Engineering Ultrafine Ir Nanocrystals for Electrochemical Hydrogen Evolution With Highly Superior Mass Activity

Valorization of lignin biowaste into Schiff base copper(II) complex as a magnetically reusable electrocatalyst for hydrogen evolution reaction

This work describes a cost-effective and sustainable copper(II) complex as an electrocatalyst for the hydrogen-evolution reaction (HER) under alkaline and acid conditions. A magnetic lignin-supported tetrazole Schiff base copper(II) complex was incorporated into a carbon paste electrode (MLS@SchTet-Cu(II)/CPE) by a surface modification and cross-linking method. The catalytic HER of the MLS@SchTet-Cu(II)/CPE electrodes was analyzed by electrochemical techniques, including linear sweep voltammetry (LSV), electrochemical impedance spectroscopy (EIS), chronopotentiometry (CP), and cyclic voltammetry (CV). The effects of solution pH and complex amount in the paste electrode on HER performance were evaluated. The results demonstrated that the MLS@SchTet-Cu(II) nanocomposite exhibits good electrocatalytic activity in both acidic and basic media. In particular, in 0.5 M H2SO4, the modified CPE electrode with 2.5 % MLS@SchTet-Cu(II) demonstrated an overpotential of 581 mV at 10 mA cm-2 (η10) and a Tafel slope of 258 mV dec-1, surpassing the performance of both the bare and other modified CPEs. These findings highlight the potential of MLS@SchTet-Cu(II) as a promising candidate for sustainable HER catalysis.

Enhance the Proportion of Fe3+ in NiFe-Layered Double Hydroxides by utilizing Citric Acid to Improve the Efficiency and Durability of the Oxygen Evolution Reaction

NiFe-layered double hydroxides (NiFe-LDH) are a type of catalyst known for their exceptional catalytic performance during the oxygen evolution reaction (OER). In this study, citric acid was incorporated into the synthesis process of NiFe-LDH, resulting in the NiFe-LDH-CA catalyst with superior OER performance. The catalytic efficacy was evaluated using linear sweep voltammetry (LSV), which demonstrated a significant reduction in the overpotential for OER from 320 mV to 240 mV at a current density of 100 mA cm-2. X-ray photoelectron spectroscopy (XPS) and X-ray absorption spectroscopy (XAS) indicate that the distribution of nickel valence states showed no significant difference between two samples. However, the NiFe-LDH-CA exhibits a markedly higher proportion of Fe3+ ions in its iron content. In-situ Raman spectroscopes reveal that Fe3+ broadens the redox potential of nickel and Pourbaix diagrams indicate that higher Fe3+ levels could facilitate the interaction with oxygen active sites. Based on the analysis of test data, we propose a hypothesis that the high proportion of Fe3+ in catalysts may accelerate the oxygen evolution process by modulating the redox potential of nickel and engaging with reactive oxygen species. This provides valuable insights into how to improve the reaction rate of nickel-based catalysts.