Tailoring the Gas Sensing Properties of ZrS2 Monolayers through Ni and Pd Modifications: A DFT Study

Abstract

The growing demand for high-performance gas sensors, driven by pressing environmental and industrial safety concerns, underscores the necessity for advanced materials beyond conventional sensors, which suffer from low sensitivity, poor selectivity, sluggish response and recovery times. Although two-dimensional (2D) materials such as zirconium disulfide (ZrS2) show significant promise, their pristine form exhibits weak gas adsorption and limited charge transfer, restricting their effectiveness in achieving efficient and reliable sensing performance. To address these limitations, this study employed density functional theory (DFT) to systematically investigate two modification strategies, surface decoration and atomic substitutional doping with Ni and Pd atoms, aimed at enhancing the sensing performance of ZrS2 monolayers for the detection of six toxic environmental gases (AsH3, NH3, PH3, SO2, SO3, and CO). The results indicated that pristine ZrS2 interacts weakly with the target gases via physisorption, as evidenced by long adsorption distances, low adsorption energies, and minimal charge transfer. In contrast, both Ni and Pd modifications markedly enhanced the surface reactivity of ZrS2, facilitating strong adsorption characterized by shorter adsorption distances, higher adsorption energies, better charge redistribution and notable modulation of electronic properties. Temperature-dependent sensitivity was dramatically enhanced in doped systems compared to decorated ones, with values declining at higher temperatures. In particular, Ni-doped ZrS2 showed extreme sensitivity to CO (1463.472), AsH3 (1328.523), and PH3 (1094.785) at 300 K, accompanied by substantial bandgap narrowing and increased conductivity. Although strong gas binding in doped systems resulted in longer recovery times, especially for CO, NH3, and PH3, while SO2 and SO3 demonstrated ultrafast recovery times, on the order of 10⁻4 to 10⁻8 s at 400 K in decorated systems. Work function analysis further confirmed distinct electronic interactions with target gases. These findings may provide a theoretical framework for the design of next-generation ZrS2-based gas sensors in environmental and industrial contexts.