Investigation of the reaction mechanism of the hydrodeoxygenation of propionic acid over a Rh(1 1 1) surface: A first principles study

Rational Construction of a Triple-Phase Reaction Zone Using CuO-Based Heterostructure Nanoarrays for Enhanced Water Oxidation Reaction

The development of high-efficiency oxygen evolution reaction (OER) electrocatalysts for the production and conversion of clean energy is paramount yet also full of challenges. Herein, we proposed a simple and universal method to precisely fabricate the hierarchically structured CuO/TMOs loaded on Cu foil (CuO/TMOs/CF) (TMO represents Mn3O4, NiO, CoO, and CuO) nanorod-array electrodes as a highly active and stable OER electrocatalyst, employing Cu(OH)2/CF as a self-sacrificing template by the subsequent H2O2-induced chemical deposition (HiCD) and pyrolysis process. Taking CuO/Mn3O4/CF as an example, we systematically investigated its structure-performance relationship via experimental and theoretical explorations. The enhanced OER activity can be ascribed to the rational design of the nanoarray with multiple synergistic effects of abundant active sites, excellent electronic conductivity of the metallic Cu foil substrate, strong interface charge transfer, and quasi-superhydrophilic/superaerophobic property. Consequently, the optimal CuO/Mn3O4/CF presents an overpotential of 293 mV to achieve a current density of 20 mA cm-2 in 1.0 M KOH media, comparable to that of commercial RuO2 (282 mV), delivering excellent durability by the electrolysis of water at a potential of around 1.60 V [vs reversible hydrogen electrode (RHE)] without evident degeneration. This work might offer a feasible scheme for developing a hybrid nanoarray OER electrocatalyst via regulating electron transportation and mass transfer.

Theoretical Investigation of the Electrochemical Oxidation of H2 and CO Fuels on a Ruddlesden-Popper SrLaFeO4-δ Anode

The electrochemical oxidation of H₂ and CO fuels have been investigated on the Ruddlesden-Popper layered perovskite SrLaFeO_4-δ (SLF) under anodic solid oxide fuel cell conditions using periodic density functional theory and microkinetic modeling techniques. Two distinct FeO₂-plane-terminated surface models differing in terms of the underlying rock salt layer (SrO or LaO) are used to identify the active site and limiting factors for the electro-oxidation of H₂, CO, and syngas fuels. Microkinetic modeling predicted an order of magnitude higher turnover frequency for the electro-oxidation of H₂ compared to CO for SLF at short-circuit conditions. The surface model with an underlying SrO layer was found to be more active with respect to H₂ oxidation than the LaO-based surface model. At an operating voltage of less than 0.7 V, surface H₂O/CO₂ formation was found to be the key rate-limiting step, and the surface H₂O/CO₂ desorption was the key charge transfer step. In contrast, the bulk oxygen migration process was found to affect the overall rate at high cell voltage conditions above 0.9 V. In the presence of syngas fuel, the overall electrochemical activity is derived mainly from H₂ electro-oxidation and CO₂ is chemically shifted to CO via the reverse water-gas shift reaction. Substitutional doping of a surface Fe atom with Co, Ni, and Mn revealed that the H₂ electro-oxidation activity of FeO₂-plane terminated anodes with an underlying LaO rock salt layer can be improved with dopant introduction, with Co yielding a three orders of magnitude higher activity relative to the undoped LaO surface model. Constrained ab initio thermodynamic analysis furthermore suggested that the SLF anodes are resistant toward sulfur poisoning both in the presence and absence of dopants. Our findings reflect the role of various elements in controlling the fuel oxidation activity of SLF anodes that could aid the development of new Ruddlesden-Popper phase materials for fuel cell applications.