Understanding the origin of high oxygen evolution reaction activity in the high Sr-doped perovskite

Effective electrocatalysis is crucial for enhancing the efficiency of water splitting to obtain clean fuels.Herein,we report a system of interesting and high-performance Sr-doped perovskite electrocatalysts with porous structures,obtained via a facile molten salt method and applied in the oxygen evolution reaction(OER).With increasing the Sr content,the valence states of Co and Fe ions do not clearly increase,according to the Co-L2,3 and Fe-L2,3 as well as the Co-K and the Fe-K X-ray absorption spectroscopy,whereas doped holes are clearly observed in the 0-K edge.High-resolution transmission electron microscopy indicates the appearance of an amorphous layer after the electrochemical reaction.We conclude that the formation of the amorphous layer at the surface,induced by Sr doping,is crucial for achieving high OER activity,and we offer insights into the self-reconstruction of the OER catalyst.

Copper foam-derived electrodes as efficient electrocatalysts for conventional and hybrid water electrolysis

Electrochemical water splitting has been demonstrated as a promising technology for the renewable generation of green hydrogen from water.Despite the extensive progress in materials science,one particular challenge for further development towards industrial application lies in the rational design and exploitation of efficient and cost-effective materials,especially oxygen evolution reaction(OER)electrocatalysts at the anode.In addition,attempts to replace the OER with other more oxidizable anode reactions are being evaluated as a groundbreaking strategy for generating hydrogen at lower potentials and reducing overall energy costs while producing valuable chemicals simultaneously.Compared with Fe/Co/Ni-based compounds,Cu-based materials have not received extensive research attention for electrode designs despite their high conductivity and abundant earth reserves.In this review,combining with the advantages of a three-dimensional network structure of metal foams,we summarize recent progress on Cu foam(CF)-derived materials as efficient electrocatalysts towards pure water electrolysis and hybrid water electrolysis.The advantages of CF and design strategies to enhance the electrocatalytic activity and operational durability are presented first.Catalyst design and fabrication strategies are then highlighted and the structure-activity relationship is also discussed.Finally,we propose challenges and perspectives on self-supported electrodes beyond CF-derived materials.

Molten salt-assisted synthesis of bulk CoOOH as a water oxidation catalyst

Different sizes of layered CoOOH were synthesized by the molten-salt-assisted method at different temperatures.X-ray diffraction and scanning electron microscope studies reveal that CoOOH grew at(003)with increasing temperature,and its size can reach dozens of microns.X-ray absorption near edge structure and XPS studies demonstrate that the Co valence state of CoOOH-750 is trivalent,and X-ray Absorption Fine Structure shows that it had a higher symmetry and lower disorder degree,indicating that CoOOH-750 has higher crystallinity and Co3+.The results of electrochemical tests show that CoOOH-750 exhibited the best oxygen-evolution-reaction(OER)catalytic activity.

Nitrogen-doped graphene supported Pd@PdO core- shell clusters for C-C coupling reactions

The introduction of nitrogen significantly decreases the metal particle size and improves the performance of metal-based graphene-supported catalysts. In this work, the density functional theory is used to understand the interaction between nitrogen-doped graphene and Pd@PdO clusters. Experiments show that small size Pd@PdO clusters （1-2 nm） can be grown uniformly on nitrogen-doped graphene sheets by a facile oxidation-reduction method. The nanoscale interaction relationship between nitrogen-doped graphene and Pd@PdO clusters is investigated through X-ray photoelectron spectroscopy （XPS） and X-ray absorption spectra （XAS）. The composite catalysts are applied in Suzuki-Miyaura reactions giving high yields and good structural stability. These results have potential impact in design and optimization of future high performance catalyst materials for cross coupling reactions.

Molten-salt synthesis of porous La0.6Sr0.4Co0.2Fe0.8O2.9 perovskite as an efficient electrocatalyst for oxygen evolution

The development of an efficient and low-cost electrocatalyst for the oxygen evolution reaction （OER） via an eco-efficient route is a desirable, although challenging, outcome for overall water splitting. Herein, an iron-rich La0.6Sr0.4Co0.2Fe0.8O2.9 （LSCF28） perovskite with an open porous topographic structure was developed as an electrocatalyst by a straightforward molten-salt synthesis approach. It was found that porosity correlates with both the iron content and the molten-salt approach. Benefiting from the large surface area, high activity of the porous internal surface, and the optimal electronic configuration of redox sites, this inexpensive material exhibits high performance with a large mass activity of 40.8A·g^-1 at a low overpotential of 0.345 V in 0.1 M KOH, surpassing the state-of-the-art precious metal IrO2 catalyst and other well-known perovskites, such as Ba0.5Sr0.5Co0.8Fe0.2O3 and SRCoO2.7. Our work illustrates that the molten- salt method is an effective route to generate porous structures in perovskite oxides, which is important for energy conversion and storage devices.