Intrinsic property and catalytic performance of single and double metal atoms incorporated g-C₃N₄ for O2 activation: A DFT insight

Highlights: • Single- and double-transition metals (TM_n) doped in g-C₃N₄ were studied. • The 3d-TM_n@g-C₃N₄ shows high thermodynamic stability. • O₂ adsorption and activation were used to evaluate the performance of TM_n@g-C₃N_4. • Three key descriptors have strong correlation with the performance of TM_n@g-C₃N_4. • Non-noble metal Fe₂@g-C₃N₄ shows the highest catalytic performance among all TMs. The intrinsic properties and catalytic performances of single- and double-transition metals on graphitic carbon nitride, TM_n@g-C₃N₄ (n = 1,2), toward the O₂ activation were investigated by DFT calculation. The 3d-TM atoms are firmly trapped inside g-C₃N₄ which prevents the metal clustering and shows high thermodynamic stability. The dimetal-dioxygen adsorption configuration of the O₂/TM₂@g-C₃N₄ promotes electron transfer from catalyst to the adsorbed O₂, which improves their catalytic performances over the O₂/TM@g-C₃N₄. We observed the two different electron transfer mechanisms for O₂ activation on TM_n@g-C₃N₄, in which the double-metal acts as an electron donor while the single-metal acts as the bridge for electron transfer from the substrate to the adsorbed O₂. Remarkably, the catalytic performance of the TM_n@g-C₃N₄ for O₂ dissociation has a strong correlation with the three factors, (i) the charge gained on adsorbed O₂, (ii) the O₂ adsorption energy, and (iii) the O-O distance. The Fe₂@g-C₃N₄ as a low-cost and non-precious metal catalyst shows the best catalytic performance with the lowest activation energy barrier of 0.26 eV for O₂ activation, and therefore, is predicted as a potential catalyst for O₂ consuming reactions. Our finding provides useful information for further design and development of high efficient few-atom catalysts based 2D-carbon materials.