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To accelerate the kinetics of oxygen evolution reaction (OER) on H2O oxidation regarding the energy conversion and storage approaches, the discovery and design of desirable cost-effective and highly efficient electrocatalysts is of prime importance. This study demonstrates a novel layered perovskite via Co-doping strategy, i.e. LaSr3Co1.5Fe1.5O10-δ, which possesses significantly higher electrocatalytic activity, considerably lower overpotential and Tafel slope, remarkably higher mass activity (MA) and specific activity (SA) together with a better long-term stability than the undoped parent perovskite, the state-of-the-art IrO2 and the most active Ba0.5Sr0.5Co0.8Fe0.2O3-δ (BSCF) under harsh OER cycling conditions in alkaline solution. These merits mainly originate from the presence of partial oxidation of surface Co3+ to Co4+ in LaSr3Co1.5Fe1.5O10-δ, an appropriate possible structure-dependent position of O p-band centre to the Fermi level and an increased amount of highly oxidative oxygen species O22-/O- in conjunction with a strong OH- adsorption and O2 desorption abilities. These findings not only improve the electrocatalytic activities of the layered perovskite family via optimal doping but also highlight the potential application of LaSr3Co1.5Fe1.5O10-δ as an earth-abundant, cost-effective, highly active and durable electrocatalyst for OER in energy conversion and storage technologies.

A hash service environment containing H2S and CO2 in oil industry usually causes corrosion of carbon steel. In this study, the chromized coatings with different deposited time were prepared on the surface of carbon steel by the method of pack cementation to enhance its corrosion resistance. Then the microstructure, hardness, corrosion resistance as well as the semiconductor behavior of coatings in the simulated solution with saturated H2S and CO2 were investigated. The results show that the content of Cr in coating was increased by prolonging deposited time, and both chromium carbides and chromium nitrides were formed. Furthermore, coatings display higher polarization resistance, Rp, than that of the substrate, indicating a higher resistance to charge transfer on coating surface. The corrosion rates of coatings with different deposited time were significantly lower than that of substrate. Chemical analysis showed the formation of heavy sulfides on the surface of substrates after corrosion, while the least corrosion products were detected on the surface of coating with deposited time of 12 h. Mott-Schottky results indicated that coating of 12 h displayed less defects than the other two coatings with deposited time of 4 h and 8 h, which will be beneficial to improve corrosion resistance. The investigation showed that chromized coatings exhibited high corrosion resistance and owned a potential application in oil industry for corrosion prevention.

Corrosion behavior of alloy 316L stainless steel capsule was studied by exposure to the supercritical water (SCW) at 500 °C and 25 MPa for 20,000 h. The microstructural observations have been conducted on the cross section of the exposed surfaces to the SCW to perceive the internal oxidation of the grains and/or grain boundaries. Transmission electron microscopy (TEM) observations as well as elemental analyses such as energy dispersive spectroscopy (EDS) and Electron energy loss spectroscopy (EELS) were used to study the internal oxidation and micro-crack initiation on the surface. Elemental analyses indicated that long-term exposure to the SCW resulted in formation of scales identified as Fe 3 O 4 (outer layer), Fe-Cr spinel/(Fe,Ni)Cr 2 O 4 /(Mn,Cr) 2 O 3 /SiO 2 (inner layer) on the substrate, and Ni-enrichment (chrome depleted region) in the alloy 316L. Micro-crack initiation was observed ahead of the oxidized grain boundaries in which elemental enrichments happened ahead of the crack tip. The relevance of the observed oxidation phenomena on the crack susceptibility of Alloy 316L was discussed. Finally, prolonging the exposure time up to 20,000 h has shown that the alloy 316L might be susceptible to micro-crack initiation in the supercritical water.

Sunlight-driven hydrogen production from water splitting, assisted with the commonly used Pt/TiO 2 catalyst, is a promising way to store clean and renewable energy. However, the photocatalytic activity of Pt/TiO 2 is limited owing to the agglomeration of Pt atoms. Herein, we successfully synthesized a Pt/TiO 2 catalyst, where Pt is atomically and selectively dispersed on the (1 0 1) facets of nanosized TiO 2 single crystals. A remarkably higher photocatalytic activity for H 2 evolution together with a considerable stability was observed as compared to commonly used Pt/TiO 2 . This study demonstrates a promising way to achieve atomically dispersed highly-active catalyst for water splitting.

Oxygen electrocatalysis is at the heart of the emerging energy conversion and storage devices including reversible fuel cells and metal-air batteries. However, replacing the noble-metal-based oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) catalysts with affordable and robust alternatives remains challenging to date. Herein, we report a cation-ordered double perovskite oxide, i.e., PrBa0.85Ca0.15MnFeO5+δ, with excellent stability and activity in both OER and ORR. The layered crystal structure provides ordered oxygen vacancy channels and a vast amount of surface oxygen defects, while the moderate amount of iron dopant keeps the B-site cations at high oxidation state with optimal eg fillings. Importantly, the DFT calculations along with the advanced TEM analysis verify that the incorporation of Ca at the A-site stabilizes the perovskite structure under potential bias. Such a bifunctional catalyst shows comparable, if not better, activity relative to the state-of-the-art perovskite oxides (e.g., Ba0.5Sr0.5Co0.8Fe0.2O3−δ) while demonstrating remarkably enhanced robustness. This work presents a rational approach of designing efficient, robust, and cost-effective perovskite oxide for oxygen electrocatalysis and sheds light on the influences of the crystallographic structure on the catalytic property.

