Reported herein is elucidation of a novel Co-based oxygen evolution catalyst generated in situ from cobalt phosphide (CoP) nanoparticles. The present CoP nanoparticles, efficient alkaline hydrogen-evolving materials at the cathode, are revealed to experience unique metamorphosis upon anodic potential cycling in an alkaline electrolyte, engendering efficient and robust catalytic environments toward the oxygen evolution reaction (OER). Our extensive ex situ characterization shows that the transformed catalyst bears porous and nanoweb-like dispersed morphologies along with unique microscopic environments mainly consisting of discrete cobalt-oxo/hydroxo molecular units within a phosphate-enriched amorphous network. Outstanding OER efficiency is achievable with the activated catalyst, which is favorably comparable to even a precious iridium catalyst. A more remarkable feature is its outstanding long-term stability, superior to iridium and conventional cobalt oxide-based materials. Twelve-hour bulk electrolysis continuously operating at high current density is completely tolerable with the present catalyst.

We show that bicarbonate is neither a general acid nor a reaction partner in the rate-limiting step of electrochemical CO reduction catalysis mediated by planar polycrystalline Au surfaces. We formulate microkinetic models and propose diagnostic criteria to distinguish the role of bicarbonate. Comparing these models with the observed zero-order dependence in bicarbonate and simulated interfacial concentration gradients, we conclude that bicarbonate is not a general acid cocatalyst. Instead, it acts as a viable proton donor past the rate-limiting step and a sluggish buffer that maintains the bulk but not local pH in CO-saturated aqueous electrolytes.

Reversible, carbon dioxide mediated chemical hydrogen storage was first demonstrated using a heterogeneous Pd catalyst supported on mesoporous graphitic carbon nitride (Pd/mpg-C 3 N 4 ). The Pd nanoparticles were found to be uniformly dispersed onto mpg-C 3 N 4 with an average size of 1.7 nm without any agglomeration and further exhibit superior activity for the dehydrogenation of formic acid with a turnover frequency of 144 h À1 even in the absence of external bases at room temperature. Initial DFT studies suggest that basic sites located at the mpg-C 3 N 4 support play synergetic roles in stabilizing reduced Pd nanoparticles without any surfactant as well as in initiating H 2 -release by deprotonation of formic acid, and these potential interactions were further confirmed by X-ray absorption near edge structure (XANES). Along with dehydrogenation, Pd/mpg-C 3 N 4 also proves to catalyze the regeneration of formic acid via CO 2 hydrogenation. The governing factors of CO 2 hydrogenation are further elucidated to increase the quantity of the desired formic acid with high selectivity.

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Direct C-H amination of arenes offers a straightforward route to aniline compounds without necessitating aryl (pseudo)halides as the starting materials. The recent development in this area, in particular in the metal-mediated transformations, is significant with regard to substrate scope and reaction conditions. Described herein are the mechanistic details on the Rh-catalyzed direct C-H amination reaction using organic azides as the amino source. The most important two stages were investigated especially in detail: (i) the formation of metal nitrenoid species and its subsequent insertion into a rhodacycle intermediate, and (ii) the regeneration of catalyst with concomitant release of products. It was revealed that a stepwise pathway involving a key Rh(V)-nitrenoid species that subsequently undergoes amido insertion is favored over a concerted C-N bond formation pathway. DFT calculations and kinetic studies suggest that the rate-limiting step in the current C-H amination reaction is more closely related to the formation of Rh-nitrenoid intermediate rather than the presupposed C-H activation process. The present study provides mechanistic details of the direct C-H amination reaction, which bears both aspects of the inner- and outer-sphere paths within a catalytic cycle.