Reconcile the contradictory wettability requirements for the reduction and oxidation half-reactions in overall CO_(2) photoreduction via alternately hydrophobic surfaces

The overall photocatalytic CO_(2) reduction reaction(OPCRR)that can directly convert CO_(2) and H_(2)O into fuels represents a promising renewable energy conversion technology.As a typical redox reaction,the OPCRR involves two half-reactions:the CO_(2) reduction half-reaction(CRHR)and the water oxidation half-reaction(WOHR).Generally,both half-reactions can be promoted by adjusting the wettability of catalysts.However,there is a contradiction in wettability requirements for the two half-reactions.Specifically,CRHR prefers a hydrophobic surface that can accumulate more CO_(2) molecules on the active sites,ensuring the appropriate ratio of gas-phase(CO_(2))to liquid-phase(H_(2)O)reactants.Conversely,the WOHR prefers a hydrophilic surface that can promote the departure of the gaseous product(O_(2))from the catalyst surface,preventing isolation between active sites and the reactant(H_(2)O).Here,we successfully reconciled the contradictory wettability requirements for the CRHR and WOHR by creating an alternately hydrophobic catalyst.This was achieved through a selectively hydrophobic modification method and a charge-transfer-control strategy.Consequently,the collaboratively promoted CRHR and WOHR led to a significantly enhanced OPCRR with a solar-to-fuel conversion efficiency of 0.186%.Notably,in ethanol production,the catalyst exhibited a 10.64-fold increase in generation rate(271.44μmol g^(-1)h~(-1))and a 4-fold increase in selectivity(55.77%)compared to the benchmark catalyst.This innovative approach holds great potential for application in universal overall reactions involving gas participation.

Internal electric field modulation by copper vacancy concentration of cuprous sulfide nanosheets for enhanced selective CO_(2) photoreduction

Although the internal electric field(IEF)of photocatalysts is acknowledged as a potent driving force for photocharge separation,modulating the IEF intensity to achieve enhanced photocatalytic performances remains a challenge.Herein,cuprous sulfide nanosheets with different Cu vacancy concentration were employed to study IEF modulation and corresponding direct charge transfer.Among the samples,Cu_(1.8)S nanosheets possessed intensified IEF intensity compared with those of Cu_(2)S and Cu_(1.95)S nanosheets,suggesting that an enhanced IEF intensity could be achieved by introducing more Cu vacancies.This intensified IEF of Cu_(1.8)S nanosheets induced numerous photogenerated electrons to migrate to its surface,and the dissociative electrons were then captured by Cu vacancies,resulting in efficient charge separation spatially.In addition,the Cu vacancies on Cu_(1.8)S nanosheets accumulated electrons as active sites to lower the energy barrier of rate-determining step of CO_(2)photoreduction,leading to the selective conversion of CO_(2)to CO.Herein,the manipulation of IEF intensity through Cu vacancy concentration regulation of cuprous sulfide photocatalysts for efficient charge separation has been discussed,providing a scientific strategy to rationally improve photocata lytic performances for solar energy conversion.

Strain‑Induced Surface Interface Dual Polarization Constructs PML‑Cu/Bi_(12)O_(17)Br_(2) High‑Density Active Sites for CO_(2) Photoreduction

The insufficient active sites and slow interfacial charge trans-fer of photocatalysts restrict the efficiency of CO_(2) photoreduction.The synchronized modulation of the above key issues is demanding and chal-lenging.Herein,strain-induced strategy is developed to construct the Bi–O-bonded interface in Cu porphyrin-based monoatomic layer(PML-Cu)and Bi_(12)O_(17)Br_(2)(BOB),which triggers the surface interface dual polarization of PML-Cu/BOB(PBOB).In this multi-step polarization,the built-in electric field formed between the interfaces induces the electron transfer from con-duction band(CB)of BOB to CB of PML-Cu and suppresses its reverse migration.Moreover,the surface polarization of PML-Cu further promotes the electron converge in Cu atoms.The introduction of PML-Cu endows a high density of dispersed Cu active sites on the surface of PBOB,significantly promoting the adsorption and activation of CO_(2) and CO desorption.The conversion rate of CO_(2) photoreduction to CO for PBOB can reach 584.3μmol g-1,which is 7.83 times higher than BOB and 20.01 times than PML-Cu.This work offers valuable insights into multi-step polarization regulation and active site design for catalysts.