For perovskites to become more competitive oxygen reduction reaction (ORR) catalysts, substantial progress is required to advance their enhanced catalytic activity and durability. Herein, a novel method is described to achieve high-performance perovskite ORR catalyst via combining nano architecture designs, internal structures engineering, and Ag nanoparticles (NPs) in situ exsolution. The as-synthesized Ag-(PrBa)0.95Mn2O5+δ catalyst exhibits favorable ORR activity with durability superior to the state-of-the-art Pt/C in alkaline solution. Several characterization techniques were applied alongside density functional theory calculations to understand the possible active sites and the synergistic coupling effects that contributed to the high ORR performance. The strong interfacial anchoring of Ag NPs on the ordered oxygen deficient perovskites leads to significant ligand effect and facilitates electron transfer and ion migration within the oxygen reduction reaction. The systematic engineering of perovskites described here represents a brand new approach to developing highly active and stable catalyst for energy conversion and storage.

Au/CeO2 hollow nanospheres were successfully synthesized by template method. Carbon spheres (CSs) were employed as the sacrificial templates, which were fabricated by hydrothermal method, and the shell of CeO2 precursor was formed on the surface of CSs through layer-by-layer self-assembled approach. Then, Au nanoparticles were deposited on the shell. Finally, the templates were removed by calcination and Au/CeO2 hollow spheres with hierarchically porous structure were obtained. The samples were characterized by XRD, SEM, TEM, TG-DSC, and BET analysis. The diameters and thickness of the nanospheres were about 250 nm and 20 nm, respectively. Samples with different loading amounts of Au were prepared and noted as L-Au/CeO2, M-Au/CeO2, and H-Au/CeO2, corresponding to the Au weight percentages of 1.8%, 4.2%, and 9.3%. The specific surface area of L-Au/CeO2 could reach 87.1 m2/g, higher than that of M-Au/CeO2 (77.8 m2/g), while M-Au/CeO2 showed the best catalytic activity that CO could be completely converted to CO2 at 81°C. The CeO2, L-Au/CeO2, and M-Au/CeO2 hollow nanospheres showed excellent catalytic stability. Moreover, this method can be easily extended to the synthesis of other metal oxide hollow nanospheres compounded with Au nanoparticles.

A series of Heusler phases Ni47Mn40Sn13−xCux (x = 0, 0.5, 1, 1.25), which are magnetic shape-memory alloys, has been synthesized by mechanical alloying (MA) and characterized. The martensite-austenite phase transition was investigated by X-ray diffraction, differential scanning calorimetry, and DC magnetization measurements. With greater Cu content, the martensitic transition temperature TM increases while the magnetic transition temperature of austenite T c A remains almost unchanged. The maximum inverse magnetic entropy changes Δ S M for the x = 0.5 and x = 1 samples are nearly twice as high as for the undoped sample. Furthermore, the martensitic transformation of the doped samples occurs around room temperature, which is important for applications. Effective refrigerant capacities (RCeff) reduced due to the higher hysteresis losses in the x = 0.5 and x = 1 samples compare to the undoped one. Refrigerant capacities (RC) were examined in T c A . The largest value of RC = 207 J/kg was measured for the undoped sample. Critical properties near the ferromagnetic–paramagnetic (FM–PM) phase transition were analyzed in detailed. The critical parameters β, γ, δ and T c A of the x = 0 and x = 0.5 samples, which were determined through use of modified Arrott plots, the Kouvel-Fisher method, and the Widom scaling relation, differed from the mean-field values. The critical behavior indicates that long-range ferromagnetic order dominates in these Cu-doped samples.

The effect of boiling bubbles on the passivation degradation of Alloy 800 in thiosulphate-containing aqueous electrolyte was experimentally investigated using corrosion potential, anodic polarization, combined with Secondary Ion Mass Spectrometry (SIMS) and X-ray Photoelectron Spectroscopy (XPS). The results showed that the boiling bubbles decreased the pitting potential by enhancing the mass transport. The specimen immersed in boiling electrolyte have a thicker anodic film and a greater amount of sulfur incorporation into the passive layer compared with the experiments at 99 °C. Moreover, a higher ratio of low valance sulfur species was detected on the specimen in boiling test electrolyte, indicating that the boiling bubbles reduced the corrosion resistance of Alloy 800.

In this work, the passivation degradation of Alloy 800 on nucleate boiling surface was studied by using polarisation curve, electrochemical impedance spectroscopy and secondary ion mass spectrometry. Experimental results indicated that boiling bubble would significantly degrade the passive film, as indicated by a decreased pitting potential and increased passive current density. Under boiling condition, the mass transfer of electrolyte is accelerated and the temperature of Alloy 800 was increased, as a result, the cathodic reaction and the dissolution rate of the passive film were increased. The passive film was Cr-depleted but Ni- and Fe-enriched, and the decreased Cr content in the passive film led to a degraded passive film.

The ideal solid oxide fuel cells (SOFCs) can be powered by readily available hydrocarbon fuels containing impurities. While this is commonly recognized as a key advantage of SOFC, it also, together with the elevated operating temperature, becomes the main barrier impeding the in-situ or operando investigations of the anode surface chemistry. Here, using a well-designed quenching experiment, we managed to characterize the near-surface structure of La0.4Sr0.6TiO3+δ (LST) anode in SOFCs fuelled by H2S-containing methane. This new method enabled us to clearly observe the surface amorphization and sulfidation of LST under simulated SOFC operating conditions. The ∼1 nm-thick two dimensional sulfur-adsorbed layer was on top of the disordered LST, containing –S, –SH and elemental sulfur species. In SOFC test, such “poisoned” anode showed increased performances: a ten-fold enhanced power density enhancement (up to 30 mW cm−2) and an improved open circuit voltage (from 0.69 V to 1.17 V). Moreover, its anodic polarization resistance in methane decreased to 21.53 Ω cm2, a difference of 95% compared with the sulfur-free anode. Control experiments confirmed that once the adsorbed sulfur species were removed electrochemically, methane conversion slowed down simultaneously till full stop.

