Metallic Ni 0 -induced in situ reduction of Cu species for enhanced furfural hydrogenation over bimetallic Cu/Ni@G catalysts

In this work, a novel bimetallic Cu/Ni@G catalyst was synthesized by a two-step strategy, involving the pyrolysis of Ni-citrate complexes to form Ni@G catalyst, followed by Cu2+ deposition using Na2CO3 as a precipitant. The as-prepared catalyst was directly applied in the selective hydrogenation of furfural (FFA) to furfuryl alcohol (FOL) without any pre-reduction treatment. For comparison, monometallic Cu/C and Ni@G catalysts, along with bimetallic Cu/Ni@G samples pre-reduced at 200 ℃ (Cu/Ni@G-200) and 400 ℃ (Cu/Ni@G-400) were also prepared and investigated for the reaction. The results revealed that the unreduced Cu/Ni@G-0 catalyst demonstrated superior catalytic performance, achieving 96.1% FFA conversion and 98.6% FOL selectivity at 100°C and 2 MPa H2, significantly outperforming both monometallic catalysts and pre-reduced bimetallic catalysts. Comprehensive characterizations including XRD, H2-TPR, XPS, and TEM, revealed that metallic Ni0 generated during pyrolysis facilitated the in-situ reduction of Cu2+ to low-valent Cu0 and Cu+ during the hydrogenation reaction. Moreover, the unreduced catalyst exhibited a higher proportion of Cu⁺ species compared to the pre-reduced samples, which effectively enhanced the adsorption and activation of furfural molecules, thereby significantly improving the hydrogenation activity. This work establishes a prereduction-free strategy for designing high-performance bimetallic hydrogenation catalysts, providing valuable insights into rational catalyst design for biomass conversion applications.