B-site Doping Boosts the OER and ORR Performance of Double Perovskite Oxide as Air Cathode for Zinc-Air Batteries.

Double perovskite oxides are key players as electrocatalytic oxygen catalysts in alkaline media. In this study, we synthesized B-site doped NdBaCoaFe2-aO5+δ (a= 1.0, 1.4, 1.6, 1.8) electrocatalysts, systematically to probe their bifunctionality and assess their performance in zinc-air batteries as air cathodes. X-ray photoelectron spectroscopy analysis reveals a correlation between iron reduction and increased oxygen vacancy content, influencing electrocatalyst bifunctionality by lowering the work function. The electrocatalyst with highest cobalt content, NdBaCo1.8Fe0.2O5+δ exhibited a bifunctional index of 0.95 V, outperforming other synthesized electrocatalysts. Remarkably, NdBaCo1.8Fe0.2O5+δ, demonstrated facilitated charge transfer rate in oxygen evolution reaction with four-electron oxygen reduction reaction process. As an air cathode in a zinc-air battery, NdBaCo1.8Fe0.2O5+δ demonstrated superior performance characteristics, including maximum capacity of 428.27 mA h at 10 mA cm-2 discharge current density, highest peak power density of 64 mW cm-2, with an outstanding durability and stability. It exhibits lowest voltage gap change between charge and discharge even after 350 hours of cyclic operation with a rate capability of 87.14%.

Designing core-shell heterostructure arrays based on snowflake NiCoFe-LTH shelled over W2N-WC nanowires as an advanced bi-functional electrocatalyst for boosting alkaline water/seawater electrolysis.

The pursuit of efficient and sustainable hydrogen production through water splitting has led to intensive research in the field of electrocatalysis. However, the impediment posed by sluggish reaction kinetics has served as a significant barrier. This challenge has inspired the development of electrocatalysts characterized by high activity, abundance in earth's resources, and long-term stability. In addressing this obstacle, it is imperative to meticulously fine-tune the structure, morphology, and electronic state of electrocatalysts. By systematically manipulating these key parameters, the full potential of electrocatalysts can unleash, enhancing their catalytic activity and overall performance. Hence in this study, a novel heterostructure is designed, showcasing core-shell architectures achieved by covering W2N-WC nanowire arrays with tri-metallic Nickel-Cobalt-Iron layered triple hydroxide nanosheets on carbon felt support (NiCoFe-LTH/W2N-WC/CF). By integrating the different virtue such as binder free electrode design, synergistic effect between different components, core-shell structural advantages, high exposed active sites, high electrical conductivity and heterostructure design, NiCoFe-LTH/W2N-WC/CF demonstrates striking catalytic performances under alkaline conditions. The substantiation of all the mentioned advantages has been validated through electrochemical data in this study. According to these results NiCoFe-LTH/W2N-WC/CF achieves a current density of 10 mA cm-2 needs overpotential values of 101 mV for HER and 206 mV for OER, respectively. Moreover, as a bi-functional electrocatalyst for overall water splitting, a two-electrode device needs a voltage of 1.543 V and 1.569 V to reach a current density of 10 mA cm-2 for alkaline water and alkaline seawater electrolysis, respectively. Briefly, this research with attempting to combination of different factors try to present a promising stride towards advancing bi-functional catalytic activity with tailored architectures for practical green hydrogen production via electrochemical water splitting process.

Controllable atoms implantation for inducing high valency nickel towards optimizing electronic structure for enhanced overall water splitting.

Adjusting the electronic structure and intrinsic activity of the active site of the catalyst based on atomic implantation is the crucial to realizing efficient electrochemical water splitting in alkaline media. Thus, we introduce vanadium (V) atoms with abundant vacant d orbitals as dopants into nickel selenides (NiSe), which has abundant variable valence states, and successfully synthesise three-dimensional bi-functional catalysts self-supported on Ni foam (NF). The electron structure characterisation reveals that, compared with the pure NiSe phase, the oxidation states of Ni cations and electron concentration at the Se site in V-NiSe increase due to the V doping. These changes are accompanied by changes in the electronic structure and active sites in V-NiSe. The as-generated V-NiSe nanorods exhibit an optimised electronic structure, high number of active sites and highly rough nanorod array structure with large electrochemically active surface area and in situ growth characteristics of conductive NF. Thus, the as-generated V-NiSe nanorods catalysts exhibit excellent bi-functional catalytic activity, with 50 mA⋅cm-2 at an overpotential of 270.2 and 251.2 mV for oxygen evolution reactions (OER) and hydrogen evolution reactions (HER), respectively, in KOH (1 M). Water electrolysis using V-NiSe as both the anode and cathode requires a cell voltage of 1.76 V to drive 50 mA⋅cm-2, continuously operating for 80 h. This study provides a systematic understanding of the design of transition-metal catalysts using heteroatomic doping to control their electronic structure and catalytic activity.