Electrochemical reduction of CO2 (CO2RR) provides great potential for intermittent renewable energy storage. This study demonstrates a predominant shape-dependent electrocatalytic reduction of CO2 to CO on triangular silver nanoplates (Tri-Ag-NPs) in 0.1 M KHCO3. Compared with similarly sized Ag nanoparticles (SS-Ag-NPs) and bulk Ag, Tri-Ag-NPs exhibited an enhanced current density and significantly improved Faradaic efficiency (96.8%) and energy efficiency (61.7%), together with a considerable durability (7 days). Additionally, CO starts to be observed at an ultralow overpotential of 96 mV, further confirming the superiority of Tri-Ag-NPs as a catalyst for CO2RR toward CO formation. Density functional theory calculations reveal that the significantly enhanced electrocatalytic activity and selectivity at lowered overpotential originate from the shape-controlled structure. This not only provides the optimum edge-to-corner ratio but also dominates at the facet of Ag(100) where it requires lower energy to in...

A proton conducting anode supported tubular fuel cell is fabricated in this research using the highly proton conductive BaZr 0.1 Ce 0.7 Y 0.1 Yb 0.1 O 3-δ (BZCYYb) electrolyte. The cell is in a Ni-BZCYYb/BZCYYb/LSCF-BZCYYb configuration consisting of a support, electrolyte and cathode with thicknesses of 680 μm, 25 μm and 90 μm, respectively. The cell delivers maximum power densities of 331, 362 and 416 mW/cm 2 at 600, 650 and 700 °C, respectively. AC impedance spectroscopy results show values of 0.94 Ω.cm 2 , 0.73 Ω.cm 2 , and 0.60 Ω.cm 2 for total resistance at the corresponding temperatures while the major resistance contributor is the ohmic resistance. The Ni-BZCYYb anode microstructure shows detachment of Ni and the BZCYYb in most regions as well as pores inside the Ni grains. Despite the low anode porosity (25%), the cell gives a very low concentration polarization value (0.05 Ω.cm 2 ) indicating that the fuel gas could readily diffuse into the microstructure. This might be attributed to water forming on the cathode side, which masks the necessity of having a high porosity anode. The cell fails when tested under CO:H 2 of 1:1 at 700 °C due to significant carbon (graphite) formation indicating that proton conductors based on barium cerates are not appropriate choices for application under hydrocarbon fuels.

We study oxidation and crack susceptibility of alloy 310S stainless steel upon exposure to supercritical water (SCW) at 500 °C and 25 MPa for 20000 h. Electron microscopy observations and elemental analyses are conducted on the static capsule sample to investigate morphological features of the oxidation, micro-crack initiation as well as chemical composition along the micro-crack surface oxides and corrosion products around the micro-crack tip area. The elemental and phase analyses indicate that long term exposure to the SCW resulted in the formation of scales identified as Fe3O4 (magnetite, outer layer), Fe-Cr spinel (FeCr2O4, inner layer), [Mn,Cr]2O3 + SiO2 (Cr-rich spinel and silicon dioxide, transition layer) on the substrate, and Ni-enrichment (chrome depleted region) in the alloy 310S. The presence of carbides along with chromium depletion region most probably result in grain boundary embrittlement around the micro-crack tip. Additionally, crack region is filled Cr-rich oxide, SiO2 and lower amount of carbides. We believe that the intergranular crack initiation occurred through grain boundary oxidation, leading to stress concentration. The oxidation mechanism and scales grown on the alloy 310S stainless steel exposed to SCW and micro-crack initiation as the results of long term exposure at high temperature SCW are discussed.

This study concentrated on the investigation of oxide scale grown on alloys 304 and 304-oxide dispersion strengthened steel in supercritical water (650 °C/25 MPa) environment. The corrosion rate was evaluated by measuring the weight change of the samples and by cross-section examinations. Results showed that weight gains vs. supercritical exposure time follows a parabolic law for alloy 304-ODS contrary to alloy 304 which possibly follows a cubic rate law. The general weight gain after 550 h exposure to the SCW was 131.8 and 621.6 mg/dm2 for alloys 304-ODS and 304, respectively. Electron microscopy observations and elemental analyses as well as X-ray diffraction and time-of-flight secondary ion mass spectrometry results revealed that the oxide scales formed on 304-ODS alloy composed of three distinct layers including Fe3O4 (outer layer), FeCr2O4/(Fe,Cr)2O3 spinel structures (inner layer) and Cr2O3 (transition layer). However, alloy 304 had two layers including Fe3O4 (outer layer) and Fe-Cr spinel structures (inner layer). It is believed that the formation of Cr2O3 layer at the diffusion layer/metal interface becomes the rate-limiting step for oxide advancement, since this change in oxide structure also corresponds to a decrease in corrosion rate in the alloy 304-ODS compared to alloy 304. Based on the results and observations, the oxidation mechanisms are discussed.

To effectively reduce and utilize the atmospheric CO2, electrochemical conversion of CO2 into CO using an efficient and stable cathode in a high temperature solid oxide electrolyzer has attracted extensive interest. A composite cathode based on lanthanum nickelate potentially opens up the possibility for CO2 electrolysis. Herein, we developed a new Ni-doped La(Sr)FeO3−δ material, which has been firstly fabricated as a cathode for CO2 electrolysis in a solid oxide electrolysis cell (SOEC). The ultra-low total polarization resistance, together with an impressive current density of 1.21 A cm−2 at a potential of 1.55 V and 850 °C, demonstrates the superior electrocatalytic activity of La0.6Sr0.4Fe0.8Ni0.2O3−δ (LSFN) for stably and effectively promoting the cathodic kinetics for the CO2 electrolytic reaction. Moreover, an ultra-high Faraday efficiency of ∼99.7% was achieved at an applied potential of 1.0 V (vs. OCV) and 850 °C. The comparable cell performance for CO2 electrolysis benefits from the extension of the reactive sites due to the improved mixed ionic and electronic conductivity and accelerated adsorption and diffusion of the adsorbed active species, resulted from the high oxygen vacancy introduced on the LSFN backbone surface. Besides the comparable electrochemical performance, the excellent redox reversibility between the reduction and re-oxidation as well as considerable coking tolerance towards CO-enriched gas reveals that this newly prepared La(Sr)Fe(Ni) is a potential cathode material for SOEC, particularly for a direct carbon-abundant cell.

