Self-Supporting Clusters Constituted of Nitrogen-Doped CoMoO₄ Nanosheets for Efficiently Catalyzing the Hydrogen Evolution Reaction in Alkaline Media

Abstract

Transition metal oxides (TMOs) have acquired much attention on account of their abundant reserves and variable components, but sluggish charge transfer rate, limited electrochemically active sites, and poor conductivity hamper their extensive applications in the hydrogen evolution reaction (HER). Herein, we have synthesized nitrogen-doped CoMoO 4 clusters constituted of nanosheets directly supported on nickel foam (N-CoMoO 4 /NF) by combining a hydrothermal process and lowtemperature ammonia annealing treatment. Experimental results reveal that the nitrogen doping can modulate the electronic structure of CoMoO 4 , in which Mo ions with +6 valence are reduced to a lower state, and thus enhance its catalytic performance for HER. The optimized N-CoMoO 4 /NF (N-CoMoO 4 /NF-1, with the annealing time of 1 h in NH 3 atmosphere) exhibits excellent activity toward alkaline HER, requiring an overpotential of 58 mV at 10 mA/cm 2 . This work possesses great potential for promoting alkaline HER performance of TMOs by the facile process of nitrogen doping.

Triggering the Intrinsic Catalytic Activity of Ni-Doped Molybdenum Oxides via Phase Engineering for Hydrogen Evolution and Application in Mg/Seawater Batteries

“…For S400, in addition to the peaks at 232.61 eV (Mo 6+ 3d 5/2 ) and 235.75 eV (Mo 6+ 3d 3/2 ), two new weak peaks at 232.61 and 235.75 eV can be observed, which are assigned to the Mo 4+ 3d 5/2 and Mo 4+ 3d 3/2 , respectively, indicating the partial reduction of MoO 3 to MoO 2 in Ni-MoO 3 during low-temperature annealing. For S500 and S600, the new peaks appearing at 229.34, 233.19, 230.41, and 234.95 eV are assigned to Mo 4+ 3d 5/2 , Mo 4+ 3d 3/2 , Mo 5+ 3d 5/2 , and Mo 5+ 3d 3/2 , respectively. ,, This suggests the transformation of large amounts of Ni-MoO 3 to Ni-MoO 2 , consistent with the XRD results. In addition, two other weak peaks at 228.07 and 232.17 eV in S600 can be assigned to Mo 0 3d 5/2 and Mo 0 3d 3/2 , respectively, , implying the formation of metallic Mo in Ni-MoO 2 .…”

“…For S500 and S600, the new peaks appearing at 229.34, 233.19, 230.41, and 234.95 eV are assigned to Mo 4+ 3d 5/2 , Mo 4+ 3d 3/2 , Mo 5+ 3d 5/2 , and Mo 5+ 3d 3/2 , respectively. 19,25,26 This suggests the transformation of large amounts of Ni-MoO 3 to Ni-MoO 2 , consistent with the XRD results. In addition, two other weak peaks at 228.07 and 232.17 eV in S600 can be assigned to Mo 0 3d 5/2 and Mo 0 3d 3/2 , respectively, 25,27 implying the formation of metallic Mo The HER activity of Ni-doped molybdenum oxides with different oxidation states was first evaluated in 1 M KOH.…”

In Situ-Grown Cobalt–Iron Phosphide-Based Integrated Electrode for Long-Term Water Splitting under a Large Current Density at the Industrial Electrolysis Temperature

“…11,12 In addition, their high price and scarcity seriously limit their widespread industrial applications. 9,13,14 Therefore, it is urgent to exploit non-noble metal-based catalysts that are earth-abundant, have low cost, and are efficient and stable for water splitting under a large current density at the industrial electrolysis temperature.…”

“…Currently, Pt-based metal/alloy and Ir/Ru-based oxides are the benchmark electrocatalysts for HER , and OER, , respectively. However, their poor stability, especially at large current densities, makes them difficult to operate efficiently. , In addition, their high price and scarcity seriously limit their widespread industrial applications. ,, Therefore, it is urgent to exploit non-noble metal-based catalysts that are earth-abundant, have low cost, and are efficient and stable for water splitting under a large current density at the industrial electrolysis temperature.…”

Development Strategies in Transition Metal Borides for Electrochemical Water Splitting

“…As shown in Equations ( 9) and (11), its Tafel value is nearly 29.5 mV dec −1 [4] as the determining rate step; while the coverage value is low, the H* couples with a proton and an electron to produce hydrogen molecular, in which the available protons depend on the pH of the electrolyte: As for acidic media, the protons can be directly captured from the electrolyte; as for neutral and alkaline media, the protons should break the H-O-H bond of H 2 O, and its Tafel slope value is about 39 mV dec −1 [4] as the determining rate step, as shown in Equations (5) and (7). For TMBs, the electrocatalytic process follows Equations (4)(5)(6)(7)(8)(9)(10)(11). In most cases, relying on the property of high electronegativity, boron element is not the direct electrocatalytic active Reproduced with permission.…”