Electrodeposition of self–supported Ni–Mg–La electrocatalyst on Ni foam for efficient hydrogen evolution reaction

Co-deposition of Ni-Mo alloy film catalysts for hydrogen evolution from an ethylene glycol system

Owing to the depletion of renewable energy sources, manufacturing stable, efficient and economical non-noble electrode materials for the hydrogen evolution reaction (HER) through electrochemical water splitting is a promising avenue. In this work, Ni-Mo alloy films containing different Mo concentrations were synthesized via potentiostatic technique, and the mechanism of Ni2+ and Mo6+ co-deposition in an ethylene glycol system (EG) was recorded. The co-deposition mechanism of Mo6+ and Ni2+ in the EG shows that the existence of Ni2+ can facilitate the reduction of Mo6+, while Mo6+ can impede the reduction of Ni2+. Furthermore, both functions could be reinforced owing to the improved content of Ni2+ and Mo6+ in the EG system. Ni-Mo alloy films containing different Mo concentrations could be obtained from the EG solution, and their microstructures could be changed by changing the Mo content. Scanning electron microscopy micrographs exhibit that Ni-Mo alloy films with 10.84 wt% Mo show a cauliflower-like pattern. Benefiting from the alloying technique to modify the Ni electronic structure with Mo, coupled with the concurrent presence of an appropriate cauliflower-like structure, Ni-Mo alloy films with 10.84 wt% Mo show remarkable catalytic activity and durability with an HER overpotential of 74 mV (η 10, overpotential was recorded at j = 10 mA cm-2) in 1.0 M KOH solution.

Facile Synthesis of Ni-MgO/CNT Nanocomposite for Hydrogen Evolution Reaction

In this study, the pristine MgO, MgO/CNT and Ni-MgO/CNT nanocomposites were processed using the impregnation and chemical vapor deposition methods and analyzed for hydrogen evolution reaction (HER) using the electrochemical water splitting process. Furthermore, the effect of nickel on the deposited carbon was systematically elaborated in this study. The highly conductive carbon nanotubes (CNTs) deposited on the metal surface of the Ni-MgO nanocomposite heterostructure provides a robust stability and superior electrocatalytic activity. The optimized Ni-MgO/CNT nanocomposite exhibited hierarchical, helical-shaped carbon nanotubes adorned on the surface of the Ni-MgO flakes, forming a hybrid metal-carbon network structure. The catalytic HER was carried out in a 1M alkaline KOH electrolyte, and the optimized Ni-MgO/CNT nanocomposite achieved a low (117 mV) overpotential value (ɳ) at 10 mA cm-2 and needed a low (116 mV/dec) Tafel value, denotes the Volmer-Heyrovsky pathway. Also, the high electrochemical active surface area (ECSA) value of the Ni-MgO/CNT nanocomposite attained 515 cm2, which is favorable for the generation of abundant electroactive species, and the prepared electrocatalyst durability was also performed using a chronoamperometry test for the prolonged duration of 20 h at 10 mA cm-2 and exhibited good stability, with a 72% retention. Hence, the obtained results demonstrate that the optimized Ni-MgO/CNT nanocomposite is a highly active and cost-effective electrocatalyst for hydrogen energy production.

Magnesium: properties and rich chemistry for new material synthesis and energy applications

Magnesium (Mg) has many unique properties suitable for applications in the fields of energy conversion and storage. These fields presently rely on noble metals for efficient performance. However, among other challenges, noble metals have low natural abundance, which undermines their sustainability. Mg has a high negative standard reduction potential and a unique crystal structure, and its low melting point at 650 °C makes it a good candidate to replace or supplement numerous other metals in various energy applications. These attractive features are particularly helpful for improving the properties and limits of materials in energy systems. However, knowledge of Mg and its practical uses is still limited, despite recent studies which have reported Mg's key roles in synthesizing new structures and modifying the chemical properties of materials. At present, information about Mg chemistry has been rather scattered without any organized report. The present review highlights the chemistry of Mg and its uses in energy applications such as electrocatalysis, photocatalysis, and secondary batteries, among others. Future perspectives on the development of Mg-based materials are further discussed to identify the challenges that need to be addressed.

Exploring the synergistic effect of alloying toward hydrogen evolution reaction: a case study of Ni3M (M = Ti, Ge and Sn) series

In this work, we have demonstrated that one can control the intrinsic activity of Ni metal toward the hydrogen evolution reaction (HER) by simply alloying Ni with different elements (i.e. Ti, Ge or Sn). The HER activities of Ni₃M (M = Ti, Ge and Sn) series and Ni metal follow the order of Ni₃Ti (η₁₀ = 68 mV) > Ni₃Sn (η₁₀ = 122 mV) > Ni₃Ge (η₁₀ = 161 mV) > Ni (η₁₀ = 273 mV). After normalizing their HER performances based on the roughness factor (RF), it was realized that Ni₃Ti and Ni₃Sn both exhibit higher intrinsic HER activities than that of Ni metal while Ni₃Ge displays the worst HER performance. This trend was later rationalized by using density functional theory (DFT) calculation, which showed that blending Ni with Ti, Ge or Sn elements will alter the corresponding electronic structure and bonding scheme. Such a change in the bonding scheme (i.e. bonding state or antibonding state) will influence the adsorption energy of the H atom (ΔG_Had) on an active site and is the main cause of the synergetic effect that results in the different HER efficiencies of Ni₃M (M = Ti, Ge and Sn). Through the present case study, it was recognized that alloying is a simple yet effective strategy to promote the HER activity of an electrocatalyst. With a suitable combination between elements, it helps single metals (e.g. Co or Ni metal) exceed the limits on their intrinsic HER activities and has the potential to replace noble metals (e.g. Pt, Ir and Ru) in the future.