Duplex Interpenetrating-Phase FeNiZn and FeNi_(3)Heterostructure with Low-Gibbs Free Energy Interface Coupling for Highly Efficient Overall Water Splitting

The sluggish kinetics of both hydrogen evolution reaction(HER)and oxygen evolution reaction(OER)generate the large overpotential in water electrolysis and thus high-cost hydrogen production.Here,multidimensional nanoporous interpenetrating-phase FeNiZn alloy and FeNi_(3)intermetallic heterostructure is in situ constructed on NiFe foam(FeNiZn/FeNi_(3)@NiFe)by dealloying protocol.Coupling with the eminent synergism among specific constituents and the highly efficient mass transport from integrated porous backbone,FeNiZn/FeNi_(3)@NiFe depicts exceptional bifunctional activities for water splitting with extremely low overpotentials toward OER and HER(η_(1000)=367/245 mV)as well as the robust durability during the 400 h testing in alkaline solution.The as-built water electrolyzer with FeNiZn/FeNi_(3)@NiFe as both anode and cathode exhibits record-high performances for sustainable hydrogen output in terms of much lower cell voltage of 1.759 and 1.919 V to deliver the current density of 500 and 1000 mA cm^(-2)as well long working lives.Density functional theory calculations disclose that the interface interaction between FeNiZn alloy and FeNi_(3)intermetallic generates the modulated electron structure state and optimized intermediate chemisorption,thus diminishing the energy barriers for hydrogen production in water splitting.With the merits of fine performances,scalable fabrication,and low cost,FeNiZn/FeNi_(3)@NiFe holds prospective application potential as the bifunctional electrocatalyst for water splitting.

Vacancies and interfaces engineering of core-shell heterostuctured NiCoP/NiO as trifunctional electrocatalysts for overall water splitting and zinc-air batteries

The electronic structures and properties of electrocatalysts,which depend on the physicochemical structure and metallic element components,could significantly affect their electrocatalytic performance and their future applications in Zn-air battery(ZAB)and overall water splitting(OWS).Here,by combining vacancies and heterogeneous interfacial engineering,three-dimensional(3D)core-shell NiCoP/NiO heterostructures with dominated oxygen vacancies have been controllably in-situ grown on carbon cloth for using as highly efficient electrocatalysts toward hydrogen and oxygen electrochemical reactions.Theoretical calculation and electrochemical results manifest that the hybridization of NiCoP core with NiO shell produces a strong synergistic electronic coupling effect.The oxygen vacancy can enable the emergence of new electronic states within the band gap,crossing the Fermi levels of the two spin components and optimizing the local electronic structure.Besides,the hierarchical core-shell NiCoP/NiO nanoarrays also endow the catalysts with multiple exposed active sites,faster mass transfer behavior,optimized electronic strutures and improved electrochemical performance during ZAB and OWS applications.

Interface and M^(3+)/M^(2+)Valence Dual-Engineering on Nickel Cobalt Sulfoselenide/Black Phosphorus Heterostructure for Efficient Water Splitting Electrocatalysis

The catalyst innovation that aims at noble-metal-free substitutes is one key aspect for future sustainable hydrogen energy deployment.In this paper,a nickel cobalt sulfoselenide/black phosphorus heterostructure(NiCoSe|S/BP)was fabricated to realize the highly active and durable water electrolysis through interface and valence dual-engineering.The NiCoSe|S/BP nanostructure was constructed by in-situ growing NiCo hydroxide nanosheet arrays on few-layer BP and subsequently one-step sulfoselenization by SeS2.Besides the conductive merit of BP substrate,holes in p-type BP are capable of oxidizing the Co^(2+)to high-valence and electron-accepting Co^(3+),benefiting the oxygen evolution reaction(OER).Meanwhile,Ni^(3+)/Ni^(2+)ratio in the heterostructure is reduced to maintain the electrical neutrality,which corresponds to the increased electron-donating character for boosting hydrogen evolution reaction(HER).As for HER and OER,the heterostructured NiCoSe|S/BP electrocatalyst exhibits small overpotentials of 172 and 285 mV at 10 mA cm^(-2)(η_(10))in alkaline media,respectively.And overall water splitting has been achieved at a low cell potential of 1.67 V at η_(10) with high stability.Molecular sensing and density functional theory(DFT)calculations are further proposed for understanding the rate-determine steps and enhanced catalytic mechanism.The investigation presents a deep-seated perception for the electrocatalytic performance enhancement of BP-based heterostructure.