Biogas, consisting of CH4, CO2 and a small amount of H2S, is one of the most promising alternative energy sources. Solid oxide fuel cells (SOFCs) are ideal technologies to efficiently utilize biogas for producing electricity and heat. However, this is precluded because the conventional Ni-Y2O3 stabilized ZrO2 (Ni-YSZ) anode for SOFC is inclined to cause carbon formation as well as to form inert and non-conductive S-containing species in biogas. To directly utilize the biogas in SOFC, a hybrid anode material, combining the slightly compromised merits of the conventional Ni-YSZ cermet and the alternative anode, i.e., PrBaMn2O5+δ perovskite oxide, is developed in this study. The PrBaMn2O5+δ dramatically resists the carbon formation and S adsorption on Ni surface and at the same time, it serves as the CO2-captor, oxygen source and the medium for O2− diffusion to accelerate both the carbon removal and S desorption processes. At 800 °C, the peak power density of the cell with the hybrid anode attains 1.35 W cm−2 in biogas, and no significant degradation is observed during the stability test. The hybrid anode, therefore, displays excellent activity, superior coke/sulfur resistance and stability in biogas, offering a promising technology for biogas utilization.

Surface mechanical attrition treatments (SMATs) were used to prepare nanostructured surface layers on alloys used in nuclear power plant steam generators (SGs). The effects of surface nanocrystallization on alloy corrosion behavior at room temperature and at 300 °C in a simulated SG environment were studied. At room temperature, the polarization curves indicated that with increasing SMAT duration, the corrosion potential of the samples shifted negatively from smaller to larger values, and alloy active dissolution rate and passive current density both increased. Nitriding treatment was used to improve the corrosion resistance. Compared with corrosion behavior observed at room temperature, corrosion resistance in the simulated SG condition was highly enhanced because the nano-sized-grain layer formed via SMAT provided a higher density of nucleation sites for the formation of a passive film and diffusion paths for Cr, leading to the rapid formation of a dense protective oxide layer.

This study presents an investigation of the on-site corrosion of carbon steel pipes with stainless steel mesh screens in a steam flood well in the Athabasca oil sand reservoirs to determine the failure patterns and mechanisms. To mitigate the corrosion of carbon steel, several candidate materials were selected, and their corrosion resistance was investigated. In this work, the corrosion behavior and film characteristics of carbon steel pipes were studied by surface analysis techniques such as scanning electron microscopy, energy dispersive spetrocsopy and X-ray diffraction. Corrosion resistant alloys (proRSf and proRSc), anti-corrosion coating (proRA05a) and pre-treated steel (proRAQa) were considered as alternative materials to carbon steel (proRAa and proRAb) and their corrosion protection performance in brine solution was evaluated by electrochemical methods such as potentiodynamic sweep and electrochemical impedance spectroscopy. Results show that severe erosion-corrosion occurred on inner wall of the pipes and caused significant wall-thinning of pipes along with localized corrosion damages, which is the dominant reason for base pipe failure. In spite of the slight corrosion on outer wall of the base pipe, severe localized corrosion appeared at the interface between the carbon steel pipe and stainless steel mesh screens due to the galvanic corrosion effect of dissimilar metals. The corrosion rates of the corrosion-resistant materials were two or three orders of magnitude lower than that of carbon steel. The corrosion resistance ranking order is proRSc > proRSf > proRA05a > proRAQa > proRAa > proRAb. This study improves the material selection procedure in thermal operations by investigating several alternatives to carbon steel. It also provides a testing procedure to assess the corrosion resistance of the material in thermal applications.

Formic acid (or formate) is a liquid fuel and chemical feedstock, and it is considered as one of the most useful value-added reductive products from electrochemical CO2 conversion. Green metallic Bi nanosheets are believed be a promising candidate for formic acid production in CO2 electroreduction. However, the complexity of their preparation with a low yield hinders their practical application on a large scale. Herein, we report that by using a cheap and commonly used industrial ingot, phase-pure two-dimensional bismuth nanosheets are fabricated on a large scale by a rapid electrochemical cathodic exfoliation method. In addition to featuring abundant active sites, the obtained Bi nanosheets possess exceptionally high adsorption capacity to CO2 compared to its bulk counterpart, resulting in remarkable enhancement in CO2 electroreduction with high selectivity toward formic acid over a wide range of negative potentials, high current density and satisfactory durability. This facile strategy opens a promising avenue for massive fabrication of metallic Bi nanosheets with excellent electrocatalytic performance for large-scale commercial utilization of CO2.

Electrolytic overall water splitting is a promising approach to produce H2 , but its efficiency is severely limited by the sluggish kinetics of the oxygen evolution reaction (OER) and the low activity of current electrocatalysts. To solve these problems, in addition to the development of efficient precious-metal catalysts, an effective strategy is proposed to replace the OER by the selective methanol oxidation reaction. Ni-Co hydroxide [Nix Co1-x (OH)2 ] nanoarrays were obtained through a facile hydrothermal treatment as the bifunctional electrocatalysts for the co-electrolysis of methanol/water to produce H2 and value-added formate simultaneously. The electrocatalyst could catalyze selective methanol oxidation (≈1.32 V) with a significantly lower energy consumption (≈0.2 V less) than OER. Importantly, methanol was transformed exclusively to value-added formate with a high Faradaic efficiency (selectivity) close to 100 %. Specifically, a cell voltage of only approximately 1.5 V was required to generate a current density of 10 mA cm-2 . Furthermore, the Ni0.33 Co0.67 (OH)2 /Ni foam nanoneedle arrays presented an outstanding stability for overall co-electrolysis.

