Hierarchical molybdenum-doped NiCoP@carbon microspheres: a highly-efficient electrocatalyst for the hydrogen evolution reaction

Designing a hybrid nanomaterial based on Cr-containing polyoxometalate and graphene oxide as an electrocatalyst for the hydrogen evolution reaction

A new polyoxometalate (POM)-based hybrid nanomaterial (denoted as PMo11-Cr-mGO) was designed via covalent interaction between the Cr(acac)3 complex and [PMo11O39]7- followed by immobilization on the surface of modified graphene oxide (mGO). The prepared nanomaterial was characterized using a series of physicochemical techniques. X-ray diffraction (XRD), Raman analysis, transmission electron microscopy (TEM), and FE-SEM-EDS revealed the preservation of layered GO during the formation of the desired hybrid nanomaterial. Fourier transform infrared (FT-IR), X-ray photoelectron spectroscopy (XPS), and elemental analysis confirmed the immobilization of POM (PMo11-Cr) on the surface of mGO and the formation of PMo11-Cr-mGO. In order to evaluate the performance of PMo11-Cr-mGO in the hydrogen evolution reaction (HER), electrochemical measurements were also performed. The resulting PMo11-Cr-mGO exhibited excellent HER activities with a low overpotential of 153 mV at 10 mA cm-2 and good durability in acidic media, thus emerging as one of the most efficient POM-based electrocatalysts.

Carbon Dots as an Electron Acceptor in the ZnIn2S4@MIL-88A Heterojunction for Enhanced Visible-Light-Driven Photocatalytic Hydrogen Evolution

In this study, visible-light-responsive carbon dots (CDs)/ZnIn2S4@MIL-88A (C/ZI@ML) photocatalysts were successfully prepared through in situ loading CDs and ZnIn2S4 nanosheets on MIL-88A(Fe) to form a ternary heterojunction. The detailed characterization indicated that the two-dimensional ZnIn2S4 nanosheets were uniformly coated on the surface of MIL-88A(Fe), and ZnIn2S4/MIL-88A(Fe) exhibited enhanced photocatalytic hydrogen production performance (1259.63 μmol h-1 g-1) compared to that of pristine MIL-88A(Fe) and ZnIn2S4 under visible light illumination. After introduction of CDs into ZnIn2S4/MIL-88A(Fe), the C/ZI@ML catalyst remarkably enhanced the photocatalytic activity and the hydrogen evolution rate of 1C/ZI@ML was up to 3609.23 μmol g-1 h-1. The photoinduced charge carriers of C/ZI@ML can be efficiently separated and migrated because of the close contacted interface, synergistic effect, and suitable band structure. In combination with photoelectrochemical experiments and electron paramagnetic resonance spectra, a possible photocatalytic mechanism over C/ZI@ML was proposed. This work demonstrated a facile preparation method for fabricating efficient visible-light-driven heterojunction photocatalysts.

Core-shell Mo2C@NC/Mo2C hollow microspheres as highly efficient electrocatalysts for the hydrogen evolution reaction

Developing low-cost and highly efficient electrocatalysts for the hydrogen evolution reaction (HER) has stimulated extensive interest. Molybdenum carbide materials have been proposed as promising alternatives to noble platinum-based catalysts due to their earth abundance and tunable physicochemical characteristics. Here, we report Mo₂C@NC/Mo₂C hollow microspheres composed of a β-Mo₂C core and small β-Mo₂C particles embedded within a nitrogen-doped carbon shell and prepared using guanosine and hexaammonium molybdate as precursors via a hydrothermal self-assembly process, which results in outstanding catalytic activity and fast kinetics in hydrogen evolution in both acidic and alkaline solutions. The significant activity improvement of Mo₂C@NC/Mo₂C can be attributed to the large ratio of exposed active sites and abundant interfacial structures. This work provides a new template-free strategy for the design of a highly active Mo₂C@NC/Mo₂C hollow microsphere HER catalyst.

Fe and P dual-doped nickel carbonate hydroxide/carbon nanotube hybrid electrocatalysts for an efficient oxygen evolution reaction

Designing cost-effective and highly active oxygen evolution reaction (OER) electrocatalysts is critical for large-scale hydrogen production from electrocatalytic water splitting. Herein, Fe and P dual-doped nickel carbonate hydroxide/carbon nanotubes (Fe, P-NiCH/CNTs) were fabricated through a solvothermal method. By virtue of the optimized electronic structure, improved conductivity and enriched active sites, the as-fabricated Fe, P-NiCH/CNT hybrid electrocatalyst exhibits superior OER activity, with a low overpotential of 222 mV at 20 mA cm^-2 and robust durability, confirming its potential as a highly efficient OER electrocatalyst. Moreover, theoretical calculations demonstrate that the doped Fe and surface adsorbed PO₄^3- can regulate the electronic structure of evolved NiOOH and decrease the energy barrier of the rate-determining step, thus leading to improved OER activity. The strategy presented in this work can also be employed to fabricate other transition metal carbonate hydroxides for various electrocatalytic applications.