Suppressing Element Inhomogeneity Enables 14.9% Efficiency CZTSSe Solar Cells.

Kesterites, Cu2ZnSn(SxSe1- x)4 (CZTSSe), solar cells suffer from severe open-circuit voltage (VOC) loss due to the numerous secondary phases and defects. The prevailing notion attributes this issue to Sn-loss during the selenization. However, this work unveils that, instead of Sn-loss, elemental inhomogeneity caused by Cu-directional diffusion toward Mo(S,Se)2 layer is the critical factor in the formation of secondary phases and defects. This diffusion decreases the Cu/(Zn+Sn) ratio to 53% at the bottom fine-grain layer, increasing the Sn-/Zn-related bulk defects. By suppressing the Cu-directional diffusion with a blocking layer, the crystal quality is effectively improved and the defect density is reduced, leading to a remarkable photovoltaic coversion efficiency (PCE) of 14.9% with a VOC of 576 mV and a certified efficiency of 14.6%. The findings provide insights into element inhomogeneity, holding significant potential to advance the development of CZTSSe solar cells.

Regulating Hetero-Nucleation Enabling Over 14% Efficient Kesterite Solar Cells.

Developing well-crystallized light-absorbing layers remains a formidable challenge in the progression of kesterite Cu2ZnSn(S,Se)4 (CZTSSe) solar cells. A critical aspect of optimizing CZTSSe lies in accurately governing the high-temperature selenization reaction. This process is intricate and demanding, with underlying mechanisms requiring further comprehension. This study introduces a precursor microstructure-guided hetero-nucleation regulation strategy for high-quality CZTSSe absorbers and well-performing solar cells. The alcoholysis of 2-methoxyethanol (MOE) and the generation of high gas-producing micelles by adding hydrogen chloride (HCl) as a proton additive into the precursor solution are successfully suppressed. This tailored modification of solution components reduces the emission of volatiles during baking, yielding a compact and dense precursor microstructure. The reduced-roughness surface nurtures the formation of larger CZTSSe nuclei, accelerating the ensuing Ostwald ripening process. Ultimately, CZTSSe absorbers with enhanced crystallinity and diminished defects are fabricated, attaining an impressive 14.01% active-area power conversion efficiency. The findings elucidate the influence of precursor microstructure on the selenization reaction process, paving a route for fabricating high-quality kesterite CZTSSe films and high-efficiency solar cells.

A zero energy-input nitrogen removal reactor based on a short-circuited microfluidic fuel cell.

Excessive discharge of ammonia nitrogen would deteriorate water quality. In this work, we designed an innovative microfluidic electrochemical nitrogen-removal reactor (MENR) based on a short-circuited ammonia-air microfluidic fuel cell (MFC). The MENR utilizes the laminar characteristics of two flows (an anolyte containing nitrogen-rich wastewater and a catholyte of acid electrolyte solution) in a microchannel to establish an efficient reactor system. At anode, ammonia was catalyzed by a NiCu/C modified electrode to N2, while O2 in the air was reduced at cathode. In essence, the MENR reactor is a short-circuited MFC. Maximum discharge currents were achieved accompanied with strong ammonia oxidation reaction. Factors indicating electrolyte flow rate, initial nitrogen concentration, electrolyte concentration, and electrode geometry have various effects on the nitrogen removal performance of the MENR. Results indicate that the MENR showed efficient nitrogen removal properties. This work proposes an energy-saving process by using the MENR to remove nitrogen from ammonia-rich wastewater.

Retrieval of Au, Ag, Cu precious metals coupled with electric energy production via an unconventional coupled redox fuel cell reactor.

