4 research outputs found
α‑Fe<sub>2</sub>O<sub>3</sub>/NiOOH: An Effective Heterostructure for Photoelectrochemical Water Oxidation
The
study of the semiconductor/electrocatalyst interface in electrodes
for photoelectrochemical water splitting is of paramount importance
to obtain enhanced solar-to-fuel efficiency. Here, we take into consideration
the multiple effects that a thin layer of photodeposited amorphous
Ni-oxyhydroxide (NiOOH) induces on hematite (α-Fe<sub>2</sub>O<sub>3</sub>) photoanodes. The reduction of overpotential produced
a photocurrent onset potential advance of 150 mV and an increase of
photocurrent of about 50% at 1.23 V vs RHE. To give an interpretation
to these phenomena, we carried out deep electrochemical investigations
by cyclic voltammetry and electrochemical impedance spectroscopy.
The effective charge injection into the electrolyte due to the reduction
of the charge transfer resistance at the electrode/electrolyte interface
was observed and increased along with the amount of deposited NiOOH.
The benefits of NiOOH deposition are ascribable to its ability to
scavenge holes from hematite surface traps. This effect is mitigated
at a potential higher than 1.25 V, since a fraction of photogenerated
holes is consumed into the Ni redox cycle
Deciphering Local Structural Complexity in Zn/Ga-ZrO<sub>2</sub> CO<sub>2</sub> Hydrogenation Catalysts
In
the last few decades, massive effort has been expended
in heterogeneous
catalysis to develop new materials presenting high conversion, selectivity,
and stability even under high-temperature and high-pressure conditions.
In this context, CO2 hydrogenation is an interesting reaction
where the catalyst local structure is strongly related to the development
of an active and stable material under hydrothermal conditions at T/P > 300 °C/30 bar. In order to
clarify
the relationship between catalyst local ordering and its activity/stability,
we herein report a combined laboratory and synchrotron investigation
of aliovalent element (Ce/Zn/Ga)-containing ZrO2 matrixes.
The results reveal the influence of similar average structures with
different short-range orderings on the catalyst properties. Moreover,
a further step toward the comprehension of the oxygen vacancy formation
mechanism in Ce- and Ga-ZrO2 catalysts is reported. Finally,
the reported results illustrate a robust method to guide local structure
determination and ultimately help to avoid overuse of the “solid
solution” definition
High-Throughput Preparation of Metal Oxide Nanocrystals by Cathodic Corrosion and Their Use as Active Photocatalysts
Nanoparticle
metal oxide photocatalysts are attractive because
of their increased reactivity and ease of processing into versatile
electrode formats; however, their preparation is cumbersome. We report
on the rapid bulk synthesis of photocatalytic nanoparticles with homogeneous
shape and size via the cathodic corrosion method, a simple electrochemical
approach applied for the first time to the versatile preparation of
complex metal oxides. Nanoparticles consisting of tungsten oxide (H<sub>2</sub>WO<sub>4</sub>) nanoplates, titanium oxide (TiO<sub>2</sub>) nanowires, and symmetric star-shaped bismuth vanadate (BiVO<sub>4</sub>) were prepared conveniently using tungsten, titanium, and
vanadium wires as a starting material. Each of the particles were
extremely rapid to produce, taking only 2–3 min to etch 2.5
mm of metal wire into a colloidal dispersion of photoactive materials.
All crystalline H<sub>2</sub>WO<sub>4</sub> and BiVO<sub>4</sub> particles
and amorphous TiO<sub>2</sub> were photoelectrochemically active toward
the water oxidation reaction. Additionally, the BiVO<sub>4</sub> particles
showed enhanced photocurrent in the visible region toward the oxidation
of a sacrificial sulfite reagent. This synthetic method provides an
inexpensive alternative to conventional fabrication techniques and
is potentially applicable to a wide variety of metal oxides, making
the rapid fabrication of active photocatalysts with controlled crystallinity
more efficient
High-Throughput Preparation of Metal Oxide Nanocrystals by Cathodic Corrosion and Their Use as Active Photocatalysts
Nanoparticle
metal oxide photocatalysts are attractive because
of their increased reactivity and ease of processing into versatile
electrode formats; however, their preparation is cumbersome. We report
on the rapid bulk synthesis of photocatalytic nanoparticles with homogeneous
shape and size via the cathodic corrosion method, a simple electrochemical
approach applied for the first time to the versatile preparation of
complex metal oxides. Nanoparticles consisting of tungsten oxide (H<sub>2</sub>WO<sub>4</sub>) nanoplates, titanium oxide (TiO<sub>2</sub>) nanowires, and symmetric star-shaped bismuth vanadate (BiVO<sub>4</sub>) were prepared conveniently using tungsten, titanium, and
vanadium wires as a starting material. Each of the particles were
extremely rapid to produce, taking only 2–3 min to etch 2.5
mm of metal wire into a colloidal dispersion of photoactive materials.
All crystalline H<sub>2</sub>WO<sub>4</sub> and BiVO<sub>4</sub> particles
and amorphous TiO<sub>2</sub> were photoelectrochemically active toward
the water oxidation reaction. Additionally, the BiVO<sub>4</sub> particles
showed enhanced photocurrent in the visible region toward the oxidation
of a sacrificial sulfite reagent. This synthetic method provides an
inexpensive alternative to conventional fabrication techniques and
is potentially applicable to a wide variety of metal oxides, making
the rapid fabrication of active photocatalysts with controlled crystallinity
more efficient