Photocorrosion Inhibition Research Articles

Novel CdLa2S4/Ni2P photocatalyst with boosting H2 evolution: Heterostructures promote photogenic carrier interface separation

Metal sulfides, often exhibited excellent photocatalytic H2 evolution ability, has attracted more and more attention, whereas their industry applications were limited due to the photocorrosion. Therefore, the inhibition of photocorrosion is the key issue to promote the industrialization of metal sulfide catalysts. In this work, CdLa2S4 /Ni2P catalysts with satisfactory H2 evolution property were designed and synthesized. Catalyst with 15 % Ni2P dosage exhibited maximum photocatalytic H2 evolution rate as 1.143 mmolh-1g−1, which was 10 times higher than that of pure CdLa2S4. Such high catalytic efficiency maintained after 5 photocatalytic cycles. According to the results of transient photocurrent and photoluminescence, the heterojunction structure formed by Ni2P and CdLa2S4 improved the separation efficiency of photogenerated electron-hole pairs, thus prompted the H2 evolution ability and the catalyst stability. Further EPR results confirmed the existence of heterojunctions in the catalyst and proposed a possible reaction mechanism. The results show that the CdLa2S4/Ni2P composite photocatalyst has good visible light response and photochemical stability, and has broad application prospects in solar driven photocatalytic decomposition of water to hydrogen production.

Unraveling the photocatalytic potential of transition metal sulfide and selenide monolayers for overall water splitting and photo-corrosion inhibition

A systematic study was carried out to identify transition metal sulfide and selenide (TMSS) monolayers, which resist both photo-degradation and photo-corrosion in a single electrolyte towards overall water splitting (OWS).

Superior dye degradation for wastewater treatment based on nanocomposites of cerium oxide, gadolinium oxide and graphene oxide

Despite the significant Progression in nanocomposites (NCs) tailoring for ecological purposes, optimizing NCs for water treatment is still a challenge. Moreover, organic coloring (dyes) agents like Congo red (CR) and methylene blue (MB) were included which have carcinogenic effects. In this regard, photo-catalytic activity utilizing NCs for organic pollutants (dyes) removal is a great concern due to its viability and low cost. In this regard, a combination of nanocomposites including cerium Oxide (CeO2), gadolinium oxide (Gd2O3), and graphene oxide (GO) could be suggested. X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR) were utilized for characterization in addition to EDX, and electron microscopes (TEM, and FESEM). TEM micrograph exhibits TNC as scattered lanthanides oxides (CeO2, and Gd2O3) grains upon GO sheets. It shows a clear decline in the average size to reach 25 nm for CeO2, and 40 nm for Gd2O3. Also, FESEM reports that GO reduces the lanthanide oxides aggregation tendency in TNC, besides forming shallow pores within its rough surface. Regarding the thermal study, It is clear that activation energy (E*) is the almost equal enthalpy of activation (ΔH). It could refer to the presence of the tested composition at a higher degree of temperature (thermally stable). Nano-composite powders exhibited improvement in photo-catalytic efficiency and inhibition of photo-corrosion as compared with pure lanthanide oxides. The MB degradation potential of CeO2/Gd2O3/GO drops from 94.4 % in the first usage to 82.1 % in the fifth.

Enhancement of CdS resistance to photocorrosion and photocatalytic removal of uranyl by complexation with N-deficient g-C3N4under aerobic conditions

