Accelerated Degradation Test Research Articles

A grey incidence-based algorithm for optimization of accelerated degradation test

PurposeThe purpose of this paper is to optimize the degradation test for products subject to multiple types of inherent stresses and external random shocks. The mechanism that shows how the variables to be optimized influence the considered multiple objectives is also aimed to be explored by using the grey incidence analysis (GIA) model.Design/methodology/approachThe Gamma process is employed to model the influences of different types of stresses and external random shocks. The GIA model is introduced to transfer multiple considered objectives as a comprehensive degree of grey incidence. The particle swarm optimization is integrated to search the globally optimal value of the characteristic variables to be optimized.FindingsThe acceleration of tested stresses and external random shocks both make the engineering systems become more vulnerable to the inherent degradation. And, the Kriging model can provide guidance of searching the optimal values of test characteristic variables and mitigate the computation burden. The grey incidence model can make the optimization focused and improve the optimality of objective values.Originality/valueThe proposed method can effectively overcome the drawbacks brought by the limitation of test data and can specify the dependence strength between the inherent degradation and external random shock. The computation cost and accuracy of optimization can be simultaneously ensured by the proposed model.

Multi-Stress Accelerated Degradation Testing Reliability Assessment of LED Lamp Beads Considering Generalized Coupling

Due to the complex operating environment of LED lamp beads (hereinafter referred to as LED), the test method that only considers the action of multiple stresses alone ignores the mutual influence between stresses, making it difficult to accurately obtain the life indicators of LEDs, resulting in a large deviation in the theoretical life results. In this regard, this paper proposes a multi-stress accelerated degradation evaluation method considering generalized coupling and conducts an accelerated degradation test (ADT) to evaluate the life of LEDs. We identified three stress sources and designed five new high-gradient ADTs. Through experimental data, we found that the three stress sources are strongly coupled on this LED. Then, a generalized coupling maximum likelihood estimation method (MLE) for the entire sample was constructed, and the particle swarm algorithm was used to solve the parameters. Finally, the life of this LED was evaluated based on the experimental data. The results show that the life of the LED considering multiple-stress coupling is within 6.5% of the historical life scatter point, which is more in line with the actual working environment.

Proton conductivity and durability of Ce-based hybrid proton exchange membranes synchronously enhanced by dual-function γ-AlOOH@Ti-supported CeO2 composite oxide

To enhance the proton conductivity and durability of Ce-based hybrid proton exchange membranes (PEMs), this study fabricates modified perfluorosulfonic acid (PFSA) hybrid membranes by incorporating the dual-function γ-AlOOH@Ti-supported CeO2 composite oxide (γ-AlOOH@Ti/CeO2). In addition to combining the inherent proton conductivity of γ-AlOOH with the excellent radical scavenging ability of CeO2, both the proton conductivity and durability of Ce-based PEMs are further improved by introducing Ti-dopant, which not only increases hydrogen vacancies on the surface of γ-AlOOH, which facilitate proton conduction, and induces electron transfer from γ-AlOOH@Ti to CeO2, which enhance free radical adsorption. As results shown, the proton conductivity and the fluoride release value of the resulting hybrid membrane are about 76 % higher and 35.25 % lower than those of the PFSA-CeO2 membrane, respectively. Moreover, the performance of cells shows that, after accelerated degradation testing, the PFSA-γ-AlOOH@Ti/CeO2 membrane exhibits the lowest peak power density decrease rate, the impedance increase rate and hydrogen crossover current density, with 11.79 %, 27.54 % and 3.04 mA cm−2, respectively. These results suggest that compared to CeO2-hybrid PEMs, γ-AlOOH@Ti/CeO2-based hybrid PEMs exhibit higher proton conductivity and superior chemical stability, indicating the potential application of γ-AlOOH@Ti/CeO2-based hybrid PEMs in proton exchange membrane fuel cells.

