High-Throughput Selection and Experimental Realization of Two New Ce-Based Nitride Perovskites: CeMoN3 and CeWN3.

Nitride perovskites have only been experimentally realized in very few cases despite the widespread existence and commercial importance of perovskite materials. From oxide perovskites used in ultrasonics to halide perovskites that have revolutionized the photovoltaics industry, the discovery of new perovskite materials has historically impacted a wide number of fields. Here, we add two new perovskites, CeWN3 and CeMoN3, to the list of experimentally realized perovskite nitrides using high-throughput computational screening and subsequent high-throughput thin film growth techniques. Candidate compositions are first down-selected using a tolerance factor and then thermochemical stability. A novel competing fluorite-family phase is identified for both material systems, which we hypothesize is a transient intermediate phase that crystallizes during the evolution from an amorphous material to a stable perovskite. Different processing routes to overcome the competing fluorite phase and obtain phase-pure nitride perovskites are demonstrated for the CeMoN3-x and CeWN3-x material systems, which provide a starting point for the development of future nitride perovskites. Additionally, we find that these new perovskite phases have interesting low-temperature magnetic behavior: CeMoN3-x orders antiferromagnetically below T N ≈ 8 K with indications of strong magnetic frustration, while CeWN3-x exhibits no long-range order down to T = 2 K but has strong antiferromagnetic correlations. This work demonstrates the importance and effectiveness of using high-throughput techniques, both computational and experimental: they are integral to optimize the process of realizing two entirely novel nitride perovskites.

Rapid Formation of a Disordered Layer on Monoclinic BiVO4 : Co-Catalyst-Free Photoelectrochemical Solar Water Splitting.

A surface disordered layer is a plausible approach to improve the photoelectrochemical performance of TiO2 . However, the formation of a crystalline disordered layer in BiVO4 and its effectiveness towards photoelectrochemical water splitting has remained a big challenge. Here, we report a rapid solution process (within 5 s) that is able to form a disordered layer of a few nanometers thick on the surface of BiVO4 nanoparticles using a specific solution with a controllable reducing power. The disordered layer on BiVO4 alleviates charge recombination at the electrode-electrolyte interface and reduces the onset potential greatly, which in turn results in a photocurrent density of approximately 2.3 mA cm-2 at 1.23 V versus the reversible hydrogen electrode (RHE). This value is 2.1 times higher than that of bare BiVO4 . The enhanced photoactivity is attributed to the increased charge separation and transfer efficiencies, which resolve the intrinsic drawbacks of bare BiVO4 such as the short hole diffusion length of around 100 nm and poor surface oxygen evolution reactivity.

Encapsulation of Single Nanoparticle in Fast-Evaporating Micro-droplets Prevents Particle Agglomeration in Nanocomposites.

This work describes the use of fast-evaporating micro-droplets to finely disperse nanoparticles (NPs) in a polymer matrix for the fabrication of nanocomposites. Agglomeration of particles is a key obstacle for broad applications of nanocomposites. The classical approach to ensure the dispersibility of NPs is to modify the surface chemistry of NPs with ligands. The surface properties of NPs are inevitably altered, however. To overcome the trade-off between dispersibility and surface-functionality of NPs, we develop a new approach by dispersing NPs in a volatile solvent, followed by mixing with uncured polymer precursors to form micro-droplet emulsions. Most of these micro-droplets contain no more than one NP per drop, and they evaporate rapidly to prevent the agglomeration of NPs during the polymer curing process. As a proof of concept, we demonstrate the design and fabrication of TiO2 NP@PDMS nanocomposites for solar fuel generation reactions with high photocatalytic efficiency and recyclability arising from the fine dispersion of TiO2. Our simple method eliminates the need for surface functionalization of NPs. Our approach is applicable to prepare nanocomposites comprising a wide range of polymers embedded with NPs of different composition, sizes, and shapes. It has the potential for creating nanocomposites with novel functions.