The kinetically sluggish oxygen evolution reaction (OER) at an anode has always been the bottleneck in the largescale application of electrocatalytic water splitting to produce ecofriendly and sustainable hydrogen. Therefore, replacing the OER with hydrazine oxidation reaction (HzOR), which requires a lower theoretical potential, has been considered as a more energyefficient strategy. Herein, a novel bifunctional Co x P@Co 3 O 4 nanocomposite with grass-like and block-like structures was fabricated on Co foam (defined as P−Co 3 O 4 /Co) via a facile hydrothermal synthesis for Co 3 O 4 and the sodium hypophosphitephosphorization method for cobalt phosphides. Compared with the Co 3 O 4 precursor on Co foam, the heterogeneous P−Co 3 O 4 / Co, composed of a mixture of CoP, Co 2 P, and Co 3 O 4 , possessed superb electrochemical catalytic activity for both the hydrogen evolution reaction and HzOR in 1.0 M KOH and 0.3 M hydrazine medium. Low overpotentials of 106 and 129 mV were required to deliver current densities of 10 and 200 mA cm −2 , respectively. Meanwhile, potentials of −100 and −83 mV are needed to drive current densities of 10 and 200 mA cm −2 , respectively, which exceed those of almost recently reported catalysts. The excellent performance can be attributed to the fact that the synergistic effect between the presence of multiphase of Co x P/Co 3 O 4 and the three-dimensional porous Co foam substrate makes the as-synthesized catalyst possess a large specific surface area and fast charge/ mass transport. Density functional theory calculations unravel that the phosphorization strategy can not only regulate the electronic structure of pristine Co 3 O 4 , enhancing the electronic conductivity, but also optimize the adsorption/desorption strength of H* and alter the free energy change of the dehydrogenation kinetics of NH 2 NH 2 *. Meanwhile, a low cell voltage of 1 V was achieved to deliver a current density of 948 mA cm −2 when P−Co 3 O 4 /Co behaved as both the cathode and anode simultaneously, which was superior to most of the nonprecious metal-based catalysts.

No abstract

Clean hydrogen energy is regarded as a promising alternative in terms of energy conversion and storage. Meanwhile, transitional metal oxides (TMOs) have stimulated more and more research attention because of their unique performance, holding broad prospects in expediting the tardy oxygen evolution reaction (OER) in electrolyzing water. However, facile and highly efficient synthesis of TMOs to garner excellent electrocatalytic performance has by far remained difficult. Herein, a three-dimensional (3D) self-supported microstrip-like Co3O4 assembled from a tiny nanocube electrocatalyst, grown in situ on commercial Co foam (denoted as Co3O4/Co), is fabricated through a facile one-step hydrothermal synthesis method, where the sluggish anodic OER is replaced by a more thermodynamically oxidized hydrazine oxidation reaction (HzOR) for assisting energy-saving hydrogen generation in alkaline media. The synthesized electrocatalyst shows appreciable HzOR performances, producing a current density of 200 mA cm–2 at −32 mV and a Tafel slope of 53.43 mV dec–1. Remarkably, an ultrasmall-cell voltage of merely 1 V is required to deliver 764 mA cm–2 in a coupled electrode electrolyzer with excellent stability at room temperature, which is outperforming the precious metal catalyst system and the reported noble-metal-free electrocatalysts. Further, the Faradaic efficiency of the as-fabricated electrocatalyst is close to 100%. Considering the high electrocatalytic efficiency for the HzOR, the Co3O4/Co proves to be a kind of energy-saving electrocatalyst for the HzOR with great potential.

Lead‐free halide perovskite nanocrystals (NCs) with the unique optical properties are of interest for broad applications. There are a few studies on near‐infrared (NIR) emission in perovskite NCs. Here, all‐inorganic rare‐earth‐based Cs2NaEr1−xBxCl6 (B: In, Sb, or Bi; x = 0, 0.13, and 0.5) double perovskite (DP) NCs have been successfully sythesized. The Cs2NaErCl6 NCs show good air stability and emit a sharp NIR photoluminescence (PL) at telecommunication wavelength of 1543 nm, originating from 4I13/2→4I15/2 transition of the Er3+, and its average lifetime is 35.7 µs. Especially for Cs2NaEr0.5Sb0.5Cl6 NCs, NIR PL can be enhanced 23‐fold with the lifetime being 119.1 µs. Moreover, femtosecond transient absorption measurements prove that a long‐lifetime trap state promotes NIR emitting in the mixed Sb/Er DP NCs.

Liquid−liquid equilibria of the ternary system water + acetic acid + methyl tert-butyl ether were studied from 293.15 K to 318.15 K at atmospheric pressure. Distribution coefficients and separation factors were evaluated for the immiscibility region. The reliability of the experimental tie-line data was ascertained by applying the Othmer−Tobias correlation. The experimental results were also correlated with the NRTL and UNIQUAC models successfully.