Heterostructured bimetallic phosphide nanowire arrays with latticetorsion interfaces for efficient overall water splitting

Designing cost-effective and high-efficiency electrocatalysts is critical to the water splitting performance during hydrogen generation.Herein,we have developed Fe_(2)P-Co_(2)P heterostructure nanowire arrays with excellent lattice torsions and grain boundaries for highly efficient water splitting.According to the microstructural investigations and theoretical calculations,the lattice torsion interface not only contributes to the exposure of more active sites but also effectively tunes the adsorption energy of hydrogen/oxygen intermediates via the accumulation of charge redistribution.As a result,the Fe_(2)P-Co_(2)P heterostructure nanowire array exhibits exceptional bifunctional catalytic activity with overpotentials of 65 and 198 mV at 10 mA cm^(-2) for hydrogen and oxygen evolution reactions,respectively.Moreover,the Fe_(2)P-Co_(2)P/NF-assembled electrolyzer can deliver 10 mA cm^(-2) at an ultralow voltage of1.51 V while resulting in a high solar-to-hydrogen conversion efficiency of 19.8%in the solar-driven water electrolysis cell.

Recent advances in elaborate interface regulation of BiVO_(4)photoanode for photoelectrochemical water splitting

Bismuth vanadate(BiVO_(4))is an excellent photoanode material for photoelectrochemical(PEC)water splitting system,possessing high theoretical photoelectrocatalytic conversion efficiency.However,the actual PEC activity and stability of BiVO_(4)are faced with great challenges due to factors such as severe charge recombination and slow water oxidation kinetics at the interface.Therefore,various interface regulation strategies have been adopted to optimize the BiVO_(4)photoanode.This review provides an in-depth analysis for the mechanism of interface regulation strategies from the perspective of factors affecting the PEC performance of BiVO_(4)photoanodes.These interface regulation strategies improve the PEC performance of BiVO_(4)photoanode by promoting charge separation and transfer,accelerating interfacial reaction kinetics,and enhancing stability.The research on the interface regulation strategies of BiVO_(4)photoanode is of great significance for promoting the development of PEC water splitting technology.At the same time,it also has inspiration for providing new ideas and methods for designing and preparing efficient and stable catalytic materials.

The diffusive fluxes of inorganic nitrogen across the intertidal sediment-water interface of the Changjiang Estuary in China

Ammonium and nitrate concentrations were analyzed in near-bottom water and pore water collected from ten stations of the intertidal flat of the Changjiang Estuary during April, July, November and February. The magnitudes of the benthic exchange fluxes were determined on the basis of concentration gradients of ammonium and nitrate at the near-bottom water and interstitial water interface in combination with calculations of a modified Fick＇ s first law. Ammonium fluxes varied from - 5.05 to 1.43 μg/（ cm^2·d） and were greatly regulated by the production of ammonium in surface sediments, while nitrate fluxes ranged from - 0. 38 to 1.36 μg/ （ cm^2·d） and were dominated by nitrate concentrations in the tidal water. It was found that ammonium was mainly released from sediments into water columns at most of stations whereas nitrate was mostly diffused from overlying waters to intertidal sediments. In total, 823.75 t/a ammonium-N was passed from intertidal sediments to water while about 521.90 t/a nitrate-N was removed from overlying waters to intertidal sediments. This suggests that intertidal sediments had the significant influence on modulating inorganic nitrogen in the tidal water.