Ultrathin origami accordion-like structure of vacancy-rich graphitized carbon nitride for enhancing CO_(2) photoreduction

Retaining the ultrathin structure of two-dimensional materials is very important for stabilizing their catalytic performances.However,aggregation and restacking are unavoidable,to some extent,due to the van der Waals interlayer interaction of two-dimensional materials.Here,we address this challenge by preparing an origami accordion structure of ultrathin twodimensional graphitized carbon nitride(oa-C_(3)N_(4))with rich vacancies.This novel structured oa-C_(3)N_(4) shows exceptional photocatalytic activity for the CO_(2) reduction reaction,which is 8.1 times that of the pristine C_(3)N_(4).The unique structure not only prevents restacking but also increases light harvesting and the density of vacancy defects,which leads to modification of the electronic structure,regulation of the CO_(2) adsorption energy,and a decrease in the energy barrier of the carbon dioxide to carboxylic acid intermediate reaction.This study provides a new avenue for the development of stable highperformance two-dimensional catalytic materials.

Synthesis of bionic-macro/microporous MgO-modified TiO_2 for enhanced CO_2 photoreduction into hydrocarbon fuels

The stems of water convolvulus were employed as biotemplates for the replication of their optimized 3D hierarchical architecture to synthesize porous MgO-modified TiO2 . The photocatalytic reduction of CO2 with H2O vapor into hydrocarbon fuel was studied with these MgO-TiO2 nanostructures as the photocatalysts with the benefits of improved CO2 adsorption and activation through incorporated MgO. Various factors involving CO2 adsorption capacity, migration of charge carriers to the surface, and the number of activity sites, which depend on the amount of added MgO, determine the photocatalytic conversion efficiency.

Fabrication of highly dispersed platinum-deposited porous g-C_3N_4 by a simple in situ photoreduction strategy and their excellent visible light photocatalytic activity toward aqueous 4-fluorophenol degradation

A series of highly dispersed platinum‐deposited porous g‐C3N4 (Pt/pg‐C3N4) were successfully fabricated by a simple in situ photoreduction strategy using chloroplatinic acid and porous g‐C3N4 as precursors. Porous g‐C3N4 was fabricated by a pretreatment strategy using melamine as a raw material.The morphology, porosity, phase, chemical structure, and optical and electronic properties ofas‐prepared Pt/pg‐C3N4 were characterized. The photocatalytic activity of as‐prepared Pt/pg‐C3N4was preliminarily evaluated by the degradation of aqueous azo dyes methyl orange under visible light irradiation. The as‐prepared Pt/pg‐C3N4 were further applied to the degradation and mineralization of aqueous 4‐fluorophenol. The recyclability of Pt/pg‐C3N4 was evaluated under four consecutive photocatalytic runs.

MgO and Au nanoparticle Co-modified g-C_(3)N_(4)photocatalysts for enhanced photoreduction of CO_(2)with H_(2)O

The photoreduction of CO_(2)to achieve high-value-added hydrocarbons under simulated sunlight irradiation is advantageous,but challenging.In this study,a series of MgO and Au nanoparticle-co-modified g-C_(3)N_(4)photocatalysts were synthesized and subsequently applied for the photocatalytic reduction of CO_(2)with H2O under simulated solar irradiation.The best photocatalytic performance was demonstrated by the Au and 3%MgO-co-modified g-C_(3)N_(4)photocatalysts with CO,CH_(4),CH3OH,and CH3CHO yields of 423.9,83.2,47.2,and 130.4μmol/g,respectively,in a 3-h reaction.We investigated the effects of MgO and Au as cocatalysts on photocatalytic behaviors,respectively.The characterizations and experimental results showed that the enhanced photocatalytic activity was due to the synergistic effect among the components of the ternary photocatalyst.The cocatalyst MgO can activate CO_(2)(adsorbed at the interface between the MgO and Au particles),and the Mg-N bonds formed in the MgO-CN nanosheets played an important role in the charge transfer.Meanwhile,the Au particles that were modified into MgO/g-C_(3)N_(4)can increase the absorption of visible light via the surface plasmon resonance effect and further reduce the activation energies of the photoreduction of CO_(2)using H2O.This study provided an effective method for the modification of traditional primary photocatalysts with promising performance for photocatalytic CO_(2)reduction.

Isotype Heterojunction‑Boosted CO_(2) Photoreduction to CO

Photocatalytic conversion of CO_(2) to high-value products plays a crucial role in the global pursuit of carbon–neutral economy.Junction photocatalysts,such as the isotype heterojunctions,offer an ideal paradigm to navigate the photocatalytic CO_(2) reduction reaction(CRR).Herein,we elucidate the behaviors of isotype heterojunctions toward photocatalytic CRR over a representative photocatalyst,g-C_(3)N_(4).Impressively,the isotype heterojunctions possess a significantly higher efficiency for the spatial separation and transfer of photogenerated carriers than the single components.Along with the intrinsically outstanding stability,the isotype heterojunctions exhibit an exceptional and stable activity toward the CO_(2) photoreduction to CO.More importantly,by combining quantitative in situ technique with the first-principles modeling,we elucidate that the enhanced photoinduced charge dynamics promotes the production of key intermediates and thus the whole reaction kinetics.

