Electrocatalysts for Hydrogen Evolution in Alkaline Electrolytes: Mechanisms, Challenges, and Prospective Solutions

This review summarizes the recent developments to overcome the kinetics issues of alkaline HER, synthesis of materials with modified morphologies, and electronic structures to tune the active sites and their applications as efficient catalysts for HER

Nasir Mahmood; Yunduo Yao; Jing-Wen Zhang; Lun Pan; Xiangwen Zhang; Ji-Jun Zou

2017

Scholarcy highlights

  • Hydrogen has been referred as fuel of fuel for various energy systems, but suffers from sluggish reaction kinetics due to additional water dissociation step
  • The Zn0.30Co2.70S4 exhibited superior HER activity and stability because of the optimized Gibbs free energy for H* adsorption and improved electrical conductivity due to the homogeneous distribution of Zn in Co3S4 lattice as shown in Figure 9. This study showed that composition plays effective role in optimizing the Gibbs free energy for H* adsorption, while the morphology tunes the exposer of active sites
  • The HER kinetics and mechanism vary with nature of used electrolytes and becomes more tough as moving from acidic to alkaline one, more sluggish kinetics involve due to additional water dissociation step
  • This is the one reason why the best performing acidic medium catalysts have very poor activity in alkaline electrolytes, even the noble metals are suffering from poor stability and large overpotentials to achieve reasonable current densities
  • Sluggish kinetics and poor activities of most of the catalysts limit the development in the alkaline HER catalysis, one of the most industrial and economically demanding hydrogen production systems
  • To overcome the challenges associated with unclear sluggish reaction mechanism of alkaline HER, recently several efforts have been put forward by combining the two different catalysts
  • Heterostructures provide easy control over their surface tuning to expose the active sites, providing the opportunity to utilize maximum material in catalysis that helps in cost reduction

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