Enhanced Carbon Monoxide Electroreduction to >1†A cm-2 C2+ Products Using Copper Catalysts Dispersed on MgAl Layered Double Hydroxide Nanosheet House-of-Cards Scaffolds.

Cu catalysts are most apt for reducing CO(2) to multi-carbon products in aqueous electrolytes. To enhance the product yield, we can increase the overpotential and the catalyst mass loading. However, these approaches can cause inadequate mass transport of CO(2) to the catalytic sites, which will then lead to H2 evolution dominating the product selectivity. Herein, we use a MgAl LDH nanosheet 'house-of-cards' scaffold to disperse CuO-derived Cu (OD-Cu). With this support-catalyst design, at -0.7 VRHE , CO could be reduced to C2+ products with a current density (jC2+ ) of -1251 mA cm-2 . This is 14× that of the jC2+ shown by unsupported OD-Cu. The current densities of C2+ alcohols and C2 H4 were also high at -369 and -816 mA cm-2 respectively. We propose that the porosity of the LDH nanosheet scaffold enhances CO diffusion through the Cu sites. The CO reduction rate can thus be increased, while minimizing H2 evolution, even when high catalyst loadings and large overpotentials are used.

Low-temperature fabrication of crystalline MnCoO spinel film on porous carbon paper for efficient oxygen evolution reaction.

Cubic MnxCo3-xO4 (x = 0-0.5) spinel nanocrystal thin films were fabricated on carbon fibre electrodes via one-step topotactic catalysis using Co(OH)2 nanosheets under aqueous and mild reaction conditions (<120 °C). The MnCo3O4 (Mn = 0.01)/CFP catalyst showed the best charge transport efficiency, exhibiting excellent OER activity and stability.

Exfoliated Single Layers of Layered Cobalt Hydroxide for Ultrafine Co3 O4 Nanoparticles on Graphene Nanosheets as an Efficient Electrocatalyst for Oxygen Reduction.

A highly effective way to produce an oxygen reduction electrocatalyst was developed through the self-assembly of exfoliated single layers of cobalt hydroxide (Co(OH)2 ) and graphene oxide (GO). These 2D materials have complete contact with one another because of their physical flexibility and the electrostatic attraction between negatively charged GO and positively charged Co(OH)2 layers. The strong coupling induces transformation of the Co(OH)2 single layer into a discrete nanocrystal of spinel Co3 O4 with an average size of 8 nm on reduced GO (RGO) during calcination, which could not be obtained with bulk-layered cobalt hydroxide because of its rapid layer collapse. The ultrafine Co3 O4 /RGO hybrid exhibited not only comparable performance in the oxygen reduction reaction but also higher durability compared with the commercial 20 wt % Pt/C catalyst.

A cobalt hydroxide nanosheet-mediated synthesis of core-shell-type Mn0.005Co2.995O4 spinel nanocubes as efficient oxygen electrocatalysts.

We developed a topotatic growth method involving an exfoliated cobalt hydroxide nanosheet, which allows water-based mild reaction conditions (90 °C) for the formation of the homogeneous cubic structure of MnxCo3-xO4 spinel oxides with Mn(ii)/Co(ii) salts. The size of the nanocubes increased as the Mn content increased, e.g., 13 nm (x = 0.0), 23 nm (x = 0.005), 50 nm (x = 0.05), and 140 nm (x = 1.0). The incorporation of Mn into Co3O4 dramatically increased the ORR performance because the catalytically active Mn cations exclusively substitute the less active Co2+ in the MnxCo3-xO4 structure. We effectively reduced the Mn content in the spinel Co3O4 structure to a value of 0.005, representing the Mn0.005Co2.995O4 spinel nanocubes that unexpectedly exhibited the best ORR activity among the samples. In addition, the XPS and ICP characterizations suggest an Mn-rich shell/Co-rich core for the MnxCo3-xO4 nanocubes.