Carbon Nanofibers Featuring Bimetallic Nanoparticle-in-Pore Structures as Water-Splitting Electrocatalysts

Abstract

Research effort has increasingly been devoted to exploiting efficient noble-metal-free electrocatalysts because of their low cost and abundancy. Herein, metallic nanoparticulate-containing carbon nanofibers (MCNFs) featuring interior, nanoparticulate-in-pore structures were fabricated by taking advantage of cationic metal species/anionic surfactant complexes (MSCs). Binary MSC mixtures containing Fe−Co, Fe−Ni, and Co−Ni species were used to control not only the size/loading amount of the metallic phases but also the microstructural characteristics of the nanofiber matrices. Compared to their single MSC counterparts, the binary MSC mixtures allowed the generation of unique metallic phases, such as binary transitionmetal oxides, and resulted in enhanced surface area/porosity and reduced charge transfer resistance. The noble-metal-free MCNFs were demonstrated as electrocatalysts for both oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). The MCNFs prepared using binary combinations of Fe−Ni and Co−Ni, viz., FeNiCNFs and CoNiCNFs, showed outstanding performances for the OER and HER, respectively. For the OER particularly, at potentials exceeding 1.6 V (vs RHE), the FeNiCNFs showed higher current densities than that of the well-known, conventionally used electrocatalyst RuO 2 . For overall water splitting, an asymmetric FeNiCNF∥CoNiCNF cell rendered performance stability that was 15% better than that of the RuO 2 ∥Pt/C control cell. Based on the results of this study, various combinations of MSCs with controlled loading into functional matrices can be prepared to yield efficient, cost-effective electrocatalysts for water splitting.

Synergistically Coupled Ni/CeOx@C Electrocatalysts for the Hydrogen Evolution Reaction: Remarkable Performance to Pt/C at High Current Density

“…Thus, there is an urgent need to explore highly active and cost-effective non-precious metal catalysts to address these issues for industrial-scale hydrogen production . Recently, nickel (Ni)-based electrocatalysts have been intensively studied due to their rich abundance, low cost, good corrosion, and dissolution resistance under alkaline conditions . However, the actual activity of mostly Ni-based reported electrocatalysts for HER is not up to mark and cannot compete with the activity and durability of precious metals.…”

Sulphur Assisted Nitrogen‐Rich CNF for Improving Electronic Interactions in Co‐NiO Heterostructures Toward Accelerated Overall Water Splitting

“…[7][8][9] A similar strategy was followed by Yoon and co-workers, which compared the physical and electronic properties of certain single metal-carbon nanofibers (sMCNF) (MFe, Co, and Ni) and bimetal CNFs (bMCNF) (FeCo, FeNi, and CoNi). [9] With the study results, the group fabricated a FeNiCNF (anode) ∥ CoNiCNF (cathode) cell for overall Electrochemical water splitting is the eco-friendly route to generate green hydrogen, which is recognized as sustainable energy for the future. However, the cost, operational efficiency, and long-term durability of the electrochemical water splitting rely on the choice of the electrocatalysts.…”

“…[ 7–9 ] A similar strategy was followed by Yoon and co‐workers, which compared the physical and electronic properties of certain single metal‐carbon nanofibers (sMCNF) (MFe, Co, and Ni) and bimetal CNFs (bMCNF) (FeCo, FeNi, and CoNi). [ 9 ] With the study results, the group fabricated a FeNiCNF (anode) ∥ CoNiCNF (cathode) cell for overall water splitting application and came out with an excellent HER activity for the CoNiCNF electrocatalyst. In addition, 3d ‐ transition metal oxides (TMO) have been studied extensively for the electrocatalytic activity, where the oxygen vacancies combined with the 3d ‐TM play a major role in determining the adsorption of the analyte for redox reactions.…”

“…As reported, the electrocatalytic activity for 3d-transition metals increases in the order Mn < Fe < Co < Ni. [7][8][9] A similar strategy was followed by Yoon and co-workers, which compared the physical and electronic properties of certain single metal-carbon nanofibers (sMCNF) (MFe, Co, and Ni) and bimetal CNFs (bMCNF) (FeCo, FeNi, and CoNi). [9] With the study results, the group fabricated a FeNiCNF (anode) ∥ CoNiCNF (cathode) cell for overall Electrochemical water splitting is the eco-friendly route to generate green hydrogen, which is recognized as sustainable energy for the future.…”

Ternary Nanohybrids Comprising N-Doped Graphene and WSe2–WO3 Nanosheets Enable High-Mass-Loading Electrodes with Long-Term Stability for Hydrogen Evolution

“…Thus, significant effort has been devoted to the development of non-noble-metal catalysts. Earth-abundant metals, such as transition-metal oxides, hydroxides, carbides, nitrides, phosphides, and dichalcogenides, have been considered as alternatives to noble metals. − Particularly, two-dimensional (2D) transition-metal dichalcogenides (TMDs), including WSe 2 and MoS 2 , have emerged as promising electrocatalysts owing to their high surface-to-volume ratios, atomically thin structures, and unique physical/chemical properties. − For example, Yang et al reported the preparation of WO 3 ·2H 2 O nanoplates/WS 2 hybrid catalysts for HER, where the WO 3 ·2H 2 O nanoplates were grown on the surface of the bulk WS 2 film via anodic oxidation . However, the sluggish reaction kinetics of TMDs in the electrocatalysis hamper their ability to effectively produce hydrogen or oxygen as renewable energy sources. , Notably, recent studies on 2D/2D heterostructures have revealed new catalysts with improved electrochemical performances. , However, 2D/2D heterostructures are primarily obtained through a multistep chemical vapor deposition and pulsed laser deposition at high temperatures and pressures. , Furthermore, the resultant heterostructures feature weak interactions between their heterosheets, thus preventing synergetic effects .…”