Cooperative Surface-Particle Catalysis: The Role of the "Active Doughnut" in Catalytic Oxidation

The synergy between electrochemical substrate oxidation and the oxygen reduction reaction to enable aerobic oxidation

Aerobic substrate oxidation reactions catalyzed by a heterogeneous catalyst can be looked upon as two independent half-cell reactions, viz. anodic substrate oxidation and the cathodic oxygen reduction reaction (ORR). In this context, Fe PANI/C, a well-known catalyst for the ORR, is chosen to validate this hypothesis, wherein the anodic reaction is hydrazine oxidation. Fe PANI/C shows excellent activity in terms of the electrochemical ORR and hydrazine oxidation in both alkaline aqueous and non-aqueous media and taken together the aerobic oxidation efficacy of hydrazine-like small organic molecules is correlated with the electrochemical outcomes.

Prudent electrochemical pretreatment to promote the OER by catalytically inert "Iron incorporated metallic Ni nanowires" synthesized via the "non-classical" growth mechanism

This study provides new insight towards the non-classical "amorphous to crystalline" growth mechanism for metal nanowire synthesis and reports an electrochemical strategy to activate inactive materials into efficient electrocatalysts for the OER. Despite considerable research on transition metal oxides/hydroxides, especially NiFe based hydroxides as OER electrocatalysts, poor conductivity of these materials plagues their catalytic efficiency. In contrast, lack of catalytic centers hinders the OER performance of conductive metals. Herein, we devised a suitable precondition strategy to transform only the surface of conductive metallic Ni nanowires into active catalytic centers. The resulting material with intimate contact between the electrically conductive core and electrocatalytically active surface showed promising "specific" and "geometric" electrocatalytic activity towards the alkaline OER at different pH. Upon iron incorporation, the Fe centers incorporated at the surface as well as in the bulk of the nanowires were found to further boost the OER activity of these materials. A one-pot strategy was adopted to produce iron free/incorporated Ni nanowires covered with nano-spikes. Growth analysis revealed a unique "non-classical amorphous-to-crystalline transformation" to be responsible for the formation of metallic nanowires.

Palladium dispersion effects on wet methane oxidation kinetics

The catalytic activity for dry and wet methane oxidation over a series of palladium–alumina catalysts with systematically varied palladium loadings and PdO dispersions was measured and compared with conceptual multiscale simulations.

Covalent structured catalytic materials containing single-atom metal sites with controllable spatial and chemical properties: concept and application

Keep your distance! A simple and effective protocol for connecting macrocycle polymers creates a new and versatile class of highly stable single-site catalytic materials.

Size-Controlled Growth of Silver Nanoparticles onto Functionalized Ordered Mesoporous Polymers for Efficient CO2 Upgrading

Highly dispersed metallic silver nanoparticles (AgNPs) are promising heterogeneous catalysts for carboxylative coupling of terminal alkynes with CO₂ under mild conditions. Yet, their size-controlled synthesis is very challenging because of the high surface energy. Here, we prepared a series of amino-functionalized ordered mesoporous polymers as hosts for anchoring AgNPs. Control experiments and computations showed that electron-rich amines were confined in mesochannels with varying electron density and steric hindrance, creating "localized active zones (LAZ)" to control the growth of AgNPs. The particle size of AgNPs grows along with the increased volume of LAZ around nitrogen species. We also revealed that the catalytic activity of Ag-based catalysts is size-dependent and increases with decreasing particle size. Building on these findings, we report a facile one-pot synthesis strategy for preparing an amine-incorporated ordered mesoporous polymer (NOMP) with a high specific surface area, small LAZ volume, and uniform amine sites with controllable loading. These features result in the formation of ultrasmall and monodispersed Ag nanoparticles. Remarkably, Ag@NOMP gave a quantitative target yield under the conditions of 1 atm CO₂ pressure and 50 °C, showing superior catalytic activity in CO₂ carboxylation compared to other mesoporous analogues.