The recovery of heavy metals from aqueous solutions or e-wastes is of upmost importance. Retrieval of Au, Ag, and Cu with electricity generation through building an ethanol-metal coupled redox fuel cells (CRFCs) is demonstrated. The cell was uniquely assembled on PdNi/C anode the electro-oxidation of ethanol takes place to give electrons and then go through the external circuit reducing metal ions to metallic on the cathode, metals are recovered. Taking an example of removal of 100mgL-1 gold in 0.5M HAc-NaAc buffer solution as the catholyte, 2.0M ethanol in 1.0M alkaline solution as the anolyte, an open circuit voltage of 1.4V, more than 96% of gold removal efficiency in 20h, and equivalent energy production of 2.0kWhkg-1 of gold can be readily achieved in this system. When gold and copper ions coexist, it was confirmed that metallic Cu is formed on the cathodic electrode later than metallic Au formation by XPS analysis. Thus, this system can achieve step by step electrodeposition of gold and copper while the two metal ions coexisting. This work develops a new approach to retrieve valuable metals from aqueous solution or e-wastes.

Elimination of ethanethiol released from municipal wastes by absorption sequencing electrochemical oxidation.

As a typical municipal waste landfill gas, ethanethiol can become an air pollutant because of its low odor threshold concentration and toxicity to human beings. A hybrid process of absorption combined with electrochemical oxidation to degrade ethanethiol was investigated. The ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM]BF4) was employed as an absorbent to capture ethanethiol from the air stream. Electrochemical oxidation demonstrated that ethanethiol could be oxidized on a ß-PbO2 anode modified with fluoride, while [BMIM]BF4 was used as an electrolyte. After a reaction time of 90 min under a current density of 50 mA/cm2, ethanethiol could be thoroughly destructed by the successive attack of hydroxyl radicals (·OH) electrogenerated on the surface of the ß-PbO2 anode, while the sulfur atoms in ethanethiol were ultimately converted to sulfate ions [Formula: see text]. The reaction mechanism is proposed, and the operating condition is also estimated with a kinetic model. This hybrid process could be a promising way to remove thiol compounds from municipal waste landfill gases.

Stabilization of carbon dioxide and chromium slag via carbonation.

As the main greenhouse gas, CO2 is considered as a threat in the context of global warming. Many available technologies to reduce CO2 emission was about CO2 separation from coal combustion and geological sequestration. However, how to deal with the cost-effective storage of CO2 has become a new challenge. Moreover, chromium pollution, the treatment of which requires huge energy consumption, has attracted people's widespread attention. This study is aimed to develop the sequestration of CO2 via chromium slag. A dynamic leaching experiment of chromium slag was designed to testify the ability of CO2 adsorption onto chromium slag and to release Cr(VI) for stabilization. The results showed that the accumulative amounts of Cr(VI) were ca. 2.6 mg/g released from the chromium slag after 24 h of leaching. In addition, ca. 89 mg/g CO2 was adsorbed by using pure CO2 in the experiment at 12 h. Calcite is the only carbonate species in the post-carbonated slag analyzed by powder X-ray diffraction and thermal analysis. The approach provides the feasibility of the utilization of chromium slag and sequestration of the carbon dioxide at the same time at ordinary temperatures and pressures.

Assembly of coupled redox fuel cells using copper as electron acceptors to generate power and its in-situ retrieval.

Energy extraction from waste has attracted much interest nowadays. Herein, a coupled redox fuel cell (CRFC) device using heavy metals, such as copper, as an electron acceptor is assembled to testify the recoveries of both electricity and the precious metal without energy consumption. In this study, a NaBH4-Cu(II) CRFC was employed as an example to retrieve copper from a dilute solution with self-electricity production. The properties of the CRFC have been characterized, and the open circuit voltage was 1.65 V with a maximum power density of 7.2 W m(-2) at an initial Cu(2+) concentration of 1,600 mg L(-1) in the catholyte. 99.9% of the 400 mg L(-1) copper was harvested after operation for 24 h, and the product formed on the cathode was identified as elemental copper. The CRFC demonstrated that useful chemicals were recovered and the electricity contained in the chemicals was produced in a self-powered retrieval process.

Self-powered denitration of landfill leachate through ammonia/nitrate coupled redox fuel cell reactor.