The Effect of Bioturbation Activity of the Ark Clam Scapharca subcrenata on the Fluxes of Nutrient Exchange at the Sediment–Water Interface

Filter-feeding shellfish are common benthos and significantly affect the biogeochemical cycle in the shallow coastal ecosystems.Ark clam Scapharca subcrenata is one of the widely cultured bivalve species in many coastal areas owing to its tremendous economic value.However,there is little information regarding the effects of the bioturbation of S.subcrenata on the fluxes of nutrient exchange in the sediment-water interface(SWI).In this regard,S.subcrenata was sampled during October 2016 to determine the effects of its bioturbation activity on the nutrient exchange flux of the SWI.The results showed that the biological activity of S.subcrenata could increase the diffusion depth and the rate of the nutrients exchange in the sediments.The bioturbation of S.subcrenata could allow the nutrients to permeate into the surface sediments at 6-10cm and increase the release rate of nutrients at the SWI.The releasing fluxes of DIN and PO43−-P in the culture area were found to be around three times higher than that in the non-cultured region.The culture of S.subcrenata has been proved to be an important contributor to nutrient exchange across the SWI in the farming area of Haizhou Bay.Nutrients exchange in the SWI contributes a part of 86%DIN,71%PO43−-P and 18%SiO32−-Si for the aquaculture farm.

Impact of Rice-Catfish/Shrimp Co-culture on Nutrients Fluxes Across Sediment-Water Interface in Intensive Aquaculture Ponds

Exchange of nitrogen and phosphorus across sediment-water interface plays an important role in the management of nutrient recycling in the aquaculture pond. In this study, a plot experiment was conducted to study the effect of rice-catfish/shrimp co-culture on the micro-profile of oxygen (O2), pH and nutrient exchange across sediment-water interface in the intensive culture ponds. The results showed that rice-catfish co-culture increased the concentration and penetrating depth of O2, but decreased the pH value across the sediment-water interface, compared with catfish monoculture. Additional rice cultivation significantly reduced the flux rates of ammonium (NH4+) and nitrate (NO3-) across sediment-water interface in the catfish and shrimp ponds. The flux rates of NO2 - and soluble phosphorus (PO43-) showed no significant difference between rice-catfish/shrimp co-culture ponds and catfish/shrimp monoculture ponds. Rice only affected the dissolved inorganic nitrogen and phosphorus fractions in the sediment. The concentrations of NH4 + were significantly lower in the sediment of co-culture ponds than in the monoculture ponds. Additional rice cultivation also significantly reduced the content and percentage of dissolved inorganic phosphorus in the sediment of catfish ponds.

Experimental research on the impact of Corbicula flumineaon DIN exchange at a tidal flat sediment-water interface

Based on a simulative experiment and a comparison analysis, the effect of bivalve Corbicula fluminea activity on sediment-water exchange of dissolved inorganic nitrogen (DIN) is studied. The areas included three intertidal flat sites of the Changjiang (Yangtze) River estuary in China. The interface exchange flux of ammonium, nitrate and nitrite in the short experiment (6 h) was 46.4-40, 74.8-929.1 and 2.5-14.6 μmol/(m2·h), respectively. It was found that the burrowing activities of C. fluminea increased NH 4+ and NO 3-release from sediments to overlying water in the short-term experiment. During long-term incubation, NH +4 and NO 3-released in turn from the sediments. At the beginning of incubation, bioturbation by C. fluminea could accelerate NH +4 release from sediments 2-17 times in different sites, resulting in stronger nitrification and increased NO 3-concentrations in the overlying water. Sediment profile analysis post-incubation shows that organic matter mineralization and sediment-water NH +4 exchange had been stimulated by C. fluminea bioturbation and bioirrigation during the experiment. Therefore, C. fluminea activities such as excretion, burrowing, irrigation and turbation can effectively alter nitrogen dynamics and accelerate and stimulate nitrogen exchange and cycling at the sediment-water interface.

