Double‐Exchange‐Induced in situ Conductivity in Nickel‐Based Oxyhydroxides: An Effective Descriptor for Electrocatalytic Oxygen Evolution

Abstract

Motivated by in silico predictions that Co,Rh, and Ir dopants would lead to low overpotentials to improve OER activity of Ni-based hydroxides,wereport here an experimental confirmation on the altered OER activities for as eries of metals (Mo,W ,F e, Ru, Co,Rh, Ir) doped into g-NiOOH. The in situ electrical conductivity for metal doped g-NiOOH correlates well with the trend in enhanced OER activities. Density functional theory (DFT) calculations were used to rationalizethe in situ conductivity of the key intermediate states of metal doped g-NiOOH during OER. The simultaneous increase of OER activity with intermediate conductivity was later rationalized by their intrinsic connections to the double exchange (DE) interaction between adjacent metal ions with various do rbital occupancies,s erving as an indicator for the key metal-oxoradical character,and an effective descriptor for the mechanistic evaluation and theoretical guidance in design and screening of efficient OER catalysts.

Nickel Nanoparticles Encapsulated in Nitrogen‐Doped Carbon Nanofibers as Excellent Bifunctional Catalyst for Hydrogen and Oxygen Evolution Processes

“…Ideal catalysts for OER it is expected to have: (i) as high as possible number of active sites along with possible large specific surface area (SSA) enlarging obtained anode current densities and facilitating charge and oxygen species transfer, (iii) high electrical conductivity, (iv) chemical, electrochemical and mechanical stability, (v) as low as possible intrinsic overpotentials during water splitting reactions [40] . Therefore, we strongly believe that the Ni@C−(N)CNF‐5 has a potential to meet the requirements for an excellent electrocatalyst for water splitting, due to its outstanding properties, such as: (i) layered structure, which is favorable for charge transfer, [41] (ii) presence of Ni with high theoretical OER activities according to the Volcano‐shaped relationship, [42] ability to redox transition [43] as well as its conductive nature [44] . To verify it detailed electrochemical characterization as electrocatalyst in OER has been conducted and presented below.…”

“…[40] Therefore, we strongly believe that the Ni@CÀ (N)CNF-5 has a potential to meet the requirements for an excellent electrocatalyst for water splitting, due to its outstanding properties, such as: (i) layered structure, which is favorable for charge transfer, [41] (ii) presence of Ni with high theoretical OER activities according to the Volcano-shaped relationship, [42] ability to redox transition [43] as well as its conductive nature. [44] To verify it detailed electrochemical characterization as electrocatalyst in OER has been conducted and presented below.…”

Double‐Exchange‐Induced in situ Conductivity in Nickel‐Based Oxyhydroxides: An Effective Descriptor for Electrocatalytic Oxygen Evolution

“…In addition to the Ni-based oxyhydroxides, DE interaction has been recently proposed to boost the OER performance in other systems such as spinel oxides. [33] Moreover, spectroscopic studies also suggested the surface reconstructed oxyhydroxides to be a general intermediate OER active phase in metal nitrides, [18b] spinel oxides and perovskites, [34] metal-organic frameworks, [35] where internal DE interaction might also exist and contribute to the OER activity. Therefore, the DE-induced transport indicator, enabled by on-chip in situ measurements demonstrated in this work, can potentially help elucidate the OER mechanisms in various classes of inorganic materials, where the mixed valence metal oxyhydroxide plays an essential role in the electro-oxidative process.…”

Interfacial Regulation of Electron‐enhanced Co2P−CuP2 Sheet‐like Heterostructure as a Robust Bifunctional Electrocatalyst for Overall Water Splitting and Zn−H2O Cell

“…H 2 ) and OER (4OH À !O 2 + 2H 2 O) by applying electrocatalysts to produce hydrogen and oxygen. [2] Currently, although noble metal-based materials (such as Pt, RuO 2 and IrO 2 ) are the most advanced catalysts, [3] the prohibitive expense and scarcity severely hinder their largescale application. [4] Therefore, it is impending to exploit the catalysts with high-efficiency and affordable to reduce overpotential and improve water splitting efficiency.…”

“…The environmental problems and energy crisis caused by excessive use of fossil fuels have led to the demand for renewable energy technologies [1] . Electrochemical water splitting is a primary step towards sustainable clean energy to accelerate the HER (2H + +2e − → H 2 ) and OER (4OH − →O 2 +2H 2 O) by applying electrocatalysts to produce hydrogen and oxygen [2] . Currently, although noble metal‐based materials (such as Pt, RuO 2 and IrO 2 ) are the most advanced catalysts, [3] the prohibitive expense and scarcity severely hinder their large‐scale application [4] .…”