Solar vapor generation represents
a promising approach to alleviate
water shortage for producing fresh water from undrinkable water resources.
Although Cu-based plasmonics have attracted tremendous interest due
to efficient light-to-heat conversion, their application faces great
challenges in the oxidation resistance of Cu and low evaporation rate.
Herein, a hybrid of three-dimensional carbonized loofah sponges and
graphene layers encapsulated Cu nanoparticles is successfully synthesized
via a facile pyrolysis method. In addition to effective light harvesting,
the localized heating effect of stabilized Cu nanoparticles remarkably
elevated the surface temperature of Cu@C/CLS to 72 °C, and a
vapor generation rate as high as 1.54 kg m–2 h–1 with solar thermal efficiency reaching 90.2% under
1 Sun illumination was achieved. A study in the purification of sewage
and muddy water with Cu@C/CLS demonstrates a promising perspective
in a practical application. These results may offer a new inspiration
for the design of efficient nonprecious Cu-based photothermal materials.
As one of the most popular photoanode materials for photoelectrochemical (PEC) water splitting, hematite (α-Fe 2 O 3 ) suffers from low conductivity, severe electron−hole recombination, and sluggish water oxidation kinetics unfortunately. Herein, we report an alkali-treatment method to effectively accelerate the water oxidation kinetics of α-Fe 2 O 3 and titanium doped α-Fe 2 O 3 (Ti:α-Fe 2 O 3 ) nanorod array photoanodes. The purpose of Ti-doping is to increase the conductivity of α-Fe 2 O 3 . The photocurrent densities increased 3-and 2-times for α-Fe 2 O 3 and Ti:α-Fe 2 O 3 photoanodes after KOH treatment, respectively. Transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) analyses demonstrated that a conformal thin layer grafted with hydroxyl (−OH) groups was formed on the hematite surface. Linear sweep voltammetry (LSV) curves under light irradiation and in the dark indicated that the thin OH-grafted overlayer behaved like an electrocatalyst to accelerate the water oxidation kinetics on hematite photoanodes. Moreover, XPS valence band (XPS-VB) spectra, Mott− Schottky analysis, and electrochemical impedance spectroscopy (EIS) revealed that a type II heterojunction was in situ formed by the OH-grafted overlayer on the hematite nanorod surface, which substantially enhanced the surface charge separation efficiency. The improved PEC performance could be attributed to the accelerated water oxidation kinetics and enhanced surface charge transfer.
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