S‐Scheme 2D/2D Bi_(2)MoO_(6)/BiOI van der Waals heterojunction for CO_(2) photoreduction

Reducing CO_(2) to hydrocarbon fuels by solar irradiation provides a feasible channel for mitigating excessive CO_(2) emissions and addressing resource depletion.Nevertheless,severe charge recombi‐nation and the high energy barrier for CO_(2) photoreduction on the surface of photocatalysts com‐promise the catalytic performance.Herein,a 2D/2D Bi_(2)MoO_(6)/BiOI composite was fabricated to achieve improved CO_(2) photoreduction efficiency.Charge transfer in the composite was facilitated by the van der Waals heterojunction with a large‐area interface.Work function calculation demon‐strated that S‐scheme charge transfer is operative in the composite,and effective charge separation and strong redox capability were revealed by time‐resolved photoluminescence and electron para‐magnetic resonance spectroscopy.Moreover,the intermediates of CO_(2) photoreduction were identi‐fied based on the in situ diffuse reflectance infrared Fourier‐transform spectra.Density functional theory calculations showed that CO_(2) hydrogenation is the rate‐determining step for yielding CH_(4) and CO.Introducing Bi_(2)MoO_(6) into the composite further decreased the energy barrier for CO_(2) photoreduction on BiOI by 0.35 eV.This study verifies the synergistic effect of the S‐scheme heterojunction and van der Waals heterojunction in the 2D/2D composite.

Improving photoreduction of CO2 with water to CH4 in a novel concentrated solar reactor

COphotoreduction is an attractive process which allows the storage of solar energy and synthesis of solar fuels. Many different photocatalytic systems have been developed, while the alternative photo-reactors are still insufficiently investigated. In this work, photoreduction of COwith HO into CHwas investigated in a modified concentrating solar reactor, using TiOand Pt/TiOas the catalysts. The TiOand Pt/TiOsamples were extensively characterized by different techniques including powder X-ray diffraction（XRD）, Nadsorption/desorption and UV–vis absorption. The catalytic performance of the TiOand Pt/TiOsamples in the gas phase was evaluated under unconcentrated and concentrated Xe-lamp light and nature solar light with different concentrating ratios. Various parameters of the reaction system and the catalysts were investigated and optimized to maximize the catalytic performance of COreduction system. Compared with the normal light irradiation, the TiOand Pt/TiOsamples show higher photocatalytic activity（about 6–7 times） for reducing COinto CHunder concentrated Xe-lamp light and nature solar light. In the range of experimental light intensity, it is found that the concentration of the light makes it suitable for the catalytic reaction, and increases the utilization efficiency of the TiOand Pt/TiOsamples while does not decrease the quantum efficiency.

Coupling of Cu Catalyst and Phosphonated Ru Complex Light Absorber with TiO2 as Bridge to Achieve Superior Visible Light CO2 Photoreduction

Visible light photocatalytic CO2 conversion is a promising solution to global warming and energy shortage.Herein,we build a well-designed bridge-like nanostructure,that is,the phosphonated Ru complex(RuP)light absorber–TiO2 bridge–Cu catalyst.In this nanostructure,brookite TiO2 serving as a bridge is spatially connected to the RuP and Cu on each of its sides and could thus physically separate the photoexcited holes and electrons over the RuP and Cu,respectively.Given its eff ective charge separation,this RuP–TiO2–Cu assembly exhibits superior CO2 photoreduction activity relative to RuP–SiO2–Cu under visible light irradiation(λ>420 nm).The catalytic activity is further optimized by adopting brookite TiO2 with various electronic band structures.Results reveal the rapid movement of electrons from the RuP through the conduction band of TiO2 and fi nally to the Cu surface.This property is crucial in CO2 photoreduction activity.

