Composite Photoelectrode Research Articles

Study on the Photoelectrocatalytic Performance of Ti/Ti-W-O Coating Photoelectrodes Prepared by the Microarc Oxidation Method.

Photoinduced cathodic protection is an environmentally friendly, economical, and sustainable technology that has been widely used in the corrosion protection of alloy materials. In this study, the corrosion-resistant Ti/Ti-W-O ceramic coatings are prepared by changing the concentration of additives, microarc oxidation voltage, pulse frequency, and time using titanium alloy (TC4) as the substrate and sodium tungstate (Na2WO4) as the main additive via the microarc oxidation (MAO) method. The optimum parameters were determined as follows: concentration of added salt (Na2WO4): 0.05 mol/L; reaction conditions: anode voltage 300 V, cathode voltage 30 V, duty cycle 1:1 (50%), frequency 800 Hz, and reaction time 5 min. They were evaluated from two perspectives: photocathodic protection and photocatalysis, respectively. The test results show that the composite coatings have more negative conduction band potentials, narrower band gaps, higher photocurrent densities, and smaller impedance arc radii under the same conditions as those analyzed in the electrochemical workstation test. In addition, the optimized Ti/Ti-W-O composite photoelectrode coupled with 304 stainless steel showed the largest negative shift in corrosion potential (447 mV vs) and improved degradation efficiency of the dyeing wastewater (improved by ∼20%). The above results demonstrate that the composite electrodes in this study exhibit good performance in photocathodic protection and photovoltaic synergy.

Enhanced Visible Light Controlled Glucose Photo-Reforming Using a Composite WO3/Ag/TiO2 Photoanode: Effect of Incorporated Plasmonic Ag Nanoparticles.

WO3/Ag/TiO2 composite photoelectrodes were formed via the high-temperature calcination of a WO3 film, followed by the sputtering of a very thin silver film and deposition of an overlayer of commercial TiO2 nanoparticles. These synthetic photoanodes were characterized in view of the oxidation of a model organic compound glucose combined with the generation of hydrogen at a platinum cathode. During prolonged photoelectrolysis under simulated solar light, these photoanodes demonstrated high and stable photocurrents of ca. 4 mA cm-2 due, on one hand, to the occurrence of the so-called photocurrent doubling and, on the other hand, to the plasmonic effect of Ag nanoparticles. The post-photoelectrolysis analyses of the electrolyte demonstrated the formation of high-value final glucose photo-reforming products, principally gluconic acid, erythrose and formic acid.

(Invited) metal Organic Framework Templates for the Fabrication of High Performance Photoanodes

The study of structure property/relationships in advanced materials is promising towards obtaining systems with desired functionalities. Such systems can then be used as building blocks for the fabrication of various emerging technologies. In particular, nanostructured materials synthesized via the bottom–up approach present an opportunity for future generation low cost manufacturing of devices. We focus in particular on recent developments in solar technologies that aim to address the energy challenge [1-5].Here we present the use of Metal Organic Frameworks (MOFs) as templates for the fabrication of high performance photoanodes in next generation solar technologies. In particular, we describe the realization of NiO, mixed phase TiO2 and In2O3/CuO p-n heterojunction composite photoelectrodes, obtained using MOFs [6-8], for photoelectrochemical hydrogen generation from water.[1] Nano Energy 79, 105416 (2021); [2] Chem. Eng. J. 446, 137312 (2022); [3] ACS Appl. Mater. Int. 15, 56413 (2023); [4] Small Meth. 8, 2300133 (2024); [5] J. Mater. Chem. A 11, 23821 (2023); [6] Appl. Cat. B 263, 118317 (2020); [7] Small 18, 2201815 (2022); [8] Small 19, 2300606 (2023).

(Invited) Boosted Photoelectrochemical Water Splitting Performance by Plasmonic Assisted Ternary Heterostructures

Traditional semiconducting metal oxide-based photoelectrodes have been extensively explored for energy and environmental applications. However, their performance is hindered by poor light absorption, high charge recombination rates, and low surface kinetics. Some of the recent results will be presented to discuss the rational design of ternary materials systems, which incorporating of metal-organic framework and plasmonic structures into semiconducting metal oxides, as one of the most promising strategies to achieve performances beyond those of bare MOF and/or conventional semiconductors. The application examples of this new generation of composite photoelectrodes in water splitting, CO2 reduction and pollution degradation will be discussed, together with the challenges and prospects.

