Structural characteristics of metal (Ni, Cu) doped cobalt phosphide catalysts and mechanism of catalytic hydrogen evolution of NH3BH3

Abstract

AbstractIn this paper, using density functional theory (DFT) methods, we meticulously investigated the structural properties of cobalt phosphide (CoP) and its Cu‐ and Ni‐doped counterpart. Then, on the surfaces of three catalysts, the hydrogen evolution reaction mechanism of ammonia borane (NH3BH3) was examined in turn, and four possible hydrogen evolution reaction paths of NH3BH3 on the catalyst surface were reviewed. The optimal reaction channel for each catalyst was found by comparing the activation energies of the control steps for several reaction paths, and activation energies of the optimal reaction for CoP, Cu, and Ni‐doped CoP were 31.4, 30.4, and 30.8 kcal/mol, respectively. Cu‐ and Ni‐ doped were beneficial to improve the hydrogen evolution reaction activity of NH3BH3. At the same time, the band structures and density of states of the stable catalysts were calculated. The results showed that near the fermi level, the electron cloud density of Cu and Ni‐doped CoP catalysts increased. The energy gap values of the three catalysts are 43.8, 41.0, and 41.7 kcal/mol, respectively, and the energy gap values of Cu and Ni doped CoP catalysts decrease. The energy gap values of the three catalysts are inversely proportional to their catalytic activities. We believe that these two factors together contribute to the increased catalytic activity of the doped CoP. Our results revealed the correlation between the physical properties of CoP and its metal‐doped catalysts and their catalytic activity.