A Study on the Photoreduction of Green House CO2 Gas Catalyzed by TiO2 to Form Methane and Methanol

A photoreduction of CO2 gas catalyzed by TiO2 powder has been studied with purpose to form methane and/or methanol as well as to prevent global warming. The photoreduction was carried out in a batch horizontal column that is by irradiating a mixture of CO2 with water vapor in the presence of TiO2 powder for a period of time. Gasses produced were analyzed by gas chromatography method. In this study the effect of reaction time and TiO2 mass on the results has been evaluated. The research results indicate that from the photoreduction, some products have been obtained. The products are CH4, CH3OH, and C2H2 and C2H4. It is found that the reaction time and TiO2 mass control the types and the concentration of the products. The photoreduction carried out for 12 h results in CH4, C2H2 and C2H4 with low concentration, but when the reaction time was extended up to 24 h and 48 h, CH4 and CH3OH with higher concentration are produced. By using 25 g and 50 g of TiO2 photocatalyst in the photoreduction, only the CH4 is yielded, meanwhile a mixture of CH4 and CH3OH is formed when 100 g of TiO2 was applied. The production of CH4 and CH3OH by photoreduction of CO2 with water vapor in the presence of TiO2 photocatalyst has been successfully achieved. However, the improvement of the quantity of the targeted products is required.

Facile Synthesis of Ag/TiO2 by Photoreduction Method and Its Degradation Activity of Methylene Blue under UV and Visible Light Irradiation

A series of Ag/TiO2 with various Ag contents were prepared by photoreduction method. Commercial TiO2 from Evonik-Degussa was used as the catalyst. Ag was used as the cocatalyst. This facial synthesis method is cheap and easy. TiO2 was suspended in water with various concentrations of silver nitrate. The solution was illuminated by UV light for 36 h. Ag would deposit on the surface of TiO2. This method can deposit all Ag cation in the starting material on TiO2 after 36 h irradiation by UV light. X-ray diffraction, high resolution-TEM, and X-ray photoelectron spectroscopy were used to characterize the surface, morphology and chemical composition of the catalysts. Photocatalytic degradation of methylene blue in water on these catalysts was carried out under UV and visible light irradiation, respectively. The methylene blue concentration in water was measured by a UV-vis spectrophotometer. The results showed that the bulk structure of TiO2 did not change and some of Ag was incorporated into the surface of TiO2 lattice. The change in the electronic state of Ti on surface is attributed to the replacement of titanium atoms by silver atoms on the TiO2 surface structure which induced visible light response and enhanced the photocatalytic activity. 1 wt% Ag is the optimum loading to have high activity.

Rapid Synthesis of Size-controlled Gold Nanoparticles by Complex Intramolecular Photoreduction

A rapid synthesis of size-controlled gold nanoparticles was proposed.The method is based on the sensitive intramolecular photoreduction reaction of Fe（Ⅲ）-EDTA complex in chloroacetic acid-sodium acetate buffer solution,where Fe（Ⅱ）-EDTA complex generated by photo-promotion acts as a reductant of AuCl-4 ions.Gold nanoparticles formed were stabilized by EDTA ligand or other protective agents added.As a result,well-dispersed gold nanoparticles with an average diameter range of 6.7 to 50.9 nm were obtained.According to the characterizations by the UV spectrum and TEM,the intramolecular charge transfer of the excited states of complex Fe（Ⅲ）-EDTA and the mechanism of forming gold nanoparticles were discussed in detail.

Photoreduction Behaviors of Micropcroxidase-11 Adsorbed on the Roughened Silver Electrodes

It was found that microperoxidase-11 (MP-if) can undergo photoreduction at the bareroughened silver electrode. No photoreduction happens at the roughened silver electrodemodified with mercaptoundecanoic carboxylic acid/poly-lysine. The photoreduction mechanismis discussed.

Influences of Organic Acids and Heavy Metals on Cr（VI） Photoreduction Catalyzed by TiO2 Suspension

Photocatalytic reduction of Cr（VI） by TiO2 suspension has been studied with the purpose of removing the toxic and carcinogenic Cr（VI） ions from water. The photocatalytic reduction was carried out in batch reactor, in which the influences of the presence ofmalonic and oxalic acids as well as of iron and lead ions on the degree of the reduction have been systematically evaluated. The results of the research indicated that the presence of malonic and oxalic acids with increasing concentration can improve the photoreduction. The increase in the Cr（V1） photoreduction is due to OH radical capturing by the organic acids so that it prevents the recombination of the OH radical and the free electron, and therefore can provide enough electron supply for Cr（VI） photoreduction. The effectiveness of Cr（VI） photoreduction is also enhanced by the addition of increasing concentration of both Fe（Ⅲ） and Pb（Ⅱ） ions through synergic effect. It is also found that the degree of the photopreduction is strongly influenced by solution acidity and the most effective Cr（VI） photoreduction is obtained at lower pH than 5, either in the absence or presence of the organic acids and the heavy metal ions.