Enhancing Photovoltaic Performance with BaTiO3/MWCNTs Composite Photoelectrodes in Dye-Sensitized Solar Cells

Dye-sensitized solar cells (DSSCs) have attracted renewed research interest as a potential low-cost substitute for conventional silicon photovoltaics. This work aims to improve the photovoltaic performance of the DSSCs by incorporating multi-walled carbon nanotubes (MWCNTs) into the BaTiO3 photoelectrode. The pure BaTiO3 and BaTiO3/MWCNT nanocomposites were sensitized with N719 dye and fabricated into solar cell devices for testing. The structural characterization confirmed the successful formation of the nanocomposite with an optimal dispersion at 6% of MWCNT incorporation, beyond which agglomeration effects manifested. The optical analysis verified the modulation of defect states and bandgap engineering induced by the MWCNT network. The morphological studies revealed irregular nanoparticle clusters with embedded nanotubes. Solar cell testing under AM1.5G-simulated sunlight demonstrated a peak power conversion efficiency of 4.044% for 6% of MWCNT doping, constituting a 6-fold increment versus pure BaTiO3 (0.693%). It originated from the simultaneous enhancements in the open-circuit voltage and short-circuit current enabled by the favorable band structure alterations and percolation-assisted charge transport. However, further increasing MWCNT content deteriorated the device metrics, owing to emerging limitations like trapping. The rational integration of multi-walled carbon nanotubes with lead-free ferroelectric metal oxides can contribute to the development of emerging organic-inorganic hybrid solar platforms.

Preparation of Ti4O7/h‐BN self‐supported ceramic photoelectrode and its photoelectrocatalytic performance for water purification

AbstractThe construction of high‐efficiency self‐supported ceramic photoelectrode based on ideal semiconductor materials is essential for achieving effective degradation of pollutants by photoelectrocatalysis (PEC) technology. Herein, a Ti4O7/h‐BN composite ceramic photoelectrode with a unique microstructure was fabricated by a step‐by‐step calcination process and used in PEC water pollution remediation. The PEC activity of Ti4O7 ceramic photoelectrode could be enhanced by introducing hexagonal boron nitride (h‐BN) nanoparticles on the surface. The most optimized Ti4O7/h‐BN photoelectrode exhibited the decolorization rate of active brilliant blue KN‐R at about 97.79% in 30 min. The PEC activities could remain stable during five degradation cycles. The excellent photoelectrocatalytic performance of Ti4O7/h‐BN ceramic photoelectrode could be attributed to the low Tafel slope, low charge transfer resistance, large electrochemical active area, and excellent photo‐generated carrier separation efficiency. A type‐II heterojunction was formed between the Ti4O7 and h‐BN, which caused more effective carrier separation and enhanced the generation of dominant active species •O2− and h+. This work provided a mature synthesis strategy of Ti4O7/h‐BN self‐supported ceramic photoelectrodes with excellent practical application prospects to achieve superior PEC performance for water purification.

Constructing core-shell structured Co3O4–MnWO4 composite photoelectrode with superior PEC water purification performance

Semiconductor photoelectrocatalytic (PEC) technology is one of the most effective methods for removing organic pollutants from wastewater in advanced oxidation processes(AOPs). The selection of suitable semiconductor materials as photoanodes is a crucial factor for achieving superior PEC performance. Here, a core-shell structured Co3O4–MnWO4 architecture is created by enveloping MnWO4 nanoparticles onto the surface of Co3O4 nanowires through a two-step hydrothermal process. The optimized Co3O4–MnWO4-5 photoelectrode showed superior PEC degradation efficiency for KN-R (∼91.2% in 2 h) and durable stability (the accelerated lifetime reached ∼9100 s at a current density of 50 mA cm−2). Three actual wastewaters were also collected to verify the practical applicability of the photoelectrode.The energy consumption was measured at 4.48 kWhm−3, with a COD removal efficiency of 83% and a decolorization rate of 98%. These results demonstrate the excellent performance and promising application of the photoelectrode. The enhancement of PEC performance for the core-shell structured Co3O4–MnWO4 architecture can be attributed to the suitable energy band structure of the Co3O4–MnWO4 composite, higher OEP, larger electrochemical active surface area, accelerated transport of interface carriers, and lower charge transfer resistance. The energy band structure of the Co3O4–MnWO4 composite showed a strong redox ability to induce electrons/holes (e−/h+), which enhances the generation of intermediate active species (hydroxyl radical ·OH and superoxide radicals ·O2-). Therefore, the rationally designed core-shell structured Co3O4–MnWO4 architecture exhibited excellent practical applicability in the degradation of organic pollutants.

