MoNi_(4)-NiO heterojunction encapsulated in lignin-derived carbon for efficient hydrogen evolution reaction

Molybdenum nickel alloy has been proved to be an efficient noble-metal-free catalyst for hydrogen evolution reaction(HER) in alkaline medium, but its electrocatalytic activity and stability need to be further improved to meet industrial requirements. In this study, carboxymethylated enzymatic hydrolysis lignin(EHL) was used as a biomacromolecule frame to coordinate with transition metal ions and reduced by pyrolysis to obtain the MoNi_(4)-NiO heterojunction(MoNi_(4)-NiO/C). The oblate sphere structure of MoNi_(4)-NiO/C exposed a large catalytic active surface to the electrolyte. As a result, the hydrogen evolution reaction of MoNi_(4)-NiO/C displayed a low overpotentials of 41 mV to achieve 10 mA cm-2and excellent stability of 100 h at 100 mA cm^(-2)in 1 mol L^(-1)KOH, which was superior to that of commercial Pt/C. Lignin assisted the formation of NiO to construct the MoNi_(4)-NiO interface and MoNi_(4)-NiO heterojunction structure, which reduced the energy barrier by forming a more favorable transition states and then promoted the formation of adsorbed hydrogen at the heterojunction interface through water dissociation in alkaline media, leading to the rapid reaction kinetics. This work provided an effective strategy for improving the electrocatalytic performance of noble-metal-free electrocatalysts encapsulated by lignin-derived carbon.

Rational design of Ni-MoO_(3–x) catalyst towards efficient hydrodeoxygenation of lignin-derived bio-oil into naphthenes

Design of a robust catalyst with high activity but the low cost for the hydrodeoxygenation(HDO) of biooils is of great importance to bring the biorefinery concept into reality.In this study,density functional theory(DFT) calculation was adopted to analyze the optimal location of Ni on MoO_(3-x) containing oxygen vacancy,and the corresponding result demonstrated that metallic Ni cluster located at the neighborhood of oxygen vacancies would significantly evoke HDO activity.Enlightened by DFT results,NiMoO_(4) was first hydrothermally synthesized and then employed to fabricate Ni-MoO_(3-x) catalyst via a low-temperature reduction,where Ni escaped from NiMoO_(4) and was reduced to its metallic state.Such an evolution of Ni species also induced the formation of oxygen vacancies around metallic Ni cluster.In the HDO of p-cresol,Ni-MoO_(3-x) exhibited high activity with a complete conversion and a methylcyclohexane selectivity of 99.4% at 150℃.Moreover,the catalyst showed good versatility in catalyzing HDO of diverse lignin-derived oxygenates and lignin oil.2D HSQC NMR,gas chromatograph and elemental analysis of the lignin oil demonstrated the high deoxygenation efficiency and saturation of the benzene ring over Ni-MoO_(3-x).In the upgrading of crude lignin oil,the deoxygenation degree was up to 99%,and the overall carbon yield of the naphthenes was as high as 69.4%.Importantly,the structures and carbon numbers of the naphthene products are similar to jet fuel-range cycloalka nes,which are expected to have a high density that can be blended into jet fuel to raise the range(or payload) of airplanes.This work demonstrates the feasibility for improving the targeted catalytic reactivity by rational tailoring the catalyst structure under the guidance of theoretical analysis,and provides an energy-efficient route for the upgrading of lignin crude oil into valuable naphthenes.

Widespread Bathyarchaeia encode a novel methyltransferase utilizing lignin-derived aromatics

Lignin degradation is a major process in the global carbon cycle across both terrestrial and marine ecosystems.Bathyarchaeia,which are among the most abundant microorganisms in marine sediment,have been proposed to mediate anaerobic lignin degradation.However,the mechanism of bathyarchaeial lignin degradation remains unclear.Here,we report an enrichment culture of Bathy-archaeia,named Candidatus Baizosediminiarchaeum ligniniphilus DL1YTT001(Ca.B.ligniniphilus),from coastal sediments that can grow with lignin as the sole organic carbon source under mesophilic anoxic conditions.Ca.B.ligniniphilus possesses and highly expresses novel methyltransferase 1(MT1,mtgB)for transferring methoxyl groups from lignin monomers to cob(I)alamin.MtgBs have no homology with known microbial methyltransferases and are present only in bathyarchaeial lineages.Heterologous expression of the mtgB gene confirmed O-demethylation activity.The mtgB genes were identified in metagenomic data sets from a wide range of coastal sediments,and they were highly expressed in coastal sediments from the East China Sea.These findings suggest that Bathyarchaeia,capable of O-demethylation via their novel and specific methyltransferases,are ubiquitous in coastal sediments.

Lignin derived multi-doped(N, S, Cl) carbon materials as excellent electrocatalyst for oxygen reduction reaction in proton exchange membrane fuel cells

Nowadays,hierarchically macro-/meso-/microporous 3D carbon materials have been paid more attention due to their imaginative application potential in specific electrochemistry.Here,we report a dualtemplate strategy using eutectic NaCl/ZnCl2 melt as airtight and swelling agent to obtain 3D mesoporous skeleton structured carbon from renewable lignin.The prepared lignin-derived biocarbon material(LN-3-1)has a high specific surface area(1289 m^2 g^-1),a large pore volume(2.80 cm^3 g^-1),and a well-connected and stable structure.LN-3-1 exhibits extremely high activity and stability in acidic medium for oxygen reduction reaction(ORR),superior to Pt/C catalyst and most non noble-metal catalysts reported in recent literatures.The prepared carbon material was used as a cathode catalyst to assemble a H2-O2 single fuel cell,and its excellent catalytic performance has been confirmed with the maximum power density of 779 mW cm^-2,which is one of the highest power densities among non-metallic catalysts so far.Density functional theory(DFT)calculations indicate that the synergy of chlorine and nitrogen reconciles the intermediate adsorption energies,leading to an appropriate theoretical ORR onset potential.We develop a cost-effective and highly efficient method to prepare biocarbon catalyst for ORR in proton-exchange membrane fuel cells.

Sources and distribution of sedimentary organic matter along the northern Bering and Chukchi Seas

In this study, lignin-derived phenols were used to determine the sources and distribution of sedimentary organic matter along the northern Bering Sea and Chukchi Sea of the Arctic Ocean. The lignin parameter syringyl/vanillyl（S/V） and cinnamyl/vanillyl（C/V） ratios are used to indicate vegetation sources; and the ratios of vanillic acid/vanillin,（Ad/Al）v and syringic acid/syringaldehyde,（Ad/Al）s are used as indicators of lignin diagenesis. Results showed the predominance of woody gymnosperm signal at the easternmost location in the northern Bering Sea, a mixture of refractory non-woody angiosperm and fresher gymnosperm tissues in the Chukchi Sea, and signal of fresher woody gymnosperm tissues in the northernmost locations in the Chukchi Sea. The lignin materials showed gradual increase in decomposition stage during transport along the northern Bering Sea. Hydrodynamic sorting process, which is the retention of coarser materials nearshore and transportation of finer particles farther offshore, most probably occurred along the east coast of the northern Bering Sea. In Chukchi Sea, the non-woody angiosperm tissues could have originated from the Canadian Arctic and gymnosperm tissues could be from the Russian Arctic side. The fresher materials in the northernmost Chukchi Sea could have been transported here via the ice-rafting process.Detection of fresh lignin materials and the occurrence of lignin decomposition mean that this region could be sensitive to the impact of climate change.