5 research outputs found
Efficient Electrocatalytic Water Oxidation by a Copper Oxide Thin Film in Borate Buffer
A robust water oxidation catalyst
based on copper oxide was prepared
by facile electrodeposition of Cu<sup>2+</sup> from borate buffer
solution under near neutral conditions. The Cu–B<sub>i</sub> thin film exhibits high activity and long-term stability in Cu<sup>2+</sup>-free pH 9 borate buffer. A steady current density of 1.2
mA/cm<sup>2</sup> was sustained for at least 10 h at 1.3 V versus
NHE without iR compensation, which sets a new benchmark for copper-based
OEC
Visible Light-Driven Water Oxidation Promoted by Host–Guest Interaction between Photosensitizer and Catalyst with A High Quantum Efficiency
A highly active supramolecular system
for visible light-driven
water oxidation was developed with cyclodextrin-modified ruthenium
complex as the photosensitizer, phenyl-modified ruthenium complexes
as the catalysts, and sodium persulfate as the sacrificial electron
acceptor. The catalysts were found to form 1:1 host–guest adducts
with the photosensitizer. Stopped-flow measurement revealed the host–guest
interaction is essential to facilitate the electron transfer from
catalyst to sensitizer. As a result, a remarkable quantum efficiency
of 84% was determined under visible light irradiation in neutral aqueous
phosphate buffer. This value is nearly 1 order of magnitude higher
than that of noninteraction system, indicating that the noncovalent
incorporation of sensitizer and catalyst is an appealing approach
for efficient conversion of solar energy into fuels
Fabrication and Kinetic Study of a Ferrihydrite-Modified BiVO<sub>4</sub> Photoanode
In
spite of great progress in the surface modification of semiconductor
photoelectrodes, the role of the metal oxide cocatalyst on photoelectrochemical
(PEC) performance is still not well understood. In this study, ferrihydrite
(Fh) as a novel cocatalyst was decorated on a wormlike nanoporous
BiVO<sub>4</sub> photoanode. A surface kinetics study of Fh/BiVO<sub>4</sub> by intensity-modulated photocurrent spectroscopy (IMPS) evidences
the primary role of Fh on PEC performance enhancement, varying with
the loading of Fh. It was found that dispersed Fh nanoparticles accelerate
hole transfer for water oxidation, but the resulting photoanode suffers
from poor stability. The thick layers of Fh address the stability
of the electrode by suppressing surface charge recombination but result
in reduced hole transfer rates. Modification of a BiVO<sub>4</sub> film with optimally thick layers of discrete nanoflakes effectively
reduces charge recombination without compromising stability, leading
to a high AM 1.5 G photocurrent of 4.78 mA/cm<sup>2</sup> at 1.23
V versus the reversible hydrogen electrode and an applied bias photon
to current efficiency of 1.81% at 0.61 V. These values are comparable
to the best results reported for undoped BiVO<sub>4</sub>
Electrochemical and Photoelectrochemical Water Oxidation by Supported Cobalt–Oxo Cubanes
Cobalt–oxo cubane clusters
were immobilized on a Nafion
film-coated fluorine-doped tin oxide (FTO) electrode and an α-Fe<sub>2</sub>O<sub>3</sub> photoanode as surface catalysts for water oxidation.
The performance of electrochemical water splitting indicated that
these earth-abundant metal complexes retain their homogeneous reactivity
on the electrode. Furthermore, efficient visible light-driven water
oxidation was realized by coupling a molecular electrocatalyst with
an inorganic semiconductor as a noble metal-free photoanode, showing
a stability significantly improved with respect to that of the homogeneous
system
Defective and “<i>c</i>‑Disordered” Hortensia-like Layered MnO<sub><i>x</i></sub> as an Efficient Electrocatalyst for Water Oxidation at Neutral pH
The
development of a highly active manganese-based water oxidation
catalyst in the design of an ideal artificial photosynthetic device
operating under neutral pH conditions remains a great challenge, due
to the instability of pivotal Mn<sup>3+</sup> intermediates. We report
here defective and “<i>c</i>-disordered” layered
manganese oxides (MnO<sub><i>x</i></sub>-300) formed on
a fluorine-doped tin oxide electrode by constant anodic potential
deposition and subsequent annealing, with a catalytic onset (0.25
mA/cm<sup>2</sup>) at an overpotential (η) of 280 mV and a benchmark
catalytic current density of 1.0 mA/cm<sup>2</sup> at an overpotential
(η) of 330 mV under neutral pH (1 M potassium phosphate). Steady
current density above 8.2 mA/cm<sup>2</sup> was obtained during the
electrolysis at 1.4 V versus the normal hydrogen electrode for 20
h. Insightful studies showed that the main contributing factors for
the observed high activity of MnO<sub><i>x</i></sub>-300
are (i) a defective and randomly stacked layered structure, (ii) an
increased degree of Jahn–Teller distorted Mn<sup>3+</sup> in
the MnO<sub>6</sub> octahedral sheets, (iii) effective stabilization
of Mn<sup>3+</sup>, (iv) a high surface area, and (v) improved electrical
conductivity. These results demonstrate that manganese oxides as structural
and functional models of an oxygen-evolving complex (OEC) in photosystem
II are promising catalysts for water oxidation in addition to Ni/Co-based
oxides/hydroxides