Enhancement of alkaline water splitting activity by Co-P coating on a copper oxide nanowire

Transition Metals-Based Water Splitting Electrocatalysts on Copper-Based Substrates: The Integral Role of Morphological Properties

Electrocatalytic water splitting is a promising alternative to produce high purity hydrogen gas as the green substitute for renewable energy. Thus, development of electrocatalysts for both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) are vital to improve the efficiency of the water splitting process particularly based on transition metals which has been explored extensively to replace the highly active electrocatalytic activity of the iridium and ruthenium metals-based electrocatalysts. In situ growth of the material on a conductive substrate has also been proven to have the capability to lower down the overpotential value significantly. On top of that, the presence of substrate has given a massive impact on the morphology of the electrocatalyst. Among the conductive substrates that have been widely explored in the field of electrochemistry are the copper based substrates mainly copper foam, copper foil and copper mesh. Copper-based substrates possess unique properties such as low in cost, high tensile strength, excellent conductor of heat and electricity, ultraporous with well-integrated hierarchical structure and non-corrosive in nature. In this review, the recent advancements of HER and OER electrocatalysts grown on copper-based substrates has been critically discussed, focusing on their morphology, design, and preparation methods of the nanoarrays.

In situ confined vertical growth of a 1D-CuCo2S4 nanoarray on Ni foam covered by a 3D-PANI mesh layer to form a self-supporting hierarchical structure for high-efficiency oxygen evolution catalysis

Inspired by the patchwork of artificial turf, where planting in a smaller area can result in a more uniform lawn that grows in one direction, here, we defined the growth position and orientation of a CuCo₂S₄ nanoarray for the first time by electroplating a PANI mesh layer onto a Ni foam to obtain a self-supporting hierarchical electrode material. The nitrogen species derived from the PANI building blocks act as bridging sites to bind with metal ions, which provides a strong coupling effect for the in situ growth of CuCo₂S₄. At the same time, the mesh structure of PANI divides the growable location into smaller blocks. Compared with a mesh plane with uniformly distributed nitrogen sites, only a small portion of the nitrogen sites are located on the narrow-width fence structure, which may make it difficult for CuCo₂S₄ to grow onto the fence structure, thereby limiting the self-growth space and confining CuCo₂S₄. The uniformly distributed growth sites direct CuCo₂S₄ to grow perpendicular to the plane while limiting their growth size. The excellent structural features further enhance the electrochemical oxygen evolution activity, and the oxygen evolution overpotential at a current density of 100 mA cm^-2 is only 291 mV, which is superior to that of the currently known cobalt-copper-based catalyst materials. In addition, the stable structure provides excellent electrode cyclic stability. The preparation of hierarchical self-supporting cobalt-copper bimetallic sulfide nanoarrays provided a reference direction for other transition metal catalytic materials and provided a basis for industrial applications.

Photocatalytic 4-nitrophenol degradation and oxygen evolution reaction in CuO/g-C3N4 composites prepared by deep eutectic solvent-assisted chlorine doping

Heterostructured Cl-CuO/g-C₃N₄ composite for OER and photocatalytic 4-nitrophenol degradation.