Operando X-ray and Mass Spectroscopy of Reduced Graphene Oxide (rGO)-Mediated Cobalt Catalysts for Boosting the Hydrogen Evolution Reaction

Abstract

Inserting underlying reduced graphene oxide (rGO) into Co aims to regulate the chemical integrity and catalytic ability of the Co upper layer for hydrogen evolution reaction (HER) as a green-hydrogen goal. Principally, an operando mass spectrometer indicates 3.8 times more considerable hydrogen generation in Co/rGO than in Co. The spectroscopical approaches, combining operando soft and hard X-ray probing, illustrate the chemical oxidation evolution of electronic Co-3d and Co-4p states differently regarding the underlying rGO contribution. A unique examination is regarded as the phase transition from the initial middle to high oxidation and to deoxidation, related to the intermediate Co^{0} existence and H_{2} generation. The chemical adsorption of Co–O(H), Co–H_{ads}, and H_{2} molecules desorption have been assigned their spectral significances. The rGO mediation indicates two significant metal Co and Co–O(H) blocks in the two-dimensional R-k domain. Density-functional-theory (DFT) calculation provides the regeneration, sustained stability, and decreasing energy barrier of Co–H_{ads} catalysts due to the rGO incorporation, thereby augmenting the HER enhancement through the alternative Volmer-Heyrovsky process. The in-situ experiment, including mass spectrometer, soft, and hard X-ray, provides evidence regarding the catalyst’s HER enhancement. This study offers insights into the chemical composition, electronic structure, and active role of Co bonded with or without the extinct OH and H bonds, advancing our comprehension of electrocatalytic reactions, thus taking our knowledge of composite materials to stepwise electrocatalytic reactions forward. This cutting-edge experiment under in-situ environment and DFT studies gives critical information regarding the catalytic mechanism and chemical stability of the Co and rGO materials.