First-Principles Studies of the Adsorption and Catalytic Properties for Gas Molecules on h-BN Monolayer Doped with Various Transition Metal Atoms

The adsorption properties for some gas molecules (H₂, N₂, CO, NO and CO₂) on pristine and transition metal-doped h-BN monolayer are investigated by using density functional theory (DFT) calculations. In contrast with N vacancy (V_N) substrates, those with B vacancy (V_B) are more easily doped with metal atoms, among which Ti atom doping shows the lowest binding energy. For the adsorption of these gas molecules, NO is most easily adsorbed on h-BN monolayer with metal dopants, especially Pt doped system yields the lowest adsorption energy of NO. Since a NO molecule on Pt doped h-BN monolayer could not be directly decomposed into O_ads and N_ads due to the high reaction energy barrier (≈ 2.00 eV), the (NO)₂ dimmer can interact with Pt to form a five-membered ring or a four-membered ring through two different Langmuir–Hinshelwood (LH) mechanisms for NO reduction catalytic reaction, respectively. The LH1 reaction process needs to overcome relatively lower energy barriers, while the product of the LH2 mechanism has a more stable structure. For the catalytic process of CO oxidation, the remained O_ads can bind with CO and form CO₂, by overcoming a much lower energy barrier of only 0.14 eV. It seems that Pt doping can enhance the adsorb capacity of h-BN monolayer for the gas molecules and the potential catalytic activity for electrochemical reduction of NO.