Most metals naturally corrode in an engineering environment and form corrosion products. The corrosion products can be either soluble or insoluble in the aqueous solution. The insoluble corrosion products (ICP) could have profound effects on the corrosion kinetics of the concerned metal. In this study, a multi-phase-field formulation is proposed to investigate the effects of ICP formation on pitting corrosion kinetics. The Gibbs free energy of the metal-electrolyte-insoluble corrosion product system consists of chemical, gradient, and electromigration free energy. The model is validated with experimental results and several representative cases are presented, including the effect of the porosity of ICP, under-deposit corrosion, corrosion of sensitized alloys, and microstructure-dependent pitting corrosion. It is observed that corrosion rate and pit morphology significantly depend on ICP and its porosity for the same applied potential.

Mesoporous bismuth nanosheets are prepared through electrochemical transformation of (100)-facet exposed BiOI. Theoretical modeling and calculations are used to simulate the in situ morphological transformation of BiOI into Bi. Mesoporous Bi nanosheets show superior electrochemical CO

Tunable In(OH)

To reduce the amount of greenhouse gas emissions and remedy related environmental damage, the research on carbon capture and storage (CCS) is gaining momentum and so is the search for a more effective way to control corrosion of pipeline steel used to transport impure supercritical (SC) CO

The development of highly efficient electrocatalysts toward the oxygen evolution reaction is imperative for advancing water splitting technology to generate clean hydrogen energy. Herein, a two dimensional (2D) nanosheet ammonium cobalt phosphate hydrate (NH4CoPO4·H2O) catalyst based on the earth‐abundant non‐noble metal is reported. When used for the challenging alkaline saline water electrolysis, the NH4CoPO4·H2O catalyst with the optimal thickness of 30 nm achieves current densities of 10 and 100 mA cm−2 at the record low overpotentials of 252 and 268 mV, respectively, while maintaining remarkable stability during the alkaline saline water oxidation at room temperature. X‐ray absorption fine spectra reveal that the activation of Co (II) ions (in NH4CoPO4·H2O) to Co (III) species constructs the electrocatalytic active sites. The 2D nanosheet morphology of NH4CoPO4·H2O provides a larger active surface area and more surface‐exposed active sites, which enable the nanosheet catalyst to facilitate the alkaline freshwater and simulated seawater oxidation with excellent activity. The facile and environmentally‐benign H2O‐mediated synthesis route under mild condition makes NH4CoPO4·H2O catalyst highly feasible for practical manufacturing. In comparison with noble metals, this novel electrocatalyst offers a cost‐effective alternative for economic saline water oxidation to advance water electrolysis technology., A two dimensional structured ammonium cobalt phosphate nanosheet is fabricated by a low‐energy consuming H2O‐mediated synthesis route at room temperature. Through adjusting the thickness of nanosheets, the optimal catalyst with high surface area and exposed active sites is achieved, which exhibits high electrocatalytic activity and stability for the oxygen evolution reaction in alkaline saline water electrolyte.

Improving the corrosion resistance while maintaining good electrical conductivity is of vital importance for the application of stainless steel in bipolar plates of polymer electrolyte membrane fuel cells (PEMFCs). Transition nitride coatings on steel surfaces, such as TiN, is considered as a possible solution. However, most coatings still fail to exhibit good corrosion resistance and high electrical conductivity simultaneously, especially after corrosion testing. This study prepares TiN on 316L stainless steel (SS) and conducts heat treatment on the TiN deposited samples at different temperatures. The corrosion behaviours of the prepared samples are investigated under the simulated working environments of fuel cell. Our results demonstrate that heat treatment at appropriate temperatures is an effective approach to improve the corrosion resistance of TiN coatings while maintaining a considerable electrical conductivity. The interfacial contact resistance (ICR) test results indicate that high temperature (450 °C) heat treatment has detrimental effect on the electrical conductivity of samples due to the formation of a thick oxide dominated layer, while samples heat treated at 300 °C only form graded layers with suitable oxide amount which endows the coated specimens with a very low ICR value both before and after corrosion tests. This suggests that the heat treatment of TiN coatings under suitable conditions is a feasible strategy to simultaneously achieve an enhanced corrosion resistance and a good electrical conductivity of the TiN coated samples for bipolar plates in PEMFCs.

Electrochemical CO2 reduction (CO2R) to value-added fuels has been actively pursued to reduce the carbon intensity of our energy and products-driven economy. Conventional CO2R is always coupled with the anodic oxygen evolution reaction (OER), resulting in high electricity input being consumed by the OER due to its large energy barrier and sluggish kinetics. Herein, OER is replaced with selective methanol oxidation reaction (MOR) on non-noble electrocatalysts. In an integrated cell, CO2R is conducted on the cathode of Bi nanoparticles and MOR is performed on the anode of Ni(OH)2 in alkaline electrolyte. Over 92% selectivity for cathodic reduction of CO2 into formate and 100% selectivity for anodic oxidation of methanol to formate are achieved at high current densities within a wide potential range. The use of the integrated system significantly lowers the specific energy consumption by 57.3% reduction for individual CO2R and 71.2% reduction for individual MOR for 1 mol formate generation. This novel strategy for concurrent formate generation at the cathode and anode dramatically increases the valuable fuels production with low electricity consumption. This study thus highlights the promise that coupling CO2R with viable alternative oxidation reaction is theoretically and technically feasible and presents significant economic benefits.

