Alkaline Water Splitting Enhancement by MOF‐Derived Fe–Co–Oxide/Co@NC‐mNS Heterostructure: Boosting OER and HER through Defect Engineering and In Situ Oxidation

Abstract

Introducing defects and in situ topotactic transformation of the electrocatalysts generating heterostructures of mixed‐metal oxides(hydroxides) that are highly active for oxygen evolution reaction (OER) in tandem with metals of low hydrogen adsorption barrier for efficient hydrogen evolution reaction (HER) is urgently demanded for boosting the sluggish OER and HER kinetics in alkaline media. Ascertaining that, metal–organic‐framework‐derived freestanding, defect‐rich, and in situ oxidized Fe–Co–O/Co metal@N‐doped carbon (Co@NC) mesoporous nanosheet (mNS) heterostructure on Ni foam (Fe–Co–O/Co@NC‐mNS/NF) is developed from the in situ oxidation of micropillar‐like heterostructured Fe–Co–O/Co@NC/NF precatalyst. The in situ oxidized Fe–Co–O/Co@NC‐mNS/NF exhibits excellent bifunctional properties by demanding only low overpotentials of 257 and 112 mV, respectively, for OER and HER at the current density of 10 mA cm−2, with long‐term durability, attributed to the existence of oxygen vacancies, higher specific surface area, increased electrochemical active surface area, and in situ generated new metal (oxyhydr)oxide phases. Further, Fe–Co–O/Co@NC‐mNS/NF (+/−) electrolyzer requires only a low cell potential of 1.58 V to derive a current density of 10 mA cm−2. Thus, the present work opens a new window for boosting the overall alkaline water splitting.

Mesoporous FeMoV Oxide Nanosheets Supported on Nickel Foam as Highly Efficient Electrocatalysts for the Oxygen Evolution Reaction

“…As shown in Figure a, Nyquist plots reveal that the charge-transfer resistance ( R ct ) of the Fe 0.5 Mo 0.1 V 0.4 /NF electrode is 1.51 Ω, which is smaller than that of Fe/NF (2.23 Ω), Fe 0.5 Mo 0.5 /NF (2.91 Ω), Fe 0.5 V 0.5 /NF (2.94 Ω), and RuO 2 /NF (1.84 Ω) electrodes. This result indicates that the electron transfer rate between the interface of the electrocatalyst and electrolyte on the Fe 0.5 Mo 0.1 V 0.4 /NF electrode is faster than those on other as-prepared electrodes, , which probably leads to the enhanced OER activity. The ECSAs of the as-prepared electrodes were estimated based on the double-layer capacitance ( C dl ) to investigate the origin of the enhanced OER activity.…”

Bimetallic sulfide particles incorporated in Fe/Co-based metal–organic framework ultrathin nanosheets toward boosted electrocatalysis of the oxygen evolution reaction

“…6c and d), indicating the formation of (oxy)hydroxides during electrochemical activation, which act as the actual active sites of the OER. 26,50,51 X-ray photoelectron spectroscopy 3+ , respectively. 52 It is notable that the binding energy of Co 2p 3/2 for the CoFe-MS/MOF decreases after electrochemical activation (ΔBE = 0.87 eV).…”

“…It is caused by metal sulfide particles conferring electrons from their electron-rich metal atoms to the surface Co and Fe centers. 51,53,54 Recent studies further indicate that the OER activity of Fe/ Co-based catalysts can be boosted through enhancing the adsorption of oxygenated intermediates such as *OH and *O on the surface. 35,55,56 As shown in Fig.…”

Hierarchical Co(OH)F/CoFe-LDH heterojunction enabling high-performance overall water-splitting

“…Both of these reactions have inherent energy barriers, and a large overpotential is required to achieve prominent catalytic efficiency in practical water-splitting devices. [6][7][8][9][10][11][12] At present, platinum (Pt) and Pt-based alloys are acknowledged as promising catalytic materials for the HER, and IrO 2 and RuO 2 are observed as state-of-the-art catalysts for the OER, delivering large current densities at low overpotentials. However, these catalysts still suffer from insufficient reserves and high price, which has greatly limited their potential for large-scale industrial applications.…”