Hierarchical Interconnected NiMoN with Large Specific Surface Area and High Mechanical Strength for Efficient and Stable Alkaline Water/Seawater Hydrogen Evolution

Abstract

NiMo-based nanostructures are among the most active hydrogen evolution reaction (HER) catalysts under an alkaline environment due to their strong water dissociation ability. However, these nanostructures are vulnerable to the destructive effects of H2 production, especially at industry-standard current densities. Therefore, developing a strategy to improve their mechanical strength while maintaining or even further increasing the activity of these nanocatalysts is of great interest to both the research and industrial communities. Here, a hierarchical interconnected NiMoN (HW-NiMoN-2h) with a nanorod-nanowire morphology was synthesized based on a rational combination of hydrothermal and water bath processes. HW-NiMoN-2h is found to exhibit excellent HER activity due to the accomodation of abundant active sites on its hierarchical morphology, in which nanowires connect free-standing nanorods, concurrently strengthening its structural stability to withstand H2 production at 1 A cm−2. Seawater is an attractive feedstock for water electrolysis since H2 generation and water desalination can be addressed simultaneously in a single process. The HER performance of HW-NiMoN-2h in alkaline seawater suggests that the presence of Na+ ions interferes with the reation kinetics, thus lowering its activity slightly. However, benefiting from its hierarchical and interconnected characteristics, HW-NiMoN-2h is found to deliver outstanding HER activity of 1 A cm−2 at 130 mV overpotential and to exhibit excellent stability at 1 A cm−2 over 70 h in 1 M KOH seawater.

Metal nitrides for seawater electrolysis

“…17j). 69 The nanowires effectively connect independent nanorods (Fig. 17k and l), enhancing the structural stability and demonstrating outstanding durability at an ultra high current density of 1 A cm −2 .…”

“…66 In order to achieve active adsorption of intermediates and reactants, an advanced three-dimensional (3D) nanostructure design strategy has been proposed. 67 This not only increases the electrochemically active surface area, but also enhances the structural robustness of the catalyst, 8,68 for example, by using inter-crosslinked nanorod-nanowire superstructures, 69 and sandwich structures with double-sided nanosheets encapsulation. 70 In addition, electrolyte substitution is also a highly effective strategy, primarily focused on the anode.…”

Interface-engineered urchin-like CoFe-layered double hydroxide for high-efficiency electrocatalytic oxygen evolution

“…To date, many efforts have been devoted to replacing the noble metallic elements by designing efficient electrocatalysts based on transition metal alloys, [12][13][14] oxides, 15-17 hydroxides, [18][19][20][21] nitrides, 22,23 sulfides, 24,25 phosphides, [26][27][28] and their composites. [29][30][31][32] Among these transition metalbased nanomaterials, both spinel oxides and layered double hydroxides (LDHs) have been widely researched for the OER under alkaline conditions due to their easily adjustable structures and physicochemical performance.…”

Tailoring the electronic environment of MoSe2via cation metal doping for the enhanced alkaline hydrogen evolution reaction

“…In addition, the HER pathway in alkaline media works under an additional Volmer step (M + H 2 O + e − → M–H ads + OH − ) for water dissociation in advance of the Heyrovsky (M–H ads + H 2 O + e − → M + H 2 + OH − ) or Tafel (2M–H ads → 2M + H 2 ) step, which leads to the sluggish water adsorption/dissociation process during HER. 7,8 Accordingly, the slow kinetics involved in the HER process, especially under basic conditions, can cause the actual electrolysis voltage to exceed the theoretical value, which results in additional energy consumption. Currently, commercial HER catalysts mostly rely on platinum (Pt)-based precious metal materials with minimum overpotential and near-zero Gibbs free energy (Δ G H* ) because of their favorable hydrogen binding energy under alkaline conditions.…”