Simple and Facile Fabrication of Anion-Vacancy-Induced MoO3−X Catalysts for Enhanced Hydrogen Evolution Activity

Abstract

Advanced catalysts for clean hydrogen generation and storage offer an attractive possibility for developing a sustainable and ecofriendly future energy system. Transition metal oxides (TMO) are appealing candidates to be largely considered as electrode catalysts. However, for practical applications, there are still challenges—the intrinsic catalytic properties of TMOs should be further improved and TMOs should be synthesized by practical routes for cost-effective and scalable production of catalysts. Therefore, finding promising ways to fabricate highly active TMOs with outstanding electrochemical hydrogen evolution performance is required. Here, we present a direct and facile synthetic approach to successfully provide highly efficient MoO3−X catalysts with electrochemically active oxygen vacancies through a one-step thermal activation process on a Mo metal mesh. Variations in the oxidation states of molybdenum oxides can significantly increase the active sites of the catalysts and improve the electrochemical activity, making these oxide compounds suitable for hydrogen evolution reaction (HER). Compared to the bare Mo mesh and fully oxidized Mo (MoO3) electrodes, the fabricated MoO3−X electrode exhibits better electrochemical performance in terms of overpotentials and Tafel slope, as well as the electrochemical 1000 cycling stability, confirming the improved HER performance of MoO3−X. This provides new insight into the simple procedure suitable for the large-production supply.

Single-step in situ synthesis of MoO2-faceted structures as highly efficient HER electrocatalysts and electrode materials for pseudocapacitors

“…[16][17][18] Among the metal oxide (MO) species, the transition metal oxides (TMOs) are being studied due to their abundance, low-cost, eco-friendly nature, and ease of fabrication. 19,20 Different TMO species like TiO 2 , MnO 2 , V 2 O 5 , Cr 2 O 3 , WO 3 , and Co 3 O 4 have been synthesized and tested for the HER and EC capacitors. [21][22][23][24][25][26] These TMOs are either doped with suitable transition metal (TM) atoms or an interfacial heterostructure is created with other metal oxides or carbon species to modify their band structures and make them viable for an improvement in their HER activity and stability.…”

“…The anion-deficient MoO 3 (MoO 3Àx ) or low oxidation-stabilized MoO 2 (MoO 3Àx , x = 1) species that maintain the structural stability and layered characteristics are highly suitable for enhancing the electrocatalytic activities. 20,29,30 (1)…”

“…The synergistic effects of anion vacancies created in TMOs, especially in the layer-structured oxide species (MoO x , x = 2-3), significantly enhanced adsorption and desorption of ions on their surfaces. 20,29 In the hydrogen evolution reaction, distorting structural ordering in the anion vacant species during the adsorption of electrolyte ions limits their proper use. The anion-deficient MoO 3 (MoO 3Àx ) or low oxidation-stabilized MoO 2 (MoO 3Àx , x = 1) species that maintain the structural stability and layered characteristics are highly suitable for enhancing the electrocatalytic activities.…”

“…The anion-deficient MoO 3 (MoO 3− x ) or low oxidation-stabilized MoO 2 (MoO 3− x , x = 1) species that maintain the structural stability and layered characteristics are highly suitable for enhancing the electrocatalytic activities. 20,29,30 Synthesis of the MoO 2 species is very critical due to comproportionation between the transformations of MoO 2 and MoO 3 via certain intermediate species as follows:MoO 2 ↔ Mo 4 O 11 ↔ MoO 3 …”

Hierarchically Ordinated Two-Dimensional MoS2 Nanosheets on Three-Dimensional Reduced Graphene Oxide Aerogels as Highly Active and Stable Catalysts for Hydrogen Evolution Reaction

“…Therefore, in recent years, transition metal oxides/sulfides have emerged as effective alternatives to Pt and Pt-based electrocatalysts. Numerous studies have been devoted to enhancing the electrochemical properties of transition metal oxides/sulfides/phosphides/ carbides [10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28]. For example, Shen and Yin's research groups reported that the bimetallic nickel-cobalt phosphide shows improved HER activity and stability, due to its unique morphology with nanosheets on the 3D integrated framework, providing a large surface area and many active sites for HER [24].…”