Ni/Ti3C2Tx catalysts for hydrogen production from ethanol via aqueous-phase reforming: Effects of surface-terminating species, residence time, and reaction temperature

MXene has been demonstrated to be a promising catalyst for Hydrogen (H 2 ) production via aqueous-phase reforming (APR). However, the influence of surface-terminating species on H 2 production in this process has not yet been fully elucidated. To address this gap, Ti 3 C 2 T x with different surface terminations (–F, –OH, and –O) was synthesized and subsequently loaded with metallic Ni. These catalysts were employed for H 2 production via APR at various residence times (10–120 min) and reaction temperatures (200 °C–275 °C), enabling systematic evaluation of the effects of surface termination, residence time, and reaction temperature. Compared with pristine Ti 3 C 2 T x , the highest H 2 yield was achieved over Ti 3 C 2 O 2 , followed by Ti 3 C 2 (OH) 2 . Notably, the Ni/Ti 3 C 2 O 2 catalyst exhibited an H 2 yield of 77%, with a H 2 production volume exceeding 350 mL and a H 2 production rate of 28.7 m mol·h −1 ·g −1 , representing increases of approximately 5, 17, and 24 times compared with pure Ti 3 C 2 O 2 , respectively. In addition, the H 2 selectivity of Ni/Ti 3 C 2 O 2 approached 90%. The superior performance of Ni/Ti 3 C 2 O 2 can be attributed to the –O termination, which provides abundant defect sites, promotes uniform Ni dispersion, constructs an open mesoporous structure, and enhances hydrophilicity as well as ethanol adsorption. Moreover, the strong Ti–O–Ni interaction significantly improves C–C bond cleavage capability. Prolonged reaction time and elevated temperature led to a nearly linear increase in ethanol conversion and H 2 production, with the conversion reaching 69.8% at 120 min. However, the advantages of extended reaction time were gradually offset by progressive carbon deposition, which diminished catalytic activity. Similarly, although increasing the temperature up to 250 °C enhanced H 2 yield, temperatures beyond this threshold induced structural oxidation and framework collapse, aggravated carbon deposition, and ultimately compromised catalyst stability.