Developing N, S-doped hierarchical porous carbon-supported Pt catalysts for hydrothermal gasification of woody biomass to hydrogen

Abstract

Hydrogen is a promising clean fuel with 0 carbon emission; only byproduct released from its use is water. The current large-scale hydrogen production methods are expensive and do not meet sustainability criteria. Finding alternative but cheaper sustainable ways for hydrogen production is important, and the catalyst plays a key role in this process. This study was designed to develop hierarchical porous carbons (HPCs)-based catalysts to enhance hydrogen production yield from lignocellulosic biomass by hydrothermal gasification. HPCs were synthesized from widely available waste materials, forest-based woody biomass, and poultry feathers with a promising approach (use of solubilized fractions of the precursors rather than direct carbonization of their solid forms, performing in-situ heteroatom doping and enhancing the porosity of the carbon by using a gas-forming salt, etc.). The HPC prepared from biomass/chicken feather mixture in the presence of a gas-forming salt, NaHCO₃, was the most promising carbon because of its high porosity structure with pore size ranging from ∼65 nm to ∼1.8 µm, and the 80% of the pores was around 200–450 nm. The specific surface area of the catalyst prepared by deposition of Pt particles on this carbon was found to be 3200 m²/g with an average pore size of 2.3 nm. On the other hand, the HPC prepared in the absence of NaHCO₃ had 2900 m²/g surface area and 1.8 nm average pore size. The hydrogen production activity of HPC-with NaHCO₃/Pt catalyst was found to be 23.81 ml H₂/mg Pt, which was the highest activity among the catalysts tested. This was attributed to the highly porous structure and the presence of sodium or sodium-containing species (e.g., Na₂O) in the carbon network. The findings of this study have the potential to open new catalytic opportunities for different reactions using HPCs-based multifunctional catalysts.