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Hybrid core-shell catalysts possess superior physiochemical properties that are closely related to their atomic structures. Here, we report novel diffusion phenomena in an Au-Ni 2 P yolk-shell structure using in situ heating transmission electron microscopy (TEM) analysis. The Au yolks can dissolve completely into and diffuse across the Ni 2 P shell at 500 °C, resulting in an inward volume expansion of the Ni 2 P shell and shrinkage of the void. The dissolved Au is subsequently segregated, forming a new crystal on the outer layer of the shell. A detailed atomic-scale resolution imaging revealed that the outward Au diffusion and aggregation occur when the Au yolks are epitaxial to the Ni 2 P shells. Theoretical analysis shows that the outward diffusion and deposition of Au atoms is primarily driven by the excess epitaxial strain energy.

A simple and feasible strategy was reported to construct Ni 2 P nanostructures entwined by graphite layers (Ni 2 P/GC). In this process, a commercial amino phosphonic acid chelating resin was adopted as both the phosphorus and carbon resources. Then, Ni 2+ was introduced into the resin framework via ionic exchange and chelation to form a resin-Ni 2+ precursor. After carbonization, the highly dispersed Ni 2 P particles, coupled with thin graphite layers, were simultaneously synthesized in situ. A ternary 7.5% Pt-Ni 2 P/GC catalyst was further obtained by loading 7.5 wt % Pt on Ni 2 P/GC. For the oxygen reduction reaction in acidic media, the 7.5% Pt-Ni 2 P/GC catalyst exhibited even more positive onset (1.03 V) and half-wave (0.93 V) potentials, as well as a rather higher mass activity of 565.3 mA mg Pt -1 and a better long-term stability than those of the commercial 20% Pt/C (JM) electrocatalyst. The improved reaction kinetics is mainly attributed to the synergistic effect between Pt and Ni 2 P/GC. This work not only provides a method for the synthesis of phosphides but also gives insight into the synergy between Pt and Ni 2 P, which is helpful for the development of more low-Pt catalysts in acidic media.

The depolymerization of lignin to bioaromatics usually requires a hydrodeoxygenation (HDO) step to lower the oxygen content. A mixed Cu-Mg-Al oxide (CuMgAlO x ) is an effective catalyst for the depolymerization of lignin in supercritical ethanol. We explored the use of Ni-based cocatalysts, i.e. Ni/SiO 2 , Ni 2 P/SiO 2 , and Ni/ASA (ASA = amorphous silica alumina), with the aim of combining lignin depolymerization and HDO in a single reaction step. While the silica-supported catalysts were themselves hardly active in lignin upgrading, Ni/ASA displayed comparable lignin monomer yield as CuMgAlO x . A drawback of using an acidic support is extensive dehydration of the ethanol solvent. Instead, combining CuMgAlO x with Ni/SiO 2 and especially Ni 2 P/SiO 2 proved to be effective in increasing the lignin monomer yield, while at the same time reducing the oxygen content of the products. With Ni 2 P/SiO 2 , the lignin monomer yield was 53 wt %, leading to nearly complete deoxygenation of the aromatic products.

Herein, we report on a high-discharge-rate Na 3 V 2 (PO 4 ) 3 -Ni 2 P/C (NVP-NP/C) composite cathode prepared using a polyol-based pyro synthesis for Na-ion battery applications. X-ray diffraction and electron microscopy studies established the presence of Na 3 V 2 (PO 4 ) 3 and Ni 2 P, respectively, in the NVP-NP/C composite. As a cathode material, the obtained NVP-NP/C composite electrode exhibits higher discharge capacities (100.8 mAhg -1 at 10.8 C and 73.9 mAhg -1 at 34 C) than the NVP/C counterpart electrode (62.7 mAhg -1 at 10.8 C and 4.7 mAhg -1 at 34 C), and the composite electrode retained 95.3% of the initial capacity even after 1500 cycles at 16 C. The enhanced performance could be attributed to the synergetic effect of the Ni 2 P phase and nanoscale NVP particles, which ultimately results in noticeably enhancing the electrical conductivity of the composite. The present study thus demonstrates that the Na 3 V 2 (PO 4 ) 3 -Ni 2 P/C nanocomposite is a prospective candidate for NIB with a high power/energy density.