Mesoporous Strontium Hydroxide Hydrate as a Nanostructure-Dependent Electrocatalyst for Hydrogen Evolution Reaction

Abstract

Tremendous efforts have been directed to developing reliable electrocatalysts to gain clean hydrogen energy from water splitting and encounter energy challenges. The morphology at the nanoscale of electrocatalysts has also a significant influence on hydrogen evolution reaction. An alkaline-based electrocatalyst, strontium hydroxide hydrate, has been synthesized at temperatures of 80, 140, and 200 °C using the hydrothermal process. The employed growth temperature capably influences the morphology and intrinsic characteristics of the strontium hydroxide hydrate for the hydrogen evolution reaction. The mesoporous nature, greater electrochemical and specific surface area of nanorods, and facile proton donation by the acid jointly enhance the HER activity. Hy-Sr(OH)2-200 nanorods have exhibited a good overpotential of 84 mV in 0.5 M H2SO4 at the current density of 10 mA cm–2, which is better than the nanopallets (Hy-Sr(OH)2-80) and the hybrid morphology consisting of nanopallets and nanorods (Hy-Sr(OH)2-140). The mesoporous nature, greater electrochemical and specific surface area, and nanorod-like morphology have promoted and facilitated the adsorption and desorption of the active hydrogen atoms at the active sites inside the Hy-Sr(OH)2-200 nanorods. As a result, Hy-Sr(OH)2-200 nanorods exhibit the Tafel slope of 81 mV dec–1 in 0.5 M H2SO4 and follow the Volmer–Heyrovsky phenomena. Moreover, Hy-Sr(OH)2-200 nanorods show a good turnover frequency of 142.84 ms–1 at the fixed reversible hydrogen potential of 0.5 V, which is better than the other employed electrolytes and electrocatalysts fabricated at temperatures of 80 and 140 °C. The symmetric system, consisting of Hy-Sr(OH)2-200 nanorods, shows a good overpotential of 240 mV at a current density of 10 mA cm–2, along with a Tafel slope of 79 mV dec–1 in 0.5 M H2SO4. The electrocatalyst of Hy-Sr(OH)2-200 nanorods comprehensively exhibits good performance for the hydrogen evolution reaction.

Enhancement of the characteristics and HER activity of molybdenum carbide nanosheets for hydrogen evolution reaction

“…A ECSA reduced with an increase in the scan rate, which might be due to an increase in the internal resistance of the electrocatalyst at higher potentials. 8,50 The Mo 2 C-1200 nanosheets exhibited a greater A ECSA at the employed scan rates compared with the Mo 2 C-600 and Mo 2 C-900 nanosheets, as shown in Fig. 4e, and the results are summarized in Table S4 †.…”

“…Moreover, the greater A ECSA and smaller Gibbs free energy suggest that the number of active sites was greater in the Mo 2 C-1200 nanosheet electrocatalyst, facilitating easy adsorption and desorption of the active hydrogen atoms during the HER process. 8,12,[51][52][53][54] Electrochemical impedance spectroscopy (EIS) was performed in 1 M KOH and 0.5 M H 2 SO 4 electrolytes, and the corresponding Nyquist plots are given in Fig. 4f and g.…”

“…7 Electrocatalysts usually consist of noble metals, and their high cost, scarcity and poor long-term stability make them unsuitable for commercial purposes. [8][9][10][11] Although several other electrocatalysts have been developed, their structural stability, internal voltage loss, low electrical conductivity, and cost are a big hindrance to their practical application at the industrial level. 12 Efficient electrocatalysts exhibit high electrical conductivity, large specic surface area, structural stability, low Gibbs free energy, rich surface chemistry, and more active sites.…”

Amorphous/Crystalline Nanostructured WP/CoP-FeP4/NF Heterojunctions for Efficient Electrocatalytic Overall Water Splitting

“…Nonprecious metals present an exciting prospect as superior alternatives to precious metal catalysts due to their lower cost and potential catalytic activity. 14,15 Transition metal-based electrocatalysts possess abundant unpaired d-orbital electrons, which endow them with highly desirable catalytic potential and make them excellent catalysts for the electrochemical process of water splitting to produce hydrogen. 16,17 The catalytic performance of transition metal-based catalysts can be enhanced in various ways to approach or even surpass that of precious metal catalysts.…”

“…Precious-metal catalysts exhibit excellent catalytic properties. , However, their prohibitive cost renders them unsuitable for large-scale commercial hydrogen production from electrochemical water splitting. Nonprecious metals present an exciting prospect as superior alternatives to precious metal catalysts due to their lower cost and potential catalytic activity. , Transition metal-based electrocatalysts possess abundant unpaired d-orbital electrons, which endow them with highly desirable catalytic potential and make them excellent catalysts for the electrochemical process of water splitting to produce hydrogen. , The catalytic performance of transition metal-based catalysts can be enhanced in various ways to approach or even surpass that of precious metal catalysts. , Consequently, low-cost alternatives can replace precious metal catalysts across all aspects, enabling large-scale production of hydrogen from electrolytic water. Researchers have endeavored to enhance the catalytic activity of transition metal-based electrocatalysts through various approaches, including composite materials, heteroatom doping, morphological modifications, , and the design of heterostructure. , Among these, the electronic structure of the catalyst can be effectively modulated by combining multiple transition metal elements, which enhances catalytic efficiency through synergistic effects. , Additionally, metal phosphides have been demonstrated to be ideal electrocatalysts for the HER .…”