Surface area enhancement of nickel foam by low-temperature chemical alloying/dealloying and its application for sodium borohydride hydrolysis

Abstract

Structured nickel catalysts for sodium borohydride hydrolysis (SBH) were synthesized by surface modification of nickel foam. The fabrication process consisted of i) nickel aluminization, ii) post-annealing, and iii) selective aluminum leaching. Through low-temperature chemical alloying, nickel was aluminized at 400 degrees C, and a 0.5 mu m-thick NiAl3 alloy outer-layer was formed. While discontinuing the influx of the aluminum source, post-annealing was conducted to transform the NiAl3 outer-layer into different Ni-Al alloys, such as NiAl3 on Ni2Al3, Ni2Al3 on NiAl, and NiAl on Ni3Al at 400, 500, and 600 degrees C, respectively. After the selective aluminum leaching, the surface treatment increased the surface area by factors of 2.2-77.1, leading to a significant enhancement of activity in SBH hydrolysis. Additionally, the catalyst undergoing post-annealing at 400 degrees C achieved superior performance in both initial activity and durability, due to the adhesion layer of Ni2Al3 formed between the outermost catalytic layer and the nickel substrate. Finally, continuous SBH-based hydrogen generation using the catalyst with postannealing at 400 degrees C was achieved and the as-developed nickel catalyst produced hydrogen at a rate of up to 400 +/- 27 sccm/g(catalyst) while exhibiting excellent durability for 3 h. (C) 2020 Elsevier B.V. All rights reserved.