Enhanced Electrocatalytic Activity of Mo-Doped NiFe Layered Double Hydroxide Nanosheet Arrays for the Hydrogen Evolution Reaction

Abstract

NiFeMo layered double hydroxide (NiFeMo-LDH) nanosheet array structures in situ grown on Ni foam were rationally designed and fabricated by a convenient and green hydrothermal strategy. The systematic characterization proved that Ni x Fe 1 Mo 1 -LDH/NF (x = 4, 6, 8, 10) composites grew on the surface of Ni foam as vertically interlaced LDH nanosheets. The electrochemical results showed that all composites possessed high electrocatalytic activity, and Ni 6 Fe 1 Mo 1 -LDH/NF exhibited the best hydrogen evolution reaction (HER) performance. Furthermore, the nanosheet array structure with the best active metal molar ratio was in situ grown on reduced graphene oxide (rGO) uniformly modified Ni foam (∼210 nm × 20 nm) with an overpotential of 90 mV at 10 cm −2 in an alkaline solution, which was superior to most non-noble metal-based catalysts. Experimental results and density functional theory with the Hubbard U (DFT + U) calculations confirmed that the active site for H adsorption changed from the Fe site to the Mo site after Mo doping in NiFe-LDH, which reduced the water dissociation energy barrier and the subsequent proton adsorption energy barrier and adjusted the electronic structure of Fe and Ni sites, thereby greatly promoting the whole Volmer− Heyrovsky process under alkaline conditions and improving the HER performance. The synergistic coupling of NiFeMo-LDH nanosheets with rGO enhanced conductivity and electrochemical performance. The growth of NiFeMo-LDH on rGO/NF facilitated the formation of bubbles and significantly improved electrochemical stability. The present electronic regulation strategies using metal doping can be extended to synthesize other types of transition metal composite catalysts and used for the development of renewable and friendly energy devices.

V-Doping coupled H2O2 pre-oxidation synergistically promote NiCo-LDH for urea oxidation-assisted hydrogen production

“…A detailed description for the synthesis of rGO/NF can be found in our previous work. [42][43][44][45] The SEM images show that bare Ni foam usually has a smooth surface, while rGO was uniformly coated on the NF surface in the rGO/ NF sample. It can be observed that the LDH nanosheets (size ∼135 nm × 15 nm) grew vertically and were interwoven on rGO/ NF.…”

“…The results suggest that during the in situ growth process of NiCoV 1.0 -LDH/rGO/NF-100, more defect sites were created due to the reduction of GO in the alkaline reaction system. [42][43][44][45] The contact angle test results (Fig. S25b-e †) showed that the contact angle of NiCoV 1.0 -LDH/rGO/NF-100 (134.0°) was higher than those of NiCoV 1.0 -LDH/NF-100 (124.1°), rGO/NF-100 (96.2°), and NF (83.8°), suggesting a faster bubble release ability and improved catalytic activity.…”

“…In our previous work, the nanosheet arrays CoFe-LDH, NiFe-LDH, and NiFeMo-LDH were in situ grown on reduced graphene oxide modied Ni foam (rGO/NF), and exhibited better electrocatalytic performance than those directly grown on Ni foam. [43][44][45] The exceptional performance of the material was due to the nanosheet array structure, which provided more active sites, and the collaboration of LDH and rGO, which enhanced the conductivity and catalytic activity.…”

Boosting the Oxygen Evolution Activity of FeNi Oxides/Hydroxides by Molecular and Atomic Engineering

“…However, non-precious metals such as Cu and Mo have been successfully introduced as dopants on NiFe oxide/hydroxides in the form of small clusters/ NPs [89] or as a third metal in the crystalline structure. [90,91] Consequently, exploring the use of non-precious metal-based SAs as dopants is a promising route to atomically tune the OER activity of NiFe oxide/hydroxides without the introduction of critical raw materials. Finally, the addition of a ligand in the NiFe oxide/hydroxide electrocatalyst (both on the surface and in the interlayer in the case of the LDH) has proven to be an effective strategy to induce second coordination sphere effects, especially important to accelerate the different proton coupled electron transfers taking place during the catalytic cycle (Scheme 1).…”

“…Most of the reported examples following this strategy are based on noble metal SAs. However, non‐precious metals such as Cu and Mo have been successfully introduced as dopants on NiFe oxide/hydroxides in the form of small clusters/NPs [89] or as a third metal in the crystalline structure [90,91] . Consequently, exploring the use of non‐precious metal‐based SAs as dopants is a promising route to atomically tune the OER activity of NiFe oxide/hydroxides without the introduction of critical raw materials.…”