The influence of Co3V2O8 morphology on the oxygen evolution reaction activity and stability

Construction of amorphous/crystalline Fe doped CoSe for effective electrocatalytic oxygen evolution

Herein, amorphous/crystalline Fe-doped CoSe was synthesized (Fe-CoSe/NF), and it exhibited high oxygen evolution reaction (OER) performance. The synergistic effect of the Fe dopant and the amorphous/crystalline structure is conducive to the formation of high valence Co3+ and Fe3+ active sites. Fe-CoSe/NF shows low overpotentials of 269 mV@50 mA cm-2 and 280 mV@100 mA cm-2.

High-Throughput Exploration of Metal Vanadate Thin-Film Systems (M-V-O, M = Cu, Ag, W, Cr, Co, Fe) for Solar Water Splitting: Composition, Structure, Stability, and Photoelectrochemical Properties

Combinatorial synthesis and high-throughput characterization of thin-film materials libraries enable to efficiently identify both photoelectrochemically active and inactive, as well as stable and instable systems for solar water splitting. This is shown on six ternary metal vanadate (M-V-O, M = Cu, Ag, W, Cr, Co, Fe) thin-film materials libraries, fabricated using combinatorial reactive magnetron cosputtering with subsequent annealing in air. By means of high-throughput characterization of these libraries correlations between composition, crystal structure, photocurrent density, and stability of the M-V-O systems in different electrolytes such as acidic, neutral and alkaline media were identified. The systems Cu-V-O and Ag-V-O are stable in alkaline electrolyte and exhibited photocurrents of 170 and 554 μA/cm², respectively, whereas the systems W-V-O, Cr-V-O, and Co-V-O are not stable in alkaline electrolyte. However, the Cr-V-O and Co-V-O systems showed an enlarged photoactive region in acidic electrolyte, albeit with very low photocurrents (<10 μA/cm²). Complete data sets obtained from these different screening sets, including information on nonpromising systems, lays groundwork for their use to predict new systems for solar water splitting, for example, by machine learning.

One-step hydrothermal synthesis of cobalt-vanadium based nanocomposites as bifunctional catalysts for overall water splitting

Designing low-cost and high-active bifunctional catalysts for overall water splitting has attracted increasing research interest. Herein, the brilliant overall water splitting performance of cobalt-vanadium bimetal-based nanocomposites is explored. Co-V based nanocomposites are synthesized through a one-step hydrothermal method, in which the cobalt species is introduced into the lepidocrocite VOOH and further cobalt vanadium oxide is formed. The additive level of cobalt is optimized and the corresponding effect on electrocatalytic activity is also investigated in this work, systematically. The targeted catalyst (denoted as Co0.2-VOOH) exhibits a unique sheet-like morphology, resulting in the high exposure of catalytically active sites. When used as the bifunctional catalyst, Co0.2-VOOH can achieve a current density of 10 mA cm-2 at the overpotentials of 210 mV for water oxidation and 130 mV for hydrogen generation, respectively. Notably, it only requires low cell voltages of 1.57 and 1.74 V to drive the catalytic current densities of 10 and 100 mA cm-2 during the water splitting process. This work significantly indicates that cobalt-vanadium based materials are promising alternatives for overall water splitting.

Advanced electrospun nanomaterials for highly efficient electrocatalysis

We highlight the recent developments of electrospun nanomaterials with controlled morphology, composition and architecture for highly efficient electrocatalysis.

Ultrathin Co3O4 nanofilm as an efficient bifunctional catalyst for oxygen evolution and reduction reaction in rechargeable zinc-air batteries

Two-dimensional (2D) nanocatalysts with a large specific surface area and efficient charge conductivity are promising candidates for catalyzing the sluggish oxygen evolution reaction (OER) and oxygen reduction reaction (ORR), which are at the heart of various electrochemical energy conversion and storage technologies. Here, we report the synthesis of an ultrathin Co₃O₄ nanofilm with a thickness of nearly 1.8 nm via a surfactant- and template-free facile hydrothermal route. The proposed synthesis strategy can be extended to the preparation of 2D Ni_xCo_3-xO₄ and Fe_xCo_3-xO₄ nanostructures. The synthesized Co₃O₄ nanofilm exhibited bifunctional activity that was superior to that of the counterpart Co₃O₄ nanoparticles, including a lower overpotential and higher reduction and evolution current densities, and demonstrated faster catalytic kinetics over the 2D nanofilm surface. In comparison with precious metal-based catalysts, to achieve an OER current density of 40 mA cm^-2 the overpotential of the nanofilm (461 mV) was lower than that of RuO₂ (526 mV), whereas the ORR on the nanofilm proceeded via a dominant 4e^- transfer mechanism, which is similar to that of commercial carbon-supported Pt (Pt/C). The Co₃O₄ nanofilm enabled the assembly of rechargeable Zn-air batteries with a lower overpotential (0.72 V), higher round-trip efficiency (62.7%), and a longer cycle lifetime (175 cycles). The remarkable bifunctional activity contributes to an increase in the number of electrochemically active sites, a large interfacial contact area with the electrolyte, and the enrichment of Co³⁺ ions on the surface, which facilitates the adsorption and activation of oxygen-containing species. This study should shed light on the future development of new electroactive materials with optimized 2D nanostructures to enhance the overall bifunctional ORR/OER performance of rechargeable metal-air batteries.

Effect of morphology on the oxygen evolution reaction for La0.8Sr0.2Co0.2Fe0.8O3−δelectrochemical catalyst in alkaline media

A series of perovskite oxides La_0.8Sr_0.2Co_0.2Fe_0.8O_3−δwith different morphologies have been synthesized as oxygen evolution reaction electrocatalysts by an electrospinning technique.