Study on the photogenerted cathodic protection of Ti-P-V-O coating photoelectrode prepared by microarc oxidation method for 304 stainless steel

Photocathodic protection is a promotion strategy for the corrosion protection of metallic materials, and the selection of photocathodic materials is a critical factor in improving the performance of photocathodic protection of metallic materials. Herein, a Ti-P-V-O composite semiconductor photoelectrode with an adjustable porous structure was prepared by the micro-arc oxidation (MAO) method using titanium alloy (TC4) as the matrix and ammonium metavanadate (NH4VO3) as the additive. The photogenerated open circuit potential, instantaneous photocurrent density response value, electrochemical impedance spectroscopy, and Tafel curve of as-prepared Ti-P-V-O photo-electrodes were measured after coupling with 304SS to clarify the cathodic protection effect for 304 stainless steel (304SS). It is found that the as-prepared Ti-P-V-O coating photoelectrode has a more negative open circuit potential, a more significant photocurrent density response, more effective interface carrier transport ability, lower resistance, lower compounding efficiency of photogenerated electron/hole pairs, and more negative conduction band level, as compared with that of TiO2 coatings. Moreover, the optimized Ti-P-V-O photoelectrode (Ti-P-V-O&300 V) exhibited the maximum negative shift of the corrosion potential (410 mV vs. SCE) for coupling with 304 stainless steel. This work presents a new strategy for constructing an efficient coating photo-electrode for photocathodic protection of metallic materials.

Fabrication of WO3 nanorod arrays modified by BiOBr and their enhanced photoelectrocatalytic activity

BiOBr/WO3 nanorod array (NRA) composite photoelectrodes were successfully prepared using a solvothermal method. The instrumental characterisation of X-ray diffraction, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, incident photoelectric conversion efficiency and ultraviolet diffuse reflectance indicates that the obtained BiOBr/WO3 NRAs exhibit good crystallinity and purity, and they can utilise light with wavelengths less than approximately 440 nm. On the surface of the WO3 nanorods, BiOBr thin nanosheets grow uniformly with strong adhesion and a 3D structure. The composite photoelectrode loaded with an appropriate amount of BiOBr (labelled BW-1 NRA) exhibits the best photoelectrocatalytic (PEC) activity. The PEC degradation efficiency of 10 mg/L of bisphenol A reached 95.7 % after 3 h at 1.0 V bias voltage. This value is 2.8 times that of individual photocatalytic degradation. After four times of recycling, the decrease in catalytic activity is insignificant, indicating the good stability of the catalyst. By analysing the results of the photoelectrochemical properties, band structures and types of free radicals, a conclusion is drawn that the excellent catalytic performance of BW-1 NRA is ascribed to the following aspects. (1) The formation of the p–n heterojunction by BiOBr and WO3 can effectively separate photogenerated electrons and holes. (2) Bias drives the migration of photogenerated electrons to the external circuit, further preventing the recombination of photogenerated electrons and holes. (3) The 3D structure of the photoelectrode has a large specific surface area and multiple active sites, improving light absorption and utilisation efficiency.

