[Research progress on nitrate isotope coupled multi-tracer tracing groundwater nitrate pollution]. / ç¡é ¸ç›åŒä½ç´ è€¦åˆå¤šç¤ºè¸ªå‰‚æº¯æºåœ°ä¸‹æ°´ç¡é ¸ç›æ±¡æŸ“ç ”ç©¶è¿›å±•.

Nitrate pollution in groundwater has become a global concern. One of the most important issues in controlling the nitrate pollution of groundwater is to identify the pollution source quickly and accurately. In this review, we firstly summarized the isotopic background values of potential sources of nitrate pollution in groundwater in 17 provinces (cities, autonomous regions) and 29 study areas in China, which could provide the fundamental database for subsequent research. Secondly, we reviewed the research progress of nitrate isotopes combined with multiple tracers for tracing nitrate in groundwater, and discussed their applicable conditions, advantages, and disadvantages. We found that halides and microorganisms combined with nitrate isotopes could accurately trace the pollution sources of domestic sewage, excrement and agricultural activities. The combination of Δ17O and nitrate isotopes could effectively distinguish the source of atmospheric deposition of nitrate in groundwater. The combination of groundwater age and nitrate isotopes could further determine the time scale of nitrate pollution. In addition, we summarized the application cases and compared the characteristics of mass balance mixing model, IsoSource model, Bayesian isotope mixing model, and EMMTE model for quantitative identification of nitrate pollution in groundwater. For the complexity and concealment of groundwater pollution sources, the coupling of nitrate isotopes with other chemical and biological tracing methods, as well as the application of nitrate isotope quantitative models, are effective tools for reliably identifying groundwater nitrate sources and transformation processes.

Photoselectively modulating main products by changing the wavelength of visible light over D-π-A-D conjugated polymers.

The diversity of catalytic products determines the difficulty of selective product modulation, which usually relies on adjusting the catalyst and reaction conditions to obtain different main products selectively. Herein, we synthesized D-π-A-D conjugated organic polymers (TH-COP) using cyclotriphosphonitrile, alkyne, 2H-benzimidazole, and sulfur units as electron donors, π bridges, electron acceptors, and electron donors, respectively. TH-COP exhibited excellent photoinduced carrier separation and redox ability under different visible light wavelengths, and the main products of its CO2 reduction are CH4 (1000.0 µmol g-1) and CO (837.0 µmol g-1) under 400-420 nm and 420-560 nm, respectively. In addition, TH-COP could completely convert phenylmethyl sulfide to methyl phenyl sulfone at 400-420 nm and diphenyl disulfide at 480-485 nm in yields up to 95 %. This study presents a novel strategy for the targeted fabrication of various main products using conjugated polymers by simply changing the wavelength range of visible light.

Effect of in situ ultrasonic wave and influent ammonia nitrogen fluctuation on stability of aerobic granular sludge.

This study elucidates the impact of fluctuating influent conditions and in situ ultrasonic wave exposure on the stability of aerobic granular sludge (AGS) in the treatment of simulated wastewater emanating from rare earth mining operations. During a stable influent period spanning from Day 1 to Day 95, the seed granules underwent an initial disintegration followed by a re-granulation phase. The secondary granulation was achieved on Day 80 and Day 40 for the ultrasonic reactor (R1) and the control reactor (R2), respectively. Notably, granules formed in R1 exhibited a more porous structure compared to those generated in R2. Subsequently, when the ammonia nitrogen in the influent oscillated between 100 and 500 mg/L during Days 96-140, both reactors yielded compact and densely structured granules. Nitrogen removal profiles were comparable between the two reactors: the removal efficiencies for ammonia nitrogen and total inorganic nitrogen escalated from 95% and 80%, respectively, during Days 1-95, to 95% and 90%, respectively, post-Day 140. A suite of performance metrics indicated that steady-state granules from R1 outperformed those from R2 across several parameters. Specifically, the nitrification/denitrification rates, and relative abundance of denitrifying bacteria were all higher in granules from R1. Conversely, the relative abundance of nitrifying bacteria was comparable between granules from both reactors. However, R1 granules demonstrated lower sludge concentration and smaller average particle size than their R2 counterparts. In conclusion, the AGS system demonstrated robust resilience to fluctuating ammonia nitrogen, and the application of ultrasonic waves significantly enhanced granular activity while achieving in situ sludge reduction.