Integrating organic upgrading and hydrogen electrolysis is recently regarded as a win-win strategy. However, it is still challenging to construct efficient robust electrocatalysts to considerably minimize their energy demand for such coupled reaction and simultaneously avoid the emission of environment-unfriendly CO2. Herein, the Cu2Se/Co3Se4 multivalent hetero-nanocrystals (CuCoSe-HNCs) are fabricated as efficient electrocatalysts through interfacial engineering, thus constructing abundant hetero-junctions on monodispersed CuCoSe-HNCs and facilitating the charge transfer at Cu–Se–Co hetero-interfaces. DFT studies reveal the multivalent CuCoSe-HNCs with hydroxylated surfaces, which possess complex species (Cu*−OOH, Co*−OOH, and SeOx) as synergistic active centers, thus effectively optimizing the surface adsorption/dissociation performance and suppress excessive oxidation to CO2. Hence, the methanol upgrading conversion to value-added formate is achieved at much low working potential (1.11V) with high faradaic efficiency (>98 %) and without CO2 emission, thus considerably decreasing the energy consumption for generating the only gas product of pure hydrogen.

Developing high-efficient and durable electrocatalysts for CO2 electroreduction reaction (CO2RR) at high current density is attractive but still challenging. In this study, ultrasmall Bi nanoparticles confined in carbon nanosheets are successfully prepared by directly annealing of dipped carbon cloth. Benefited from the uniform distribution of the ultrasmall Bi nanoparticles and the in‐situ‐formed carbon nanosheets, the resultant self-supported electrocatalysts exhibit excellent CO2RR activity in a synergistic way. The optimized Bi-PVP/CC600 exhibits high formate faradaic efficiency of over 81 % at high current densities in a wide potential range. Impressively, high durability is also achieved for this binder-free electrode, with a remarkable high current density of 54 mA∙cm−2 for nearly 40 h. The high performance associated with this facile and potentially scalable synthetic method suggests the great application potential of ultrasmall Bi nanoparticles in CO2RR. The strategy developed herein is versatile and can be extended to prepare other high‐performance ultrasmall metal nanoparticles catalysts.

This study investigated corrosion performance of SS310 and Alloy 740 in supercritical CO2 with the impurity of 100 ppm H2O or O2 at 600 °C and 30 MPa for up to 1000 h. The addition of 100 ppm H2O remarkably enhanced general and localized oxidations while the presence of O2 led to the opposite tendency. Alloy 740 exhibited better resistance to carburization compared to SS310, possibly due to the higher solubility of carbides in Ni-based alloys than those in Fe-based alloys. Both alloys exhibit near parabolic oxidation behavior and acceptable corrosion resistance in the supercritical CO2 environments.

Solid oxide electrolysis cells (SOECs) could convert CO2 greenhouse gas into valuable fuels and chemicals with high energy efficiency. Unfortunately, the lack of efficient cathode materials obstructs their practical applications. Herein, a promising cathode material with high activity and stability is developed, with the partial replacement of the transition metal Mo by the alkaline-earth metal Mg in the double perovskite structure of Sr2FeMoO6-σ. The replacement of Mo by Mg could not only improve its redox stability, but also enhance the CO2 electrolysis performance. In the same test environment, the electrolytic current of the LSGM electrolyte-supported single cell with Sr2FeMo2/3Mg1/3O6−δ as the cathode is almost two times higher than that of the Sr2FeMoO6-σ cathode. Density functional theory with Hubbard correlation reveals that the improved electrocatalytic performance results from the reduced d-p band coupling introduced by the dopant of Mg, which is short of d electrons, favoring the formation of oxygen vacancies for the MgB-VO-FeB′ and FeB-VO-FeB′ bonds. These newly formed oxygen vacancies have highly catalytic activity toward CO2 activation and the subsequent dissociation process. Our strategy demonstrates a general method for the development of promising new catalysts for efficient CO2 reutilization by modulating the electronic structures using d-electron-free elements.

Fouling phenomena are commonly observed in oil production processes, which have caused many challenging issues. Many previous studies focused on fouling in aqueous environment. However, the characterization of foulants and underlying interaction mechanism in organic media still remain limited, which is of fundamental and practical importance. In this work, the foulants on slotted liner samples were characterized, which have served in an oil wellbore based on steam-assisted gravity drainage (SAGD) operation for about six months. The foulants were demonstrated to be fine mineral solids (e.g., silica) and organic materials (e.g., asphaltenes). Atomic force microscope (AFM) colloidal probe technique was employed to quantify the interaction forces of silica particles or asphaltenes with carbon steel (L80) substrates with or without electroless nickel-phosphorus (EN) coating in organic media. The results demonstrated that the corrosion on L80 surface could significantly enhance the adhesion with silica particles and asphaltenes, aggravating the fouling phenomena; while the EN coating could effectively eliminate the corrosion and show good antifouling property. Quartz crystal microbalance with dissipation monitoring (QCM-D) technique was applied to investigate the dynamic adsorption behaviors of asphaltenes on iron (a major component of L80) and EN coating surfaces. The QCM-D results showed that much less asphaltenes were adsorbed on EN coating than that on iron, which agrees well with the force measurements. This work provides useful insights on the fouling processes and fundamental surface interaction mechanisms of fine solids, asphaltenes and substrates in oil, with implications on developing effective antifouling strategies (e.g., functional coatings) in oil production.

Ni(OH)2 nanosheet arrays are in situ prepared on Ni foam through very straightforward ultrasonication in HCl solution and the following rinsing and drying procedures. Value-added formate and hydrogen could be co-produced by selective oxidation of methanol without carbon dioxide emissions and water reduction over Ni(OH)2 nanosheet arrays bifunctional electrocatalysts. Energy depletion for hydrogen evolution from water could be reduced by integrating with selective methanol oxidation rather than oxygen evolution. The prepared Ni(OH)2 nanosheet arrays exhibits high activity for selective methanol oxidation in alkaline methanol-water solution. It gives a low potential of only 1.36 V (vs. reversible hydrogen electrode) to drive the current density of 100 mA cm−2. The faradaic efficiencies of formate are approximately 100% with the current densities from 10 mA cm−2 to 100 mA cm−2. Moreover, it is easy to separate the anodic and cathodic products without help of any membrane, which greatly simplifies the electrolysis system.

