Yuting Zhu,Ning Li,Huifang Liu,Cheng Cai,Yehong Wang,Junju Mu,Feng Wang
Oxidative catalytic fractionation (OCF) represents an efficient approach to valorize lignocellulose for coproduction of monophenols and cellulose. To achieve an adequate monophenol yield, lignin oxidation, typically, requires high O2 pressure and an excess of Cu catalysts (the Cu dosage is approximately 3–5 mol equiv relative to the aromatic units in lignin). However, these conditions are relatively harsh for cellulose, resulting in severe decomposition to aliphatic acids. To address the trade-off between the monophenol yield and cellulose production, we develop an enhanced OCF using a CuMnCeO2 solid solution as the catalyst. Under relatively mild conditions (specifically, 0.1 MPa O2), 28.7 wt % monophenols were released from birch, using catalytic amounts of Cu (the Cu dosage was about 0.03 mol equiv relative to the aromatic units in lignin). Meanwhile, up to 83.9% of cellulose was collected as a solid pulp. The synergistic effect between doped metals (Cu and Mn) and oxygen vacancies was found to be crucial for enhanced lignin oxidation under mild conditions with minimized cellulose loss. The abundant surface oxygen vacancies facilitated oxygen activation by well-dispersed Cu and Mn species, while the strong interaction between these metals enhanced the catalyst’s reducibility. Key intermediates such as β-vinyl aryl ethers and byproduct glycolic acid were identified by model experiments, confirming that lignin oxidation primarily followed a 1,2-dioxetane homolysis mechanism. Overall, this enhanced OCF demonstrates the potential viability of lignin oxidation in practical biorefinery applications.
Spinel-type Co3O4 has been identified as a highly prospective cathode catalyst for lithium-oxygen batteries (LOBs), attributable to its distinctive bimetallic active sites that manifest exceptional bifunctional catalytic characteristics. Nonetheless, the practical implementation of this process is constrained by the inherent conductivity limitations of Co3O4 and the suboptimal utilization of active sites. In this study, a Cu-Mn bimetallic doping strategy is employed to prepare a spherical-like structure of Co3O4 formed by self-assembling one-dimensional nanorods. The introduction of Cu²⁺ results in a reduction of the surface energy of the system, thereby facilitating the directional growth of the nanorods. The redox-active Mn³⁺/Mn⁴⁺ pairs exhibit an inhibitory effect on Ostwald ripening, achieved by stabilizing the fine particles during synthesis and regulating solute diffusion kinetics. This combined action of Cu and Mn enhances active site exposure and optimizes charge transfer kinetics. Furthermore, the doping of bimetallic ions resulted in the redistribution of the Co3+/Co2+ ratio, optimizing the electronic structure for efficient charge transfer during the reaction. The combination of tailored electronic states and optimized nanostructures demonstrates excellent dual-functional catalytic activity for ORR and OER, with a half-wave potential of 0.71 V (vs RHE) for OER and an overpotential of 400 mV (10 mA cm-2) for ORR. The assembled LOBs can be stably cycled up to 450 cycles and an ultra-high discharge capacity of 7268 mAh g-1 for LOBs. This study provides a novel reference for the design of efficient bifunctional catalysts.
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