Engineering Ni(0)/Ni(II) interfaces in LDH-Derived Ni-Al catalysts for mild lignin depolymerization

As the primary renewable reservoir of aromatic carbon, lignin motivates the development of efficient catalysts as a promising route to depolymerization under mild conditions. To address this challenge, layered double hydroxide (LDH) derived Ni-Al catalysts with varying Ni/Al ratios, engineering Ni(0)/Ni(II) interfaces, were developed. Beyond achieving complete β-O-4 conversion of the 2-phenethyl phenyl ether at 125 °C and 25 bar, outperforming previously reported noble- and non-noble-metal catalysts for this model compound, the catalyst also effectively depolymerizes organosolv lignin under 150 °C. A suite of characterizations, including in situ XAFS, confirmed the coexistence of Ni(0) and Ni(II) and the formation of Ni(0)/Ni(II) interfacial sites. Additionally, DFT calculations employing a Ni(1 1 1)/NiO(1 0 0) nanowire model showed that Ni(II) modulates the electronic structure of Ni(0), significantly enhancing its catalytic activity. Reaction pathways identified at the Ni(1 1 1)/NiO(1 0 0) interface exhibit superior thermodynamic and kinetic profiles relative to conventional Ni(1 1 1) surfaces. Combined experimental evidence and DFT analyses establish the Ni(0)/Ni(II) interface as the decisive active site enabling hydrogenolysis under mild conditions. This work provides an efficient platform for mild lignin depolymerization and elucidates the synergistic catalysis at the Ni(0)/Ni(II) interface, paving the way for sustainable biomass conversion.