Understanding the evolution of molybdenum-nitrogen doped carbon with long-term durability for efficient oxygen reduction reaction

The performance and durability of catalyst for Oxygen Reduction Reaction (ORR) still are challenges for fuel cell applications. Mo-NC catalyst system was established and showed the activity comparable with commercial Pt/C in alkaline conditions. An activation phenomenon during longer operation was confirmed with an obvious positive shift after 30 k cycles in accelerated degradation tests, which is rarely observed in the ORR process. The X-ray absorption fine structure (XAFS) indicated a coordination structure transform in electrochemical conditions cause the activated performance. The Density Function Theory (DFT) calculation reveals the transformation of the coordination structure is thermodynamically feasible and also conducive to lower the energy barriers of the key steps in the ORR performance, explaining the origin of the activate phenomenon. These findings give potential guidance to improve both activity and stability of catalyst.

The Change of Sealing Property in the Aging Process of NBR Sealing Equipment Based on Finite Element Analysis

Sealing rings are the core components of flange sealing structures and play a crucial role in the storage and operation of gas generators. The aging and deformation of seals affect the safe operation of the device. This paper aims to investigate the effect of rubber aging on the sealing performance of the components, which is realized by nonlinear finite element analysis. Firstly, an accelerated degradation test method was used to obtain the compression permanent deformation and stress–strain curve of rubber during the aging process. A two-dimensional finite element model of the sealing structure was constructed and the Yeoh model was utilized to describe the mechanical response of rubber. During the simulation, the contact area was modified based on the compression permanent deformation, and the Yeoh model was updated based on the stress–strain curve changes obtained by the test. The impact of key parameters such as material property changes, rubber physical section deformation, and fluid pressure on sealing performance during the seal ring aging process was systematically studied. The numerical results indicate that due to the aging deformation of rubber seals, there is a significant decrease in contact stress and contact width, as well as a shift in maximum equivalent stress area. Taking into account these findings, this study proposes a new design concept for sealing structures. This provides a relatively simple research method for studying flange sealing structure performance.

Diatomic Iron with a Pseudo-Phthalocyanine Coordination Environment for Highly Efficient Oxygen Reduction over 150,000 Cycles.

Atomically dispersed Fe-N-C catalysts emerged as promising alternatives to commercial Pt/C for the oxygen reduction reaction. However, the majority of Fe-N-C catalysts showed unsatisfactory activity and durability due to their inferior O-O bond-breaking capability and rapid Fe demetallization. Herein, we create a pseudo-phthalocyanine environment coordinated diatomic iron (Fe2-pPc) catalyst by grafting the core domain of iron phthalocyanine (Fe-Nα-Cα-Nβ) onto defective carbon. In situ characterizations and theoretical calculation confirm that Fe2-pPc follows the fast-kinetic dissociative pathway, whereby Fe2-pPc triggers bridge-mode oxygen adsorption and catalyzes direct O-O radical cleavage. Compared to traditional Fe-N-C and FePc-based catalysts exhibiting superoxo-like oxygen adsorption and an *OOH-involved pathway, Fe2-pPc delivers a superior half-wave potential of 0.92 V. Furthermore, the ultrastrong Nα-Cα bonds in the pPc environment endow the diatomic iron active center with high tolerance for reaction-induced geometric stress, leading to significantly promoted resistance to demetallization. Upon an unprecedented harsh accelerated degradation test of 150,000 cycles, Fe2-pPc experiences negligible Fe loss and an extremely small activity decay of 17 mV, being the most robust candidate among previously reported Fe-N-C catalysts. Zinc-air batteries employing Fe2-pPc exhibit a power density of 255 mW cm-2 and excellent operation stability beyond 440 h. This work brings new insights into the design of atomically precise metallic catalysts.