Molecular dynamics simulation of thermal transport properties of phonons at interface of Au-TiO<sub>2</sub> photoelectrode

Thermoplasmonics originating from the relaxation process of plasmon resonances in nanostructures can be utilized as an efficient and highly localized heat source in solar-hydrogen conversion, but there have been few researches on the interfacial heat transport properties of photoelectrode with the thermoplasmonics effect in a photoelectrochemical water splitting system. In this work, the effects of temperature, interfacial coupling strength and the addition of graphene layers on the interfacial thermal conductance of Au-TiO<sub>2</sub> electrodes are investigated by the non-equilibrium molecular dynamics simulation, and the variation of interfacial thermal conductance is analyzed by the phonon density of states. The results show that the interfacial thermal conductivity is increased by 78.55% when the temperature increases from 300 to 800 K. This is related to the fact that more low-frequency phonons participate in the interface heat transport, allowing more heat to be transferred to TiO<sub>2</sub> to promote the interface reaction. As the coupling strength of the Au-TiO<sub>2</sub> interface increases, the interfacial thermal conductivity of the electrode increases and then tends to stabilize. The interfacial thermal conductivity can be optimized by increasing the degree of overlap of the phonon state densities of Au and TiO<sub>2</sub>. The addition of a single layer of graphene can increase the interfacial thermal conductivity to 98.072 MW⋅m<sup>–2</sup>⋅K<sup>–1</sup>, but the addition of 2 and 3 layers of graphene can hinder interfacial heat transfer in Au and TiO<sub>2</sub> due to the interaction between the layers of graphene. When adding graphene layer, medium-frequency phonons and high-frequency phonons are stimulated to participate in the interfacial heat transfer, but with the increase of the graphene layers, the number of low-frequency phonons in a range of 0—30 THz decreases, and these low-frequency phonons make the greatest contribution to the interfacial thermal conductivity. The obtained results are useful in regulating the thermal transport properties of the photoelectrode interface, which can provide new insights into and theoretical basis for the design and construction of composite photoelectrodes.

A dual optimization approach for photo-electric catalysis: Heterojunction of BiOBr/Ba0.7Sr0.3TiO3 system construction and ferroelectric polarization

The spontaneous polarization of ferroelectrics is used to promote the separation of photogenerated electrons and holes, showing the great potential of solar-driven photo-electric catalysis. However, the rapid recombination of photogenerated electrons and holes seriously restricts the photo-electric catalysis efficiency. In this study, Ba0.7Sr0.3TiO3 nanoparticles combined with BiOBr nanosheets are synthesized by hydrothermal method to prepare BiOBr/Ba0.7Sr0.3TiO3 composite photoelectrodes. Under different Curie temperature(Tc) conditions and visible light irradiation, the photocurrent density of ferroelectric Ba0.7Sr0.3TiO3 (≤Tc) (0.54 mA∙cm−2) is superior to that of cis-electric Ba0.7Sr0.3TiO3 (≥Tc) (0.46 mA∙cm−2).The potential difference at the interface of BiOBr/Ba0.7Sr0.3TiO3 can effectively promote the separation of photogenerated carriers, while the internal polarization electric field of ferroelectric Ba0.7Sr0.3TiO3 further promotes the separation and transfer of photogenerated electrons and holes in the photoelectrodes, allowing more charges to be injected into the heterojunction interface to participate in the surface redox reaction, which significantly improves the photo-electric catalysis performance of BiOBr/Ba0.7Sr0.3TiO3. We believe that this work may open up new avenues for the research and development of highly efficient polarized ferroelectric material photoelectrodes for photo-electric catalysis.

Rational design of ternary NiCoFe hydrotalcite nanosheet co-catalysts to enhance the photoelectrochemical performance of α-Fe2O3 photoelectrodes

The reasonable construction of oxygen evolution co-catalysts on semiconductors is an effective means to enhance the photoelectrocatalytic performance of photoelectrodes. In this work, NiCoFe-LDH nanosheets with trimetallic active sites were integrated into α-Fe2O3 photoelectrodes by hydrothermal method and cation exchange reaction method. The NiCoFe-LDH acts as an effective co-catalyst, which significantly reduces the onset potential of the photoelectrode and enhances its photocurrent and stability. The photocurrent density of α-Fe2O3/NiCoFe-LDH composite photoelectrode reaches 0.62 mA/cm2, which is 6.8 and 1.4 times that of pure α-Fe2O3 and α-Fe2O3/NiCo-LDH, respectively and its starting potential is reduced to 0.52 V. At the same time, the co-catalyst with ternary metals provides more active sites on the surface of the photoelectrode, promoting the migration of photogenerated holes to the solution and enhancing the rapid separation of carriers. In addition, the synergistic interaction between multivalent transition metal ions in LDH plays an important role in improving the photoelectrocatalytic performance of the photoelectrodes. The co-catalyst introduced in this paper is expected to enhance the intrinsic photoelectrochemical activity of other semiconductor photoelectrodes and further explore their applications in solar energy conversion.

