Co₃O₄/WO₃/C Nanorods with Porous Structures as High-Performance Electrocatalysts for Water Splitting

Abstract

The recent promise of the hybridization of mesoporous carbon with transition metal oxides as a desirable catalyst for the oxygen evolution reaction (OER), and its extension to the hydrogen evolution reaction (HER) to achieve the goal of overall water splitting applications, remains a major challenge. Here, a unique environmentally benign mesoporous Co 3 O 4 /WO 3 /C bifunctional electrocatalyst is developed from converting cellulose waste, specifically in the form of sugarcane bagasse, by pyrolysis followed by a twostep hydrothermal strategy that can catalyze electrochemically OER and HER activity in an efficient and robust manner. The electrocatalyst delivers low overpotentials of 229/295 mV and a Tafel slope of 63/77 mV/dec −1 for both alkaline and acidic media, respectively, for OER along with the overpotential of 123 mV and a Tafal slope of 36 mV/dec −1 for HER to reach a current density of 10 mA/cm 2 . We hypothesized that an electronic synergistic effect between the transition metals might be responsible for promoting HER and OER activity, which was confirmed by density functional theory studies. This work opens a unique pathway to develop highly efficient, but low cost, electrocatalysts for water splitting applications.

Hollow and Ultrathin Mo-Doped CoP Bamboo-Leaf Nanoarrays for pH-Universal Hydrogen Evolution

“…Nowadays, the widespread use of fossil energy not only occasions nonrenewable energy shortage but also leads to serious environmental pollution and unsustainable economic development. − In the cause of facilitating the continuable progress of the global economy, it is exigent to exploit reproducible clean energy and substitute fossil energy. − Hydrogen is deemed to be a desired replacement due to its environmental friendliness and high energy density. , Noble metal-based electrocatalysts appear to have outstanding activity to produce hydrogen for the HER, but their low reserve and high cost prevent actual application. − Consequently, it is still imperative to utilize nonprecious metal hydrogen evolution substances with ample sources, low price, supernal activity, and stability. , In recent years, transition metal-based materials are being widely explored, such as sulfides, , nitrides, , oxides, − and phosphides, , as preponderant HER electrocatalysts, thanks to their advantages of economical efficiency and environmental protection. Among them, transition metal phosphides (TMPs) have attracted much attention because of their low Gibbs adsorption energy. , In particular, cobalt-based phosphides possess obvious catalytic activity and durability. , In order to further improve the electrocatalytic activity, rational metal doping has been demonstrated to be a practical method. , Dopant atom substitution is finely acknowledged as an efficient tactic to ameliorate catalytic properties on account of the fact that the foreign atom can optimize the electronic structure of catalysts and the adsorption energy of intermediates. − As a common n-type dopant, Mo has the peculiarity of a large atomic radius and strong electronegativity compared with Co.…”