Search

Transition metal-based oxides have been reported as an important family of electrocatalysts for water splitting owing to their possible large-scale applications that are highly desirable for the hydrogen generation industry. Herein, we report a facile method for the preparation of phosphate-decorated NiFe oxides on nickel foam as efficient oxygen evolution reaction (OER) electrocatalysts for water oxidation. The OER electrocatalysts were developed through the pyrolysis of MIL(Fe) metal–organic frameworks (MOFs), which were modified with Ni and P species. It was found that the formation of NiO on the Fe2O3 surface (NiO@Fe2O3) can enrich electrocatalytic active sites for the OER. Meanwhile, the incorporation of P into NiO@Fe2O3 (Px-NiO@Fe2O3) creates abundant oxygen vacancies, which facilitates the surface charge transfer for OER electrocatalysis. Benefiting from the structure and composition advantages, P2.0-NiO@Fe2O3/NF exhibits the best performance for OER electrocatalysis among other prepared electrocatalysts, with an overpotential of 208 mV at the OER current density of 10 mA cm−2 and a small Tafel slope of 69.64 mV dec−1 in 1 M KOH solution. Additionally, P2.0-NiO@Fe2O3/NF shows an outstanding durability for the OER electrocatalysis, maintaining the OER current density above 20 mA cm−2 for more than 100 h. [ABSTRACT FROM AUTHOR]

Efficient and robust electrocatalysts towards the oxygen evolution reaction (OER) are highly desirable in electrochemical systems for applications including water splitting and metal-air batteries. Herein, we report the preparation of an amorphous FeCoNiMnCr high-entropy alloy (HEA) on the surface of flower-like 2H-MoS2 (FeCoNiMnCr@MoS2) as a highly efficient electrocatalyst for the OER. The flower-like 2H-MoS2 is prepared on the flexible conductive carbon cloth (MoS2-CC) via a hydrothermal method, and subsequently the amorphous FeCoNiMnCr HEA is loaded on the surface of 2H-MoS2via an electrodeposition method to form FeCoNiMnCr@MoS2-CC electrocatalysts. Owing to the unique microstructure of 2H-MoS2 and abundant active sites of FeCoNiMnCr HEA, the FeCoNiMnCr@MoS2-CC electrocatalysts exhibit significantly improved OER electrocatalytic performances with a low overpotential of 210 mV at a current density of 10 mA cm−2 and a small Tafel slope of 40.3 mV dec−1 in 1.0 M KOH solution. Moreover, it shows excellent stability for OER electrocatalysis with the potential barely increased for at least 50 h. This work sheds light on the development of highly efficient OER electrocatalysts based on HEAs. [ABSTRACT FROM AUTHOR]

Graphical abstract Abstract We investigate the possibility of utilizing benzyl alcohol oxidation reaction to replace sluggish oxygen evolution reaction (OER) for the charging process in a rechargeable zinc-air battery, catalyzed by NiCo alloy nanoparticles supported on activated carbon (NiCo/AC) with the multifunctional electrocatalytic activities of the oxygen reduction, oxygen evolution and benzyl alcohol oxidation reactions. As an electrocatalyst for the oxygen reduction reaction (OER), NiCo/AC exhibits superior catalytic activity with an onset potential of 0.85 V (vs. RHE), a half-wave potential of 0.74 V (vs. RHE) and a large limiting current density of 4.65 mA cm−2 at 0.2 V (vs. RHE). Moreover, NiCo/AC also demonstrates the electrocatalytic oxidation activities toward water and benzyl alcohol, moreover, the benzyl alcohol oxidation reaction is more thermodynamically and kinetically favourable with 254 mV smaller overpotential than water oxidation at 10 mA cm−2. Owing to these advantages, NiCo/AC as air cathode material is assembled into a home-made rechargeable zinc-air battery, resulting an almost 200 mV lower charging voltage at the current density of 50 mA cm−2 in the presence of 0.1 M benzyl alcohol compared to the battery without benzyl alcohol, consequently obtaining 10.5% energy saving at the charging current density of 50 mA cm−2 with high durability. [ABSTRACT FROM AUTHOR]

