Spent NCM111 Cathode Material as a Catalyst for Oxidative Cleavage of β-O-4 Linkage in Lignin

The recovery and reuse of electrode materials of spent lithium-ion batteries (LIBs) are important for the sustainable development of the LIB industry. Herein, NCM111 (LiNi0.33Co0.33Mn0.33O2) cathode material from spent LIBs is recovered and its catalytic activity for the oxidative cleavage of β-O-4 linkages in model compounds and organosolv lignin is explored. The spent NCM111 is rich in oxygen vacancies (OVs) accumulated during the long-term charge-discharge cycling. The reactive oxygen species trapping experiments and density functional theroy (DFT) calculation indicate that the abundant OVs can adsorb and activate the oxygen molecules, which afford the NCM111 with the catalytic activity. It is found that besides the catalytic activity in oxidative cleavage of the β-O-4 linkage in lignin model compounds, the spent NCM111 can also catalyze the depolymerization of organosolv lignin, yielding 17.5% aromatics, such as vanillin, benzoic acid, and phthalic acid, indicating the potential economic value of spent NCM materials.

Visualization of the Key Proton Activities in Hydrogen Evolution Reaction by Electrochromic Catalyst

The electrocatalytic hydrogen evolution reaction (HER) is a promising route to produce sustainable hydrogen energy carrier for global carbon neutrality. The HER performance is largely determined by the overall proton activities, but the identification of such key proton activities in microscopic HER process is rather difficult. Herein, the study demonstrates a visualized HER concept by integrating the fundamental HER process with electrochromic technology on a well-designed Pt@WO3 platform in acidic electrolyte, where the overall proton activities in HER process can be rapidly discriminated by the color changes of Pt@WO3 electrochromic electrode. In contrast to bare WO3 counterpart, the Pt@WO3 electrochromic electrode displays a rather more positive potential of initial-coloration state and faster decoloration rate associated with significantly improved reaction kinetics of hydrogen intercalation and deintercalation within WO3 component. Correspondingly, the as-prepared Pt@WO3 catalyst electrode exhibits a remarkable HER activity with a lower onset-potential (45 mV, proton adsorption and accumulation) and smaller Tafel slope (50 mV dec-1, proton desorption), nearly 11.1- and 3.5-fold enhancement than those of bare WO3 counterpart. It is believed that the work in integrating the interesting visualization functionality into fundamental HER process may improve the readability of such microscopic electrocatalytic reaction and advance the exploration of more intelligent electrocatalysts.

Oxidative Cleavage of β-O-4 Linkage in Lignin via Co Nanoparticles Embedded in 3DNG as Catalyst

The cleavage of β-O-4 linkage in lignin is one of the key steps for oxidative conversion of lignin to low-molecular-weight aromatics. Herein, Co nanoparticles embedded in three-dimensional network of nitrogen-doped graphene (Co/NG@3DNG-X) were prepared through an immersion-pyrolysis procedure, in which X denotes the pyrolysis temperature. The detailed characterization of Co/NG@3DNG-X shows that the Co nanoparticles are coated with a few layers of nitrogen-doped graphene (NG) sheets that are further embedded in 3DNG matrix. The catalytic activities of the Co/NG@3DNG-X for the oxidative cleavage of β-O-4 linkage in lignin model compounds with O₂ as oxidant are explored. It is demonstrated that catalytic activities of as-prepared Co/NG@3DNG-X can be tuned by varying the pyrolysis condition, and the Co/NG@3DNG-900 shows the highest catalytic activity, which is attributed to the enriched Co-N_x species, the strong surface basicity, the high specific surface and the mesoporous motif of 3DNG network. More pronouncedly, the Co/NG@3DNG-900 can also effectively catalyze the oxidative cleavage of organosolv lignin, generating certain monomeric aromatics. Additionally, the intrinsic magnetic property of Co nanoparticles makes the Co/NG@3DNG-X be easily recovered from the reaction mixture, and the as-coated thin NG layer can protect Co nanoparticle from oxidation condition, which putting together afford the Co/NG@3DNG-X with good reusability and stability.

Sustainable production of active pharmaceutical ingredients from lignin-based benzoic acid derivatives via “demand orientation”

Catalytic production of several representative active pharmaceutical ingredients (APIs) from lignin.

Reversible hydrogen spillover in Ru-WO3-x enhances hydrogen evolution activity in neutral pH water splitting

Noble metal electrocatalysts (e.g., Pt, Ru, etc.) suffer from sluggish kinetics of water dissociation for the electrochemical reduction of water to molecular hydrogen in alkaline and neutral pH environments. Herein, we found that an integration of Ru nanoparticles (NPs) on oxygen-deficient WO_3-x manifested a 24.0-fold increase in hydrogen evolution reaction (HER) activity compared with commercial Ru/C electrocatalyst in neutral electrolyte. Oxygen-deficient WO_3-x is shown to possess large capacity for storing protons, which could be transferred to the Ru NPs under cathodic potential. This significantly increases the hydrogen coverage on the surface of Ru NPs in HER and thus changes the rate-determining step of HER on Ru from water dissociation to hydrogen recombination.

While water splitting electrolysis offers an appealing means to produce H₂ fuel, catalysts show sluggish reaction rate in neutral media. Here, authors utilize hydrogen spillover from oxygen-deficient tungsten oxides to Ru nanoparticles to boost the neutral-pH H₂ evolution performances.

Lignin valorization: Status, challenges and opportunities

As an abundant aromatic biopolymer, lignin has the potential to produce various chemicals, biofuels of interest through biorefinery activities and is expected to benefit the future circular economy. However, lignin valorization is hindered by a series of constraints such as heterogeneous polymeric nature, intrinsic recalcitrance, strong smell, dark colour, challenges in lignocelluloses fractionation and the presence of high bond dissociation enthalpies in its functional groups etc. Nowadays, industrial lignin is mostly combusted for electricity production and the recycling of inorganic compounds involved in the pulping process. Given the research and development on lignin valorization in recent years, important applications such as lignin-based hydrogels, surfactants, three-dimensional printing materials, electrodes and production of fine chemicals have been systematically reviewed. Finally, this review highlights the main constraints affecting industrial lignin valorization, possible solutions and future perspectives, in the light of its abundance and its potential applications reported in the scientific literature.