Electro-oxidative organic upgrading is recently considered as a promising strategy for energy saved H2 co-generation but still challenging for high productivity of value-added chemicals at large current density. Herein, the synthesized defects-rich Ni3S2-CNFs nanoheterostructures exhibit robust electrocatalytic performance for selectively catalyzing methanol to value-added formate with high productivity and without CO2 emission, in which the large current density (> 700 mA cm−2) is achieved with high faradaic efficiency (> 90%). By replacing the sluggish OER, the methanol upgrading reaction can greatly boost H2 co-generation from water with reduced energy consumption. DFT calculations indicate the in situ formed Ni–OOH and SOx species with synergistic effect can effectively modulate the d band center of Ni3S2 in Ni3S2-CNFs nanoheterostructures, acting as unique collaborative active sites for the thermodynamically favorable conversion from methanol to formate and suppressing the further oxidation to CO2, resulting in the high activity and selectivity of CO2-emission-free methanol upgrading reaction.

Advanced pressurized oxy-fuel combustion technology has been developed for the significantly improved thermal energy conversion efficiency and reduced greenhouse gas emission. However, significant knowledge gap exists in terms of the selection of appropriate boiler tube materials, which has delayed the commercialization of this promising technology. In this study, the corrosion performance of the three candidate alloys (SS347, Alloy 800AT and Alloy 825) was investigated in the hot flue gas mixtures (60% H2O + 33% CO2 + 2–7% O2) at 600 °C and 15 MPa to simulate typical pressurized oxy-fuel natural gas combustion environments. On all the alloys, Cr2O3 was the main surface oxide and several alloying elements (including Si, and/or Al+Ti) accumulated at the interface of oxide layer/substrate. Among the gas species, O2 acted as the dominant oxidizing agent with a critical content of ∼2%, above which nodular oxidation was suppressed and corrosion rates of alloys were greatly reduced. H2O was likely to enhance the growth and evaporation of oxides, while CO2 did not trigger carburization during the testing period. From a corrosion perspective, three alloys exhibit promising potential for boiler tube constructions while Alloy 825 exhibited the best corrosion performance.

Solid oxide cells (SOCs) including solid oxide fuel cells (SOFCs) and solid oxide electrolysis cells (SOECs) are advanced electrochemical energy storage and conversion devices. However, the lack of highly active and stable fuel electrode materials impedes their practical applications. Herein, in-situ exsolved CoFe nanoparticles on perovskite matrixes with abundant defects are developed as bifunctional fuel electrocatalysts for SOCs from the Sr2FeMo1-xCoxO6−δ (x = 0, 0.15, 0.25, 0.45) precursor. Increasement of Co doping promotes CoFe alloy exsolution and the formation of more defects in the remaining perovskite matrix under reducing atmosphere at high temperatures. Consequently, with increasing Co dopant content, the electrocatalytic activity towards CO2 electrolysis and hydrogen (H2) fuel oxidation are both significantly enhanced for the reduced Sr2FeMo1-xCoxO6−δ. The reduced Sr2FeMo1-xCoxO6−δ with high Co doping content of x = 0.45 electrocatalysts also exhibits respectable coking resistance and excellent long-term stability. The high performance may be owing to the unique simultaneously in-situ formed nanoalloy-oxide heterostructure and electron-ion mixed conductive perovskite matrixes with abundant defects.

In this study, the influence of solutionizing and aging treatments on the microstructure and mechanical properties of alloy 625 superalloy samples produced by powder bed binder jet printing was investigated. Vacuum melted argon atomized 625 superalloy powder was used to fabricate green parts. Samples vacuum sintered at 1280 °C for 4 h to optimize density to 99.6% were subjected to solution and aging treatments at 1150 °C for 2 h and 745 °C for 20 h and 60 h, respectively, in order to improve microstructure and mechanical properties. Elemental analysis, phase formation and microstructure of the sintered, solution treated and aged samples were investigated by using optical, scanning/transmission electron microscopy with electron dispersive spectroscopy, and X-ray diffraction. The results indicate that the aging treatment resulted in the formation of intermetallic phases such as Ni3Nb and Ni2(Cr,Mo) as well as carbides such as NbC, Cr23C6 in the microstructure. While the microhardness and tensile strength of the aged specimen increased due to these phases, the ductility value decreased. This study shows that alloy 625 produced by binder jet printing subjected to aging treatments has comparable properties to cast alloy 625. Keywords: Additive manufacturing, Inconel 625, Heat treatment, Tensile test, TEM, Precipitation

The oxide scale grown of static capsules made of alloy 310S stainless steel was investigated by exposure to the supercritical water at 500 °C 25 MPa for various exposure times up to 20,000 h. Characterization techniques such as X-ray diffraction, scanning/transmission electron microscopy, energy dispersive spectroscopy, and fast Fourier transformation were employed on the oxide scales. The elemental and phase analyses indicated that long term exposure to the SCW resulted in the formation of scales identified as Fe 3 O 4 (outer layer), Fe-Cr spinel (inner layer), Cr 2 O 3 (transition layer) on the substrate, and Ni-enrichment (chrome depleted region) in the alloy 310S. It was found that the layer thickness and weight gain vs. exposure time followed parabolic law. The oxidation mechanism and scales grown on the alloy 310S stainless steel exposed to SCW are discussed.