Preparation, characterization, and photoelectric properties of poly(1,3,5-tri(thiophene-2-yl)benzene) film electrodes

Here, poly(1,3,5-tri(thiophene-2-yl)benzene) (PTTB) membrane electrodes with porous surface structures were prepared by using an electropolymerization method. Firstly, a series of PTTB film electrodes with different morphologies are obtained, including open nanotubes, stacked flocs, dispersed cauliflower-like, and aggregated spheres, by separately depositing the PTTB films on different conductive substrates (GCE, silicon wafers, ITO, FTO). Secondly, this study explored the factors affecting the photoelectric properties and stability of PTTB film electrodes by varying the solvent, electrochemical method, scan rate, and number of scan cycles. Finally, the CV method and DCM/ACN mixed solvent were used in this experiment, and the best photoelectric effect of 3.2 μA was obtained under 3 scan cycles. In this study, the factors influencing the properties of PTTB by electrochemical polymerization methods are obtained through the exploration of PTTB film electrodes, providing a reference value for further combining PTTB films with other materials to prepare composite photoelectrodes.

Rational design of nanostructured BiVO4/FeOx photoanode coupling with 2D Co(OH)2 cocatalyst for enhanced photoelectrochemical water splitting

Efficient charge transport and separation is of prime significance to achieve high efficiency of photoelectrochemical (PEC) solar energy conversion. In this study, we designed a novel ternary nanostructured BiVO4/FeOx/Co(OH)2 composite as photoelectrode for enhanced PEC water splitting. Compared with pristine BiVO4, the fabricated BiVO4/FeOx/Co(OH)2 photoelectrode produced a doubled increase in photocurrent (from 0.36 to 0.72 mA cm−2 at 1.23 V versus RHE) with a negative shift of 390 mV in the initial potential (from 0.72 to 0.33 V). In addition, the conversion efficiency and photostability for PEC water oxidation were also improved. The elevated PEC properties of ternary composite photoelectrode were originated from the synergy of heterojunction construction and 2D cocatalyst loading that provides effective pathway for promoting charge separation as well as sufficient sites for photoelectrochemical reaction. These findings could provide an exemplary PEC model for enhanced solar hydrogen evolution of BiVO4 photoanode.

Nano structured diatom frustules incorporated into TiO2 photoelectrodes to enhance performance of quasi-solid-state dye-sensitized solar cells

Diatom frustules are incorporated into multilayer photoelectrodes intending to enhance efficiency in dye-sensitized solar cells utilizing their light interaction properties. A specific, but ubiquitous in all oceans, pennate-type diatom frustules were used to form the composite layers. Single, double, and triple-layer photoelectrodes were constructed with pure TiO2 (control measurements) as well as with a TiO2/diatom frustule composite. The electrodes were prepared using TiO2 nanoparticles of two sizes (13 and 21 nm) and were analyzed using UV visible absorption and XRD spectra. The morphology of frustules and electrodes were analyzed using scanning electron microscopy. The performance for each photoanode configuration was measured by assembling photoelectrochemical solar cells fabricated with a Pt counter electrode and a gel polymer electrolyte that excludes volatile solvents. The efficiency of the control cell is 3.37%. After replacing the topmost TiO2 layer with a TiO2/diatom frustule composite layer, efficiency increases to 6.78%. This is an impressive efficiency enhancement of 101%. The short circuit current density of frustule-incorporated three-layer cells is 18.1 mA cm−1 while for the control cell it is 8.98 mA cm−1. The enhanced efficiency of cells made with TiO2/diatom frustule composite electrodes and a polyethylene oxide-based gel polymer electrolyte can be attributed to the improved light absorption by the photoanode due to optical scattering and light-trapping effects caused by the presence of diatom frustules. Frustules also can assist in enhancing dye adsorption by increasing the effective specific surface area of the composite photoelectrode due to their nanoporous structure.

