RESUMEN
Iron-nitrogen-carbon single atom catalyst (SAC) is regarded as one of the promising electrocatalysts for NO3 - reduction reaction (NO3 RR) to NH3 due to its high activity and selectivity. However, synergistic effects of topological defects and FeN4 active moiety in Fe-N-C SAC have rarely been investigated. By performing density functional theory (DFT) calculations, 13 defective graphene FeN4 with 585, 484, and 5775 topological line defects are constructed, yielding 585-68-FeN4 with optimal NO3 RR catalytic activity, high selectivity, as well as robust anti-dissolution stability. The high NO3 RR activity on 585-68-FeN4 is well explained by the high valence state of Fe center as well as asymmetric charge distribution on FeN4 moiety influenced by 5- and 8-member rings. This DFT work provides theoretical guidance for engineering NO3 RR performance of iron-nitrogen-carbon catalysts by modulating periodic topological defects.
RESUMEN
Single-atom catalysts with a tunable coordination structure have shown grand potential in flexibly altering the selectivity of oxygen reduction reaction (ORR) toward the desired pathway. However, rationally mediating the ORR pathway by modulating the local coordination number of the single-metal sites is still challenging. Herein, we prepare the Nb single-atom catalysts (SACs) with an external-shell oxygen-modulated unsaturated NbN3 site in carbon nitride and the NbN4 site anchored in nitrogen-doped carbon carriers, respectively. Compared with typical NbN4 moieties for 4e- ORR, the as-prepared NbN3 SACs exhibit excellent 2e- ORR activity in 0.1 M KOH, with the onset overpotential close to zero (9 mV) and the H2O2 selectivity above 95%, making it one of the state-of-the-art catalysts in the electrosynthesis of hydrogen peroxide. Density functional theory (DFT) theoretical calculations indicate the unsaturated Nb-N3 moieties and the adjacent oxygen groups optimize the interface bond strength of pivotal intermediates (OOH*) for producing H2O2, thus accelerating the 2e- ORR pathway. Our findings may provide a novel platform for developing SACs with high activity and tunable selectivity.
RESUMEN
Ethanol as a fuel for direct ethanol fuel cells (DEFCs) has the advantages of being highly energetic, environmentally friendly, and low-cost, while the slow anodic ethanol oxidation reaction (EOR), intermediate poisoning effect, and incomplete oxidation of ethanol became obstacles to the development of DEFCs. Herein, a 2D ternary cyclic Pd3 Pt1 Rh0.1 nanorings (NRs) catalyst with efficient EOR performance is prepared via a facile one-pot solvothermal approach, and systematic studies are carried out to reveal the mechanisms of the enhanced performance and C-C bond selectivity. In particular, the optimized catalyst exhibits impressive mass activity, stability, toxicity resistance, and C-C bond cleavage ability. It's proposed that the considerable performance is attributed to the unique hollow structure, providing abundant active sites. The high toxicity resistance is not only attributed to the electronic modulation of the catalyst material by Rh atoms, but also depends on the excellent water activation properties of Rh, which contribute to the removal of intermediates, such as CO. In addition, the density functional theory calculations showed that the introduction of Rh significantly enhances the C-C bond cleavage ability of the catalyst, further improving the EOR activity.
