Effect of Ball-Milling Pretreatment of Cellulose on Its Photoreforming for H2 Production

Photoreforming of cellulose is a promising route forsustainable H2production. Herein, ball-milling (BM, with variedtreatment times of 0.5-24 h) was employed to pretreat microcrystallinecellulose (MCC) to improve its activity in photoreforming over a Pt/TiO2catalyst. It was found that BM treatment reduced the particle size,crystallinity index (CrI), and degree of polymerization (DP) of MCCsignificantly, as well as produced amorphous celluloses (with >2 htreatment time). Amorphous cellulose water-induced recrystallizationto cellulose II (as evidenced by X-ray diffraction (XRD) and solid-stateNMR analysis) was observed in aqueous media. Findings of the workshowed that the BM treatment was a simple and effective pretreatmentstrategy to improve photoreforming of MCC for H2production, mainlydue to the decreased particle size and, specifically in aqueous media, the formation of the cellulose II phase from the recrystallizationof amorphous cellulose, the extent of which correlates well with the activity in photoreforming.