Topology engineering of UiO-66@TiO2-based photoelectrocatalyst for highly efficient degradation of binary pollutants

Photoelectrocatalysis (PEC) is an efficient strategy for addressing organic pollutants in the environmental water system. Titanium dioxide (TiO2) based composite photoelectrodes have been widely researched due to excellent photocatalytic performance and chemical durability. However, light transmission and mass transport at the active sites inside photoelectrode are substantially limited because of topological irrationality. Herein, topology engineering of UiO-66@TiO2-based photoelectrocatalyst is presented to overcome this disadvantage. Compared to the edge-structure of cubic UiO-66 wrapped TNFs (CU@T/T), center-structure of octahedral UiO-66 embedded TNFs (OU@T/T) can enhance the light capture capability and mass transport, and then improve the PEC activity. Simultaneously photoelectrocatalytic degradation of RhB and MO also shows that topologically optimized OU@T/T exhibits excellent catalytic activity and durability. At 2.0 V of bias potential, RhB and MO (both 5 mg/L) can be almost completely removed at 200 min (99.06 % and 98.81 %) in the solution with 7.0 of pH under the action of active species (⋅O2– and ⋅OH), and no attenuation after five cycles. This work highlights that topology engineering of UiO-66@TiO2-based photoelectrocatalyst not only facilitates charge transfer but also promotes mass transport, which greatly improves the PEC degradation performance of binary pollutants.

Self-powered biosensor using photoactive ternary nanocomposite: Testing the phospholipid content in rhodotorula glutinis oil

In the field of oil refining, the presence of excessive residual phosphorus in crude oil can significantly impact its quality, thereby emphasizing the necessity for compact and convenient testing equipment. This study primarily focuses on developing of self-powered biosensor (SPB) using immobilizing Choline Oxidase with a photoactive ternary nanocomposite complex (CHOx-BiOI-rGO-Fe3O4 NPs-ITO) as the anode and utilizing a Pt electrode as the cathode. The successful preparation of the ternary composite photoelectrode for the anode was confirmed through a range of characterization techniques, including X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Transmission electron microscopy (TEM), Scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), N2 absorption/desorption, Dynamic light scattering (DLS), and Ultraviolet–visible diffuse reflection spectrometer (UV–vis DRS). The electrochemical and photoelectrochemical properties were assessed using an electrochemical workstation, revealing a significant enhancement photoelectrical responsiveness attributed to the formation of heterojunction structures. The SPB exhibited a remarkable linear relationship between the instantaneous photocurrent and phosphatidylcholine (PC) concentration, with a regression equation of I (μA) = 39.62071C (mM) + 3.47271. The linear range covered a concentration range of 0.01–10 mM, and the detection limit (S/N = 3) was determined to be 0.008 mM. It demonstrated excellent reproducibility and storage stability, positioning it a promising alternative to High-performance liquid chromatography (HPLC) for accurate quantification of PC content in rhodotorula glutinis oil. The standard recovery PC content ranged from 98.48% to 103.53%, with a relative standard deviation (RSD) ranging from 1.4% to 2.4%. This research presents a convenient and precise detection device that has the potential to address the issue of lagging detection in the oil refining process.

In2S3@TiO2/In2S3 Z-Scheme Heterojunction with Synergistic Effect for Enhanced Photocathodic Protection of Steel.

In this work, a TiO2/In2S3 heterojunction film was successfully synthesized using a one-step hydrothermal method and applied in the photocathodic protection (PCP) of 304SS. The octahedral In2S3 and In2S3@TiO2 nanoparticles combined and coexisted with each other, with In2S3 quantum dots growing on the surface of TiO2 to form In2S3@TiO2 with a wrapping structure. The composite photoelectrode, which includes TiO2 with a mixed crystalline phase and In2S3, exhibited significantly enhanced PCP performance for 304SS compared with pure In2S3 and TiO2. The In2S3@TiO2/In2S3 composites with 0.3 g of P25 titanium dioxide (P25) showed the best protection performance, resulting in a cathodic shift of its OCP coupled with 304SS to -0.664 VAgCl. The electron transfer tracking results demonstrate that In2S3@TiO2/In2S3 forms a Z-scheme heterojunction structure. The enhanced PCP performance could be attributed to the synergistic effect of the mixed crystalline phase and the Z-scheme heterojunction system. The mixed crystalline phase of TiO2 provides more electrons, and these electrons are gathered at higher energy potentials in the Z-scheme system. Additionally, the built-in electric field further promotes the more effective electrons transfer from photoelectrode to the protected metals, thus, leading to enhanced photoelectrochemical cathodic protection of 304SS.