A monitoring platform based on electrical impedance and AI techniques to enhance the resilience of the built environment

Structural Health Monitoring (SHM) and early warning systems (EWSs) play a pivotal role in enhancing seismic resilience for both buildings and occupants. This paper introduces a monitoring platform that collects electrical impedance data from scaled concrete beams undergoing load and accelerated degradation tests. Artificial Intelligence (AI) algorithms are employed for predictive analysis, scrutinizing historical impedance data, and forecasting future trends. These algorithms adapt to environmental parameters, becoming valuable tools in data-driven decision-making processes. In particular, the study investigates concrete specimens in different test conditions, utilizing a distributed sensor network based on electrical impedance as well as temperature and relative humidity sensors. Real-time data are transmitted to a cloud infrastructure during accelerated degradation tests (both in water and in chloride-rich solution) and in room conditions. An AI-based forecasting approach using Prophet is proposed, ingesting electrical impedance and temperature data, and tested to predict electrical impedance corresponding to approximately 10 % of the time series balancing responsiveness with predictive accuracy, crucial for effective EWS operations and management requirements. The performance of the tested models is evaluated employing metrics such as Mean Average Error (MAE), Root Mean Square Error (RMSE), Mean Absolute Percentage Error (MAPE), and correlation. The proposed approach surpasses statistical methods and deep learning techniques, reporting a MAPE always lower than 3.20 % and a correlation higher than 81.65 % (in wet-dry cycles in water these values are 0.65 Ω and 91.85 %, respectively). This proves to be a promising step towards transparent SHM, which integrates AI models facilitating self-monitoring and early maintenance prediction, thus enhancing the resilience of the built environment.

Synthesis and characterization of amine-functionalized graphene as a nitric oxide-generating coating for vascular stents.

Drug-eluting stents are commonly utilized for the treatment of coronary artery disease, where they maintain vessel patency and prevent restenosis. However, problems with prolonged vascular healing, late thrombosis, and neoatherosclerosis persist; these could potentially be addressed via the local generation of nitric oxide (NO) from endogenous substrates. Herein, we develop amine-functionalized graphene as a NO-generating coating on polylactic acid (PLA)-based bioresorbable stent materials. A novel catalyst was synthesized consisting of polyethyleneimine and polyethylene glycol bonded to graphene oxide (PEI-PEG@GO), with physicochemical characterization using x-ray diffraction, Raman spectroscopy, Fourier transform infrared spectroscopy, and thermogravimetric analysis. In the presence of 10 μM S-nitrosoglutathione (GSNO) or S-nitroso-N-acetylpenicillamine (SNAP), PEI-PEG@GO catalyzed the generation of 62% and 91% of the available NO, respectively. Furthermore, PEI-PEG@GO enhanced and prolonged real-time NO generation from GSNO and SNAP under physiological conditions. The uniform coating of PEI-PEG@GO onto stent material is demonstrated via an optimized simple dip-coating method. The coated PLA maintains good biodegradability under accelerated degradation testing, while the PEI-PEG@GO coating remains largely intact. Finally, the stability of the coating was demonstrated at room temperature over 60 days. In conclusion, the innovative conjugation of polymeric amines with graphene can catalyze the generation of NO from S-nitrosothiols at physiologically relevant concentrations. This approach paves the way for the development of controlled NO-generating coatings on bioresorbable stents in order to improve outcomes in coronary artery disease.

Effective strategy for enhancing the activity and durability of gas diffusion electrode in high-temperature polymer electrolyte membrane fuel cells: In-situ growth of Pt nanowires on dual microporous layers

High-temperature polymer electrolyte membrane fuel cells (HT-PEMFCs) suffer from high platinum (Pt) loading and limited lifetime issues due to the low Pt efficiency of the conventional electrode and poor durability of Pt/C catalyst under harsh operating conditions. Thus, dual microporous layer (MPL) structured gas diffusion layers were developed, utilizing formic acid reduction for the in-situ growth of Pt nanowires (NWs). The optimal ratio of the hydrophilic and hydrophobic MPLs was determined to be 1:1. The resulting Pt NWs gas diffusion electrode (GDE) achieved a significantly high Pt mass-specific peak power density, which was 2.48 times higher than the conventional Pt/C GDE. After accelerated degradation tests, the peak power density and the electrochemically active surface area of Pt NWs GDE decreased by 10.84 % and 4.47 %, respectively, significantly lower than those of the conventional Pt/C GDE. The superior activity and durability of Pt NWs GDE are attributed to its binder-free characteristic, the outstanding activity and stability of one-dimensional Pt NWs, and the strong adherent force between the in-situ grown Pt and the carbon substrate. This study provides a straightforward and effective strategy to reduce the Pt loading and enhance electrode durability, thereby facilitating the large-scale application of HT-PEMFCs.

