The chemoselective hydrodeoxygenation of natural lignocellulosic materials plays a crucial role in converting biomass into value-added chemicals. Yet their complex molecular structures often require multiple active sites synergy for effective activation and achieving high chemoselectivity. Herein, it is reported that a high-entropy alloy (HEA) on high-entropy oxide (HEO) hetero-structured catalyst for highly active, chemoselective, and robust vanillin hydrodeoxygenation. The heterogenous HEA/HEO catalysts were prepared by thermal reduction of senary HEOs (NiZnCuFeAlZrO_x), where exsolvable metals (e.g., Ni, Zn, Cu) in situ emerged and formed randomly dispersed HEA nanoparticles anchoring on the HEO matrix. This catalyst exhibits excellent catalytic performance: 100% conversion of vanillin and 95% selectivity toward high-value 2-methyl-4 methoxy phenol at low temperature of 120 ℃, which were attributed to the synergistic effect among HEO matrix (with abundant oxygen vacancies), anchored HEA nanoparticles (having excellent hydrogenolysis capability), and their intimate hetero-interfaces (showing strong electron transferring effect). Therefore, our work reported the successful construction of HEA/HEO heterogeneous catalysts and their superior multifunctionality in biomass conversion, which could shed light on catalyst design for many important reactions that are complex and require multifunctional active sites.

Heterogeneous nanostructured metals are emerging strategies for achieving both high strength and ductility, which are particularly attractive for high entropy alloys (HEAs) to combine the synergistic enhancements from multielement composition, grain boundaries, and heterogeneity effects. However, the construction of heterogeneous nanostructured HEAs remains elusive and can involve delicate processes that are not practically scalable. Herein we report using composition design (i.e., enthalpy engineering) to create hierarchical, nanostructured HEAs as demonstrated by adding Ni into FeCrCoAlTi_0.5 HEA. The strong enthalpic interaction between (Ni,Co) and (Al,Ti) pairs in FeCrCoAlTi_0.5Ni_x (x = 0.5–1.5) induced phase partitions into B2 (ordered phase, hard) matrix and A2 (disordered phase, soft) precipitates, resulting in a hierarchical structure of B2 grains and sub-grains of near-coherent A2 nanodomains (~ 12.5 nm) divided by A2 interdendritic regions. As a result, the FeCrCoAlTi_0.5Ni_1.5 HEA with this unique hierarchical nanostructure exhibits the best combination of strength and plasticity, i.e., a 2-fold increase in compressive strength (2.60 GPa) and significant enhancement of plastic strain (15.8%) as compared with the original FeCrCoAlTi_0.5 HEA. Enthalpy analysis and simulation study reveal the phase partition process during cooling induced by an enthalpy-driven order-disorder transition while the order parameters illustrate the strong ordering in (Ni,Co)(Al,Ti)-rich B2 phase and high entropy mixing in less interactive FeCrCo-rich A2 phase. Our work therefore provides a strategy for hierarchical nanostructured HEA formation by composition design considering enthalpy and entropy interplay.