Operando Investigation of Structural and Chemical Origin of Co3O4 Stability in Acid under Oxygen Evolution Reaction.

Replacement of an expensive anode electrocatalyst in proton exchange membrane water electrolysis is of great importance. Recently explored Co3O4 shows good activity and stability toward oxygen evolution reaction (OER) in acid; however, the stability is not adequately explained. Lack of such information delays the design of an acid-stable OER electrocatalyst. Here, we investigate the structural origin of cobalt dissolution by various local atomic configurations of Co3O4. Operando Raman studies and voltammetric data reveal that chemical reduction of the CoO2 intermediate accompanied by lattice oxygen loss leads to undercoordinated CoO sites, which then react with water and form an amorphous three-dimensional (3D) porous network of CoO(OH)x, called the hydrous oxide layer (HOL). Growth of HOL mainly depends on the oxygen vacancies and near-surface OI- that impair the crystalline integrity and favor dissolution. These insights provide a fundamental relation between OER activity and stability and offer a specific guideline for the electrocatalyst design.

3D Flower-Like Gadolinium Molybdate Catalyst for Efficient Detection and Degradation of Organophosphate Pesticide (Fenitrothion).

Three-dimensional (3D) nanostructured materials have received enormous attention in energy and environment remediation applications. Herein, we developed a novel 3D flower-like gadolinium molybdate (Gd2MoO6; GdM) and used as a bifunctional catalyst for the electrochemical detection and photocatalytic degradation of organophosphate pesticide fenitrothion (FNT). The flower-like GdM catalyst was prepared via a simple sol-gel technique with the assistance of urea and ethylene glycol. The properties of GdM were confirmed by various spectroscopic and analytical techniques. The GdM catalyst played a significant role in electrochemical reduction of FNT and results in a very low detection limit (5 nM), wide linear ranges (0.02-123; 173-1823 µM), and good sensitivity (1.36 µA µM-1 cm-2). Interestingly, the GdM electrocatalyst had good recoveries to FNT in soil and water sample analysis. In addition to trace level detection, the flower-like GdM was used as the photocatalyst which portrayed an excellent photocatalytic degradation behavior to eliminate the FNT in the aqueous system. The GdM photocatalyst could degrade above 99% of FNT under UV light irradiation with good stability even after five cycles.