An Assessment Method for the Step-Down Stress Accelerated Degradation Test Considering Random Effects and Detection Errors

An Assessment Method for the Step-Down Stress Accelerated Degradation Test Considering Random Effects and Detection Errors

Detachment Suppression of NiCo Oxide Catalyst Layer for Oxygen Evolution Anode in Alkaline Medium Using Start and Stop Simulated Accelerated Degradation Test Protocol

INTRODUCTION While the alkaline water electrolysis (AWE) has the advantage of low cost and mass production, it has the issue of catalyst coated electrode degradation caused mainly by catalyst layer detachment due to reverse currents generated by the start and stop of variable renewable electricity. A previous study reported that heat treatment of a NiCo2O4 spinel catalyst-supported electrode (NiCo) on a Ni substrate suppress delamination of the catalyst layer with decrease in initial activity due to increase of electrode resistance. [1] In this study, in order to find optimize preparation for both initial activity and durability of the anode electrode catalyst, we compared and evaluated the degradation behavior of NiCo electrodes prepared various conditions. EXPERIMENTAL The accelerated durability test (ADT) was performed in a three-electrode cell with 7 M KOH aqueous solution as electrolyte at 25℃. RHE, Ni coil and 1 cm2 electrode of NiCo spinel catalyst supported on Ni mesh substrate prepared with 8 to 24 of layered thermal decomposition coating at various temperature are used as reference, counter and working electrodes, respectively. Here, the thickness of the coting was determined by Co loading measured with XRF. Constant current electrolysis at 1 A cm-2 for 2 hours was conducted as pretreatment at 80℃ before ADT. The ADT protocol consisted of three steps [2] (Fig.1): (1) constant current electrolysis at 600 mA cm-2 for 1 min, (2) potential scanning from open-circuit potential (OCP) to anodic potential E min (= 0.5 V vs. RHE) at sweep rate of -500 mV s-1, and (3) holding at constant potential of E min for 1 min. To evaluate the anode activity, CV (potential range: 0.5 to 2.0 V vs. RHE, sweep rate: 5 and 50 mV s-1, 3 cycles) and AC impedance measurements (bias potential: 1.6, 1.7 V vs. RHE, frequency range: 106-10-1 Hz, amplitude: 10 mV) were performed at every 200 ADT cycles in 2,000 cycles of ADT. RESULTS AND DISCUSSION As shown in Fig. 2 of the anode potential as a function of the ADT cycle, the potential of the 350°C prepared anode significantly increased around 800 cycles toward around 1.9 V vs. RHE, while the 450°C prepared anode showed slowly and constantly increase in potential.As shown in Fig. 3 of the redox peaks in cyclic voltammograms, the NiCo redox peaks around 1.2 V vs. RHE disappeared and the Ni redox peaks around 1.2 V vs. RHE appeared at the end of the ADT,. The NiCo redox peak of the 350°C prepared anode was significantly larger than the Ni redox peak in the initial period, whereas the Ni redox peaks became larger than the NiCo redox peak around 700 cycles. The charge of NiCo redox peak of the 450°C prepared anode gradually decreased and that of the Ni oxidation peak increased and they reversed for 8, 16, and 24 layered anodes at 1000, 1400, and 1600 cycles, respectively, but NiCo redox peak still remained. These results means that the consumption of the NiCo oxide electrocatalyst occurs during the ADT and the 450°C preparation suppress rapidly detachment of the 450°C prepared anode around 700 cycles.As shown in Fig. 4 of the polarization curves, the OER activity of the 8 layered at the 450°C prepared was almost same as that of the 350°C prepared anode at 200 cycles, and the 16 and 24 layered at 450°C prepared were higher activity than the 350°C prepared and the 8 layered at 450°C prepared. The Tafel slopes of the initial ADT (200 cycles) were almost the same for the 350°C and 450°C. The slope for the 450°C prepared anodes after 2000 cycles were almost same as the initial regardless of the number of applications, but the slope for the 350°C prepared increased. This result also suggests NiCo oxide of the 450°C prepared still remained at the end of the ADT and it dominates oxygen evolution reaction, while the 350°C prepared electrocatalyst completely consumed during the ADT. ACKNOWLEDGEMENTS This study was based on results obtained from the Development of Technologies for Realizing a Hydrogen Society (P20003) commissioned by the New Energy and Industrial Technology Development Organization (NEDO). REFERENCES [1] N. Todoroki, K. Nagasawa, H. Enjoji, S. Mitsushima., ACS Appl. Mater. Interfaces, 15, 20, 24399 24407 (2023).[2] A. Abdel Haleem, K. Nagasawa, Y. Kuroda, Y. Nishiki, A. Zaenal, S. Mitsushima., Electrochem., 89, 2, 186 191 (2021). Figure 1