Effects of pH on Au-Deposited TiO2 for Catalytic Photoreduction of CO2 with H2O

The photoreduction of CO2 to hydrocarbons is a sustainable energy technology that not only reduces emissions but also the need for alternative fuels.In this study,Au nanoparticles were deposited on anatase TiO2 using various pH controlled Au ion solutions(from pH=6 to 9).Photoreduction experiments were performed in an FT-IR gas reactor using CO2 gas with 50%relative humidity as the reactant for the four Au/TiO2 samples.CH4 was mainly detected as the CO2 reduction product,along with a small amount of CO.The amounts of CH4 produced normalised by Au weight were 437 ppm(pH 6),664 ppm(pH 7),1,040 ppm(pH 8)and 2,356 ppm(pH 9).Therefore,the pH of the solution used in Au nanoparticle deposition strongly influenced the amount of CH4 produced.The highest production efficiency was obtained when the pH of the solution was 9.Considering the experimental results,we performed X-ray photoelectron spectroscopy and transmission electron microscope measurements and found that Au particle size was influenced by the pH of the solution with the size at pH 9 being smaller than that at pH 6.It was also found that there were Au-O states at the interface of Au nanoparticles and anatase TiO2.

Advances in understanding of the primary reactions of protochlorophyll(ide) photoreduction in cells and model systems

The key step in chlorophyll biosynthesis is photoreduction of its immediate precursor, protochlorophyllide. This reaction is catalyzed by a photoenzyme, protochlorophyllide oxidoreductase (POR) and consists in the attachment of two hydrogen atoms in positions C17 and C18 of the tetrapyrrole molecule of protochlorophyllide;the double bond is replaced with the single bond. Two hydrogen donors involved in protochloro-phyllide photoreduction are NADPH [1,2] and a conserved tyrosine residue Tyr193 of the photoenzyme POR [3]. The structure of active pigment-enzyme complex (Pchlide-POR-NADPH) ensures a favorable steric conditions for the transfer of hydride ion and proton. This review does not examine the ternary complex structure, but concentrates upon the mechanisms of primary photophysical and photochemical reactions during formation of chlorophyllide from protochlorophyllide in living objects (etiolated leaves and leaf homogenates) and model systems.

Photoreduction and Thermal Properties of Graphene-Based Flexible Films

In the present study, we report on an efficient method for large-area photoreduction of graphene oxide flexible films. The laser-based reduction can be carried out in situ and can be tuned to attain the properties required. A systematic study has been conducted to evaluate the variation of the degree of reduction with the actual reduction temperature, which is measured using an infrared thermal camera. Local reduction temperature is varied up to 350&#176C, and the degree of reduction is measured using the C/O ratio. The C/O ratio is increased from 2:1 for graphene oxide to 10:1 for reduced graphene oxide. This high degree of reduction is observed at low temperatures, and also in a short period of time. Thermal conductivity properties calculated using the temperature distribution shows the in-plane thermal conductivities of graphene oxide and reduced graphene oxide are a few orders of magnitude lower than single layer graphene. This can be attributed to oxygen-defect scattering, and also due to the heat conduction through the thickness of the sample by way of contact between adjacent flakes. This photoreduction method provides a way for roll-to-roll scalable production of graphene-based flexible films.

Bismuth clusters pinned on TiO_(2) porous nanowires boosting charge transfer for CO_(2) photoreduction to CH_(4)

Artificial photosynthesis in carbon dioxide(CO_(2))conversion into value-added chemicals attracts considerable attention but suffers from the low activity induced by sluggish separation of photogenerated carriers and the kinetic bottleneck-induced unsatisfied selectivity.Herein,we prepare a new-style Bi/TiO_(2) catalyst formed by pinning bismuth clusters on TiO_(2) nanowires through being confined by pores,which exhibits high activity and selectivity towards photocatalytic production of CH_(4) from CO_(2).Boosted charge transfer from TiO_(2) through Bi to the reactants is revealed via in situ X-ray photon spectroscopy and time-resolved photoluminescence(PL).Further,in situ Fourier transform infrared results confirm that Bi/TiO_(2) not only overcomes the multi-electron kinetics challenge of CO_(2) to CH_(4) via boosting charge transfer,but also facilitates proton production and transfer as well as the intermediates*CHO and*CH_(3)O generation,ultimately achieving the tandem catalysis towards methanation.Theoretical calculation also underlies that the more favorable reaction step from*CO to*CHO on Bi/TiO_(2) results in CH_(4) production with higher selectivity.Our work brings new insights into rational design of photocatalysts with high performance and the formation mechanism of CO_(2) to CH_(4) for solar energy storage in future.