Bi-functional 3D-NiCu-Double Hydroxide@Partially Etched 3D-NiCu Catalysts for Non-Enzymatic Glucose Detection and the Hydrogen Evolution Reaction.

Hydrogen production, which is in the spotlight as a promising eco-friendly fuel, and the need for inexpensive and accurate electronic devices in the biochemistry field are important emerging technologies. However, the use of electrocatalytic devices based on expensive noble metal catalysts limits commercial applications. In recent years, to improve performance and reduce cost, electrocatalysts based on cheaper copper or nickel materials have been investigated for the non-enzymatic glucose oxidation reaction (GOR) and hydrogen evolution reaction (HER). In this study, we demonstrate a facile and easy electrochemical method of forming a cheap nickel copper double hydroxide (NiCu-DH) electrocatalyst deposited onto a three-dimensional (3D) CuNi current collector, which can effectively handle two different reactions due to its high activity for both the GOR and the HER. The as-prepared electrode has a structure comprising abundant 3D-interconnected porous dendritic walls for easy access of the electrolyte ions and highly conductive networks for fast electron transfer; additionally, it provides numerous electroactive sites. The synergistic combination of the dendritic 3D-CuNi with its abundant active sites and the self-made NiCu-DH with its excellent electrocatalytic activity toward the oxidation of glucose and HER enables use of the catalyst for both reactions. The as-prepared electrode as a glucose sensor exhibits an outstanding glucose detection limit value (0.4 µM) and a wide detection range (from 0.4 µM to 1.4 mM) with an excellent sensitivity of 1452.5 µA/cm2/mM. The electrode is independent of the oxygen content and free from chloride poisoning. Furthermore, the as-prepared electrode also requires a low overpotential of -180 mV versus reversible hydrogen electrode to yield a current density of 10 mA/cm2 with a Tafel slope of 73 mV/dec for the HER. Based on this performance, this work introduces a new paradigm for exploring cost-effective bi-functional catalysts for the GOR and HER.

Bimetallic Metal-Organic Framework Derived Metal-Carbon Hybrid for Efficient Reversible Oxygen Electrocatalysis.

Development of cost-effective electrocatalysts for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is key to enabling advanced electrochemical energy conversion technologies. Here, a novel nitrogen-doped metal-carbon hybrid (NiCo/CN) with a unique 3D hierarchical structure, consisting of uniformly distributed bimetallic nanoparticles encapsulated by partially graphitized N-doped carbon shells, is fabricated by a one-step pyrolysis of a nanoscale metal-organic framework as precursor, which exhibits excellent activity for both ORR and OER. The surface chemical changes on the carbon hybrid probed by X-ray photoelectron spectroscopy (XPS) reveal the presence of favorable electronic interaction at the metal-nitrogen-carbon interface. Remarkably, the NiCo/CN catalyst prepared at high temperature (800°C) manifests a comparable performance to a commercial Pt/C catalyst for the ORR, but also superior stability, path selectivity and methanol tolerance. On the other hand, the E onset (1.48 V vs. reversible hydrogen electrode) and E j = 10 mA/cm 2 of NiCo/CN-800 for OER is very close to the state-of-the-art noble catalyst RuO2 (Eonset = 1.46 and E j = 10 mA/cm 2 ) along with superior stability over 20 h of operation. The excellent catalytic property is attributable to the unique nanostructure, high porosity and the constructive synergistic effects of the elements M, N, and C.

Co2P@NiCo2O4 bi-functional electrocatalyst with low overpotential for water splitting in wide range pH electrolytes.

The Co2P@NiCo2O4 bi-functional electrocatalyst was fabricated for hydrogen evolution reaction and oxygen evolution reaction in acidic, neutral and alkaline media. The Co2P@NiCo2O4 in alkaline media exhibites an extremely low overpotential of 170 mV in oxygen evolution to achieve a current density of 10 mA cm-2 and produces stable water splitting nearly 30 h. The anchored-Co2P can enhance the electrochemical performance of pristine NiCo2O4 as well as increase the tolerance in acidic media of NiCo2O4. Additional, the Co2P is oxidized to oxides/hydroxides species during the electrocatalytic reaction, which acts as the active centers of the electrocatalysis. The Co2P@NiCo2O4 catalyst can be used as an effective bifunctional synergistic center in a wide range of pH values (from 0 to 14).