Nearly monodisperse Cu|pd alloyed Nanocrystals: Ultrasound induced stepwise thermoreduction in organic Medium, and catalytic alcoholysis for hydrogen evolution

Abstract

Active search for efficient and inexpensive catalyst is the basic premise and urgent requirement to promote the practicality of the new hydrogen storage material-ammonia borane. We herein propose an ultrasonic-induced stepwise thermoreduction protocol to fabricate serial bimetal Cu|Pd alloyed nanocrystals with various metal molar ratios, and scientifically evaluate respective catalytic activity for alcoholyzing ammonia borane. Comprehensive characterizations and analysis confirm that the as-fabricated Cu|Pd crystalline grains appear as nearly monodisperse microspheres with mean size of about 10 nm, taking on almost superlattice arrangement. The ultrasound and precursor molar ratio can affect grain size and dispersity to varying degrees. Regardless of the Pd/Cu molar ratio, alloy phase microstructure can be formed. The Pd-rich nanoagent Cu40Pd60 unfold the upmost catalytic ability for alcoholyzing ammonia borane, even exceeding Pd NCs, with the turnover frequency (TOF) value of 66.51 mol (H2)·min−1·(mol Pd)-1 and apparent activation energy of 30.35 kJ·mol−1. Moreover, the Cu40Pd60 nanocrystals possess the exceptional stability with only 10% loss of the original catalytic activity after 5 round cyclic utilization. The catalytic methanolysis at the given conditions is identified as first-order reaction. The current findings can enrich the family of the serial bimetal alloyed nanocatalyst, also offer an optional strategy for fabricating the poly-metal composite catalysts with high activity.