Promoting nickel oxidation state transitions in single-layer NiFeB hydroxide nanosheets for efficient oxygen evolution

Abstract

Promoting the formation of high-oxidation-state transition metal species in a hydroxide catalyst may improve its catalytic activity in the oxygen evolution reaction, which remains difficult to achieve with current synthetic strategies. Herein, we present a synthesis of single-layer NiFeB hydroxide nanosheets and demonstrate the efficacy of electron-deficient boron in promoting the formation of high-oxidation-state Ni for improved oxygen evolution activity. Raman spectroscopy, X-ray absorption spectroscopy, and electrochemical analyses show that incorporation of B into a NiFe hydroxide causes a cathodic shift of the Ni2+(OH)2 → Ni3+δOOH transition potential. Density functional theory calculations suggest an elevated oxidation state for Ni and decreased energy barriers for the reaction with the NiFeB hydroxide catalyst. Consequently, a current density of 100 mA cm–2 was achieved in 1 M KOH at an overpotential of 252 mV, placing it among the best Ni-based catalysts for this reaction. This work opens new opportunities in electronic engineering of metal hydroxides (or oxides) for efficient oxygen evolution in water-splitting applications.

Self‐Supporting Iron‐Modified Nickel Phosphide Electrode Realizing Superior Bifunctional Performance for Water Splitting

“…[4][5][6] However, the four-electron transfer process of the OER leads to a slow kinetic reaction process, which greatly limits the energy conversion efficiency of electrocatalytic water splitting. [7][8][9] Precious metal materials are considered to be a better system for improving the efficiency of water electrolysis, but their low reserves and high prices limit a wider range of practical applications. [10,11] Thus, the development of highly efficient bifunctional electrocatalysts for improving the energy conversion efficiency of hydrogen generation is imperative.…”

“…Electrocatalytic water splitting technology, including two‐half reactions of HER and OER, is considered an important means of large‐scale preparation of hydrogen fuel [4–6] . However, the four‐electron transfer process of the OER leads to a slow kinetic reaction process, which greatly limits the energy conversion efficiency of electrocatalytic water splitting [7–9] . Precious metal materials are considered to be a better system for improving the efficiency of water electrolysis, but their low reserves and high prices limit a wider range of practical applications [10,11] .…”

Facilitating Reconstruction of the Heterointerface Electronic Structure by the Enriched Oxygen Vacancy for the Oxygen Evolution Reaction

“…In response to today’s ever-increasing global energy and environmental issues, the quest for sustainable and clean energy systems is constantly on the move. The electrochemical oxygen evolution reaction (OER) has been envisioned as playing an unequivocally vital role in a variety of decarbonized energy storage and energy conversion technologies, including water electrolyzers, rechargeable metal–air batteries, regenerative fuel cells, and electrochemical CO 2 reduction. , However, the sluggish kinetics associated with the four sequential proton-coupled electron-transfer processes involved in the OER (4OH – → 2H 2 O + O 2 + 4e – in base), which rely on two steps of O–H bond cleavage and one rigid OO bond formation, severely compromise the overall efficiency of electrochemical systems. − Up to now, in order to promote the reaction rate, noble metal-based catalysts, such as commercial RuO 2 and IrO 2 oxides, still occupy the benchmark position in the OER catalysts, while their unaffordable price and scarcity severely restrict their commercialization in practical devices. − With such concerns, relentless efforts from both industry and academia alike have been devoted to the development of a myriad of alternative OER catalysts based on cost-effective elements (Ni, Co, Fe, and Mn) or their compounds, which would be a very promising answer to the aforesaid problems. − In particular, earth-abundant and environmentally friendly transition metal oxides (TMOs), especially Ni-based materials, have exhibited excellent performance in OER catalysis, taking advantage of their reasonable activity and reactivity, since the OER activities of single TMOs follow the order NiO x > CoO x > FeO x > MnO x . Although encouraging progress has been made, the deficiency of highly active reactive sites, low intrinsic conductivity, and wide energy bandgap of NiO-based catalysts are still major obstacles to the replacement of OER catalysts based on precious metals. − …”

Complete reconstruction of NiMoO4/NiFe LDH for enhanced oxygen evolution reaction

“…The presence of high-oxidation-state Ni can accelerate the reaction kinetics to offer highly intrinsic OER activity. 8,29 The surface oxygen species were also characterized (Fig. 3f).…”

“…The electronic states near the Fermi level ( E f ) are predominantly from the Ni 3d orbitals, further suggesting that Ni serves as catalytic active sites for the OER. 29 The reaction pathway for the OER is displayed in Fig. 4c.…”