The effect of oxygen on the reduction of uranyl and photocorrosion of CdS remains a pressing issue when CdS is used as a photocatalyst for the removal of uranyl in uranium-containing wastewater. In this study, composites (CdS/PCN) were prepared by designing N-deficient g-C3N4 composite with CdS for efficient photocatalytic reduction of uranyl under aerobic condition. Meanwhile, a series of characterizations of the CdS/PCN composites were carried out by XRD, FT-IR, XPS, EDS and UV–vis. Surprisingly, the CdS/PCN not only showed very high photocatalytic reduction activity for uranyl under aerobic condition, but also the photocorrosion of CdS by oxygen and h+ was inhibited. With a starting uranium (VI) concentration of 20 ppm, the uranium (VI) removal efficiency could reach 97.33% (dark: 30 min, light: 10 min). Interestingly, the removal efficiency was better in air condition than in pure nitrogen or 30% oxygen atmosphere, i.e. a proper amount of oxygen has accelerated the reduction reaction, while excess oxygen weakened the reduction. Finally, a new mechanism of reduction of uranyl by CdS/PCN photocatalyst was given under aerobic condit ions. This work presents a novel strategy for reduction of U(VI) by photocatalysis and the inhibition of photocorrosion of photocatalysts under aerobic conditions.

Optimization of processing parameters for the preparation of dip-coated CuO photocathodes and modification with Au nanoparticles for water-splitting

Here, the processing parameters for preparing dip-coated CuO photocathodes such as withdrawal velocity, film thickness, and calcination temperature were optimized for photoelectrochemical (PEC) applications. CuO films were prepared at varying withdrawal rates between 50 and 200 mm/min, made to consist of 239.7–693.6 ± 40 nm film thicknesses, and annealed at 400–650 °C for 1 h. Furthermore, Au nanoparticles (Au NPs) were deposited on the CuO films that were prepared at 150 mm/min withdrawal velocity, 432.8 ± 27 nm thick, and treated at 600 °C to protect the films against photo-corrosion during PEC reactions. The prepared films were confirmed to be of high purity via Raman spectroscopy and X-ray diffraction (XRD) studies. The maximum photocurrent density of 2.9 mA/cm2 at 0.35 V vs RHE was obtained for the CuO photocathodes prepared at 150 mm/min withdrawal velocity, with the thickness of 432.8 nm, and treated at 600 °C. The high photocurrent density has been linked to the combine effect of the optimization of film thickness, optical absorbance, crystallization, and the low resistance to charge transfer at the photocathode/electrolyte junction exhibited by the films. The deposition of Au NPs on the pristine CuO photocathodes resulted in a 62% drop in their photocurrent density due to the inhibition of high photo-corrosion occurring on the film's surface. A potential-time scan at 0.6 V vs RHE for 500 s yielded a 3-fold improvement in the photo-stability of the Au coated films in electrolyte over the pristine CuO photocathodes. This study emphasized the role of optimizing multiple processing parameters in the fabrication of CuO photocathodes before the deposition of protective layers for water splitting applications.

Antiphotocorrosion UV‐Bi2O3@PANI Photocatalyst Rich in Oxygen Vacancy Defects: Building Processes, Preparation Mechanisms, and Photocatalysis Performance

Low content of oxygen vacancy defects (OVs) and limited resistibility to photocorrosion are the core problems in the heterogeneous photocatalytic processes of bismuth oxide (Bi2O3). Herein, the strategy of “ultraviolet (UV) light‐inducing OVs” coupling with “polyaniline (PANI) combination inhibiting photocorrosion” is employed on the modification of Bi2O3. First, the high methylene blue (MB) degradation efficiency by UV3h‐Bi2O3@PANI0.5 wt% above 99.5% and the low Bi3+ dissolved concentration below 0.20 mg L−1 under visible light signify the high photocatalytic activity and stability. Then, the mechanisms for generation of OVs and inhibition of photocorrosion are proposed as follows. 1) Holes (h+) forming under irradiation, diffusing through the lattice, and reaching the surface of Bi2O3 can be regarded as a monatomic oxygen ion (OS−); 2) OS− combines and continues to be oxidized by h+, leading to the generation of O2 with the OVs left in the lattice; 3) UV‐Bi2O3 and PANI are excited to produce electrons/holes (e−/h+); 4) e−/h+ transfer in UV‐Bi2O3@PANI heterojunction leads to the separation of h+ from UV‐Bi2O3 and the inhibition of photocorrosion. Through the core problems being overcome, a new idea for the development and application of Bi2O3 with excellent performances in the field of water treatment is provided.

