Effective Hydrogen Production from Alkaline and Natural Seawater using WO_3–x@CdS_1–x Nanocomposite-Based Electrocatalysts

Abstract

Offshore hydrogen production through water electrolysis presents significant technical and economic challenges. Achieving an efficient hydrogen evolution reaction (HER) in alkaline and natural seawater environments remains daunting due to the sluggish kinetics of water dissociation. To address this issue, we synthesized electrocatalytic WO 3−x @ CdS 1−x nanocomposites (WCSNCs) using ultrasonic-assisted laser irradiation. The synthesized WCSNCs with varying CdS contents were thoroughly characterized to investigate their structural, morphological, and electrochemical properties. Among the samples tested, the WCSNCs with 20 wt % CdS 1−x in WO 3−x (W x @S x -20%) exhibited superior electrocatalytic performance for hydrogen evolution in a 1 M KOH solution. Specifically, the W x @S x -20% catalyst demonstrated an overpotential of 0.191 V at a current density of −10 mA/cm 2 and a Tafel slope of 61.9 mV/dec. The W x @S x -20% catalysts demonstrated outstanding stability and durability, maintaining their performance after 24 h and up to 1000 CV cycles. Notably, when subjected to natural seawater electrolysis, the W x @S x -20% catalysts outperformed in terms of electrocatalytic HER activity and stability. The remarkable performance enhancement of the prepared electrocatalyst can be attributed to the combined effect of sulfur vacancies in CdS 1−x and oxygen vacancies in WO 3−x . These vacancies promote the electrochemically active surface area, enhance the rate of charge separation and transfer, increase the number of electrocatalytic active sites, and accelerate the HER process in alkaline and natural seawater environments.

Chestnut-like Molybdenum-Doped Nickel Cobaltite Spinel Oxide Nanoparticles Grown on Ni Foam as the Electrocatalyst for the Hydrogen Evolution Reaction

“…The Tafel slope has been widely employed to investigate the rate-determining steps in the HER mechanism process for enhanced comprehension. The Volmer, Heyrovsky, and Tafel reactions are widely recognized as the three primary steps involved in converting hydrogen protons into molecular hydrogen. ,,,, Based on the underlying mechanisms, the amalgamation of the Volmer pathway alongside either the Heyrovsky or Tafel pathway could produce molecular hydrogen. Typically, when the slope is approximately 120 mV/dec, the Volmer step mechanism is the reaction rate’s limiting factor.…”

“…The electrodes’ catalytic efficacy − was assessed through linear sweep voltammetry (LSV), electrochemical impedance spectroscopy (EIS), Tafel slopes, electrochemically active surface area (ECSA), cyclic voltammetry (CV), C dl (electrochemical double-layer capacitance), roughness factor (RF), specific activity (SA), “ n ” (surface-active sites), and chronopotentiometry (CP) analysis (1 M KOH solution). The detailed calculations and procedures are incorporated in the Supporting Information.…”