Synthesis of Pt-CeVO4 nanocomposites and their enhanced photocatalytic hydrogen evolution activity under sunlight

The environmental pollution problem caused by fossil fuels, a nonrecyclable resource, becomes more serious every year. Therefore, the development of technology to produce alternative energy in a carbon–neutral way is urgent. In this regard, solar-powered H2 production from water using particulate photocatalysts is considered the most economical and robust approach to producing carbon–neutral H2 fuels. Using Pt-CeVO4 nanocomposites with controllable amounts of Pt nanoparticles (NPs) on CeVO4 as a photocatalyst, a superior H2 production rate of 220.68 mmol g-1h−1 was achieved, which was five times higher than that of Pt NPs. In the Pt-CeVO4 catalyst, CeVO4 affected the electron density of Pt through upward band bending, which dramatically improved the H2 generation ability. Our research is a competent study that satisfies the dual purpose of 1) achieving maximum reaction efficiency using a small amount of noble metal while providing important insights that 2) proper contact of metal and semiconductor materials can exponentially enhance photocatalytic performance. © 2023 The Korean Society of Industrial and Engineering ChemistryFALS

Electrochemical Dealloying of Ni-Rich Pt–Ni Nanoparticle Network for Robust Oxygen-Reduction Electrocatalysts

Increasing the electrochemically active surface area (ECSA) and alloying Pt with transition metals (TMs) are well-known strategies for enhancing the oxygen reduction reaction (ORR) catalytic activities. Herein, we introduce a strategy to produce highly active ORR electrocatalysts with a large ECSA using an electrochemical dealloying process involving leaching of Ni from a Ni-rich Pt–Ni nanoparticle network. The dealloying process yielded a dealloyed Pt–Ni nanoparticle network with rugged surfaces from the Ni-rich Pt–Ni nanoparticle network, resulting in a large ECSA. We also increased the mass activity and utilization efficiency of Pt by modulating the interactions between Pt and Ni. The dealloyed nanoparticle network exhibited a high ORR mass activity, six times higher than that of commercial Pt/C. Moreover, the dealloyed Pt–Ni nanoparticle network exhibited better catalytic stability than the Pt/C after 10000 potential cycles, even without carbon support. The reduced binding energy of the O intermediate due to the effects of Ni (ligand and strain effects) enhanced the ORR activity of the dealloyed nanoparticle network, according to the results of a mechanistic study performed using density functional theory. This study opens new avenues for designing TM-alloy catalysts with high ORR activity for various applications

Metastable hexagonal close-packed palladium hydride in liquid cell TEM

Metastable phases-kinetically favoured structures-are ubiquitous in nature1,2. Rather than forming thermodynamically stable ground-state structures, crystals grown from high-energy precursors often initially adopt metastable structures depending on the initial conditions, such as temperature, pressure or crystal size1,3,4. As the crystals grow further, they typically undergo a series of transformations from metastable phases to lower-energy and ultimately energetically stable phases1,3,4. Metastable phases sometimes exhibit superior physicochemical properties and, hence, the discovery and synthesis of new metastable phases are promising avenues for innovations in materials science1,5. However, the search for metastable materials has mainly been heuristic, performed on the basis of experiences, intuition or even speculative predictions, namely 'rules of thumb'. This limitation necessitates the advent of a new paradigm to discover new metastable phases based on rational design. Such a design rule is embodied in the discovery of a metastable hexagonal close-packed (hcp) palladium hydride (PdHx) synthesized in a liquid cell transmission electron microscope. The metastable hcp structure is stabilized through a unique interplay between the precursor concentrations in the solution: a sufficient supply of hydrogen (H) favours the hcp structure on the subnanometre scale, and an insufficient supply of Pd inhibits further growth and subsequent transition towards the thermodynamically stable face-centred cubic structure. These findings provide thermodynamic insights into metastability engineering strategies that can be deployed to discover new metastable phases. © 2022. The Author(s), under exclusive licence to Springer Nature Limited.11Nsciescopu

Bi1-xSbx Alloy Nanocrystals: Colloidal Synthesis, Charge Transport, and Thermoelectric Properties

Nanostructured Bi1-xSbx alloys constitute a convenient system to study charge transport in a nanostructured narrow-gap semiconductor with promising thermoelectric properties. In this work, we developed the colloidal synthesis of monodisperse sub-10 nm Bi 1-xSbx alloy nanocrystals (NCs) with controllable size and compositions. The surface chemistry of Bi1-xSbx NCs was tailored with inorganic ligands to improve the interparticle charge transport as well as to control the carrier concentration. Temperature-dependent (10-300 K) electrical measurements were performed on the Bi1-xSbx NC based pellets to investigate the effect of surface chemistry and grain size (???10-40 nm) on their charge transport properties. The Hall effect measurements revealed that the temperature dependence of carrier mobility and concentration strongly depended on the grain size and the surface chemistry, which was different from the reported bulk behavior. At low temperatures, electron mobility in nanostructured Bi1-xSbx was directly proportional to the average grain size, while the concentration of free carriers was inversely proportional to the grain size. We propose a model explaining such behavior. Preliminary measurements of thermoelectric properties showed a ZT value comparable to those of bulk Bi1-xSbx alloys at 300 K, suggesting a potential of Bi1-xSbx NCs for low-temperature thermoelectric applications.close