Photoelectrochemical properties of texture-controlled nanostructured α-Fe2O3 thin films prepared by AACVD

This is the author accepted manuscript. The final version is available from the publisher via the DOI in this record.Nanostructured α-Fe2O3 thin film electrodes were deposited by aerosol-assisted chemical vapour deposition (AACVD) for photoelectrochemical (PEC) water splitting on conducting glass substrates using 0.1 M methanolic solution of Fe(acac)3. The XRD analysis confirmed that the films are highly crystalline α-Fe2O3 and free from other iron oxide phases. The highly reproducible electrodes have an optical bandgap of ~2.15 eV and exhibit anodic photocurrent. The current-voltage characterization of the electrodes reveals that the photocurrent density strongly depended on the film morphology and deposition temperature. Scanning electron microscopy (SEM) analysis showed a change in the surface morphology with the change in deposition temperature. The films deposited at 450 °C have nanoporous structures which provide a maximum electrode/electrolyte interface. The maximum photocurrent density of 455 μA/cm2 was achieved at 0.25 V vs. Ag/AgCl/3M KCl (~1.23 V vs. RHE) and the incident photon to electron conversion efficiency (IPCE) was 23.6% at 350 nm for the electrode deposited at 450 °C

Efficient Photoelectrochemical Performance of Gamma Irradiated gC3N4 and its g-C3N4@BiVO4 Heterojunction for Solar Water Splitting

This is the author accepted manuscript. The final version is available from the American Chemical Society via the DOI in this recordComprehensive experimental and density functional theory simulations have been performed for the enhanced photoelectrochemical performance of gamma irradiated g-C3N4 and its heterojunction with BiVO4. The structure and morphology of g-C3N4@BiVO4 as a heterojunction were analyzed and verified from the correlation of experimental and theoretical data. It is found that gamma radiations have changed the bonding structure of g-C3N4 which ultimately reduces the optical bandgap energy. Moreover, the performance of gamma-irradiated g-C3N4 is two-fold, compared to that of non-irradiated one; increases from 3.59 to 5.86 µAcm-2 at 1.23 V versus Ag/AgCl in 0.5 M Na2SO4 electrolyte solution (pH 7). Finally, it is observed that the performance of gamma irradiated g-C3N4 in g-C3N4@BiVO4 heterojunction increased from 0.53 mA cm-2 to 1.38 mA cm-2, compared to that of the non–irradiated one. In summary, it has been concluded that gamma-irradiated g-C3N4 and its heterojunction is potentially be applied in PEC solar water splitting.National University of Malaysi

An overview of the recent progress in polymeric carbon nitride based photocatalysis

This is the author accepted manuscript. The final version is available from Wiley via the DOI in this record Recently, polymeric carbon nitride (g-C3 N4 ) as a proficient photo-catalyst has been effectively employed in photocatalysis for energy conversion, storage, and pollutants degradation due to its low cost, robustness, and environmentally friendly nature. The critical review summarized the recent development, fundamentals, nanostructures design, advantages, and challenges of g-C3 N4 (CN), as potential future photoactive material. The review also discusses the latest information on the improvement of CN-based heterojunctions including Type-II, Z-scheme, metal/CN Schottky junctions, noble metal@CN, graphene@CN, carbon nanotubes (CNTs)@CN, metal-organic frameworks (MOFs)/CN, layered double hydroxides (LDH)/CN heterojunctions and CN-based heterostructures for H2 production from H2 O, CO2 conversion and pollutants degradation in detail. The optical absorption, electronic behavior, charge separation and transfer, and bandgap alignment of CN-based heterojunctions are discussed elaborately. The correlations between CN-based heterostructures and photocatalytic activities are described excessively. Besides, the prospects of CN-based heterostructures for energy production, storage, and pollutants degradation are discussed.National Natural Science Foundation of ChinaMinistry of Science and Technology of Chin

Enhanced hydrogen evolution reaction performance of anatase–rutile TiO2 heterojunction via charge transfer from rutile to anatase

This is the final version. Available on open access from the Royal Society of Chemistry via the DOI in this recordIn light of recent doubts surrounding the industrial viability of photo(electro)catalysis technology for sustainable hydrogen production, it becomes imperative to align materials development with rationalized synthesis protocols. In this study, we present an innovative technique utilizing atmospheric-pressure chemical vapor deposition (APCVD) to rapidly produce TiO2 in just 5 minutes using pure TiCl4 as the sole reagent. The resulting photoanode exhibits exceptional photoelectrochemical (PEC) water-splitting performance, achieving a photocurrent density of 2.06 mA cm−2 at 1.23 V RHE. Moreover, the photoanode demonstrates sustained operation for 16 hours, leading to the successful collection of 138 μmol of H2 and 62 μmol of O2. These remarkable results are attributed to the controlled formation of an anatase–rutile phase-junction, the presence of well-balanced oxygen vacancies, and the bifrustum nanoparticle–nanoflake structure with a unique light trapping effect and large surface area. Density functional theory calculations confirm that the water-splitting reaction primarily occurs at undercoordinated Ti and O atoms in both anatase and rutile TiO2. Notably, the calculated Gibbs free energy values for the hydrogen evolution reaction (HER) differ significantly between rutile (−0.86 eV) and anatase TiO2 (0.22 eV). In the heterojunction, charge transfer enhances the HER performance through shared electronic density, resulting in a synergistic effect that surpasses the capabilities of individual surfaces and underscores the importance of electronic interactions within the junction.Universiti Kebangsaan MalaysiaCenter of Excellence for Innovation in ChemistryProgram Management Unit for Human Resources & Institutional Development, Research and InnovationHuman Resource Development in Science Project Science Achievement Scholarship of Thailand (SAST

