Showing papers by "Yanshan University published in 2022"

Promoted self-construction of β-NiOOH in amorphous high entropy electrocatalysts for the oxygen evolution reaction

Abstract: The exploration of an efficient electrocatalyst for the oxygen evolution reaction (OER) is urgently required for sustainable renewable-energy conversion and storage. Due to the increased chemical complexity, multimetallic catalysts provide flexibility to alter their electronic and crystal structure to attain a superior intrinsic catalytic activity via synergistic effects, which is seldom accomplished using single metal catalysts. However, the high chemical complexity increases the difficulty to prepare elemental homogenous catalysts and reveal their synergistic effect during OER process, which further hinder the design of multimetallic catalysts. Here, high entropy concept is utilized to design an NiFeCoMnAl oxide with amorphous structure as OER catalyst. The direct evidence of active Ni sites is provided by the operando Raman measurements and Fe can modify oxygen intermediates binding energy on Ni sites. The X-ray photoelectron spectroscopy (XPS) and X-ray absorption spectroscopy (XAS) reveal that the incorporation of Mn can construct the electron-rich environment of active Ni center, and the relatively lower oxidation state of Ni facilitates the self-construction of β-NiOOH intermediates, which shows promoted OER activity as confirmed by density functional theory calculations. Doping Co can enhance the conductivity and doping Al leads to the formation of nanoporous structure through dealloying process, thus each component is essential for improving OER performance. The optimized NiFeCoMnAl catalyst exhibits an overpotential of 190 mV at 10 mA cm−2 in 1 M KOH solution, much superior to the ternary and quaternary counterparts. This work sheds light on understanding the origin of high entropy catalysts’ OER activity and thereby enables the rational design of multinary transition metallic catalysts.

Promoted self-construction of β-NiOOH in amorphous high entropy electrocatalysts for the oxygen evolution reaction

Abstract: The exploration of an efficient electrocatalyst for the oxygen evolution reaction (OER) is urgently required for sustainable renewable-energy conversion and storage. Due to the increased chemical complexity, multimetallic catalysts provide flexibility to alter their electronic and crystal structure to attain a superior intrinsic catalytic activity via synergistic effects, which is seldom accomplished using single metal catalysts. However, the high chemical complexity increases the difficulty to prepare elemental homogenous catalysts and reveal their synergistic effect during OER process, which further hinder the design of multimetallic catalysts. Here, high entropy concept is utilized to design an NiFeCoMnAl oxide with amorphous structure as OER catalyst. The direct evidence of active Ni sites is provided by the operando Raman measurements and Fe can modify oxygen intermediates binding energy on Ni sites. The X-ray photoelectron spectroscopy (XPS) and X-ray absorption spectroscopy (XAS) reveal that the incorporation of Mn can construct the electron-rich environment of active Ni center, and the relatively lower oxidation state of Ni facilitates the self-construction of β-NiOOH intermediates, which shows promoted OER activity as confirmed by density functional theory calculations. Doping Co can enhance the conductivity and doping Al leads to the formation of nanoporous structure through dealloying process, thus each component is essential for improving OER performance. The optimized NiFeCoMnAl catalyst exhibits an overpotential of 190 mV at 10 mA cm−2 in 1 M KOH solution, much superior to the ternary and quaternary counterparts. This work sheds light on understanding the origin of high entropy catalysts’ OER activity and thereby enables the rational design of multinary transition metallic catalysts.

Stabilizing zinc anode via a chelation and desolvation electrolyte additive

Abstract: The uncontrollable dendrites growth and intricately water-induced side reactions occurred on zinc anode leads to safety issues and poor electrochemical kinetics, which largely limit the widespread application of zinc-ion batteries (ZIBs). Herein, ethylenediaminetetraacetic acid disodium salt (EDTA-2Na) is utilized as an electrolyte additive to strengthen the reversibility and cycling stability of zinc anode. Experimental results and theoretical calculation demonstrate that the EDTA-2Na presents a much stronger coordination with Zn2+ when comparing with H2O molecular, implying the EDTA-2Na is capable to enter the solvation shell of [Zn(OH2)6]2+ and coordinate with Zn2+ ions, thus achieving a flat and smooth zinc deposition with less by-products (Zn4SO4(OH)6·xH2O and H2). Consequently, the zinc symmetric battery with EDTA-2Na additive delivers an excellent cycling stability up to 1800 h under current density of 1 mA cm-2, and the hydrogen evolution reaction (HER), corrosion, by-product issues are significantly inhibited. Moreover, the rate performance and stability of coin-type and pouch-type Zn||MnO2/graphite batteries are significantly boosted via EDTA-2Na additive (248 mAh g-1 at 0.1 A g-1, 81.3% after 1000 cycles at a A g-1). This kind of electrolyte additive with chelation and desolvation functions shed lights on strategies of improving zinc anode stability for further application of ZIBs.