Steam pretreatment-mediated catalytic activity modulation for ammonia borane hydrolysis over ruthenium nanoclusters on nitrogen/oxygen-rich carbon nanotubes

Abstract

Supported metal nanoclusters (NCs) have been demonstrated as essential kinds of catalytic materials for hydrolysis of ammonia borane (AB). The uniform anchoring of metal NCs on carbon matrix is challenging using traditional impregnation and immobilization routes without any stabilizing ligands. In this study, we report an economical, simple and efficient steam pretreatment-mediated strategy of using nitric acid vapor to adjust the surface chemistry and textural structure of carbon nanotubes (f-CNTs) and thereby achieving the uniform deposition of well-defined Ru NCs onto the f-CNTs toward hydrogen production from AB hydrolysis. Compared to its pristine carbon nanotube analogues, the rich N/O-functional groups, increased defects and specific surface area of f-CNTs enable the formation of Ru NCs (1.71 nm in diameter) with high dispersion, which considerably boost the catalytic hydrolysis of AB to produce hydrogen under mild conditions. Specifically, Ru@f-CNTs with an optimal metal loading of 2 wt% delivers a considerable activity in hydrogen generation from AB hydrolysis with turnover frequency of 764 min−1 at 298 K, superior to many reported Ru-based catalysts. The present strategy provides an efficient way to prepare various carbon supported metal catalysts that possess great promise in catalytic application.