Converting commercial Bi2O3 particles into Bi2O2Se@Bi4O8Se nanosheets for "rocking chair" zinc-ion batteries.

The development of a low-cost, high-capacity, and insertion-type anode is key for promoting "rocking chair" zinc-ion batteries. Herein, commercial Bi2O3 (BiO) particles are transformed into Bi2O2Se@Bi4O8Se (BiOSe) nanosheets through a simple selenylation process. The change in morphology from commercial BiO particle to BiOSe nanosheet leads to an increased specific surface area of the material. The enhanced electronic/ionic conductivity results in its excellent electrochemical kinetics. Ex situ XRD and XPS tests prove the intercalation-type mechanism of BiO and BiOSe as well as the superior electrochemical reversibility of BiOSe compared to BiO. Furthermore, the H+/Zn2+ co-insertion mechanism of BiOSe is revealed. This makes BiOSe to have low discharge plateaus of 0.38/0.68 V, a high reversible capacity of 182 mA h g-1 at 0.1 A g-1, and a long cyclic life of 500 cycles at 1 A g-1. Besides, the BiOSe//MnO2 "rocking chair" zinc-ion battery offers a high capacity of ≈90 mA h g-1 at 0.2 A g-1. This work provides a reference for turning commercial material into high-performance anode for "rocking chair" zinc-ion batteries.

Stability of aerobic granular sludge for treating inorganic wastewater with different nitrogen loading rates.

This paper investigated the effect of nitrogen loading rates (NLRs) on the stability of aerobic granular sludge (AGS) for treating simulated ionic rare earth mine wastewater with high ammonia nitrogen and extremely low organic content. Mature AGS from a sequencing batch reactor (SBR) was seeded into five identical SBRs (R1, R2, R3, R4 and R5). The five reactors were operated with different NLRs (0.2, 0.4, 0.8, 1.2 and 1.6 kg/m3·d). After 30 days of operation, R1, R2 and R5 were dominated by broken granules, while most of the granules in R3 and R4 still maintained a complete structure. The properties of granules from R1, R2, R3, R4 and R5 deteriorated to varying degrees, while the granules from R3 and R4 showed better stability than that from R1, R2 and R5. In R1, R2, R3 and R4, the steady-state ammonia nitrogen removal efficiencies were all greater than 90%, and the steady-state removal efficiencies of total inorganic nitrogen (TIN) were approximately 30%. In R5, the removal efficiencies of ammonia nitrogen and TIN were both approximately 70%. The dominant nitrifying and denitrifying bacterial genera of the granules from the five reactors were Nitrosomonas and Thauera, respectively, and their relative abundance was much higher in granules from R3 and R4. The results demonstrated that a relative equilibrium between the growth and metabolism of nitrifying/denitrifying bacteria was achieved when NLR was between 0.8 and 1.2 kg/m3·d, which could provide technical support for the stability maintenance of AGS in the treatment of ionic rare earth mine wastewater.

Ni-doped Bi2O2CO3 nanosheet with H+/Zn2+ co-insertion for "rocking chair" zinc-ion battery.

