Comparison of gas-sensitive properties of Pb, Pd and Pt metal-doped Ti3C2X2 for aqueous zinc ion battery H2 gas

This work aims to provide early warning of uncontrolled reactions in aqueous zinc-ion batteries by timely and effectively detecting H-2 gas. The large specific surface area and rich pore structure of Ti3C2X2 (X = F, O, and OH) make it a good gas-sensitive sensing material, and the gas-sensitive properties of the material can be improved by metal doping. Therefore, in this paper, the gas-sensitive response properties of Pb, Pd and Pt metal-doped Ti3C2X2 (M-Ti3C2X2) to H-2 are compared based on density functional theory (DFT) calculations. The adsorption mechanism was analyzed by structure optimization, density of states, frontier molecular orbital theory and differential charge density, and the results were in high agreement. Doping of three metals, Pb, Pd and Pt, improved the adsorption capacity of Ti3C2X2 for H-2 gas to different degrees. The simulation results show that the energy gap of Pb-Ti3C2(OH)(2) adsorbed gas changes most obviously, and the maximum change value of energy gap (E-g) is 297.56 %. And Pt-Ti3C2F2 and Pt-Ti3C2O2 adsorbed H-2 with large adsorption energies and large charge transfers indicating that they can be used as H-2 removers. The energy gaps after the adsorption of H-2 by M-Ti3C2O2 are 0.109 eV, 0.163 eV, and 0.082 eV, and the change of E-g is 24.77 %, 16.56 %, and 67.07 %, respectively. The change of E-g for the adsorption of H-2 by Pt-Ti3C2O2 adsorbed H-2 with a resistivity change of 67.07 %. This is caused by the irreversibility of adsorption due to too strong adsorption resulting in elongation of Pt-O bond length after adsorption. For the detection of H-2, the properties of several doped materials were ranked as follows: Pb-Ti3C2(OH)(2) > Pt-Ti3C2O2 > Pb-Ti3C2F2 > Pb-Ti3C2O2 > Pd-Ti3C2O2 > Pd-Ti3C2(OH)(2) > Pt-Ti3C2F2 > Pt-Ti3C2(OH)(2) > Pd-Ti3C2F2. In summary, it is shown that Ti3C2X2 doped with Pb, Pd and Pt metals is a potential H-2 gas-sensitive material that can be a new material for online monitoring of fault gas content in aqueous zinc-metal energy storage batteries.