The development of efficient, stable and low-cost electrocatalysts towards the seawater oxidation is highly desirable for hydrogen-based industries. In this work, we report the efficient preparation of phosphate-decorated hierarchical porous CoNiFe medium-entropy alloys as promising electrocatalysts for the oxygen evolution reaction in seawater via the solution combustion synthesis. The hierarchical porous structure of CoNiFe medium-entropy alloys enhances exposure to catalytic sites and facilitates the efficient diffusion of gas products as well as electrolytes. Moreover, the in-situ formed PO 4 3− anions not only improve the electrocatalytic performance of CoNiFe medium-entropy alloys for oxygen evolution reaction, but also prevent Cl− from contacting the catalytic sites. Thanks to these structural benefits, the optimized CoNiFeP 0.1 @NF electrode demonstrates superior electrocatalytic performance for oxygen evolution reaction, showing an overpotential of 250 mV at 10 mA cm−2, a low Tafel slope of 47.6 mV dec−1, and satisfactory stability in the 1.0 M KOH +0.5 M NaCl electrolyte. • Phosphate-decorated CoNiFe alloys were prepared via solution combustion synthesis. • The hierarchical porous structure of CoNiFe benefits the exposure of active sites. • PO 4 3− anions enhance the performance of CoNiFe alloys for seawater oxidation. [ABSTRACT FROM AUTHOR]

• Medium-entropy oxyhydroxides are prepared by surface oxidation and electrodeposition. • The key to obtain medium-entropy oxyhydroxides is the reactive-O atoms. • Medium-entropy oxyhydroxides deliver good stability for OER in alkaline seawater. Hydrogen production via electrochemical splitting of seawater is highly desirable but still facing great challenges. Herein, we report the facile preparation of medium-entropy oxyhydroxides on Ni(OH) 2 nanosheets via surface reconstruction and entropy engineering strategies, achieving enhanced electrocatalytic activity and stability for oxygen evolution reaction (OER) in alkaline seawater. The electrochemical oxidation is conducted on Ni(OH) 2 nanosheets to create abundant reactive oxygen (reactive-O) atoms on the reconstructed surface, thus forming a reactive-O enriched surface on Ni(OH) 2 (NiO x /Ni(OH) 2). Additionally, cations are incorporated onto the reconstructed surface of NiO x /Ni(OH) 2 via an electrodeposition method, forming the medium-entropy oxyhydroxides on Ni(OH) 2 nanosheets ((FeCoCrNi)O x /Ni(OH) 2). Benefiting from the composition and structure advantages, the resulting (FeCoCrNi)O x /Ni(OH) 2 @NF demonstrates obviously enhanced performances for OER electrocatalysis, with an overpotential of 239 mV at the current density of 10 mA cm−2 and a low Tafel slope of 24.66 mV dec−1 in 1.0 M KOH + 0.5 M NaCl solution. Furthermore, it exhibits exceptional durability for OER electrocatalysis in alkaline seawater, maintaining over 90.7 % of the OER current density after 100 h. [ABSTRACT FROM AUTHOR]

The development of efficient and stable oxygen evolution reaction (OER) electrocatalysts with nonprecious materials is still a great challenge for the hydrogen-based energy industry. Here, we report the rational design and effective synthesis of hierarchical porous medium-entropy alloys (MEAs) as promising electrocatalysts for OER via a solution combustion method. Owing to the compositional advantages and unique hierarchical porous structure, the as-prepared CoNiFeCu 0.1 MEA on nickel foam (CoNiFeCu 0.1 @NF) shows superior electrocatalytic performance for OER with an overpotential of about 255 mV at 10 mA cm−2 and a small Tafel slope of 42.7 mV dec−1 in 1.0 M KOH solution. Moreover, it is revealed that the alloying of element Cu in CoNiFe MEA can significantly enhance the charge transfer ability for OER electrocatalysis. The present work shows the hierarchical porous MEAs prepared by solution combustion method have great potential as efficient and robust electrocatalysts for water oxidation in alkaline medium. [Display omitted] • Hierarchical porous medium-entropy alloys are prepared by solution combustion method. • The alloying of Cu in CoNiFe alloy can improve electrocatalytic performances. • CoNiFeCu 0.1 @NF is stable for OER electrocatalysis for 100 h in alkaline medium. • It has an overpotential of 255 mV at 10 mA cm−2 and a Tafel slope of 42.7 mV dec−1. [ABSTRACT FROM AUTHOR]