Developing insertion-type anode is key to advancing "rocking chair" zinc-ion batteries, though there are few reported insertion-type anodes. Herein, the Bi2O2CO3 is a high-potential anode, with a special layered structure. A one-step hydrothermal method was used to prepare Ni-doped Bi2O2CO3 nanosheet, and also a free-standing electrode consisting of Ni-Bi2O2CO3 and CNTs was designed. Both cross-linked CNTs conductive networks and Ni doping improve charge transfer. Ex situ tests (XRD, XPS, TEM, etc.) reveal the H+/Zn2+ co-insertion mechanism of Bi2O2CO3 and that Ni doping improves its electrochemical reversibility and structural stability. Therefore, this optimized electrode offers a high specific capacity of 159 mAh g-1 at 100 mA g-1, a suitable average discharge voltage of ≈0.400 V, and a long-term cycling stability of 2200 cycles at 700 mA g-1. Besides, the Ni-Bi2O2CO3//MnO2 "rocking chair" zinc-ion battery (based on the total mass of cathode and anode) delivers a high capacity of ≈100 mAh g-1 at 50.0 mA g-1. This work provides a reference for designing high-performance anode in zinc-ion batteries.

BiOIO3@Zn3(PO4)2·4H2O Heterojunction with Fast Ionic Diffusion Kinetics for Long-Life "Rocking-Chair" Zinc Ion Batteries.

Increasing insertion host materials are developed as high-performance anodes of "rocking-chair" zinc ion batteries. However, most of them show unsatisfactory rate capabilities. Herein, layered BiOIO3 is reported as an excellent insertion host and a zinc ion conductor, i.e., Zn3(PO4)2·4H2O (ZPO), is introduced to construct a BiOIO3@ZPO heterojunction with a built-in electric field (BEF). Both ZPO and a BEF obviously enhance Zn2+ transfer and storage, which is proven by theoretical calculations and experimental studies. The conversion-type mechanism of BiOIO3 is revealed through ex situ characterizations. The optimized electrode exhibits a high reversible capacity of 130 mAh g-1 at 0.1 A g-1, a low average discharge voltage of 0.58 V, an ultrahigh rate performance with 68 mAh g-1 at 5 A g-1 (52% of capacity at 0.1 A g-1), and an ultralong cyclic life of 6000 cycles at 5 A g-1. Significantly, the BiOIO3@ZPO//Mn3O4 full cell shows a good cyclic life of 67 mAh g-1 over 1000 cycles at 0.1 A g-1. This work provides a new insight into the design of anodes with excellent rate capability.

Coupling of endogenous/exogenous nitrification and denitrification in an aerobic granular sequencing batch reactor.

The performance of endogenous/exogenous nitrification and denitrification in an aerobic granular sequencing batch reactor was investigated for treating inorganic wastewater with ammonia nitrogen of 250 mg/L. The sequencing batch reactor with an effective volume of 120.5 L was started by seeding autotrophic nitrifying granular sludge (ANGS) and operated under oxic (110 min)/anoxic (120 min)/oxic (110 min) aeration mode. The total inorganic nitrogen (TIN) removal efficiency of ANGS was between 60% and 70% without external carbon sources in days 1-25. However, the operation mode was unsustainable as endogenous nitrification and denitrification would lead to an obvious decrease of sludge concentration. After sodium acetate (the contributed chemical oxygen demand in the reactor was 250-300 mg/L) was added at the beginning of the anaerobic/anoxic stage from day 26, aerobic granules were inadaptable in a few days, which resulted in particle disintegration and SVI increase. As microbes gradually acclimated to the new environment, the aerobic granular sludge became smoother and denser, the relative abundance of denitrifying bacteria increased to 66.07%, and the removal efficiency of TIN gradually increased to more than 90% from day 89. Contributions of endogenous/exogenous nitrification and denitrification to TIN removal were 54.09% and 46.01%, respectively. The coupling of endogenous/exogenous nitrification and denitrification could reduce the aeration consumption, save the external carbon source dosage and decrease the alkalinity consumption, which provided another option for treating wastewater from ionic rare earth mine.

Cultivation of autotrophic nitrifying granular sludge for simultaneous removal of ammonia nitrogen and Tl(I).