Novel Ru-Based PEM Electrolysis Catalyst – Development from the Nano- to the Industrial-Scale

For the de-fossilization of sectors like chemicals, steel, and transportation, green H2 generated via water electrolysis provides a path towards net-zero. The broad use of H2 across hard-to-abate sectors confirms the urgent need for green hydrogen at scale.Within water electrolysis, there are several competing technologies: the so-called solid oxide electrolysis cell (SOEC), alkaline water electrolysis (AEL) and polymer electrolyte membrane electrolysis (PEM EL). Here, the latter shows significant benefits, such as high current density operation (> 2 A/cm2) and thus a smaller footprint, highly dynamic operation mode, high gas purity, and generation of pressurized hydrogen. However, at present, PEM EL requires precious metal catalysts; in particular, the O2 evolution on the anode currently relies on iridium, a metal which is rather scarce and expensive [1].To meet the demand of iridium with respect to the announced increase in electrolyzer capacities in the multi-GW range, material innovation to reduce the use of this precious metal must be implemented. Successful catalyst and electrode developments have already been demonstrated in the BMBF funded project Kopernikus P2X, whereby loadings of approx. 0.3 mg/cm2 (< 0.1 g/kW1) have been achieved without any significant losses in activity over time [2, 3].Here, we present a material innovation in the form of Ru-based electrocatalysts with a significantly reduced Ir content. This ruthenium-iridium oxide can be adjusted in a wide range of Ir content down to less than 15 wt.% (Ir). Consequently, iridium-based electrode loadings of less than 0.1 mg/cm2 and mass activities of about 3,500 A/g are feasible. Moreover, in accelerated degradation tests those mixed-oxides have demonstrated the often-missing stability by showing low degradation rates, similar to that of pure IrO2, in up to 30,000 potential-induced stress cycles.This achievement stems from a remarkable screening approach that combines synthesis, characterization and testing at the nanoscale at Mattiq, and on industrial scale in the multi-gram range at Heraeus Precious Metals GmbH & Co. KG. Remarkably the alignment of degradation testing on both scales showcases the power of the applied method, providing a blueprint for high throughput screening for future material developments, both within water electrolysis and beyond.

Programmable Oxygen Reduction Reaction Performance of Atomic Ir-Clusters Anchored Pd Nanoparticles on the Ni-Oxide Support

Fuel cells is severely restricted by the sluggish oxygen reduction reaction (ORR) kinetics at the cathode side, which demands highly active and enduring catalysts for producing adequate rates. Herein, we report a systematic study to investigate the effect of structure configuration on the oxygen reduction reaction (ORR) activity of tri-metallic nanocatalysts (NC)s comprising atomic Ir-clusters (0.5 wt.% of Ir) anchored Pd nanoparticles on the tetrahedral symmetric Ni-oxide support (denoted as NPI). The electrochemical activities of NPI NCs are programmable via a temperature-controlled wet chemical reduction method. For the optimum condition when the Ni-crystal impregnation temperature is 40oC, the Ir-clusters decorated Ni@Pd nanoislands are formed (hereafter denoted as NPI-40), outperforming the commercial J.M.-Pt/C (20 wt.% Pt) catalyst by ~180-folds with an unprecedented high mass activity of ~12,000 mAmgIr -1 at 0.85 V vs RHE in 0.1 M KOH. More importantly, NPI-40 NC retained 100 % ORR performance with no degradation up to 20k accelerated degradation test cycles, while only a 5 mV loss in half-wave potential (E1/2 ) is observed after 30k ADT cycles. The results of physical structure inspections and electrochemical analysis suggest that such an exceptional ORR performance of NPI-40 NC originates from the potential synergetic effect between the high density of occupied Ir-d-orbital and adjacent compressively strained Ni-Pd interface. With this structure configuration, Ir-sites offer optimal adsorption energy for O2 splitting and Ni-Pd interface facilitates the subsequent desorption of hydroxide ions (OH-). We believe that the obtained results will open new approach for the design of Pt-free NCs for fuel cell cathode. Keywords: Oxygen reduction reaction, Fuel cells, Mass activity, Ir clusters