Hysteresis-free perovskite transistor with exceptional stability through molecular cross-linking and amine-based surface passivation

This is the author accepted manuscript. The final version is available from the Royal Society of Chemistry via the DOI in this recordOrgano-metal halide perovskite field-effect transistors present serious challenges in terms of device stability and hysteresis in the current-voltage characteristics. Migration of ions located at grain boundaries and surface defects in the perovskite film are the main reasons for instability and hysteresis issues. Here, we introduce a perovskite grains molecular cross-linking approach combined with amine-based surface passivation to face these issues. Molecular cross-linking was achieved through hydrogen bond interactions between perovskite halogens and dangling bonds present at grain boundaries and a hydrophobic cross-linker, namely diethyl-(12-phosphonododecyl)phosphonate, added to the precursor solution. With our approach we obtained smooth and compact perovskite layers composed of few and tightly bound grains hence significantly suppressing the generation and migration of ions. Moreover, we obtained efficient surface passivation of the perovskite films upon surface treatment with an amine-bearing polymer, namely polyethylenimine ethoxylated. With our synergistic grain and surface passivation approach we were able to demonstrate the first perovskite transistor with complete lack of hysteresis and unprecedented stability upon continuous operation under ambient conditions. Added to the merits are its ambipolar transport of opposite carriers with balanced hole and electron mobilities of 4.02 and 3.35 cm2 V−1 s−1, respectively, its high Ion/Ioff ratio >104 and the lowest sub-thresshold swing of 267 mV dec-1 reported to date for any perovskite transistor. These remarkable achievements obtained through a cost-effective molecular cross-linking of grains combined with amine-based surface passivation in the perovskite films open new eras and pave the way for the practical application of perovskite transistors on low-cost electronic circuits.European Unio

A novel photoanode based on Thorium oxide (ThO<inf>2</inf>) incorporated with graphitic Carbon nitride (g-C<inf>3</inf>N<inf>4</inf>) for Photoelectrochemical water splitting

In this study, a new insight into the doping engineering with nuclear fuel (ThO2) was performed and applied in photoelectrochemical (PEC) water splitting. The successfully synthesized g-C3N4/ThO2 (~5.8%) via thermal treatment and g-C3N4 polymerization (precursor: Urea, 30 min; 520 ˚C) manifested a remarkable and superior photocatalytic activity. The photocurrent density achieved for g-C3N4/ThO2 was 9.71 μcm−2 at 1.23 V vs. Ag/AgCl under simulated light (100 mW/cm2) that is more than twice compared with the un-doped g-C3N4 (~4.23 μA cm−2). The introduction of Thorium Nitrate during g-C3N4 polymerization altered the chemical bonding, structure, and morphology, with the improved PEC stability of the photoanode. Besides, doping with ThO2 increased the intensity of triazine and C-N bond in the g-C3N4 network, as observed by FT-IR analysis. The unique “hollow cylindrical” architecture also increased the surface area, light absorption, as well as the catalytic sites. The enhanced separation of photo-generated electron–hole pairs reduced the carrier recombination that was obviously probed via Photoluminescence spectra. Therefore, due to the photostability and the good performance, the g-C3N4/ThO2 composite can be envisioned as a potential candidate in the field of photocatalysis and prospectively be applied in PEC solar water splitting

Electrodeposition of BiVO<inf>4</inf> with needle-like flower architecture for high performance photoelectrochemical splitting of water

Photoelectrochemical (PEC) water splitting is a green and sustainable approach capable of driving mass hydrogen production in the future. To realize this vision, development of a well-performing photoelectrode is highly demanded. In this comprehensive study, electrodeposition technique was applied for fabricating BiVO4 films by regulating the deposition time from 1 min until 9 min. Interestingly, the morphology, crystallinity, chemical structure, and optical properties of BiVO4 films depend strongly on the deposition time. It is found that BiVO4 layer deposited for 7 min with a cross-section thickness of around 321.1–326.5 nm showed the optimum performance, whereby the photocurrent reached up to ~0.32 mA/cm−2 at 1.23 V vs. RHE. The deposited BiVO4 represents tiny and long petals, similar to “needle” nanostructures, which is embedded closely into compact agglomerates. Such morphology enables the BiVO4 films to perform efficiently as photoanode in PEC cells. Besides, high crystallinity is detected from the sharp peaks of XRD and Raman analysis, as well as good light absorption capability that are the main contributors to the enhancement of PEC performance. In addition to the facile fabrication offered by electrodeposition method, the non-toxic attributes and the impressive PEC performance of the optimum BiVO4 layer could serve as an interesting option for other applications such as gas sensors, solar cells, degradation of pollutants and photocatalytic water splitting

