Sintering-resistant and active-species-adjustable Ni catalysts supported on P-doped biochar via nanopore-confined activation for efficient levulinic acid hydrogenation

Nanopore-confining strategy is an effective way to inhibit catalyst sintering and improve catalytic performance. However, the expensive material precursors and complex preparation process greatly limit the scale utilization of this particularly structured catalyst. Herein, nanopore-confined catalysts (Ni@PAC) with adjustable active species were successfully prepared by a very simple method exploiting the characteristics of phosphoric acid-activated biochar (PAC). The abundant phosphorous functional groups in PAC confined Ni well in pores and significantly inhibited sintering through the spatial-confined effect of nanopore. Moreover, the evolution and migration of P functional groups can be regulated by changing the reduction temperature, and the modulation of active species of Ni metal or nickel phosphide can be achieved. Using biomass-based levulinic acid hydrogenation as the probe reaction, it was found that the catalytic activity of 20Ni@PAC-600 was one order of magnitude higher than that of the non-phosphated 20Ni/ZAC-600 catalyst, and γ-valerolactone could be selectively prepared at near atmospheric pressure (1 bar). The formation of Ni2P and the spatial-confined effect of nanopore could be the main reasons for the high catalytic activity.