The deposition of alumina ALD films on Li ion battery cathode particles is known to enhance the cycling stability of lithium ion batteries fabricated from those coated particles. It is commonly assumed that the film on the particles is of uniform thickness and is optimally thin enough to facilitate lithium diffusion while blocking side reactions of the electrolyte with the cathode substrate. Here, we elucidate the nature of thin alumina films deposited with between 2 and 15 ALD cycles on lithium nickel manganese cobalt oxide cathode precursor particles. Low energy ion scattering (LEIS) and secondary ion mass spectroscopy (SIMS) methods were used to characterize thin (<2 nm) films that were deposited by ALD. Surface analysis showed that low-cycle number ALD films were not uniform nor uniformly thick over the surface of the cathode particles and that alumina ALD preferentially deposited on transition metal bound sites on the cathode particle surface and coated Li on the surface to a lesser extent. Lithium was found to still be present on the cathode powder surface, even after 10 ALD cycles. Contrary to current supposition, low-cycle ALD appeared to improve the cycling stability of battery cathode active materials through this preferential growth that stabilized the transition metal oxides in the presence of electrolyte without blocking lithium intercalation pathways. This is the first study to determine that Li remains exposed on the as-synthesized surface of ALD coated cathode particles and that the ALD film is nonuniform and nonuniformly thick when less than 10 ALD cycles are used.

Hydrogenation of aromatic molecules in fossil- and bio-derived fuels is essential for decreasing emissions of harmful combustion products and addressing growing concerns around urban air pollution. In this work, we used atomic layer deposition to significantly enhance the hydrogenation performance of a conventional supported Pd catalyst by applying an ultrathin coating of TiO2 in a scalable powder coating process. The TiO2-coated catalyst showed substantial gains in the conversion of multiple aromatic molecules, including a 5-fold improvement in turnover frequency versus the uncoated catalyst in the hydrogenation of naphthalene. This activity enhancement was maintained upon scaling the coating synthesis process from 3 to 100 g. Based on the results from X-ray photoelectron spectroscopy, X-ray absorption spectroscopy, and computational modeling, the activity enhancement was attributed to ensemble effects resulting from partial TiO2 coverage of the Pd surface rather than fundamental changes to the Pd electronic structure. Additional durability testing confirmed that the TiO2 coating improved the thermal and hydrothermal stability of the catalyst as well as tolerance toward sulfur impurities in the reactant stream. Using an economic model of an industrial deep hydrogenation process, we found that an increase in catalyst activity or lifetime of 2× would justify even a relatively high estimate for the cost of TiO2 atomic layer deposition coatings at scale.

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Extended thin-film electrocatalyst structures based on PtNi nanowires, synthesized via spontaneous galvanic displacement, have shown great promise as efficient and durable catalysts for the oxygen reduction reaction in polymer electrolyte membrane fuel cells. In this work, atomic layer deposition (ALD) of Pt onto Ni nanowire (NiNW) substrates is demonstrated for the first time with the goal to develop a more scalable synthesis route based on vapor-phase deposition. ALD was used to deposit variable amounts of Pt onto NiNWs, producing PtNi nanowires with 3–16 wt % Pt. The Pt nanoparticle growth mechanism with increasing ALD cycles and physiochemical properties of as-received materials and ALD-modified catalysts was examined through a variety of techniques, including electron microscopy, X-ray diffraction, and rotating-disk-electrode analysis. A total of 30 cycles of Pt ALD followed by H2 annealing was found to produce a catalyst with mass activity of over 4 times greater than the U.S. Department of Energy 2020 target, thereby demonstrating the potential of ALD as a method for producing gram-scale quantities of high-performing extended surface electrocatalysts.

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