional metal dichalcogenides (TMDCs) have raised wide attraction because of its unique physical and chemical properties. This work focuses on the effect of single surface vacancy (Se and Te vacancy) on adsorption and sensing properties of Janus HfSeTe monolayer to several hazardous gases (CO, H₂S, NH₃, NO, NO₂, and SO₂). The adsorption structures, adsorption energy, charge transfer, electronic properties and work function are calculated using density functional theory. It is found that different surface vacancy (Se or Te vacancy) brings different adsorption behavior, and the introduction of vacancy significantly enhances the chemical interactions between Janus HfSeTe monolayer and adsorbed gases. The adsorption energy and charge transfer obviously increase for all these molecules compared to the adsorption on pristine HfSeTe monolayer. More notably, the adsorption of CO, NO, NO₂ and SO₂ brings new chemical bond formation, and the atomic density of states (DOS) suggests that there exist states overlapping between dangling Hf atom and atom in molecule. In addition, H₂S and NH₃ adsorptions make the work function decrease while other adsorptions lead to the risen of work function. Based on the distinguished adsorption properties and different degree of work function variation, Janus HfSeTe is a potential candidate in hazardous gas scavenger and sensing material.

Janus 过渡金属二硫化物 (TMDCs) 因其独特的物理和化学性质而受到广泛关注。这项工作的重点是单表面空位（Se 和 Te 空位）对 Janus HfSeTe 单层对几种有害气体（CO、H ₂ S、NH ₃、NO、NO ₂和 SO _{2的吸附和传感特性的影响）}）。使用密度泛函理论计算吸附结构、吸附能、电荷转移、电子性质和功函数。发现不同的表面空位（Se或Te空位）带来不同的吸附行为，空位的引入显着增强了Janus HfSeTe单层与吸附气体之间的化学相互作用。与原始 HfSeTe 单层上的吸附相比，所有这些分子的吸附能和电荷转移明显增加。更值得注意的是，CO、NO、NO ₂和SO ₂的吸附带来了新的化学键形成，并且原子态密度（DOS）表明悬空Hf原子与分子中的原子之间存在态重叠。此外，H ₂S和NH ₃吸附使功函数降低，而其他吸附导致功函数升高。基于出色的吸附特性和不同程度的功函数变化，Janus HfSeTe 是危险气体清除剂和传感材料的潜在候选者。