Enhanced Electrochemical Hydrogenation of Benzaldehyde to Benzyl Alcohol on Pd@Ni-MOF by Modifying the Adsorption Configuration

Electrocatalytic hydrogenation (ECH) approaches under ambient temperature and pressure offer significant potential advantages over thermal hydrogenation processes but require highly active and efficient hydrogenation electrocatalysts. The performance of such hydrogenation electrocatalysts strongly depends not only on the active phase but also on the architecture and surface chemistry of the support material. Herein, Pd nanoparticles supported on a nickel metal-organic framework (MOF), Ni-MOF-74, are prepared, and their activity toward the ECH of benzaldehyde (BZH) in a 3 M acetate (pH 5.2) aqueous electrolyte is explored. An outstanding ECH rate up to 283 μmol cm-2 h-1 with a Faradaic efficiency (FE) of 76% is reached. Besides, higher FEs of up to 96% are achieved using a step-function voltage. Materials Studio and density functional theory calculations show these outstanding performances to be associated with the Ni-MOF support that promotes H-bond formation, facilitates water desorption, and induces favorable tilted BZH adsorption on the surface of the Pd nanoparticles. In this configuration, BZH is bonded to the Pd surface by the carbonyl group rather than through the aromatic ring, thus reducing the energy barriers of the elemental reaction steps and increasing the overall reaction efficiency.

Cobalt-Iron Oxyhydroxide Obtained from the Metal Phosphide: A Highly Effective Electrocatalyst for the Oxygen Evolution Reaction at High Current Densities

The development of high current density anodes for the oxygen evolution reaction (OER) is fundamental to manufacturing practical and reliable electrochemical cells. In this work, we have developed a bimetallic electrocatalyst based on cobalt-iron oxyhydroxide that shows outstanding performance for water oxidation. Such a catalyst is obtained from cobalt-iron phosphide nanorods that serve as sacrificial structures for the formation of a bimetallic oxyhydroxide through phosphorous loss concomitantly to oxygen/hydroxide incorporation. CoFeP nanorods are synthesized using a scalable method using triphenyl phosphite as a phosphorous precursor. They are deposited without the use of binders on nickel foam to enable fast electron transport, a highly effective surface area, and a high density of active sites. The morphological and chemical transformation of the CoFeP nanoparticles is analyzed and compared with the monometallic cobalt phosphide in alkaline media and under anodic potentials. The resulting bimetallic electrode presents a Tafel slope as low as 42 mV dec^-1 and low overpotentials for OER. For the first time, an anion exchange membrane electrolysis device with an integrated CoFeP-based anode was tested at a high current density of 1 A cm^-2, demonstrating excellent stability and Faradaic efficiency near 100%. This work opens up a way for using metal phosphide-based anodes for practical fuel electrosynthesis devices.