Metallic Co and crystalline Co-Mo oxides supported on graphite felt for bifunctional electrocatalytic hydrogen evolution and urea oxidation

Oxygen evolution reaction (OER) and urea oxidation reaction (UOR) play important roles in the field of hydrogen energy preparation and pollution treatment. In this work, by merging bimetallic Co-Mo oxides with metallic Co on the graphite felt (GF), we effectively manufacture a 3D bifunctional and highly efficient electrocatalyst (CoMoO@Co/GF) with multi-site functionality for the simultaneous reduction of water and the oxidation of urea in an alkaline medium. The presence of metallic Co causes Co-Mo oxides to evolve from amorphous to crystalline structures. The coupling interface produced between metallic Co and Co-Mo oxides is proven to facilitate electron transport in addition to extensively accessible and highly electroactive Co-Mo oxide nanoflower architecture. The experimental results reveal that the over-potentials for OER and UOR in the CoMoO@Co/GF electrode require only 269 and 115 mV to obtain a current density of 10 mA cm(-2), respectively. Furthermore, with the aid of urea, the over-potential for HER at the current density of 10 mA cm(-2) is lowered to 155 mV. Most notably, the constructed CoMoO@Co/GF-based electrolytic cell only requires a 1.5 V dry battery to achieve effective H-2 evolution and noteworthy stability, outperforming the commercial catalyst-based device and many previous results. The combination of experiments and theoretical calculations further clarifies the active sites in the catalyst. What's more, the pathway of electron transfer in the catalytic process is defined. (C) 2021 Published by Elsevier Inc.

Automated summary

In this study, a 3D bifunctional electrocatalyst was successfully fabricated by merging bimetallic Co-Mo oxides with metallic Co on a graphite felt substrate. It exhibited multi-site functionality for water reduction and urea oxidation simultaneously. The electrocatalyst showed low overpotentials for both oxygen evolution reaction (OER) and urea oxidation reaction (UOR) in an alkaline medium, indicating high efficiency.