Autotrophic nitrifying granular sludge (ANGS) was cultivated for the simultaneous removal of ammonia nitrogen and Tl(I) from inorganic wastewater. The chemical oxygen demand (COD) in the influent gradually decreased to approximately zero in four parallel sequencing batch reactors (B1: blank controller, B2: 10 mL of added nitrifying bacteria concentrate in each cycle, B3: 1 mg/L Tl(I) added in each cycle and B4: 10 mL of added nitrifying bacteria concentrate and 1 mg/L Tl(I) in each cycle) within 15 days. The main properties, such as the granulation rate and specific oxygen uptake rate (SOUR) of the ANGS in B1, B2, B3 and B4 tended to be stable within 40, 33, 30 and 33 days, the removal efficiencies of Tl(I) were 59.5%-82.9% and 57.1%-88.6% in B3 and B4 after Day 30, the removal efficiencies of ammonia nitrogen in B1, B2, B3 and B4 were usually above 90% after Day 33, and the total inorganic nitrogen (TIN) in the effluent of B1, B2, B3 and B4 gradually stabilized after Day 36, 32, 32 and 36, indicating that mature ANGS was successfully cultivated in B1, B2, B3 and B4 within 40, 33, 33 and 36 days. The nitrogen degradation kinetic parameters of ANGS indicated that B3 had the strongest ability to remove ammonia and nitrite, suggesting that Tl(I) stress was beneficial to ammonia nitrogen removal and nitrite oxidation. The adsorption of Tl(I) can be described by the Freundlich equation, and the addition of external nitrifying bacteria improved the adsorption ability of ANGS.

Construction of dual active sites on the CuAg plasmonic aerogel for simultaneously efficient photocatalytic CO2 reduction and H2 production.

Photocatalytic CO2 reduction and H2 production are a competitive reaction, and existing active sites cannot take into account the simultaneous gas-solid and liquid-solid reaction processes. Hence, a metallic aerogel (CuAg2.5) with dual active sites was constructed via straightforward in-situ reduction process. CuAg2.5 aerosol has larger porosity and CO2 adsorption capacity, which enables H2O and CO2 to fully contact it. The CuAg2.5 can also construct the cooperative dual active sites, which can conduct CO2 reduction reaction on Ag surface and proton reduction reaction on Cu surface, respectively, thereby efficiently guiding the rapid migration of photogenerated carriers. The yields of CO (18533 µmol g-1) and H2 (20340 µmol g-1) for CuAg2.5 are much higher than those of single metals. The ratio of CO and H2 can also regulated via changing the ratio of Ag and Cu. This work gives new insights into the fabrication of unique high-efficiency plasmonic photocatalysts.

Few-Atomic-Layered Co-Doped BiOBr Nanosheet: Free-Standing Anode with Ultrahigh Mass Loading for "Rocking Chair" Zinc-Ion Battery.

Insertion host materials are considered as a candidate to replace metallic Zn anode. However, the high mass loading anode with good electrochemical performances is reported rarely. Herein, a few-atomic-layered Co-doped BiOBr nanosheet (Co-UTBiOBr) is prepared via one-step hydrothermal method and a free-standing flexible electrode consisting of Co-UTBiOBr and CNTs is designed. Ultrathin nanosheet (3 atomic layers) and CNTs accelerate Zn2+ and electron transfer respectively. The Co-doping is conducive to the reduced Zn2+ diffusion barrier, the improved volume expansion after Zn2+ intercalation, and the enhanced electronic conductivity of BiOBr, verified by experimental and theoretical studies. An insertion-conversion mechanism is proposed according to ex situ characterizations. Benefiting from many advantages, Co-UTBiOBr displays a high capacity of 150 mAh g-1 at 0.1 A g-1 and a long-term cyclic life with ≈100% capacity attention over 3000 cycles at 1 A g-1 . Remarkably, excellent electrochemical performances are maintained even at an ultrahigh mass loading of 15 mg cm-2 . Co-UTBiOBr//MnO2 "rocking chair" zinc-ion battery exhibits a stable capacity of ≈130 mAh g-1 at 0.2 A g-1 during cyclic test and its flexible quasi-solid-state battery shows outstanding stability under various bending states. This work provides a new idea for designing high mass loading anode.

