AbstractThe catalytic hydrothermal carbonization (C-HTC) method is proposed as a way to convert renewable feedstocks into carbon nanomaterial, using α-cellulose as the model compound. In this study, cellulose reacted with a controlled amount of Lewis acid catalyst (FeCl2 and FeCl3) under hydrothermal conditions, at temperatures ranging from 180 to 220 °C, for 6 to 24 h. The Lewis acid catalyst’s effect on the formation of carbon nanomaterials in the C-HTC reaction was investigated. This study showed that Lewis acid catalysts promoted the complete carbonization of cellulose at a reduced temperature of 200 °C. The addition of FeCl2 in C-HTC also promoted greater C=O functionality compared to FeCl3. Furthermore, the surface area of the carbon nanomaterials derived from the hydrothermal carbonization of cellulose increased from 7.92 to 15.87 and 12.96 m2 g-1 for the uncatalysed, FeCl2 and FeCl3-catalysed HTC, respectively. The findings in this study shed light on the effect of Lewis acid properties on the tunability of functional groups in the preparation of carbonaceous materials for high-end applications.