Double-shelled CeO2 coupled CdZnS nanoparticles as an efficient heterojunction visible light photocatalyst for hydrogen evolution

Designing of novel semiconductor photocatalysts toward high-efficient catalytic H2 generation has played a potential role in developing sustainable energy. Here, nanostructured CeO2/CdZnS/ZnO composite material has been synthesized through simple hydrothermal process. The present photocatalyst exhibits high photocatalytic activity for H2 generation under visible light irradiation (λ > 420 nm). It can be possibly explained: First, the ZnO layer formed on double-shelled CeO2 hollow spheres (D-CeO2) by the priority adsorption of Zn2+ exhibits both efficient hole consumption and photo-corrosion inhibition. Second, superior charge separation and charge transfer efficiency originates from the Z-scheme CeO2/CdZnS heterojunction.

Photocatalytic overall water splitting hydrogen evolution enhancement of ZnO nanoarrays/LaCrO3 film heterojunction via HER/OER synergism of CoP/FTO

The synergism of HER/OER would be an important issue for achieving overall water splitting. Herein, the CoP/FTO synergetic modified ZnO/LaCrO3 nanoarrays heterojunction is fabricated via a continuous annealing-hydrothermal-electrodeposition method. Evaluated by the photocatalytic performance, the CoP-ZnO-LaCrO3-FTO exhibits an enhanced HER performance of ∼30 folds than single LaCrO3 and ∼40 folds than single ZnO, and achieves a decent overall water splitting performance of ∼2418.1(H2)/1185.9(O2) μmol∙m−2∙h−1, which can be mainly ascribed to the synergism of HER/OER and formation of nanoarrays heterojunction. There, the CoP obtains sufficient HER active sites can accelerate the photo-generated electrons diffusing into water for HER, the FTO with hole­related species can promote OER, and the ZnO/LaCrO3 nanoarrays heterojunction can improve carrier efficiency and solar efficiency. Additionally, the nanoarrays heterojunction with high physical stability and photocorrosion inhibition can maintain good stability during photocatalytic process.

Photocorrosion protection of BiVO4 electrode by α-Cr2O3 core–shell for photoelectrochemical hydrogen production

• BiVO 4 with a novel electrochemical Bi film deposition is performed and a new precursor solution. • Optimum pH of precursor solution is investigated architect design of α-Cr 2 O 3 core–shell on BiVO 4 surface. • BiVO 4 photocorrosion inhibition is decreased with α-Cr 2 O 3 core–shell by 54.3 %. • α-Cr 2 O 3 core–shell layer also is enhanced photocatalytic performance of BiVO 4 . The development of high-performance and robust photoelectrode with architecture design is a popular research area. In this study, BiVO 4 photo corrosion protection carries out with α- Cr 2 O 3 core–shell under solar light irradiation for photoelectrochemical hydrogen production. BiVO 4 nanoparticles are coated with α-Cr 2 O 3 core–shell by various hydrothermal deposition solutions at various pH values (4.0, 4.5, 5.0 and 5.5), indicating coverage processes of α-Cr 2 O 3 on BiVO 4 depend on the pH of deposition bath. A p-type α- Cr 2 O 3 core–shell layer leads to the V fb value of n -type BiVO 4 shifting to a positive energy level, suggesting reducing BiVO 4 anodic photocorrosion under solar light. BiVO 4 / Cr 2 O 3 photo corrosion efficiency is investigated by Electrochemical Impedance Spectroscopy, Cr 2 O 3 core–shell layer photocorrosion protection efficiency (c ef %) of BiVO 4 /Cr 2 O 3 pH 4.0, BiVO 4 / Cr 2 O 3 pH 4.5 and BiVO 4 / Cr 2 O 3 pH 5.0 electrodes are calculated as 34.7 %, 54.3 % and 49.2 %, respectively. The photoelectrochemical hydrogen production performance demonstrates that BiVO 4 photo response enhanced in terms of surface passivation layers cause to improve the charge-separation and excited electron pathway semiconductor–electrolyte boundary.

