Enhanced hydrogen evolution reaction in Sr doped BiFeO3 by achieving the coexistence of ferroelectricity and ferromagnetism at room temperature

Structural, optical and photocatalytic properties of Sr‐doped and Ca‐doped BiFeO3 compounds prepared by Pechini method

“…In the case of the compounds with Sr content, (Fig. 1a) these extra signals correspond to trace amounts of mullite‐type Bi 2 Fe 4 O 9 , and its content is relatively low compared with others reports 39‐44 . On the other hand, in the BCaFO samples (Fig.…”

“…1a) these extra signals correspond to trace amounts of mullite-type Bi 2 Fe 4 O 9 , and its content is relatively low compared with others reports. [39][40][41][42][43][44] 44 On the other hand, in the BCaFO samples (Fig. 1b), the mullitetype Bi 2 Fe 4 O 9 was found in the specimens with Ca content at x = 0.05 and 0.10, while the Bi 2 O 3 phase was identified in the specimen BCaFeO-15.…”

Perovskite Oxides as Electrocatalysts for Hydrogen Evolution Reaction

“…With increasing the size of A-site cation, the O–Co–O bond angle increases and gets close to 180°, which enhances the overlap of the electron cloud . This effect, combined with an increase in hole carrier concentration, leads to an improvement in electron transport and an increase in electrical conductivity, which correlates with a decrease in efficiency loss during the HER. ,− The overpotentials of this series in 1 M KOH range from η 10 = 441 mV for EuBaCo 2 O 5+δ to η 10 = 156 mV for LaBaCo 2 O 5+δ . Other studies have also proposed that the enhanced overlap and hybridization between the orbitals of the B-site and oxygen atom, arising from larger A-site cations, can shift the position of the e g band center toward the Fermi level, which makes the e g electrons more easily transportable to the antibonding orbitals of the adsorbed H species …”

“…On the other hand, the higher valence Co 4+ may help this cation to serve as the active site for the initial adsorption of water molecules due to an enhanced electrostatic attraction . It is proposed that the molecular water prefers to interact with more positive cations, which can lead to better HER activity in alkaline medium for B-site cations with a higher valence. ,,,, Another example is the series Pr x (Ba 0.5 Sr 0.5 ) 1– x Co 0.8 Fe 0.2 O 3−δ (Pr x BSCF, 0 ≤ x ≤ 1), where the HER activity as a function of Pr content increases from x = 0 to x = 0.5 but after that decreases, as a structural transformation from cubic to orthorhombic occurs. The Pr doping on the A-site partially oxidizes the cobalt species which acts as an active center for the HER.…”

“…3 Other studies have also proposed that the enhanced overlap and hybridization between the orbitals of the B-site and oxygen atom, arising from larger A-site cations, can shift the position of the e g band center toward the Fermi level, which makes the e g electrons more easily transportable to the antibonding orbitals of the adsorbed H species. 8 Some researchers have also correlated the HER activity to the change in the structural tolerance factor as a result of A-site substitution and have proposed that the near ideal cubic perovskite oxides with Goldschmidt tolerance factor close to unity are favorable for catalyzing the alkaline HER. 3,12 Goldschmidt tolerance factor, t, is a measure of the stability of perovskite oxides and is described by r = (r A + r o )/√2(r B + r o ), where r A , r B , and r o represent the ionic radii of the A-site cation, the B-site cation, and the oxide ion, respectively.…”