Influential factors on the exchange rate of dissolved inorganic nutrients at the sediment-water interface in Jiaozhou Bay, China

Incubation experiments are carried out to study the exchange rates of dissolved inorganic nutrients including silicate, phosphate, ammonium, nitrite, and nitrate (vSiO3-Si, vPO4-P, vNH4-N, vNO2-N and vNO3-N) at the sediment-water interface in the Jiaozhou Bay. Major factors influencing the exchange rates are discussed in detail, which include the dissolved inorganic nutrient concentrations in porewater (Cpw), water and clay contents, and grain size of the sediments (CH2O, Cclay and GSsed). The results may provide insight into the dynamics of nutrient transport and the environmental capacity of nutrients in Jiaozhou Bay, and should be beneficial to solving the problems caused by excessive nutrient input this area.

Nitrogen and Phosphorus Diffusive Fluxes Across the Sediment-Water Interface in Estuarine and Coastal Tidal Flats

Nitrogen and phosphorus contents are analyzed in the overlying waters and pore waters taken from the Changjiang Estuary and Shanghai coastal tidal flats in this study. In addition, the diffusion fluxes of nitrogen and phosphorus across the sediment-water interface in tidal flats are estimated according to the nutrient concentration gradients at the interface. It has been indicated that the concentrations of ammonium, nitrite, nitrate and dissolved phosphorus in overlying waters range from 0.0082～2.56, 0.03～0.58, 0.69～5.38 and 0.035～0.53 mg/L, respectively, while 0.0025 ～ 1.35 mg/L for NH4+-N, 0. 0055 ～ 0.20mg/L for NO2--N, 0.61～1.14 mg/L for NO3--N and 0.11～0.53mg/L for DP insurface pore waters.The findings have revealed that ammonium, nitrite, nitrate and dissolved phosphorus diffusion fluxes across the sediment-water interface are between -0.024～0.99, -0.39～ -0.0019, -3.09～the source of phosphorus and an important sink for nitrogen in the waters.

Nutrient exchange and release experiment and its simulation study in lake water-sediment interface

The sediment distributed and insolated under lake was collected for experiments. The nutrient layer distribution conditions of sampled sediment and its physical and chemical characteristics were analyzed to simulate and assess the influence degree to lake water quality. Based on the dynamic water exchanging experiments the nutrient release process in sediment and influence mechanism to substance exchanging on water-sediment interface was studied, and the correlation between the changing content of total phosphors and total nitrogen in sediment and covered water were analyzed for setting up a simulation model. At the same time the influence degree is explained in detail. The experimental results indicated that even if clean water without nutrient contents was used for water exchangement so as to decrease pollution or prevent eutrophication, however owing to the vertical nutrient distribution in lake sediment, it will lead to the increasing release amount greatly especially when the organic nutrient contained in sediment turns into inorganic status because of isolation. Besides the release process of total phosphate （TP） and total nitrogen （TN） were modeled and each nutrient＇s exchanging equation at interface caused by covered water nutrient concentration changing was set up. According to the simulating prediction, TP and TN content of cover water will also sustain a steady higher level in a long period. The nutrient release amount of sediment is not only affected by the covered water concentration but also connects with accumulative time. The experiments provide the fundamental theoretical and practical basis for taking ecological restoration project. And research is helpful to prevent or restore lake eutrophication.

Nutrient profiles in interstitial water and flux in water-sediment interface of the Zhujiang Estuary of China in summer

The profiles of nutrient salts in the interstitial water of sediment were analyzed in the Zhu- jiang Estuary in the summer of 1999, and based on the profiles of content and characteristic of nutri- ents, the relationship between nutrients in the interstitial water and organic matter decomposition in sediment was discussed. The results showed that ammonium with high content was the main existence form of nutrients in the interstital water of sediment, and the organic matter decomposition was com- pleted in anaerobic condition. The increase of ammonium content in the bottom water resulted from the decomposition of organic matter and release of metabolic production, and the ammonium bottom flux was an important resource for nutrients geochemistry in the Zhujiang Estuary.

