No abstract

Although considerable efforts have been made toward converting syngas to liquid fuels and value-added chemicals, selectively converting syngas to aromatics remains a big challenge because of severe deactivation and low selectivity. Here, we reported a bifunctional catalyst composed of Fe3O4@MnO2 and hollow HZSM-5, which could synthesize aromatics from syngas with a high selectivity of 57% at CO conversion >90%. The catalyst retained good stability for 180 h under industrially relevant conditions. The electron transfer from the Mn to Fe species in the core–shell Fe3O4@MnO2 catalyst promoted the formation of olefins intermediates, which were subsequently diffused onto the acid sites of HZSM-5, further converting to aromatics. Shortened channels and cavity structures of hollow HZSM-5 strengthened the diffusion of reactants and products, enhancing the catalyst stability via the suppression of carbon deposition. The present research provides insight into developing a potential bifunctional catalyst candidate for selectively converting syngas to aromatics.

Redox-active organic imides are potential alternatives to the transition-metal based cathodes for material-sustainable and environment-friendly Na-ion batteries; however, their poor cyclability remains a challenge for battery applications. To address this issue, we use a redox-active anthraquinone to link the small carbonyl molecules to obtain a conjugated polymer with multiple redox-active centers. Herein, we synthesize four cathode-active poly(anthraquinonyl imide)s (PAQIs) from pyromellitic dianhydride (or 1,4,5,8-naphthalenetetracarboxylic dianhydride) and 1,4-diaminoanthraquinone (or 1,5-diaminoanthraquinone). The as-prepared PAQI materials exhibit a high reversible capacity of 190 mAh g −1 and a stable cyclability with 93% capacity retention over 150 cycles, suggesting a possible use of these organic cathode materials for high capacity Na-ion batteries. 11 denoted in different colors. As seen in Fig. 5a, the main CV feature of PAQI-B14 (red curve) emerges as two pairs of redox peaks with similar areas at 1.42/1.58 and 1.85/2.15 V, resembling very much the CV patterns of PAQS. 8 As a reversible two-electron transfer can occur for both of pyromellitic diimide (PMDI, Fig. S2, ESI) and AQ groups,8,14,15,21,22 it is speculated that the two pairs of redox peaks of PAQI-B14 are ascribed to the stepwise two-electron transfer for both of the PMDI and AQ units. A detailed examination of the curve indicates that a shoulder oxidation peak appears at 1.95 V, which is originated from the PMDI unit. On the other hand, PAQI-B15 shows similar CV pattern (green, Fig. 5a) as PAQI-B14, but its redox peaks are better separated in the higher potential region. Hence, in the case of PAQI-B15, the redox potentials of PMDI unit are 1.35/1.65 and 1.8/2.0 V, and those of AQ unit are 1.35/1.65 and 1.9/2.25 V. Similarly, the redox potentials of PAQI-N15 can be determined. As shown in Fig. 5b, four pairs of redox peaks are observed for PAQI-N15 (orange curve) at 1.42/1.78, 1.65/2.0, 2.0/2.25, and 2.12/2.40 V. Based on the data of NTCDI 12 and AQ groups, 8 the CV peaks at 1.65/2.0 and 2.12/2.40 V can be attributed to the redox reactions of NTCDI groups, and the peaks at 1.42/1.78 and 2.0/2.25 V are given rise by the AQ groups. In comparison, PAQI-B15 and PAQI-N15 show a larger separation in the oxidation and reduction peaks, i.e, a larger polarization, than PAQI-B14 and PAQI-N14, respectively, implying that PAQI-B14and PAQI-N14 undergo their redox reactions more reversibly and easily than PAQI-B15 and PAQI-N15, most likely due to their lower steric hindrance for Na + intercalation/deintercalation. 24