High hydrogen production from raw biomass via crystal phase regulation of Al2O3 supported Ni catalyst

Abstract

Naturally abundant biomass exhibited a complex structure with diversified chemical bonds, it brought about great challenges for the directly high-efficiency conversion of raw biomass into hydrogen under mild conditions. Here, it developed an efficient approach to catalyze cleavage of O-H, C-H and C-C bonds with the sequential water gas shift in lignocellulosic biomass through the enhanced catalytic performance of Ni-supported catalysts with the crystal phase regulation of Al₂O₃. The introduction of Ba(OH)₂ greatly enhanced the production of hydrogen over Ni/γ-Al₂O₃, and H₂ production of 69.9 mmol $g_{\text{wood}}^{‐1}$ was acquired from the directly catalytic conversion of raw biomass. Further reaction pathway investigation revealed that more basic sites in Ni/γ-Al₂O₃ were beneficial to the cleavage of O-H bonds and form the adsorbed ethoxide, which facilitated the further cleavage of α-C-H bonds. Meanwhile, the hydrogen spillover in Ni/γ-Al₂O₃ could promote the H₂ generation, and it also provided more NiAl₂O₄ species to break the C-C bonds and form Ni_x (CO)_y species, which accelerated the water gas shift to produce hydrogen. Our strategy provides guidance in the catalytic production of sustainable hydrogen as well as the low carbon future.