Novel Outlier-Robust Accelerated Degradation Testing Model and Lifetime Analysis Method Considering Time-Stress-Dependent Factors

Novel Outlier-Robust Accelerated Degradation Testing Model and Lifetime Analysis Method Considering Time-Stress-Dependent Factors

Systematic study of the N concentration effects on metal-free ORR electrocatalysts derived from corncob: Less is more

We report nitrogen-doped biomass-derived porous carbon materials with great performance for the Oxygen Reduction Reaction (ORR) in alkaline media. The level of nitrogen doping in a simple pyrolysis of corncob (CC) was varied systematically, a 1:1 CC:urea ratio (CC1U) gave the best performance in terms of onset potential (Eonset = 0.97 V vs. RHE), maximum current density (jmax = -3.22 mA cm−2), hydroperoxide ion yield (%HO2– = 1.18 % at 0.5 V), and electron transfer number (n = 3.86 at 0.5 V). Unexpectedly, for higher CC:urea ratios the doping decreases, instead of plateauing, with lower concentration of C-N sites and more sp2 sites as determined by XPS, as well as lower specific surface area (SSA), while increasing both porosity and carbon (002) interplanar distance (d(002)). These materials should be durable and robust, since their performance actually improved after accelerated degradation tests. This study proves that renewable “waste” can be upconverted into metal-free electrocatalysts for electrochemical energy conversion technologies and emphasizes the need for studying and controlling doping levels to enhance performance.

Optimization design method for multi-stress accelerated degradation test based on Tweedie exponential dispersion process

In the operational environment of electronic products, simultaneous multiple stresses contribute to product degradation, with their interactions often being intricate. To effectively analyze and optimize multi-stress accelerated degradation tests, we introduce a Multi-Stress Generalized Coupling accelerated degradation model based on the Tweedie exponential dispersion process, coupled with a multi-decision optimization approach for test design. The model integrates stress interactions elucidated through fuzzy correlation analysis, reflecting the accelerated degradation behavior consistent with the Tweedie exponential dispersion process. Addressing the complexities of multi-parameter estimation, we propose a parameter estimation method underpinned by the Sine Cosine Algorithm for multi-objective optimization within the proposed framework. Considering budgetary constraints, D-optimization and V-optimization strategies are deployed to finetune test scheme allocations, optimizing resource utilization. Validation through a three-stress accelerated degradation test on LED chips confirms the model's efficacy in reliability assessment. Our findings indicate the superior descriptive power of the Tweedie exponential dispersion model for complex degradation phenomena and the proposed model's closer approximation to stress conditions in real-world settings, with a methodological error maintained below 2 %. Furthermore, the test optimization method enhances the D-optimization and V-optimization objective values by 21.20 % and reduces them by 4.08 %, respectively, marking a substantial improvement over traditional schemes and endorsing the holistic advancement of multi-stress accelerated degradation testing methodologies.

Multiple stresses optimization design of constant-stress accelerated degradation test based on Wiener process

Multiple stresses optimization design of constant-stress accelerated degradation test based on Wiener process

Oxide-Encapsulated Silver Electrocatalysts for Selective and Stable Syngas Production from Reactive Carbon Capture Solutions.

