Pd₂ and CoPd dimers/N-doped graphene sensors with enhanced sensitivity for CO detection: A first-principles study

The detection and monitoring of CO gas are essential to avoid human health problems. Therefore, the CO adsorption on Pd₂ and PdCo dimers deposited on pyridinic N_x-doped graphene (PN_xG; x = 1 - 3) was investigated employing the auxiliary density functional theory. In the most stable arrangements for the Pd₂ dimer supported on PN_xG, a Pd atom is in the PN_xG vacancy, and the other Pd atom is placed on C atoms. For the PdCo dimer deposited on PN_xG, the most stable interaction is like Pd₂ dimer supported on PN_xG, but with the Co atom centered over the vacancy site. Concerning the stability of the Pd₂ and PdCo dimers supported on PN_xG, the interaction energies (E_int) of the PdCo dimer deposited on PN_xG are higher than those obtained with the Pd₂ dimer. Also, the E_int of Pd₂ and PdCo dimers deposited on PN_xG are higher than those supported on pristine graphene. The CO adsorption energies on Pd₂/PN_xG and PdCo/PN_xG composites are higher than those reported in the literature for pristine graphene, showing that the Pd₂/PN_xG and PdCo/PN_xG composites have a good sensitivity toward the CO molecule.

All electronic structure calculations were performed using the auxiliary density functional theory implemented in the deMon2k program. For exchange and correlation functional, the revised PBE was used. The Pd atoms were treated with an 18-electron QECP|SD basis set, while the remaining atoms were subjected to a DZVP-GGA basis set. The GEN-A2* auxiliary-function-set was used for all computations.