The Influence of Element Diffusion at the Sediment-Water Interface on the Basic Chemical Composition of Overlying Water Mass in Lake Lugu, China

Little work has been done on the influence of sediments on the basic chemical composition of overlying water mass. This paper deals with the vertical profile of the basic constituents such as Ca2 +, K +, Na+, and HCO3, as well as of pH in the overlying water mass and sediment porewater of Lake Lugu-a semi-closed, deep lake in Yunnan Province. The results revealed that those basic constituents may diffuse and transport from bottom sediments to overlying water mass through porewater. In the paper are also quantitatively evaluated the diffusive fluxes and the extent of their influence on overlying water mass, indicating that the lake sediment-water interface diffusion plays an important role in controling the basic chemical composition of water in the whole lake.

REE distribution in water-sediment interface system at deep ocean floor

REE concentrations and distribution patterns in the different phases of water-sediment interface system at deep ocean floor were studied on the basis of samples of bottom water, sediments, interstitial water and polymetallic nodules collected from the East Pacific Basin by R/V Haiyang 4 during HY4-871 and HY4-881Cruises. It is suggested that REE concentrations in oxic interstitial water are lower than that in bottom weter,REE contents of polymetallic nodules, except Ce, are similar to that of sediments. Bottom water, sediments and interstitial water are almost the same in REE distribution patterns. MREE enrichment relative to LREE and HREE and negative Ce anomalies, MREE earichment has been found in polymetallic nodules,and Ce shows positive anomalies. REE contents in sediments increase with depth, and the vacations of distribution patterns with depth have not been found.

Impact of Forestry Interventions on Groundwater Recharge and Sediment Control in the Ganga River Basin

Water related services of natural infrastructure will help to combat the risk of water crisis, and nature-based solutions involve the management of ecosystems to mimic or optimize the natural processes for the provision and regulation of water. Forested areas provide environmental stability and supply a high proportion of the world’s accessible freshwater for domestic, agricultural, industrial and ecological needs. The present work on “Forestry Interventions for Ganga” to rejuvenate the river is one of the steps toward the Ganga River rejuvenation programme in the country. The consequences of forestry interventions for Ganga will be determined on the basis of water quantity and water quality in the Ganga River. The study conservatively estimated the water savings and sedimentation reduction of the riverscape management in the Ganga basin using the Soil Conservation Service Curve Number (SCS-CN) & GEC, 2015 and Trimble, 1999 & CWC, 2019 methodologies, respectively. Forestry plantations and soil and moisture conservation measures devised in the programme to rejuvenate the Ganga River are expected to increase water recharge and decrease sedimentation load by 231.011 MCM·yr-1 and 1119.6 cubic m·yr-1 or 395.20 tons·yr-1, respectively, in delineated riverscape area of 83,946 km2 in Ganga basin due to these interventions. The role of trees and forests in improving hydrologic cycles, soil infiltration and ground water recharge in Ganga basin seems to be the reason for this change. Forest plantations and other bioengineering techniques can help to keep rivers perennial, increase precipitation, prevent soil erosion and mitigate floods, drought & climate change. The bioengineering techniques could be a feasible tool to enhance rivers’ self-purification as well as to make river perennial. The results will give momentum to the National Mission of Clean Ganga (NMCG) and its Namami Gange programme including other important rivers in the country and provide inputs in understanding the linkages among forest structure, function, and streamflow.

Photophysics and electrochemistry relevant to photocatalytic water splitting involved at solid–electrolyte interfaces

