Controlling the Incorporation of Phosphorus Functionalities on Carbon Nanofibers: Effects on the Catalytic Performance of Fructose Dehydration

Abstract

Phosphorylated carbons have been reported to be effective catalysts in dehydration reactions for biomass valorization. The amount and the nature of P groups are a key parameter affecting the catalytic performances of functionalized materials. Herein, we investigate the role of structural and surface properties of carbon-based materials, specifically carbon nanofibers, in determining the amount of P-functionalities. In order to incorporate P groups on carbon surfaces, various carbon nanofibers (CNFs) with different graphitization degrees have been functionalized through treatment with a H 3 PO 4 -HNO 3 mixture at 150 • C. The pristine materials, as well as the functionalization protocol, were properly selected to achieve an effective functionalization without drastically altering the morphology of the samples. Surface and structural properties of the synthesized functionalized materials have been investigated by means of transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy. The catalytic behavior of phosphorylated carbon nanofibers has been evaluated in the selective dehydration of fructose to hydroxymethylfurfural (HMF) to elucidate structure-activity relationships.

Catalytic Performances of Au–Pt Nanoparticles on Phosphorous Functionalized Carbon Nanofibers towards HMF Oxidation

“…XPS analysis confirmed the presence of P on the catalyst surface. Single P peaks with BE in the range of 133.5-134.0 eV revealed that P is prevalently present as phosphate groups in all the catalysts, as reported in our previous work [45]. Compared with the reference XPS data from bulk metal materials (84.0 eV and 71.0 eV for Au 4f 7/2 and Pt 4f 7/2 , respectively), slight shifts toward higher binding energy were observed in both Au and Pt XPS peaks.…”

“…A portion of these materials have been functionalized, introducing phosphorus-containing groups on the surface. We have previously shown that the surface chemistry of CNFs, in particular the graphitization degree, could influence the amount of introduced P [45]. XPS analysis has shown the presence of 1.19% of P on the surface of P-HHT-CNFs, whereas a lower amount has been observed for P-PS-CNFs and P-LHT-CNFs (0.23% and 0.24%, respectively, Table 2).…”

“…Three commercial carbon nanofibers (CNFs) with different graphitization degree, PS-CNFs, LHT-CNFs, and HHT-CNFs, have been selected as pristine carbon materials to be doped with P-containing functionalities and then used as support for bimetallic Au-Pt NPs. The incorporation of phosphorus on these materials has been previously reported to proceed successfully [45]. Moreover, as-obtained P-doped CNFs have demonstrated to be effective metal-free catalysts for the selective fructose dehydration to 5-hydroxymethyl furfural (HMF) [44].…”

“…We have recently used P-functionalized carbon nanofibers (P-CNFs) for the transformation of fructose into 5-hydroxymethylfurfural (HMF), showing that the incorporation of P groups on carbon nanofibers, with different graphitization degrees (pyrolytically striped carbon nanofibers (PS-CNFs), low-temperature heat treated carbon nanofibers (LHT-CNFs), and high-temperature heat treated carbon nanofibers (HHT-CNFs)), produces effective catalysts for this reaction [45].…”

Cutting the Green Waste. Structure‐Performance Relationship in Functionalized Carbon Xerogels for Hydrolysis of Cellobiose

“…The lowest BE species (i. e. O a ) was assigned to double bonded oxygen to carbon in carbonyls and quinones as well as non‐bridging oxygen in the phosphate group (P=O). O b species could be assigned to C−O−C ether groups, esters, phenolic groups (C‐OH), anhydrides and lactones as well as C−O−P species . The highest BE peak (i. e. O c ) was assigned to C−O, non‐carbonyl oxygen in esters and anhydrides, carboxyl groups, adsorbed water and P−O‐P pyrophosphate groups ,.…”