General design of self-supported Co-Ni/nitrogen-doped carbon nanotubes array for efficient oxygen evolution reaction

The development of earth-abundant oxygen evolution reaction (OER) electrocatalysts with high activity and durability is critical for replacing noble-metal-based catalysts in the applications of scalable water electrolysis. A freestanding electrode architecture offers significant advantages over conventional coated powder forms due to enhanced kinetics and stability. However, precise control over electrode composition and the construction of uniformly distributed active sites within these electrodes remain challenging. Herein, a general strategy is proposed to utilize metal-organic frameworks (MOFs)/nickel foil to controllable synthesize self-supported Co-Ni/nitrogen-doped carbon nanotubes array (CoNi-NCNT/NiF) as efficient electrocatalyst for OER. The results of the experiments and density functional theory (DFT) calculations show that the synergistic effect of Co nanoparticles, heteroatomic doping, and the confinement effect of the NCNTs could enhance the electronic transmission and accelerate electrocatalytic kinetics. Furthermore, the porous structure and optimized composition of CoNi-NCNT/NiF will enhance mass and charge transfer as well as intermediate adsorption, all together lead to the catalyst with excellent electrocatalytic activity and stability. A low and stable OER overpotential of 268 mV is needed for CoNi-NCNT/NiF to reach a current density of 20 mA cm-2 in an alkaline electrolyte, which ranks among the top of the non-precious metal catalyst reported to date. This work offers new guidance for the precise construction of self-supported electrocatalysts for sustainable clean energy.

Recent Progress on Bimetallic-Based Spinels as Electrocatalysts for the Oxygen Evolution Reaction

Electrocatalytic water splitting is a promising and viable technology to produce clean, sustainable, and storable hydrogen as an energy carrier. However, to meet the ever-increasing global energy demand, it is imperative to develop high-performance non-precious metal-based electrocatalysts for the oxygen evolution reaction (OER), as the OER is considered the bottleneck for electrocatalytic water splitting. Spinels, in particular, are considered promising OER electrocatalysts due to their unique properties, precise structures, and compositions. Herein, the recent progress on the application of bimetallic-based spinels (AFe₂ O₄ , ACo₂ O₄ , and AMn₂ O₄ ; where A = Ni, Co, Cu, Mn, and Zn) as electrocatalysts for the OER is presented. The fundamental concepts of the OER are highlighted after which the family of spinels, their general formula, and classifications are introduced. This is followed by an overview of the various classifications of bimetallic-based spinels and their recent developments and applications as OER electrocatalysts, with special emphasis on enhancing strategies that have been formulated to improve the OER performance of these spinels. In conclusion, this review summarizes all studies mentioned therein and provides the challenges and future perspectives for bimetallic-based spinel OER electrocatalysts.

Comparison of the effects of cation and phosphorus doping in cobalt-based spinel oxides towards the oxygen evolution reaction

Phosphorus incorporation further boosted the OER activity of cation-doped Co-based spinel oxides via remarkably tuning the oxygen vacancies, crystallinity and electrochemically active surface area on the surface.

Co3 O4 @Cu-Based Conductive Metal-Organic Framework Core-Shell Nanowire Electrocatalysts Enable Efficient Low-Overall-Potential Water Splitting

In the work reported herein, the electrocatalytic properties of Co₃ O₄ in hydrogen and oxygen evolution reactions have been significantly enhanced by coating a shell layer of a copper-based metal-organic framework on Co₃ O₄ porous nanowire arrays and using the products as high-performance bifunctional electrocatalysts for overall water splitting. The coating of the copper-based metal-organic framework resulted in the hybridization of the copper-embedded protective carbon shell layer with Co₃ O₄ to create a strong Cu-O-Co bonding interaction for efficient hydrogen adsorption. The hybridization also led to electronically induced oxygen defects and nitrogen doping to effectively enhance the electrical conductivity of Co₃ O₄ . The optimal as-prepared core-shell hybrid material displayed excellent overall-water-splitting catalytic activity that required overall voltages of 1.45 and 1.57 V to reach onset and a current density of 10 mA cm^-2 , respectively. This is the first report to highlight the relevance of hybridizing MOF-based co-catalysts to boost the electrocatalytic performance of nonprecious transition-metal oxides.