Synthesis of nanostructured NiO/Co3O4 through thermal decomposition of a bimetallic (Ni/Co) metal-organic framework as catalyst for cyclooctene epoxidation

Controlled reconstruction of metal-organic frameworks via coordination environment tuning as oxygen evolution electrocatalysts

During the oxygen evolution reaction (OER), metal-organic framework (MOF) catalysts undergo structural reorganization, a phenomenon that is still not fully comprehended. Additionally, designing MOFs that undergo structural reconstruction to produce highly active OER catalysts continues to pose significant challenges. Herein, a bimetallic MOF (CoNi-MOF) with carboxylate oxygen and pyridine nitrogen coordination has been synthesized and its reconstruction behavior has been analyzed. The CoNi-MOF electrocatalyst attains a current density of 10 mA cm-2 with a minimal overpotential of just 250 mV, along with a Tafel slope of 91.57 mV dec-1, which is relatively low. After undergoing CV cycling tests, changes were observed in its catalytic activity, as well as in the microstructure and electrochemically active surface area, which are related to its activity. Importantly, in situ Raman analysis indicates that during the electrocatalytic process, the MOFs undergo a transition to MOOH, signifying the occurrence of reconstruction. Notably, compared to monometallic MOFs, bimetallic MOFs undergo reconstruction at lower voltage and with a faster reconstruction rate. Further analysis has revealed that the electrochemical reconstruction rate of the Co-N/O coordination mode at the active center is higher than that of Ni-N/O, playing a crucial role in enhancing OER activity. This study underscores the significance of the reconstruction strategy in enhancing the activity of MOF catalysts, providing new insights for the development of high-activity materials.

Boosting oxygen evolution reaction activity by tailoring MOF-derived hierarchical Co–Ni alloy nanoparticles encapsulated in nitrogen-doped carbon frameworks

The growing demand for sustainable energy has led to in-depth research on hydrogen production from electrolyzed water, where the development of electrocatalysts is a top priority. We here report a controllable strategy for preparing the cobalt–nickel alloy nanoparticles encapsulated in nitrogen-doped porous carbon by annealing a bimetal–organic framework. The delicately tailored hierarchical Co₂Ni@NC nanoparticles effectively realize abundant synergistic active sites and fast mass transfer for the oxygen evolution reaction (OER). Remarkably, the optimized Co₂Ni@NC exhibits a small overpotential of 310 mV to achieve a current density of 10 mA cm⁻² and an excellent long-term stability in alkaline electrolyte. Furthermore, the underlying synergistic effect mechanism of the Co–Ni model has been pioneeringly elucidated by density functional theory calculations.

The hierarchical Co₂Ni@NC nanoparticles realize fast mass transfer for the oxygen evolution reaction (OER). The synergistic effect between Co and Ni can effectively adjust the binding energy tending to an optimal value, further improving the energetics for the OER.

Single step synthesis of bio-inspired NiO/C as Pd support catalyst for dual application: Alkaline direct ethanol fuel cell and CO2 electro-reduction

Carbon dioxide (CO₂) is considered a useful greenhouse gas that can be captured and be used in the electro-syntheses of useful chemicals or fuels. On the other hand, there's also a tremendous interest on ethanol beneficiation as it is largely produced from crops, and it is regarded as a potential candidate for low temperature fuel cell applications. Although ethanol possesses good advantages, its resistant to oxidation poses a threat. The main objective of the study is to synthesis bio-inspired metal oxide-support catalyst which will help enhance the activity, efficiency and selectivity of Pd catalyst in CO₂ reduction, Fuel cell performance and ethanol oxidation. Here, Pd nanoparticles were supported on NiO/C through a green facile one-step process using pomegranate peel extracts as reducing agent. A series of characterizations were carried out to provide proof for and to quantify the presence of Pd, Ni, O and C in the prepared sample. Microscopic methods confirmed the successful preparation of pure NiO/C and (%5 Pd) Pd-NiO/C, evident by the key elemental components, mixed nanostructures and co-existence of Pd and NiO/C. The resultant Pd-NiO/C nanocatalyst revealed higher activity towards the oxidation of ethanol and that the nanocatalyst is more tolerant to poising by intermediate oxidation species. Enhanced cell performance with current and power densities of 66 mA cm^-2 and 26 mW cm^-2 relative to the commercial Pd/C were obtained under passive conditions at 1 M ethanol in 1MKOH. In addition, the nanocatalyst showed good selectivity to HCOOH with enhanced current efficiencies of 45%.