Recent advances on silver-based photocatalysis: Photocorrosion inhibition, visible-light responsivity enhancement, and charges separation acceleration

As one of the most promising approaches to overcome current energy and environmental crises, semiconductor-based photocatalysis has increasingly attracted attention. The silver-based compound has become a promising candidate for highly reactive photocatalyst. And silver-based compounds have been widely applied in water splitting, wastewater treatment, air purification, disinfection, and many more. This review comprehensively summarized the advanced silver-based compounds (oxide, sulfide, halides, and multi-component oxides) photocatalyst to date, expounded the challenges facing of these semiconductors (including photocorrosion, dissatisfactory visible-light utilization, and fast photogenerated charges combination) and corresponding feasible approaches, and proposed suggestions for future works.

Photocorrosion inhibition of sulphide‐based nanomaterials for energy production through photocatalytic water splitting

Photocorrosion inhibition of sulphide‐based nanomaterials for energy production through photocatalytic water splitting

One-pot hydrothermal synthesis of CdS–CuS decorated TiO2 NTs for improved photocatalytic dye degradation and hydrogen production

TiO2 nanotube arrays (TiO2 NTs) were regarded as the outstanding semiconductors for the photocatalytic application in waste water treatment and H2 generation, and CdS nanoparticles as the visible light sensitizers were traditionally used to enhance the photocatalytic performance. In this paper, CdS–CuS co-sensitizers were deposited on TiO2 NTs by one-pot hydrothermal method, and the Cu/Cd ratio was changed to adjust the hybrid photocatalyst composition and electron transfer. The photocatalytic data indicated that suitable CdS–CuS composition could effectively enhance the photocatalytic pollutant removal and photocurrent/H2 evolution and the hybrid photocatalyst also exhibited the high stability by the inhibition of CdS photocorrosion. The p-n heterojunction construction of TiO2 NTs/CdS–CuS benefited the solar response, photoelectron separation and photocatalytic reaction, and the photocatalytic mechanism and photoelectron transfer were investigated. The p-n heterojunctional photocatalyst is supposed to apply in environmental remediation and new energy development.

Rational design of stratified material with spatially separated catalytic sites as an efficient overall water-splitting photocatalyst

The development of metal sulfide catalysts with remarkable activity toward efficient overall photocatalytic water splitting remains challenging owing to the dominant charge recombination and deficient catalytic active sites. Moreover, in the process of water oxidation catalysis, the inhibition of severe photocorrosion is an immense task, requiring effective photogenic hole-transfer kinetics. Herein, stratified Co-MnO2@CdS/CoS hollow cubes with spatially separated catalytic sites were rationally designed and fabricated as highly efficient controllable catalysts for photocatalytic overall water splitting. The unique self-templated method, including a continuous anion/cation-exchange reaction, integrates a Co-doped oxidation co-catalyst (Co-MnO2) and a reduction co-catalyst (CoS) on the nanocubes with uniform interface contact and ultrathin two-dimensional (2D) nanometer sheets. We demonstrate that the stratified Co-MnO2@CdS/CoS hollow cubes can provide an abundance of active sites for surface redox reactions and contribute to the separation and migration of the photoionization charge carriers. In particular, CoS nanoparticles dispersed on the walls of CdS hollow cubes were identified as reduction co-catalysts accelerating hydrogen generation, while Co-MnO2 nanosheets attached to the inner walls of the CdS hollow cube were oxidation co-catalysts, promoting oxygen evolution dynamics. Benefiting from the desirable structural and compositional advantages, optimized stratification of Co-MnO2@CdS/CoS nanocubes provided a catalytic system devoid of precious metals, which exhibited a remarkable overall photocatalytic water-splitting rate (735.4 (H2) and 361.1 (O2) μmol h−1 g−1), being among the highest values reported thus far for CdS-based catalysts. Moreover, an apparent quantum efficiency (AQE) of 1.32% was achieved for hydrogen evolution at 420 nm. This study emphasizes the importance of rational design on the structure and composition of photocatalysts for overall water splitting.

