Cobalt oxides have been paid much attention in oxygen evolution reaction (OER). To enhance the catalysis reaction performance, here we reported Co3O4 nanocrystals anchored on phosphorus-doped carbon nitride (P-CN) sheets via Co–N bonds for highly efficient OER. By simply sintering the mixture of Co3O4 nanocrystals with P-CN sheets in the tube furnace, the Co–N bonds were well-formed as indicated by X-ray photoelectron spectroscopy analysis, forming efficient charge transfer channels to conquer the barriers between glassy carbon electrode surface and Co3O4 active sites. The Co3O4 nanocrystals distributed on the P-CN substrates homogeneously and exposed most of the potential active sites of Co3O4 during electrochemical processes. Because of the synergy between Co3O4 and P-CN, the OER performance of as-fabricated Co3O4/P-CN catalyst showed the lowest overpotential (320 mV), the lowest Tafel slope (66.8 mV dec–1), and the highest electrochemical active surface area (ESCA, 133.58 mF cm–2).

The magnetic performance of nanomaterials depends on size, shape, and surface of the nanocrystals. Here, the exposed crystal planes of CoO nanocrystals were analyzed to research the dependence of magnetic properties on the configuration environment of the ions exposed on different surfaces. The CoO nanocrystals with exposed (1 0 0), (1 1 0), (1 1 1), and (1 1 2) planes were synthesized using a hydrothermal method in the shapes of nanocube, nanorod, hexagonal nanoplatelet, and nanolaminar, respectively. Ferromagnetic performance was detected in the (1 0 0) and (1 1 1) plane-exposed samples. First-principles calculation results indicate that unlike the nonmagnetic nature in the bulk, the Co ions exposed on or close to the surface possess sizable magnetic moments because of the variation of coordination numbers and lattice distortion, which is responsible for the ferromagnetic-like behavior. The (1 1 0)-exposed sample keeps the natural antiferromagnetic behavior of bulk CoO because either the surface Co ions have no magnetic moments or their moments are in antiferromagnetic coupling. The (1 1 2)-exposed sample also displays antiferromagnetism because the interaction distances between the magnetized Co ions are too long to form effective ferromagnetic coupling.

Surface reconstruction of AgPd nanoalloy can improve the catalytic activity, however, the instability of surface oxides formed by reconstruction greatly limits the further application of catalysts. Herein, a density functional...

Surface reconstruction and surface oxide formation on Pd(111) facet are investigated using density functional theory calculations coupled with particle swarm optimization (PSO) algorithms, and a series of surface oxides and isomers are obtained and evaluated for the catalytic activity toward formate oxidation reactions for the first time. A globally stable Pd 4 O 3 subsurface oxide is identified on Pd(111) facet during the oxygen adsorbedinduced surface reconstruction and featured by three subsurface oxygen atoms. The Pd(111) surface during the surface reconstruction undergoes two phase transitions starting from the oxygen-adsorbed surface to the surface oxide with an activation energy barrier of 0.366 eV and then to the Pd 4 O 3 subsurface oxide with an activation energy barrier of 0.231 eV. During the formate oxidation reaction, the limiting potentials for the Pd(111) clean surface, Pd(111) oxygen-adsorbed surface, Pd 4 O 3 surface oxide, and Pd 4 O 3 subsurface oxide are 0.612, 0.232, 0.828, and 0.141 eV, respectively, indicating that the catalytic activity is suppressed when the surface is oxidized to form Pd 4 O 3 surface oxide and then enhanced as Pd 4 O 3 subsurface oxide further forms. The reconstructed Pd 4 O 3 subsurface oxide has the highest activity among various Pd 4 O x (x = 1−4) (sub)surface oxides and isomers. Overall, this work identifies a previously unknown surface reconstruction on Pd(111) facet and proposes a mechanism of oxygen-induced surface reconstruction on Pd(111) facet and a new strategy to identify active species for reconstructed electrocatalysts in the formate oxidation reactions.