The
use of hexagonal boron nitride (hBN) to modify a semiconductor
photocatalyst is one of the promising methods for the production of
hydrogen from water splitting. This is due to the unique characteristics
of the hBN-suppressing recombination of the photogenerated charge
carriers and hence increase in the redox reactions. In the present
work, a hBN-modified Ni2P-containing excess boron composite
(B-hBN-Ni2P) was prepared through an electroless plating
method. The solid structure, elemental composition, and morphology
were investigated via X-ray diffraction, energy-dispersive X-ray spectroscopy,
scanning electron microscopy, UV–visible spectroscopy, and
photoluminescence spectroscopy. The composite coating was tested for
solar water splitting, and a hydrogen evolution rate of 883 μmol/h
was achieved. The role of excess B was revealed through an electrochemical
acidic leaching. By gradually removing boron from the structure, a
monotonous drop in the water splitting activity was observed. Our
study identifies B as a sacrificial agent/hydrogen production booster.
It contributes to the higher catalytic activity with an additional
hydrogen generation through the oxidation of its surplus amount from
the composite coating. The enhanced hydrogen evolution activity for
the composite coating in the present study is highly competitive with
the other modern photocatalysts.
The present study
reports about the fabrication of a three-dimensional
(3D) macroporous steel-based scaffold as an anode to promote specifically
bacterial attachment and extracellular electron transfer to achieve
power density as high as 1184 mW m–2, which is far
greater than that of commonly used 3D anode materials. The unique
3D open macroporous configuration of the anode and the microstructure
generated by the composite coating provide voids for the 3D bacterial
colonization of electroactive biofilms. This is attributed to the
sizeable interfacial area per unit volume provided by the 3D corrugated
electrode that enhanced the electrochemical reaction rate compared
to that of the flat electrode, which favors the enhanced mass transfer
and substrate diffusion at the electrode/electrolyte interface and
thereby increases the charge transfer by reducing the electrode overpotential
or interfacial resistance. In addition, bacterial infiltration into
the interior of the anode renders large reaction sites for substrate
oxidation without the concern of clogging and biofouling and thereby
improves direct electron transfer. A very low overpotential (−27
mV) with a very low internal resistance (7.104 Ω cm2) is achieved with the fabricated microbial fuel cell (MFC) that
has a modified 3D corrugated electrode. Thus, easier and faster charge
transfer at the electrode–electrolyte interface is confirmed.
The study presents a revolutionary practical approach in the development
of highly efficient anode materials that can ensure easy scale-up
for MFC applications.
The design of water‐stable photo and electrocatalysts of metal–organic frameworks (MOFs) for its promising catalytic applications at long‐term irradiations or persisted current loads is extremely necessary but still remains as challenging. A limited number of reports on Ti‐MOF‐based catalysts for water splitting are only available to explain and understand the correlation between the nature of materials and MOFs array. Herein, spherical Ti‐MOFs and corresponding partially annealed hollow core–shell Ti‐MOFs (Ti‐MOF/D) are designed and the correlation with their photo(electro)catalytic water splitting performance is evaluated. The switchable valence state of Ti for the Ti‐MOF as a function of molecular bonding is the possible reason behind the observed photocatalytic hydrogen generation and light‐harvesting ability of the system. Besides, the defect state, solid core–shell mesoporous structure, and active sites of Ti‐MOF help to trap the charge carriers and the reduction of the recombination process. This phenomenon is absent for hollow core–shells Ti‐MOF/D spheres due to the rigid TiO2 outer surface although there is a contradiction in surface area with Ti‐MOF. Considering the diversity of Ti‐MOF and Ti‐MOF/D, further novel research can be designed using this way to manipulate their properties as per the requirements.
Ni 2 P has a significant importance in the field of photocatalytic water splitting, irrespective of its narrow band gap (1.0 eV). The photocatalytic performance of bare Ni 2 P is highly limited due to the fast recombination rate of the electron−hole pairs. However, it can be used suitably for tuning the band gap of wide band gap semiconductors. The present study involves the development of an effective heterojunction with tuned band gap by Ni 2 P engineered SrTiO 3 nanocubes in the form of a coating after successful compositional tuning. This is accomplished by an in situ decoration of SrTiO 3 nanocubes at the active sites of Ni 2 P via a chemical reduction method. Morphological and physical features of the developed catalyst are tuned in the coating in order to have Ni 2 P as the major phase for maintaining the physical structure and to impart enhancement in photocatalytic performance and stability to the catalyst system. As the conduction band of SrTiO 3 lies at a more negative potential compared to that of Ni 2 P, the excited electrons from SrTiO 3 can easily be injected to the active sites of Ni 2 P for proton reduction. Thus, in addition to tuning the composite energy band gap, Ni 2 P acts as the reaction center for hydrogen generation and as the stable catalyst bed for SrTiO 3 nanocube decoration. The appearance of SrTiO 3 enriches the electron density at the Ni 2 P active sites, and Ni 2 P with negatively charged phosphorus has the ability to capture more protons at these sites for accelerating the rate of hydrogen generation. The enhancement in the microsurface properties of Ni 2 P in the composite coating are evaluated with OSP technique. The hydrogen generation rate as high as 7.03 mmol/g/h is achieved with the as-engineered catalyst coating, with an apparent quantum yield of 23.72% at 400 nm. The catalyst system shows a sustained hydrogen generation rate even after 15 cycles confirming the suitability of large scale production for industrial applications.
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