Plasma-assisted catalysis decomposition of BPA over graphene-CdS nanocomposites in pulsed gas-liquid hybrid discharge: Photocorrosion inhibition and synergistic mechanism analysis

In this work, plasma-assisted catalytic degradation of bisphenol A (BPA) has been performed over series of the graphene-CdS (rGO(x)/CdS) nanocomposites in aqueous solution. A pulsed gas-liquid hybrid discharge (PHD) was proposed to induce the “pseudo photocatalysis” effect of the rGO(x)/CdS nanocomposites and promote the formation of ·OH radicals. Compared to pure CdS, the rGO(x)/CdS nanocomposites present narrower band gap, more appropriate conduction band position, and higher separation rate of electron-hole (e−-h+) pairs, which result in higher BPA degradation performance in plasma-assisted catalysis process. The highest degradation efficiency of 87.58% and energy efficiency of 4.22 mg/kJ were obtained after 60 min plasma-assisted catalytic degradation over rGO(5)/CdS, which are 20.05% and 0.97 mg/kJ higher than those in single PHD system. It is also worth noting that rGO can provide perfect protection to CdS, diminishing the photocorrosion and improving the stability of rGO(5)/CdS nanocomposite, and the leaching of Cd2+ greatly decreases from 3.32% to 0.96% in the gas-liquid plasma environment. The possible synergetic degradation mechanism and toxicological evaluation for BPA and its decomposition intermediates in the plasma-assisted catalysis process have been proposed according to the function analysis of reactive species, the identification of organic intermediates, theoretical density functional theory (DFT) calculation, as well as quantitative structure-activity relationship (QASR) analysis. The strategy of integrating PHD with rGO(x)/CdS nanocomposites proposed in this work is expected to offer a feasible and potential technique for the industrial application of organic wastewater treatment.

Construction of hollow TiO2/CuS nanoboxes for boosting full-spectrum driven photocatalytic hydrogen evolution and environmental remediation

The plasma semiconductor Cu2-xS has disclosed enormous potential in the field of broad-spectrum driven photocatalyst design due to its unique LSPR effect in the NIR region. Nevertheless, ineffective carrier separation and severe photocorrosion hinder the further functional applications of this promising material. Here, the TiO2@CuS double-shell nanoboxes were successfully constructed via a multistep control strategy involving template participation, and were firstly employed to broad-spectrum photocatalytic hydrogen evolution and pollutant elimination. The hollow core-shell nanocubes with LSPR effect have prominent advantages in broad-spectrum light response, improved photocharge separation and effective photocorrosion inhibition. Besides, the heterogeneous cavity structure also provides a larger specific surface area and ameliorates the light efficiency. Consequently, the optimized TiO2@CuS double-shell nanoboxes exhibit superior activity for H2 production under full-spectrum/NIR light irradiation (2467 and 173 μmol g−1 h−1, respectively), and maintain high activity in the photodegradation of stubborn pollutants. This work will motivate hollow photocatalysts designed to effectively utilize the spectrum and protect the sulfide core.

Stabilization and Utilization of Pyrite under Light Irradiation: Discussion of Photocorrosion Resistance.

The control of pyrite (FeS2) oxidation from a source is a problem of great concern on treatment of acid mine drainage (AMD). Compared with air and water, the effect of light on pyrite oxidation has not attracted enough attention. However, we found that pyrite photocorrosion in the light promoted the oxidation of pyrite. Herein, we introduce a method of coating pyrite with graphene oxide (GO), which can inhibit the oxidation and photocorrosion of pyrite while it can also degrade organic pollutants. The characterization results show that a covalent bond forms between the GO and pyrite. The stable and uniform GO coating prevents the permeation of O2 and H2O and promotes the transfer of photogenerated electrons. Moreover, it changes the conduction band (CB) and valence band (VB) levels of GO–pyrite. All of these are vital for preventing the corrosion of pyrite and promoting its photocatalytic ability. More importantly, the effect of CB and VB levels on the oxidized species was discussed. The inhibition of photocorrosion is achieved by the reaction of GO with the photoinduced h+, •OH, and •O2–. The study provides insights for source treatment of AMD under light and the reuse of massive abandoned pyrite.