In order to explore the feasibility of energy-free denitrifying N-rich wastewater, a self-powered device was uniquely assembled, in which ammonia/nitrate coupled redox fuel cell (CRFC) reactor was served as removing nitrogen and harvesting electric energy simultaneously. Ammonia is oxidized at anodic compartment and nitrate is reduced at cathodic compartment spontaneously by electrocatalysis. In 7.14 mM ammonia+0.2M KOH anolyte and 4.29 mM KNO3+0.1M H2SO4 catholyte, the nitrate removal efficiency was 46.9% after 18 h. Meanwhile, a maximum power density of 170 mW m(-2) was achieved when applying Pd/C cathode. When NH4Cl/nitrate and ammonia/nitrite CRFCs were tested, 26.2% N-NH4Cl and 91.4% N-NO2(-) were removed respectively. Nitrogen removal efficiency for real leachate at the same initial NH3-N concentration is 22.9% and nitrification of ammonia in leachate can be used as nitrate source. This work demonstrated a new way for N-rich wastewater remediation with electricity generation.

Heavy metal pollution in soils from abandoned Taizhou Chemical Industry Zone in Zhejiang province.

Heavy metal (HM) pollution in soils from an abandoned Taizhou Chemical Industry Zone (TCIZ) was investigated. By analysing soils, including sediments, collected from the study zone, the main pollutants were quantitatively identified and their spatial distribution patterns were clearly displayed. Eleven types of HM pollutants were obtained and the results indicated a significant correlation in most of the elements of the soil and sediment. A pollution index Pi was employed to classify the degree of contamination and characterize the main pollutant, which was controlled with the evaluation standard value instead of background one. As was characterized to be one of the main pollutants with the mean concentrations at the pollution source, in the surrounding area, and in the sediment of 603, 20.4, and 22.5 mg/kg, respectively. Our study suggested that the contaminated area of TCIZ may necessitate remediation before it can be considered for reuse. Pollution index method could be a useful tool for assessing soils quality to provide comparable criteria.

Elimination of sulphur odours at landfills by bioconversion and the corona discharge plasma technique.

Hydrogen sulphide (H2S) contributes a lot to odours at landfills, which is a threat to the environment and the health of the staff therein. To mitigate its emission, the bioconversion within landfill cover soils (LCSs) was introduced. H2S emission and concentration both in the field air above the landfill and in microcosm testing were surveyed. Results indicated that H2S emission and concentration in the landfill varied with landfill seasons and sites. There existed relationship between H2S concentration and fluxes spatially and temporally. To characterize and assess the spatial and temporal diversity of sulphur-oxidizing bacteria (SOB) and sulphate-reducing bacteria (SRB) in the LCSs, the terminal-restriction fragment length polymorphism technique was employed. Using the functional genes of dsrB and soxB, SOB, including Halothiobacillus, Rhodothalassium, Paracocccus, Allochromatium, and Thiobacillus, and SRB, including Desulfovibrio, Syntrophobacter, Desulfomonile and Desulfobacca, were identical and exhibited the dominant role in the LCSs. By employing an alternative available corona reactor, more than 90% removal efficiencies of sulphides were demonstrated, suggesting that the LCSs for eliminating odours in a lower concentration would be feasible.

Remediation of chromium-slag leakage with electricity cogeneration via a urea-Cr(VI) cell.

Chromium pollution has been historically widespread throughout the world. Most available remediation technologies often require energy consumption. This study is aimed to develop electrochemical remediation for Cr(VI) in chromium-slag leakage with self-generated electricity. Dynamic leaching experiments of chromium-slag samples were conducted to survey the release and leaching behavior of Cr(VI). Based on previous work, a unique urea-Cr(VI) was designed, in which urea was employed as the fuel and Cr(VI) from the leakage of the dichromate slag served as the oxidant. Furthermore, the electrochemical results showed that the removal percent of Cr(VI) was more than 96% after 18 h with the leakage Cr(VI) concentration of 2.69 mM. The open circuit potential (OCP) varied in the range of 1.56 ~ 1.59 V under different initial Cr(VI) leakage concentrations. The approach explores the feasibility of the promising technique without the need of energy input for simultaneous chromium-slag remediation and generation of electricity.