Amorphous molybdenum sulfide/polymeric carbon nitride composite with multiple interfaces for boosting photoelectrochemical water splitting performance

Rational interface design is an important way to improve the photoelectrochemical activity of catalysts in the sustainable energy and the environment. Herein, we simultaneously realize the construction of polymeric carbon nitride (PCN)-based homojunction (HPCN) and amorphous molybdenum sulfide (a-MoSx) /PCN heterojunction (a-MoSx/HPCN) in the composite catalyst system by one-pot calcination. The presence of a-MoSx was confirmed by X-ray photoelectron spectroscopy (XPS) and element mapping. X-ray diffraction (XRD) and transmission electron microscopy (TEM) revealed the amorphous characteristics of molybdenum sulfide. The photoluminescence (PL) spectroscopy indicated that the photo-generated carrier recombination of composite is effectively inhibited after constructing the homojunction and loading molybdenum sulfide. The confined effect of the PCN matrix induced the formation of ultrafine size a-MoSx, and its co-catalyst function is prominent. The optimized composite catalyst showed obvious boosting activity in photoelectrochemical water slitting. Photocathode current of −161 μA cm−2 (0 V vs. RHE) and photoanode current of 10 μA cm−2 (1.23 V vs. RHE) are almost 12 and 5 times than single PCN homojunction under the irradiation of 25 W light-emitting diode light source. This boosted activity can be attributed to the multiple interface effect of the n-n junction of PCN/PCN and the p-n junction of a-MoSx/PCN as well as the co-catalysis of amorphous molybdenum sulfide. The synergies between various merits effectively improved the absorption of visible light, the separation of photogenerated electrons and holes, and the addition of more reactive sites. This paper provides a new idea for interface engineering of PCN-based composite photoelectrode.

Photocatalytic activity of B-doped nano graphene oxide over hydrogenated NiO-loaded TiO2 nanotubes

A hydrogenated NiO-loaded anatase TiO2 with unique heterostructure nanotube arrays (denoted as H:(NiO/TiO2)) NTs were synthesized, followed by the attachment of boron-doped reduced nanographene oxide nanoparticles (B-nGO NPs) to form a vigorous composite photoelectrode B-nGO/H:(NiO/TiO2) NTs. The p-n junction created between p-type NiO and n-type TiO2 produces sufficient built-in electric field to facilitate the electron–hole pair separation and boost the interfacial electron transfer, subsequently a hydrogenation treatment to adjust the donor density and maximize the electron–hole separation. The microstructure characterization with synchrotron-based X-ray techniques straightened out that the created NiO oxygen vacancies can provide emptier d-orbitals to accept more photoexcited electrons. With the incorporation of B-nGO NPs, the partially replacement of C atoms of nGO by B atoms can form an electron–hole-rich configuration in the heterostructure to decrease the Fermi level, with a more rapid electron transfer toward TiO2 substrate during photocatalysis, which also confirmed by quantum-chemical calculations. The as-synthesized B-nGO/H:(NiO/TiO2) NTs exhibited a high photocurrent density (2.0 mA/cm2) and an effective photoconversion efficiency (2.07%) under simulated sunlight irradiation (AM1.5G, 100 mW/cm2). The eventuated photoconversion efficiency is 6 times enhanced with respect to the pristine TiO2, along with an impressive hydrogen evolution rate of 31 μmol/h/cm2. Moreover, the photocurrent durability test has confirmed the stability of B-nGO/H:(NiO/TiO2) electrode, with only a slight decay of <1% after continuous illumination for more than 4 h. Incident photon conversion efficiency spectra have revealed a boosted photo-response under visible light region (extended to ∼520 nm) with the synergistic attachment of NiO and B-nGO.