Stability of aerobic granular sludge for simultaneous nitrogen and Pb(II) removal from inorganic wastewater.

ABSTRACTIn this paper, we proposed a strategy for the establishment of an aerobic granular sludge (AGS) system for simultaneous nitrogen and Pb(II) removal from inorganic wastewater. AGS was stored in lead nitrate solution to select functional bacteria resistant to lead poison, and then an AGS system for ammonia nitrogen (180-270 mg/L) and Pb(II) (15-30 mg/L) removal was established based on carbon dosing and a two-stage oxic/anoxic operational mode. After storage for 40 days, the stability of AGS decreased because specific oxygen uptake rate, nitrification rate and abundance of Nitrosomonas decreased to different degrees compared with those before storage. During the first 70 days of the recovery process, AGS in R1 (the blank reactor) and R2 (the control reactor) both experienced a first breakage and then regranulation process. The main properties of AGS in reactors R1 and R2 tended to be stable after days 106 and 117, respectively, but the structure of steady-state AGS in R2 was more compact. The total inorganic nitrogen (TIN) in effluent from R1 and R2 basically remained below 25 mg/L after days 98 and 90, respectively. The Pb(II) concentration in effluent from R2 was always below 0.3 mg/L. On day 140, the relative abundance of Nitrosomonas in R2 (6.17%) was significantly lower than that in R1 (12.15%), whereas the relative abundance of denitrifying bacteria was significantly higher than that in R1 (62.44% and 46.79%). The system removed 1 kg of influent TIN only consuming approximately 1.85 kg of carbon source, demonstrating clear advantages in energy savings.

BiOI Nanopaper As a High-Capacity, Long-Life and Insertion-Type Anode for a Flexible Quasi-Solid-State Zn-Ion Battery.

The development of intercalation anodes with high capacity is key to promote the progress of "rocking-chair" Zn-ion batteries (ZIBs). Here, layered BiOI is considered as a promising electrode in ZIBs due to its large interlayer distance (0.976 nm) and low Zn2+ diffusion barrier (0.57 eV) obtained by density functional theory, and a free-standing BiOI nanopaper is designed. The process and mechanism of Zn(H2O)n2+ insertion in BiOI are proved by ex situ X-ray diffraction, Raman, and X-ray photoelectron spectroscopy. The suitable potential (0.6 V vs Zn/Zn2+), high reversible capacity (253 mAh g-1), good rate performance (171 mAh g-1 at 10 A g-1), long cyclic life (113 mAh g-1 after 5000 cycles at 5 A g-1), and dendrite-free operation of BiOI nanopaper prove its potential as a superior anode. When it is coupled with Mn3O4 cathode, the quasi-solid-state battery exhibits a high initial capacity of 149 mAh g-1 (for anode) and a good capacity retention of 70 mAh g-1 after 400 cycles. The self-assembled flexible battery also shows stable charge-discharge during the cyclic test. This work shows the feasibility of BiOX anode for dendrite-free ZIBs.

[Effect of Controlling Heavy Metals in Soil of Rare Earth Mining Area by Biochar Supported Graphene Oxide].

