Topics in Current Chemistry (2020) 378:6
1 3
obtained by Jiménez-Miramontes et al. by modifying the crystallization conditions in the Pechini synthetic method [156]. Among the three crystalline phases,
the activity towards hydrogen production under UV irradiation was maximum for
the cubic one, with the hexagonal phase yielding a two orders of magnitude lower
amount of hydrogen as a result of unsuitable band positions.
The perovskite-type lanthanum ferrite, LaFeO 3 , has been studied for photocatalytic hydrogen evolution in a number of articles. It is considered as a promising catalyst for this application by combining adequate band positions, visible light absorption and (photo)chemical stability. Parida and co-workers actually
reported that LaFeO 3 was active both for hydrogen evolution from water by using
an electron-donating (methanol) sacrificial agent and for oxygen evolution with an
electron-scavenging (Ag
+
) agent. High productions were obtained in both cases
(see Table 5 for the case of hydrogen), although no overall water splitting experiments were reported [83]. Using ethanol as sacrificial agent, Tijare and co-workers
reported a relatively similar hydrogen evolution rate (even if the usual difficulties
to quantitatively compare different works must be considered) that could be further
boosted by using platinum as co-catalyst [157]. However, in this case the improvement caused by platinum was considerably low if compared to its effect on other
semiconducting catalysts [148]. Indeed, Iervolino and co-workers studied LaFeO 3
as a promising noble-metal-free hydrogen evolution photocatalyst [158]. Interestingly, they reported stoichiometric overall water splitting (i.e. without any sacrificial
reagent) under UV light over LaFeO 3 photocatalysts synthesized using the solution
combustion method. The hydrogen yield increased by a factor of 4 when using glucose as sacrificial electron donor. Under purely visible light irradiation (440 nm),
the activity of the best-performing catalyst, obtained from an optimized synthetic
method, for glucose photoreforming was above 70% of that under UV, revealing the
interest of this material as a visible-light-active photocatalyst. Using a similar synthetic procedure, Chen et al. obtained a homogeneously nanocrystalline LaFeO 3 that
was further modified by encapsulation with a conductive polyaniline (PANI) aerogel (Fig. 12) as a means to control the hydrophilicity of the surface and to improve
charge mobility. An improvement of hydrogen evolution activity of about four times
with respect to the unmodified ferrite was observed, using in this case platinum as
co-catalyst and triethanolamine as electron donor [159]. Doping Ru
3+
into the Fe
3+
positions of the LaFeO 3 structure improved the hydrogen evolution rate in this reaction by a factor of ca. 4.5 under UV irradiation [158], which was ascribed to the
role of the dopant cation as electron scavenger, preventing electron–hole recombination. The optimum doped catalyst was also active in glucose photoreforming
under visible light and, in an especially interesting result, in the valorisation of real
waste water from a brewing company by using it as sacrificial agent for the production of hydrogen. Partial substitution of Sr
2+
for La
3+
and Ti
4+
for Fe
3+
, using a
flux growth synthetic method, was studied by Domen and co-workers as a way of
further improving the photocatalytic activity of LaFeO 3 for hydrogen evolution by
methanol photoreforming, using Pt as co-catalyst [160]. Simultaneous cation substitution led to improvement in photocatalytic activity attributed to the concurrence of
modified structural properties by Sr doping and electronic characteristics due to Ti
doping, as well as reduced grain boundaries and lattice defects, which relates to the
140
Reprinted from the journal
1 3
obtained by Jiménez-Miramontes et al. by modifying the crystallization conditions in the Pechini synthetic method [156]. Among the three crystalline phases,
the activity towards hydrogen production under UV irradiation was maximum for
the cubic one, with the hexagonal phase yielding a two orders of magnitude lower
amount of hydrogen as a result of unsuitable band positions.
The perovskite-type lanthanum ferrite, LaFeO 3 , has been studied for photocatalytic hydrogen evolution in a number of articles. It is considered as a promising catalyst for this application by combining adequate band positions, visible light absorption and (photo)chemical stability. Parida and co-workers actually
reported that LaFeO 3 was active both for hydrogen evolution from water by using
an electron-donating (methanol) sacrificial agent and for oxygen evolution with an
electron-scavenging (Ag
+
) agent. High productions were obtained in both cases
(see Table 5 for the case of hydrogen), although no overall water splitting experiments were reported [83]. Using ethanol as sacrificial agent, Tijare and co-workers
reported a relatively similar hydrogen evolution rate (even if the usual difficulties
to quantitatively compare different works must be considered) that could be further
boosted by using platinum as co-catalyst [157]. However, in this case the improvement caused by platinum was considerably low if compared to its effect on other
semiconducting catalysts [148]. Indeed, Iervolino and co-workers studied LaFeO 3
as a promising noble-metal-free hydrogen evolution photocatalyst [158]. Interestingly, they reported stoichiometric overall water splitting (i.e. without any sacrificial
reagent) under UV light over LaFeO 3 photocatalysts synthesized using the solution
combustion method. The hydrogen yield increased by a factor of 4 when using glucose as sacrificial electron donor. Under purely visible light irradiation (440 nm),
the activity of the best-performing catalyst, obtained from an optimized synthetic
method, for glucose photoreforming was above 70% of that under UV, revealing the
interest of this material as a visible-light-active photocatalyst. Using a similar synthetic procedure, Chen et al. obtained a homogeneously nanocrystalline LaFeO 3 that
was further modified by encapsulation with a conductive polyaniline (PANI) aerogel (Fig. 12) as a means to control the hydrophilicity of the surface and to improve
charge mobility. An improvement of hydrogen evolution activity of about four times
with respect to the unmodified ferrite was observed, using in this case platinum as
co-catalyst and triethanolamine as electron donor [159]. Doping Ru
3+
into the Fe
3+
positions of the LaFeO 3 structure improved the hydrogen evolution rate in this reaction by a factor of ca. 4.5 under UV irradiation [158], which was ascribed to the
role of the dopant cation as electron scavenger, preventing electron–hole recombination. The optimum doped catalyst was also active in glucose photoreforming
under visible light and, in an especially interesting result, in the valorisation of real
waste water from a brewing company by using it as sacrificial agent for the production of hydrogen. Partial substitution of Sr
2+
for La
3+
and Ti
4+
for Fe
3+
, using a
flux growth synthetic method, was studied by Domen and co-workers as a way of
further improving the photocatalytic activity of LaFeO 3 for hydrogen evolution by
methanol photoreforming, using Pt as co-catalyst [160]. Simultaneous cation substitution led to improvement in photocatalytic activity attributed to the concurrence of
modified structural properties by Sr doping and electronic characteristics due to Ti
doping, as well as reduced grain boundaries and lattice defects, which relates to the
140
Reprinted from the journal