Fabrication of exfoliated graphitic carbon nitride, (g-C<inf>3</inf>N<inf>4</inf>) thin film by methanolic dispersion

This paper reports the successful exfoliation of nanosheets from bulk g-C N by using urea as a precursor. The alteration from bulk g-C N powder, changed its semiconductor arrangements such as the optical absorption, chemical bonding, and topography images. A slow direct low thermal treatment (∼40 °C, 24 h) was proposed as a formation of a thinner layer by layer, complete and effective polymerization for an exfoliated g-C N . The photocurrent responses were more than two times higher for exfoliated g-C N compared with bulk g-C N , reaching ∼4.37 μA cm up to 10.21 μA cm at 1.23 vs. (Ag/AgCl). This fabrication method involved dispersing of the highly stable g-C N suspension onto FTO surface via spin coating, followed by a moderate post-annealing temperature at 350 °C. The monolayer g-C N act as a photoelectrode, responding to light and dark current, and maintained its own intrinsic n-types properties. The interaction of the C and N atom with molecules of methanol (CH OH) followed with vibration force (ultrasonication) produces the ultrafast drying and can transmit to disrupt the van der Waals forces within the g-C N structure. Therefore, due to the ability the good performance, the exfoliated g-C N can be envisioned as a potential application such as water splitting, solar cell, and environmental remediation. 3 4 3 4 3 4 3 4 3 4 3 4 3 4 3 3 4 3 4 −2 −

Enhanced photoelectrochemical performance of Z-scheme g-C3N4/BiVO4 photocatalyst

This is the author accepted manuscript. The final version is available from Elsevier via the DOI in this record.BiVO 4 is a considerably promising semiconductor for photoelectrochemical water splitting due to its stability, low cost and moderate band gap. In this research, g-C 3 N 4 was proposed in Z-scheme configuration which boosted the performance of BiVO 4 up to four times. The experimental observations were counterchecked with Density Functional Theory (DFT) simulations. A TiO 2 /BiVO 4 heterojunction was developed and its performance was compared with that of g-C 3 N 4 /BiVO 4 . The photocurrent for g-C 3 N 4 /BiVO 4 was 0.42 mAcm −2 at 1.23 V vs. RHE which was the highest among g-C 3 N 4 based Z-scheme heterojunction devices. Lower charge transfer resistance, higher light absorption and more oxygen vacancy sites were observed for the g-C 3 N 4 based heterojunction. The simulated results attested that g-C 3 N 4 and BiVO 4 formed a van der Waals type heterojunction, where an internal electric field facilitated the separation of electron/hole pair at g-C 3 N 4 /BiVO 4 interface which further restrained the carrier recombination. Both the va lence and conduction band edge positions of g-C 3 N 4 and BiVO 4 changed with the Fermi energy level. The resulted heterojunction had small effective masses of electrons (0.01 m e ) and holes (0.10 m e ) with ideal band edge positions where both CBM and VBM were well above and below the redox potential of water.The authors would like to acknowledge financial support from Universiti Kebangsaan Malaysia through internal grant GUP-2016-089 and also for providing facilities to perform this research. H.U. acknowledges the supercomputing facilities of ESI Beowulf Cluster, University of Exeter, UK

High-humidity processed perovskite solar cells

Perovskite solar cells (PSCs) are considered the next-in-line technology in the solar industry. This technology can reduce the cost of solar energy to an unprecedented level given their remarkably high efficiency and ease of manufacturing. Hitherto, many studies have preferred well-regulated inert conditions or a low-humidity atmosphere (relative humidity < 30%) for fabricating highly efficient PSCs to avoid the adverse impact of humidity on a perovskite film. This is because humidity is the main reason for perovskite instability and can alter the film growth kinetics during the fabrication process, thereby ultimately affecting the morphology of the grown film and the device performance. The requirement for an inert or low-humidity environment can increase the capital costs of setting up the fabrication facilities and hamper the large-scale production of PSCs. Therefore, efforts have been devoted to preparing PSC devices in a high-humidity environment to comprehend perovskite crystal growth kinetics and improve the morphological properties and stability of the perovskite film. This review highlights the modifications implemented towards (1) perovskite materials, (2) charge-selective layers, and (3) deposition protocols by spin-coating, to adapt a high-humidity atmosphere (RH ≥ 30%) for developing efficient PSCs. The progress of scalable processing methods such as blade-coating, inkjet printing, slot-die coating, and spray-coating, and the translation of spin-coating-modified protocols into these methods are also discussed. Finally, this review provides the remaining challenges to realizing the high-humidity fabrication of PSCs for commercialization