Nickel-cobalt bimetallic anode catalysts for direct urea fuel cell.

Nickel is an ideal non-noble metal anode catalyst for direct urea fuel cell (DUFC) due to its high activity. However, there exists a large overpotential toward urea electrooxidation. Herein, NiCo/C bimetallic nanoparticles were prepared with various Co contents (0, 10, 20, 30 and 40 wt%) to improve the activity. The best Co ratio was 10% in the aspect of cell performance, with a maximum power density of 1.57 mW cm(-2) when 0.33 M urea was used as fuel, O2 as oxidant at 60 °C. The effects of temperature and urea concentration on DUFC performance were investigated. Besides, direct urine fuel cell reaches a maximum power density of 0.19 mW cm(-2) with an open circuit voltage of 0.38 V at 60 °C.

Preparation by low-temperature nonthermal plasma of graphite fiber and its characteristics for solid-phase microextraction.

Low-temperature nonthermal plasma has been used to prepare solid-phase microextraction (SPME) fibers with high adsorbability, long-term serviceability, and high reproducibility. Graphite rods serving as fiber precursors were treated by an air plasma discharged at 15.2-15.5 kV for a duration of 8 min. Sampling results revealed that the adsorptive capacity of the homemade fiber was 2.5-34.6 times that of a polyacrylate (PA) fiber for alcohols (methanol, ethanol, isopropyl alcohol, n-butyl alcohol), and about 1.4-1.6 times and 2.5-5.1 times that of an activated carbon fiber (ACF) for alcohols and BTEX (benzene, toluene, ethylbenzene, and xylenes), respectively. It is confirmed from FTIR (Fourier transform infrared spectrophotometer) and SEM (scanning electron microscope) analyses that the improvement in the adsorptive performance attributed to increased surface energy and roughness of the graphite fiber. Using gas chromatography (GC)-flame-ionization detector (FID), the limits of detection (LODs) of the alcohols and BTEX ranged between 0.19 and 3.75 microg L(-1), the linear ranges were between 0.6 and 35,619 microg L(-1) with good linearity (R(2)=0.9964-0.9997). It was demonstrated that nonthermal plasma offers a fast and simple method for preparing an efficient graphite SPME fiber, and that SPME using the homemade fiber represents a sensitive and selective extraction method for the analysis of a wide range of organic compounds.

Nitrification of human urine for its stabilization and nutrient recycling.

Nitrification of human urine performed for its stabilization, and culture of Spirulina platensis in the nitrified human urine were investigated for nutrient recovery. With daily adjusting to pH 8 and keeping high dissolved oxygen concentration, mean 95.0% of NH(4)-N in human urine can be finally stabilized and oxidized to NO(3)-N. Furthermore, this nitrified human urine seems to be an ideal culture medium for S. platensis. Without pH adjustment, only about 50.0% NH(4)-N could be converted, i.e. NH(4)NO(3) would be formed. Under low dissolved oxygen concentration, mainly short nitrification (from NH(4)-N to NO(2)-N) occurred.

Culture of Spirulina platensis in human urine for biomass production and O(2) evolution.

Attempts were made to culture Spirulina platensis in human urine directly to achieve biomass production and O(2) evolution, for potential application to nutrient regeneration and air revitalization in life support system. The culture results showed that Spirulina platensis grows successfully in diluted human urine, and yields maximal biomass at urine dilution ratios of 140 approximately 240. Accumulation of lipid and decreasing of protein occurred due to N deficiency. O(2) release rate of Spirulina platensis in diluted human urine was higher than that in Zarrouk medium.

[Effect of flue gas conditions on NO oxidation process by DC corona radical shower].

