关键词: 密度泛函理论, 过渡金属碳化物, 过渡金属氮化物, 氧化还原位, 酸性/碱性

Abstract: Transition metal carbides and nitrides are attractive materials for electrodes in many electrochemical energy storage and conversion applications. In the present study, we use density functional theory slab calculations to characterize the surface chemical properties of molybdenum (Mo) and tungsten (W) carbides and nitrides, namely, Mo₂C, W₂C, Mo₂N and W2N with the adsorption of CO, CO₂ and O₂. These probing molecules provide measures of in both acidity/basicity and redox property of for the surfaces of these carbides and nitrides. Our results show that Lewis basic sites were responsible for CO₂ adsorption and the basicity follows followed an order of α-W₂C(001) > α-W₂N(001) > β-Mo₂C(001) > γ-Mo₂N(100). Both CO and O₂ adsorption provide measures of in the reducing ability of these carbides and nitrides. The results showed a reducing ability in the order of β-W₂C(100) > α-Mo₂C(100) > α-W₂N(001) > α-W₂C(001) > β-Mo₂C(001) > γ-Mo₂N(100). The reducing nature of these carbides and nitrides make them good candidates to substitute noble metals in various catalytic reactions.

Key words: Density functional theory, Transition metal carbides, Transition metal nitrides, Redox sites, Acidity/basicity.