Bimetallic co-doping engineering over nickel-based oxy-hydroxide enables high-performance electrocatalytic oxygen evolution.

Enhancing the electrocatalytic oxygen evolution reaction (OER) performance is essential to realize practical energy-saving water electrolysis and CO2 electroreduction. Herein, we report a bimetallic co-doping engineering to design and fabricate nickel-cobalt-iron collaborative oxy-hydroxide on nickel foam that labeled as NiCoFeOxHy-NF. As expected, NiCoFeOxHy-NF exhibits an outstanding OER activity with current density of 10 mA cm-2 at 194 mV, Tafel slope of 53 mV dec-1, along with the robust long-term stability, which is significantly better than bimetallic NiCo and NiFe combinations. Comprehensive computational simulations and characterizations jointly unveil that the twisted ligand environment induced by heteroatoms ensures the balance strength between the metal-oxygen hybrid orbital states and the oxidized intermediates adsorption, thus lowering the oxygen cycling energy barriers for overcoming the sluggish OER kinetics. Moreover, a novel phase transition behavior is monitored by in-situ Raman spectra under OER operating conditions, which facilitates electron-mass transfer as well as boosts the exposure of activity sites. For practical applications, Ni2P-NF || NiCoFeOxHy-NF and Cu || NiCoFeOxHy-NF couples were constructed to realize high-efficiency water electrolysis and CO2 electrochemical reduction for the production of valuable H2 and C2H4, respectively. This work elucidates a novel mechanism by which bimetallic co-doping improves the electrocatalytic OER activity of nickel-based hydroxides.

Magnesium-regulated oxygen vacancies of cobalt-nickel layered double hydroxide nanosheets for ultrahigh performance asymmetric supercapacitors.

Rational design of layered double hydroxide (LDH) electrodes is of great significance for high-performance supercapacitors (SCs). Herein, ultrathin cobalt-nickel-magnesium layered double hydroxide (CoNiMg-LDH) nanosheets with plentiful oxygen vacancies are synthesized via sacrificial magnesium-based replacement reaction at room temperature. Self-doping and mild reduction of magnesium can significantly increase the concentration of oxygen vacancies in CoNiMg-LDH, which promotes the electrochemical charge transfer efficiency and enhances the adsorption ability of electrolytes. Density functional theory (DFT) calculations also indicate that Mg2+ doping can decrease the formation energy of oxygen vacancies in CoNiMg-LDH nanosheets, which increases the concentration of oxygen vacancies. Thus, the assembled asymmetric supercapacitor CoNiMg-LDH//Actived Carbon accomplishes a superior capacity of âˆ¼ 333 C g-1 (208 F g-1) at 1 A g-1 and presents a gravimetric energy density of 73.9 Wh kg-1 at 0.8 kW kg-1. It presents only 13% capacity loss at 20 A g-1 after 5000 cycles. This discovery emphasizes the positive role of magnesium in regulating oxygen vacancies to improve the performance of supercapacitors, which should be beneficial for extending the scope of superior SCs active materials.