Using an air-H2O DC corona radical shower system, the influences of reside time of flue gas in the reactor, velocity of flue gas and NO concentration on NO oxidation process were studied. The results show that the increasing velocity of flue gas can restrain corona development and the increasing NO concentration can make discharge more easy. The reside time of flue gas in the reactor has less effect on the NO oxidation. The NO oxidation rate increased only from 54.5% to 57.6% at 2 W input power when the reside time of flue gas in the reactor increased from 8.5 s to 34.2 s. However, the velocity of flue gas has important effect on the NO oxidation. At 1.7 W x h/m3 energy density, when the velocity of flue gas increased from 1.4 cm/s to 6.3 cm/s, the NO oxidation rate dropped from 60.0% to 38.6% and the energy yield also falled from 20.8 g/(kW x h) to 13.3 g/(kW x h). Under the certain flux of humid air, NO initial concentration has a best value, which was about 100 x 10(-6) in this experiment.

A new configuration of membrane stack for retrieval of nickel absorbed in resins.

A new configuration integrated ion exchange effect system with both electro-migration and electrochemical reaction in a single cell was developed to effectively retrieve metal ions from simulated wastewater using ion exchange resins without additive chemicals. By simply assembling cation exchange resins and anion exchange resins separated by homogeneous membranes, we found that the system will always be acidic in the concentrate compartment so that ion exchange resins could be in-situ regenerated without hydroxide precipitation. Such a realizable design will be really suitable for wastewater purification.

Dechlorination by combined electrochemical reduction and oxidation.

Chlorophenols are typical priority pollutants listed by USEPA (U.S. Environmental Protection Agency). The removal of chlorophenol could be carried out by a combination of electrochemical reduction and oxidation method. Results showed that it was feasible to degrade contaminants containing chlorine atoms by electrochemical reduction to form phenol, which was further degraded on the anode by electrochemical oxidation. Chlorophenol removal rate was more than 90% by the combined electrochemical reduction and oxidation at current of 6 mA and pH 6. The hydrogen atom is a powerful reducing agent that reductively dechlorinates chlorophenols. The instantaneous current efficiency was calculated and the results indicated that cathodic reduction was the main contributor to the degradation of chlorophenol.

[Utilizing fereducer reaction to enhance DC corona radical shower for benzene treatment].

Fereducer reaction is introduced to enhance DC corona radicals shower for removal of benzene in air. In the presence of nozzle electrode gas containing Fereducer reagent, the enhanced decomposing efficiencies were 21% and 4.2% for benzene concentration of 953 mg/m3 and 63 mg/m3, respectively. The enhancement of benzene removal was remarkable in the presence of nozzle electrode gas (O2, H2O) with the highest removal rate of 89.6%. Lower initial concentration of benzene has higher removal efficiency. However, higher absolute removal rate would be achieved when initial concentration of benzene was higher.

Degradation of chlorophenol by in-situ electrochemically generated oxidant.

A novel in-situ electrochemical oxidation method was applied to the degradation of wastewater containing chlorophenol. Under oxygen sparging, the strong oxidant, hydrogen dioxide, could be in-situ generated through the reduction of oxygen on the surface of the cathode. The removal rate of chlorophenol could be increased 149% when oxygen was induced in the electrochemical cell. The promotion factor was estimated to be about 82.63% according to the pseudo-first-order reaction rate constant (min(-1)). Important operating parameters such as current density, sparged oxygen rate investigated. Higher sparged oxygen rate could improve the degradation of chlorophenol. To make full use of oxygen, however, sparged oxygen rate of 0.05 m(3)/h was adopted in this work. Oxidation-reduction potential could remarkably affect the generation of hydrogen peroxide. It was found that the removal rate of chlorophenol was not in direct proportion to the applied current density. The optimum current density was 3.5 mA/cm(2) when initial chlorophenol concentration was 100 mg/L and sparged oxygen rate was 0.05 m(3)/h.