Using navel orange peels and natural graphite as raw materials, biochar-supported graphene oxide (BGO) material was prepared using an improved hummer and co-pyrolysis method. The effects of BGO on the forms of heavy metals in the soil of a rare earth mining area were investigated via a soil passivation experiment. The soil column leaching experiment was carried out to explore the change characteristics of heavy metal content in leaching filtrate and the vertical migration law of heavy metals in soil, and the accumulation and release model of heavy metals under leaching conditions was determined. The results showed that pH value and organic matter content of soil with BGO composite increased, and acid-extractable Pb of raw ore and tailings soil decreased by 17% and 8.6%, respectively. The content of Mn form in the raw ore soil did not change significantly, whereas the content of acid-extractable, reducible, and oxidizable state in tailings soil decreased. The accumulation and release characteristics of heavy metals in soil could be divided into two stages:rapid release stage and slow stage. The release rate of heavy metals in soil with BGO composite was lower than that without addition, and the Pb and Mn removed from the tailings soil decreased by 2.5% and 28.4%, respectively, compared with that of the control group, whereas the raw ore soil decreased by 5.7% and 1.1%, respectively. The release of heavy metals in soil is a complex reaction process controlled by a variety of diffusion mechanisms. BGO composites can effectively inhibit the migration of heavy metals by increasing soil pH, surface complexation, and precipitation.

Molten salt synthesis of KCl-preintercalated C3N4 nanosheets with abundant pyridinic-N as a superior anode with 10 K cycles in lithium ion battery.

The graphitic carbon nitride is considered as the promising anode of lithium ion battery due to its high theoretical capacity (>1000 mAh g-1) and easy synthesis method. But the electrochemical inactivity and the structural collapse during cycles lead to its poor electrochemical performance in practice. Here, an interesting molten salt method is used to obtain the KCl-preintercalated carbon nitride nanosheets with abundant N vacancies and pyridinic-N. The KCl as a prop enhances the interlayer distance and the structural stability. And the N vacancy and the pyridinic-N increase the conductivity, the active sites and the reversibility of Li+ storage. Thus, the optimized electrode shows a higher specific discharge capacity (389 mAh g-1 at 0.1 A g-1) and a longer cyclic life (66% capacity retention after 10 K cycles at 3.0 A g-1) compared to those of bulk g-C3N4.

Turning commercial MnO2 (≥85 wt%) into high-crystallized K+-doped LiMn2O4 cathode with superior structural stability by a low-temperature molten salt method.

The obtainment of low-cost, easily prepared and high-powered LiMn2O4 is the key to achieve its wide application in various electronic devices. In this work, a mild and easily scaled molten salt method (KCl@LiCl) is utilized to convert commercial MnO2 to the high-performance LiMn2O4. At the same reaction temperature, the molten salt method leads to the formation of K+-doped LiMn2O4 with higher crystallinity compared to the conventional solid state method, which contributes to the improved inner charge transfer. The Li3PO4 protective layer is coated on the surface of K+-doped LiMn2O4 to elevate the interfacial stability and the Li+ transfer on interface. Thus, the optimized electrode shows a higher specific discharge capacity (103/60 mAh g-1 at 0.02/2 A g-1) and a longer cyclic life (80 mAh g-1 after 500 cycles at 0.5 A g-1) compared to those of LiMn2O4 by solid state method (49/2 mAh g-1 at 0.02/2 A g-1 and 20 mAh g-1 after 500 cycles at 0.5 A g-1).

Fast synthesis of porous iron doped CeO2 with oxygen vacancy for effective CO2 photoreduction.

The activity of photocatalytic CO2 conversion to carbon-containing products is determined by the adsorption and activation of CO2 molecules on the surface of catalyst. Here, iron doped porous CeO2 with oxygen vacancy (PFeCe) was prepared by one-step combustion method. The amount of CO2 adsorbed via using the porous structure has been significantly increased in the case of a relatively small specific surface area and CO2 molecules are more easily captured and undergo a reduction reaction with photoinduced carriers. In addition, oxygen vacancies are formed in the iron doped CeO2 lattice as the active sites for CO2 reduction, which can form strong interactions with CO2 molecules, thereby effectively activating CO2 molecules. The reduction products of CO2 over PFeCe composite are CO and CH4, which is approximately 9.0 and 7.7 folds than that of CeO2. This work offers insights for the construction of efficient ceria-based photocatalysts to further achieve robust solar CO2 conversion.

