ALD (Atomic Layer Deposition) Synthesis of Novel Nanostructured Metal Borohydrides

Recipient National Renewable Energy Laboratory/NREL (PI: Steven Christensen)

Abstract The goal of this project is to develop a completely new reversible hydrogen storage materials matrix based on encapsulation via atomic layer deposition (ALD) of nanostructured metal borohydrides. ALD is a vapor phase method to grow thin films layer-by-layer. The metal borohydride-encapsulation architecture will include layers that will protect against loss of the nanostructure hydride and impart chemical additives to enhance kinetics and reversibility. The concept was motivated by a substantial research where ALD coatings provided protective and catalytic properties to heterogeneous catalysts. ALD offers: (1) Conformal coatings of materials like aluminum oxide that are inert to hydrogenation/dehydrogenation conditions; (2) A wide variety of chemical additives previously shown to enhance metal borohydride reversibility and kinetics like palladium or cerium oxide; and (3) A facile means to combine these materials to tailor properties to performance. Recent developments in ALD manufacturing have demonstrated >100 kg per day throughput on powders and other granular materials. Thus, ALD solutions to the challenges with metal borohydrides will bring to front new scientific knowledge with the potential to be scaled.