Electrolysis of bicarbonate-containing CO2 capture solutions is a promising approach towards achieving low-cost carbon-neutral chemicals production. However, the parasitic bicarbonate-mediated hydrogen evolution reaction (HER) and electrode instability in the presence of trace impurities remain major obstacles to overcome. This work demonstrates that the combined use of titanium dioxide (TiO2) overlayers with the chelating agent ethylene diamine tetra-acetic acid (EDTA) significantly enhances the selectivity and stability of Ag-based electrocatalysts for bicarbonate electrolysis. The amorphous TiO2 overlayers suppress the HER by over 50 % at potentials more negative than -0.7 V vs. RHE, increasing the CO faradaic efficiency (FE) by 33 % (relative). In situ surface-enhanced Raman spectroscopy (SERS) measurements reveal the absence of near-surface bicarbonate species and an abundance of CO2 reduction intermediates at the Ag|TiO2 buried interface, suggesting that the overlayers suppress HER by blocking bicarbonate ions from reaching the buried active sites. In accelerated degradation tests with 5 ppm of Fe(III) impurity, the addition of EDTA allows stable CO production with >47 % FE, while the electrodes rapidly deactivate in the absence of EDTA. This work highlights the use of TiO2 overlayers for enhancing the CO : H2 ratio while simultaneously protecting electrocatalysts from impurities likely to be present in "open" carbon capture systems.

Oxide‐Encapsulated Silver Electrocatalysts for Selective and Stable Syngas Production from Reactive Carbon Capture Solutions

AbstractElectrolysis of bicarbonate‐containing CO2 capture solutions is a promising approach towards achieving low‐cost carbon‐neutral chemicals production. However, the parasitic bicarbonate‐mediated hydrogen evolution reaction (HER) and electrode instability in the presence of trace impurities remain major obstacles to overcome. This work demonstrates that the combined use of titanium dioxide (TiO2) overlayers with the chelating agent ethylene diamine tetra‐acetic acid (EDTA) significantly enhances the selectivity and stability of Ag‐based electrocatalysts for bicarbonate electrolysis. The amorphous TiO2 overlayers suppress the HER by over 50 % at potentials more negative than −0.7 V vs. RHE, increasing the CO faradaic efficiency (FE) by 33 % (relative). In situ surface‐enhanced Raman spectroscopy (SERS) measurements reveal the absence of near‐surface bicarbonate species and an abundance of CO2 reduction intermediates at the Ag|TiO2 buried interface, suggesting that the overlayers suppress HER by blocking bicarbonate ions from reaching the buried active sites. In accelerated degradation tests with 5 ppm of Fe(III) impurity, the addition of EDTA allows stable CO production with &gt;47 % FE, while the electrodes rapidly deactivate in the absence of EDTA. This work highlights the use of TiO2 overlayers for enhancing the CO : H2 ratio while simultaneously protecting electrocatalysts from impurities likely to be present in “open” carbon capture systems.

Accelerated degradation testing impacts the degradation processes in 3D printed amorphous PLLA.

Additive manufacturing and electrospinning are widely used to create degradable biomedical components. This work presents important new data showing that the temperature used in accelerated tests has a significant impact on the degradation process in amorphous 3D printed poly-l-lactic acid (PLLA) fibres. Samples (c. 100 m diameter) were degraded in a fluid environment at C, C and C over a period of 6months. Our findings suggest that across all three fluid temperatures, the fibres underwent bulk homogeneous degradation. A three-stage degradation process was identified by measuring changes in fluid pH, PLLA fibre mass, molecular weight and polydispersity index. At C, the fibres remained amorphous but, at elevated temperatures, the PLLA crystallised. A short-term hydration study revealed a reduction in glass transition (Tg), allowing the fibres to crystallise, even at temperatures below the dry Tg. The findings suggest that degradation testing of amorphous PLLA fibres at elevated temperatures changes the degradation pathway which, in turn, affects the sample crystallinity and microstructure. The implication is that, although higher temperatures might be suitable for testing bulk material, predictive testing of the degradation of amorphous PLLA fibres (such as those produced via 3D printing or electrospinning) should be conducted at C.