Metal-Decorated InN Monolayer Senses N₂ against CO₂

Poor selectivity is a common problem faced by gas sensors. In particular, the contribution of each gas cannot be reasonably distributed when a binary mixture gas is co-adsorbed. In this paper, taking CO₂ and N₂ as an example, density functional theory is used to reveal the mechanism of selective adsorption of a transition metal (Fe, Co, Ni, and Cu)-decorated InN monolayer. The results show that Ni decoration can improve the conductivity of the InN monolayer while at the same time demonstrating an unexpected affinity for binding N₂ instead of CO₂. Compared with the pristine InN monolayer, the adsorption energies of N₂ and CO₂ on the Ni-decorated InN are dramatically increased from -0.1 to -1.93 eV and from -0.2 to -0.66 eV, respectively. Interestingly, for the first time, the density of states demonstrates that the Ni-decorated InN monolayer achieves a single electrical response to N₂, eliminating the interference of CO₂. Furthermore, the d-band center theory explains the advantage of Ni decorated in gas adsorption over Fe, Co, and Cu atoms. We also highlight the necessity of thermodynamic calculations in evaluating practical applications. Our theoretical results provide new insights and opportunities for exploring N₂-sensitive materials with high selectivity.