The porous nanofiber Co doped Pr0.5Ba0.5MnO3-δ (PrBaMnO) was successfully synthesized through electrospinning technology and served as a bifunctional catalyst for the oxygen reduction reaction (ORR) and oxygen evolution reaction(OER). The catalytic activities of the composite catalyst consisting of 50 wt% perovskite catalyst and 50 wt% carbon black (CB) was investigated in alkaline solution. Comparing to the PrBaMnO parent perovskite, remarkable enhancement of ORR and OER performance were achieved on Pr0.5Ba0.5MnCo0.2O3-δ with respect to decreased overpotential and increased current density. A maximum current density of 19.4 mA cm-2 was achieved at 1.95 V (versus. RHE) on Co doped Pr0.5Ba0.5MnO3-δ electrospun nanofiber/CB composite catalyst in OER. In addition, a preferable four electron transfer pathway was demonstrated in the ORR process. All the electrochemical test results suggest the promising application of Co doped Pr0.5Ba0.5MnO3-δ electrospun nanofiber/CB composite as an efficient bi-functional catalyst on fuel cells and metal-air batteries.

The massive emission of carbon dioxide (CO2), the major portion of greenhouse gases, has negatively affected our ecosystem. Developing new technologies to effectively reduce CO2 emission or convert CO2 to useful products has never been more imperative. In response to this challenge, we herein developed novel in situ exsolved Fe–Ni alloy nanospheres uniformly socketed on an oxygen-deficient perovskite [La(Sr)Fe(Ni)] as a highly stable and efficient catalyst for the effective conversion of CO2 to carbon monoxide (CO) in a high-temperature solid oxide electrolysis cell (HT-SOEC). The symmetry between the reduction and reoxidation cycles of this catalyst indicates its good redox reversibility. The cathodic reaction kinetics for CO2 electrolysis is significantly improved with a polarization resistance as low as 0.272 Ω cm2. In addition, a remarkably enhanced current density of 1.78 A cm–2, along with a high Faraday efficiency (∼98.8%), was achieved at 1.6 V and 850 °C. Moreover, the potentiostatic stability te...

We report the development of a novel Co–W bimetallic anode catalyst for solid oxide fuel cells (SOFCs) via a facile infiltration-annealing process. Using various microscopic and spectroscopic measurements, we find that the formed intermetallic nanoparticles are highly thermally stable up to 900 °C and show good coking resistance in methane. In particular, a fuel cell fitted with Co3W anode shows comparable activity (relative to Co) in the electro-oxidation of hydrogen and methane at 900 °C without suffering significant degradation during a longevity test.

This study investigates the oxidation behavior of several stainless steels and nickel-based superalloys exposed to supercritical water at 800 °C for 12 h. Characterization of the resulting oxide layers were conducted using weight change measurements, X-ray diffraction, scanning/transmission electron microscopy, and energy dispersive spectroscopy. Although the exposure time is only 12 h, the thickness of the oxide layers formed was as high as 1 μm, comprising different spinel structures. The influence of alloying elements such as Al, Nb, Mo, Mn and Ti on the corrosion behavior is investigated and possible corrosion mechanisms for each candidate alloy are discussed.

Conventional anode materials for solid oxide fuel cells (SOFCs) are Ni-based cermets, which are highly susceptible to deactivation by contaminants in hydrocarbon fuels. Hydrogen sulfide is one of the commonly existed contaminants in readily available natural gas and gasification product gases of pyrolysis of biomasses. Development of sulfur tolerant anode materials is thus one of the critical challenges for commercial viability and practical application of SOFC technologies. Here we report a viable approach to enhance substantially the sulfur poisoning resistance of a Ni-gadolinia-doped ceria (Ni-GDC) anode through impregnation of proton conducting perovskite BaCe0.9Yb0.1O3-δ (BCYb). The impregnation of BCYb nanoparticles improves the electrochemical performance of the Ni-GDC anode in both H2 and H2S containing fuels. Moreover, more importantly, the enhanced stability is observed in 500 ppm of H2S/H2. The SEM and XPS analysis indicate that the infiltrated BCYb fine particles inhibit the adsorption of sulfur and facilitate sulfur removal from active sites, thus preventing the detrimental interaction between sulfur and Ni-GDC and the formation of cerium sulfide. The preliminary results of the cell with the BCYb+Ni-GDC anode in methane fuel containing 5000 ppm of H2S show the promising potential of the BCYb infiltration approach in the development of highly active and stable Ni-GDC-based anodes fed with hydrocarbon fuels containing a high concentration of sulfur compounds.

Ni–Cr–Mo coating was prepared by a high power diode laser (HPDL) on X70 steel substrate (X70). In order to widen the application of this coating in oil industry, its surface morphology and corrosion behavior in simulated solutions separately with CO2, H2S as well as a mixed gas of them were studied and compared with those of X70 and 316 stainless steel (316 SS). The results show that X70 and 316 SS display inclusions on the surface before corrosion, while Ni–Cr–Mo coating exhibits a uniform and compact microstructure. Moreover, Ni–Cr–Mo coating has no change in morphology after corrosion, while X70 and 316 SS display severe corrosion and pitting corrosion, respectively. For each simulated solution, Ni–Cr–Mo coating exhibits higher corrosion resistance than X70 and 316 SS. Also, it shows higher polarization resistance than 316 SS and X70 as immersion time lasts, revealing an enhanced and stable anticorrosion performance. Furthermore, the variation trends of electrochemical response was opposite for X70 and 316 SS/Ni–Cr–Mo coating in simulated solutions with CO2, H2S as well as the mixed gas accordingly, which is caused by different corrosion mechanisms.

In this letter, two functional reaction sites, i.e., massive Co core–shell nanoparticles and oxygen-deficient layered perovskite, have been combined into a bifunctional catalyst, which exhibits very high activity in soot combustion. Environmental transmission electron microscopy (TEM), in situ Raman spectroscopy, and other characterizations were applied simultaneously to study the soot consumption process online.