SARS-CoV-2 with transcription regulatory sequence motif mutation poses a greater threat / 南方医科大学学报

OBJECTIVE@#To analyze the mutations in transcription regulatory sequences (TRSs) of coronaviruss (CoV) to provide the basis for exploring the patterns of SARS-CoV-2 transmission and outbreak.@*METHODS@#A combined evolutionary and molecular functional analysis of all sets of publicly available genomic data of viruses was performed.@*RESULTS@#A leader transcription regulatory sequence (TRS-L) usually comprises the first 60-70 nts of the 5' UTR in a CoV genome, and the body transcription regulatory sequences (TRS-Bs) are located immediately upstream of the genes other than ORF1a and 1b. In each CoV genome, the TRS-L and TRS-Bs share a specific consensus sequence, namely the TRS motif. Any changes of nucleotide residues in the TRS motifs are defined as TRS motif mutations. Mutations in the TRS-L or multiple TRS-Bs result in superattenuated variants. The spread of super-attenuated variants may cause an increase in asymptomatic or mild infections, prolonged incubation periods and a decreased detection rate of the viruses, thus posing new challenges to SARS-CoV-2 prevention and control. The super-attenuated variants also increase their possibility of long-term coexistence with humans. The Delta variant is significantly different from all the previous variants and may lead to a large-scale transmission. The Delta variant (B.1.617.2) with TRS motif mutation has already appeared and shown signs of spreading in Singapore, which, and even the Southeast Asia, may become the new epicenter of the next wave of SARS-CoV-2 outbreak.@*CONCLUSION@#TRS motif mutation will occur in all variants of SARS-CoV-2 and may result in super-attenuated variants. Only super-attenuated variants with TRS motif mutations will eventually lose the abilities of cross-species transmission and causing outbreaks.

Line defects in plasmatic hollow copper ball boost excellent photocatalytic reaction with pure water under ultra-low CO2 concentration.

By using a low CO2 concentration as a C1 source, the design of a plasmonic catalyst that can effectively photocatalytic CO2 reduction is of great significance for sustainable and ecological development. Herein, the space confinement effect and liquid environment of the molten salt result in uniform hollow structure, while the strong aggressive force furnished via using molten salt enhances the formation of line defects. This special structure can not only provide a large number of active sites but also greatly accelerate the transport of photoinduced charge carriers. The hollow copper ball with line defects (CCu) shows excellent photocatalytic activity with pure water (1028.57 µmol g-1), and it also shows good catalytic activity even under ultra-low CO2 content, which far exceeds the catalytic activity of most semiconductor-based catalysts. This work is designed to simultaneously construct line defect and hollow structure in plasmatic metal nanoparticles for efficient photocatalytic CO2 reduction.

Controllable synthesis of porous silver cyanamide nanocrystals with tunable morphologies for selective photocatalytic CO2 reduction into CH4.

The conversion of CO2 driven by solar energy into carbon-containing fuel has huge potential applications. However, most photocatalysts can only promote the two-electron reduction process to generate CO, and it is difficult to produce eight-electron CH4, which is more valuable and can store more solar energy. Herein, we prepared porous silver cyanamide nanocrystals with tunable morphologies via a facile synthesis strategy. Compared with ball/rectangular plate (RAP) and ball/leaf-like plate (SAP), the ball/porous leaf-like plate (LAP) can provide more internal reaction microenvironment, which is not only conducive to the transport of photoinduced charge carriers, but also can expand the active sites for photocatalytic CO2 reduction. Moreover, the suitable band gap of LAP sample can capture more visible light to provide more photoinduced electron-hole pairs to participate in the reduction reaction. Consequently, the LAP sample can convert CO2 to CH4 with remarkable activity and high selectivity (nearly 100%) without cocatalyst and photosensitizer under visible light irradiation. This work provides a promising way to design new photocatalysts for various applications in solar energy conversion.