Stable Cocatalyst‐Free BiVO4 Photoanodes with Passivated Surface States for Photocorrosion Inhibition

AbstractImproving charge transport and reducing bulk/surface recombination can increase the activity and stability of BiVO4 for water oxidation. Herein we demonstrate that the photoelectrochemical (PEC) performance of BiVO4 can be significantly improved by potentiostatic photopolarization. The resulting cocatalyst‐free BiVO4 photoanode exhibited a record‐high photocurrent of 4.60 mA cm−2 at 1.23 VRHE with an outstanding onset potential of 0.23 VRHE in borate buffer without a sacrificial agent under AM 1.5G illumination. The most striking characteristic was a strong “self‐healing” property of the photoanode, with photostability observed over 100 h under intermittent testing. The synergistic effects of the generated oxygen vacancies and the passivated surface states at the semiconductor–electrolyte interface as a result of potentiostatic photopolarization reduced the substantial carrier recombination and enhanced the water oxidation kinetics, further inhibiting photocorrosion.

Stable Cocatalyst‐Free BiVO4 Photoanodes with Passivated Surface States for Photocorrosion Inhibition

Improving charge transport and reducing bulk/surface recombination can increase the activity and stability of BiVO4 for water oxidation. Herein we demonstrate that the photoelectrochemical (PEC) performance of BiVO4 can be significantly improved by potentiostatic photopolarization. The resulting cocatalyst-free BiVO4 photoanode exhibited a record-high photocurrent of 4.60 mA cm-2 at 1.23 VRHE with an outstanding onset potential of 0.23 VRHE in borate buffer without a sacrificial agent under AM 1.5G illumination. The most striking characteristic was a strong "self-healing" property of the photoanode, with photostability observed over 100 h under intermittent testing. The synergistic effects of the generated oxygen vacancies and the passivated surface states at the semiconductor-electrolyte interface as a result of potentiostatic photopolarization reduced the substantial carrier recombination and enhanced the water oxidation kinetics, further inhibiting photocorrosion.

Yttrium-Induced Regulation of Electron Density in NiFe Layered Double Hydroxides Yields Stable Solar Water Splitting

In situ catalyst regeneration of NiFe-based oxygen evolution catalyst (OEC) has been recognized as one of the best approaches for photocorrosion inhibition on water splitting photoelectrodes. Howev...

Decoupling Strategy for Enhanced Syngas Generation from Photoelectrochemical CO2 Reduction.

SummaryPhotoelectrochemical CO2 reduction into syngas (a mixture of CO and H2) provides a promising route to mitigate greenhouse gas emissions and store intermittent solar energy into value-added chemicals. Design of photoelectrode with high energy conversion efficiency and controllable syngas composition is of central importance but remains challenging. Herein, we report a decoupling strategy using dual cocatalysts to tackle the challenge based on joint computational and experimental investigations. Density functional theory calculations indicate the optimization of syngas generation using a combination of fundamentally distinctive catalytic sites. Experimentally, by integrating spatially separated dual cocatalysts of a CO-generating catalyst and a H2-generating catalyst with GaN nanowires on planar Si photocathode, we report a record high applied bias photon-to-current efficiency of 1.88% and controllable syngas products with tunable CO/H2 ratios (0–10) under one-sun illumination. Moreover, unassisted solar CO2 reduction with a solar-to-syngas efficiency of 0.63% is demonstrated in a tandem photoelectrochemical cell.