Four different plant biomass, bamboo, cotton, soft wood and hard wood, were utilized as carbon precursors to fabricate porous carbon catalyst supports via a chemical free approach. Large surface area with unique mesoporous structure was successfully created in the carbon, which made them suitable for catalyst support. After decorating silver nanoparticles onto these carbon supports, nitroaromatics reduction reactions were performed to evaluate the catalyst activity. Results indicate that chemical composition and surface groups of carbon supports determine the metal catalyst nucleation/growth while the porous microstructure of support affects the mass transport of reactant/product across the liquid/catalyst interface. Among the four selected biomass, porous carbon manufactured from soft wood acquires the highest average pore size, pore volume, mesopore volume fraction and best catalytic activity after decorating silver nanoparticles. This work not only presents an environmental benign process that converts natural biomass into effective porous carbon catalyst supports, but also offers a comprehensive understanding of biomass structure/composition relating to their suitability as catalyst support.

Alcohols (methanol, ethanol and isopropanol) have been found to affect the heterogeneous nucleation and growth of Ag nanoparticles onto oxygenated mesoporous carbon support and the corresponding catalytic property of Ag/Carbon nanocomposite in nitroaromatics (4-nitrophenol and 2-nitroaniline) reduction reactions. Ethanol exhibits unique capability to regenerate reactive CH2OH groups on carbon surface and successfully control Ag particle size through extending the nucleation process. Catalyst prepared with ethanol shows well-controlled particle size and dispersion and thus the highest catalytic activity in reduction reactions. The mechanism of catalyst structure control by alcohols is also investigated in this work.

A chemical-free method is developed to convert cotton fabric into reactive mesoporous carbon via optimized carbonization and oxidation processes. The processed carbon serves as both catalyst support and reactant which controls the nucleation/growth of Ag nanoparticles. The particle size is successfully controlled below 5 nm with mono-dispersion on carbon support. Various characterization techniques including scanning/transmission electron microscopies, N-2 adsorption-desorption, X-ray diffraction, X-ray photoelectron spectrum are used to study the evolution of carbon support microstructure and surface composition during thermal oxidation as well as the in-situ reaction between carbon support and Ag precursor during hybridization. These Ag/carbon catalysts, with well-controlled Ag nanoparticle size and excellent dispersion, out-perform other existing catalysts reported from literature in terms of activity and stability. The unique property of these catalysts promises potential applications in other chemical reactions besides the demonstrated capability in nitroaromatics reduction. Moreover, this green technology of processing biomass into effective catalyst support provides a great platform to design metal/carbon hybrid catalysts from wider biomass resources and target to broader catalytic reactions. (C) 2015 Elsevier B.V. All rights reserved.