Atomic layer deposition (ALD) is a well‐established vapor‐phase technique for depositing thin films with high conformality and atomically precise control over thickness. Its industrial development has been largely confined to wafers and low‐surface‐area materials because deposition on high‐surface‐area materials and powders remains extremely challenging. Challenges with such materials include long deposition times, extensive purging cycles, and requirements for large excesses of precursors and expensive low‐pressure equipment. Here, a simple solution‐phase deposition process based on subsequent injections of stoichiometric quantities of precursor is performed using common laboratory synthesis equipment. Precisely measured precursor stoichiometries avoid any unwanted reactions in solution and ensure layer‐by‐layer growth with the same precision as gas‐phase ALD, without any excess precursor or purging required. Identical coating qualities are achieved when comparing this technique to Al2O3 deposition by fluidized‐bed reactor ALD (FBR‐ALD). The process is easily scaled up to coat >150 g of material using the same inexpensive laboratory glassware without any loss in coating quality. This technique is extended to sulfides and phosphates and can achieve coatings that are not possible using classic gas‐phase ALD, including the deposition of phosphates with inexpensive but nonvolatile phosphoric acid.

a b s t r a c tThe use of metal oxide overcoats over supported nanoparticle catalysts has recently led to impressive improvements in catalyst stability and selectivity. The deposition of alumina is especially important for renewable catalysis due to its robustness in liquid-phase conditions. However, there are limited reports of work on alumina deposition and stabilization that goes beyond atomic layer deposition (ALD). Here, we present a layer-by-layer deposition technique for the controlled formation of conformal alumina overcoats in the liquid phase. This technique is easy to perform in common wet chemistry conditions. Alternated exposure of the substrate to stoichiometric amounts of aluminum alkoxide and water in liquidphase conditions leads to the formation of a porous overcoat that was easily tunable by varying synthesis parameters. The deposition of 60 Al 2 O 3 layers onto Al 2 O 3 -supported copper nanoparticles suppressed irreversible deactivation during the liquid-phase hydrogenation of furfural -a key biomass-derived platform molecule. The porous overcoat leads to highly accessible metal sites, which significantly reduces the partial site blocking observed in equivalent overcoats formed by ALD. We suggest that the ease of scalability and the high degree of control over the overcoat's properties during liquid-phase synthesis could facilitate the development of new catalyst overcoating applications.

The surface of a material is not only a window into its bulk physical properties, but also hosts unique phenomena important for understanding the properties of a solid as a whole. Surface sensitive techniques, like ARPES (Angle-resolved photoemission spectroscopy), STM (Scanning tunneling microscopy), AFM (Atomic force microscopy), pump-probe optical measurements etc. require flat, clean surfaces. These can be obtained by cleaving, which is usually possible for layered materials. Such measurements have proven their worth by providing valuable information about cuprate superconductors, graphene, transition metal dichalcogenides, topological insulators and many other novel materials. Unfortunately, this was so far not the case for the cubic, organo-metallic photovoltaic perovskite which morsels during the cleavage. Here we show a method which results in flat, clean surfaces of CH3NH3PbBr3 which allows surface sensitive measurements, badly needed for the understanding and further engineering of this material family.

Pt-group metal (PGM)-free catalysts of the Me-N-C type based on abundant and inexpensive elements have gained importance in the field of oxygen reduction reaction (ORR) electrocatalysis due to their promising...