Direct photon to chemical energy conversion using semiconductor–electrocatalyst–electrolyte interfaces has been extensively investigated for more than a half century. Many studies have focused on screening materials for efficient photocatalysis. Photocatalytic efficiency has been improved during this period but is not sufficient for industrial commercialization. Detailed elucidation on the photocatalytic water splitting process leads to consecutive six reaction steps with the fundamental parameters involved: The photocatalysis is initiated involving photophysics derived from various semiconductor properties(1: photon absorption, 2: exciton separation). The generated charge carriers need to be transferred to surfaces effectively utilizing the interfaces(3: carrier diffusion, 4: carrier transport). Consequently, electrocatalysis finishes the process by producing products on the surface(5: catalytic efficiency, 6: mass transfer of reactants and products). Successful photocatalytic water splitting requires the enhancement of efficiency at each stage. Most critically, a fundamental understanding of the interfacial phenomena is highly desired for establishing 'photocatalysis by design' concepts, where the kinetic bottleneck within a process is identified by further improving the specific properties of photocatalytic materials as opposed to blind material screening. Theoretical modeling using the identified quantitative parameters can effectively predict the theoretically attainable photon-conversion yields. This article provides an overview of the state-of-the-art theoretical understanding of interfacial problems mainly developed in our laboratory.Photocatalytic water splitting(especially hydrogen evolution on metal surfaces) was selected as a topic,and the photophysical and electrochemical processes that occur at semiconductor–metal, semiconductor–electrolyte and metal–electrolyte interfaces are discussed.

Interface Engineering of NixSy@MnOxHy Nanorods to Efficiently Enhance Overall-Water-Splitting Activity and Stability

Exploring highly active and stable transition metal-based bifunctional electrocatalysts has recently attracted extensive research interests for achieving high inherent activity, abundant exposed active sites, rapid mass transfer, and strong structure stability for overall water splitting. Herein, an interface engineering coupled with shell-protection strategy was applied to construct three-dimensional(3D) core-shell NixSy@MnOxHy heterostructure nanorods grown on nickel foam(NixSy@MnOxHy/NF) as a bifunctional electrocatalyst. NixSy@MnOxHy/NF was synthesized via a facile hydrothermal reaction followed by an electrodeposition process. The X-ray absorption fine structure spectra reveal that abundant Mn-S bonds connect the heterostructure interfaces of N ixSy@MnOxHy, leading to a strong electronic interaction, which improves the intrinsic activities of hydrogen evolution reaction and oxygen evolution reaction(OER). Besides, as an efficient protective shell, the MnOxHy dramatically inhibits the electrochemical corrosion of the electrocatalyst at high current densities, which remarkably enhances the stability at high potentials. Furthermore, the 3D nanorod structure not only exposes enriched active sites, but also accelerates the electrolyte diffusion and bubble desorption. Therefore, NixSy@MnOxHy/NF exhibits exceptional bifunctional activity and stability for overall water splitting, with low overpotentials of 326 and 356 mV for OER at 100 and 500 mA cm^(–2), respectively, along with high stability of 150 h at 100 mA cm^(–2). Furthermore, for overall water splitting, it presents a low cell voltage of 1.529 V at 10 mA cm^(–2), accompanied by excellent stability at 100 mA cm^(–2) for 100 h. This work sheds a light on exploring highly active and stable bifunctional electrocatalysts by the interface engineering coupled with shell-protection strategy.

Interface-strengthened CoP nanosheet array with Co2P nanoparticles as efficient electrocatalysts for overall water splitting

Highly active and durable bifunctional electrocatalysts for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) play a pivotal role in overall water splitting. Herein, we demonstrate the construction of interface-strengthened CoP nanosheet array with Co2P nanoparticles as such an electrocatalyst through a facile hydrothermal reaction and the subsequent phosphorization process. The twodimensional (2D) nanosheets with thickness of^55 nm expose a great number of active sites. The surface chemical state indicates that the strongly coupled CoP/Co2P electrocatalysts can adsorb or generate more targeted intermediates (e.g. OH- or OOH*) for both HER/OER. As a result, the CoP/Co2P electrocatalysts exhibit small overpotentials of 68 and 256 mV to drive 10 mA cm^-2 for HER and OER, respectively, outperforming most of the recently reported Co-based electrocatalysts. Furthermore, an alkaline electrolyzer assembled by using CoP/Co2P as both cathode and anode can achieve a current density of 10 mA cm^-2 at a low voltage of 1.57 V and work continuously for over 58 h. This work provides a feasible structural design for transition metal phosphides electrocatalysts with efficient and stable overall water splitting.