Corina Andronescu
@uni-due.de
Faculty of Chemistry
University Duisburg-Essen
Scopus Publications
Scholar Citations
Scholar h-index
Scholar i10-index
Scopus Publications
Adarsh Jain, Vineetha Vinayakumar, André Olean‐Oliveira, Christian Marcks, Mohit Chatwani, Anna K. Mechler, Corina Andronescu, and Doris Segets
Wiley
AbstractIn this study, we developed a statistical framework, named multistage data quantification (MSDQ), to evaluate representative surface characteristics such as surface roughness, surface area, and homogeneity score of cobalt oxide‐based anodes, and contributing to a deeper insight into the quality of the anode surface. Atomic force microscopy (AFM) was employed to capture the surface morphology of two anodes that have a comparable loading of cobalt oxide but exhibit distinct morphological features. Application of MSDQ exposed notable disparities in surface characteristics across these anodes, underlining the critical importance of MSDQ in precise surface characterization. Specifically, surface roughness, surface area and homogeneity score effectively elucidated the disparities in electrocatalytic activity for the oxygen evolution reaction (OER), as quantified through scanning droplet cell (SDC) measurements. By conducting a systematic comparative analysis, the respective contributions of the extrinsic surface characteristics of the anodes to the intrinsic electrocatalytic material property could be differentiated and quantified. Applications of our findings range from benchmarking of anodes to optimization of anode manufacturing processes.
Vimanshu Chanda, Dennis Blaudszun, Lucas Hoof, Ignacio Sanjuán, Kevinjeorjios Pellumbi, Kai junge Puring, Corina Andronescu, and Ulf‐Peter Apfel
Wiley
AbstractCarbon dioxide electroreduction (CO2R) is a promising technology for mitigating industrial CO2 emissions and generating valuable chemicals using renewable energy sources. Recent advances have centered on fine‐tuning catalyst materials and their micro‐environments, stimulating interest within the CO2R community. However, testing novel catalyst materials often occurs under conditions different from those relevant to industrial applications. In this study, we explore the transferability of CO2R results obtained using Ag‐based gas diffusion electrode (GDEs) in an easy to fabricate, assemble and test zero‐gap half‐cell (ZGHC) to a zero‐gap electrolyzer (ZGE). Our investigation reveals that the transferability of results is not only influenced by the reactor design, but also partially dependent on the type of additive used in the catalyst layer of the GDE. Moreover, we show that the humidity of the CO2 is a crucial operational parameter that not only impacts the selectivity of the electrode but also influences its stability during testing in the ZGHC. These findings highlight the importance of comprehensively considering operational conditions as well as reactor designs when comparing results between the ZGHC and ZGE, presenting finally a pathway on how to minimize such differences.
Zhuo Gao, Ignacio Sanjuán, Ulrich Hagemann, Alexandra S. M. Wittmar, Corina Andronescu, and Mathias Ulbricht
Wiley
AbstractBecause of their tunable porosity and specific surface area, porous materials are of high interest for the purification of wastewater by adsorption as well as in electrocatalysis, where, in particular, developing metal‐free carbon‐based catalysts for the oxygen reduction reaction (ORR) is researched. The carbon spheres presented here can meet these two requirements simultaneously. Porous polyacrylonitrile (PAN) spheres were firstly prepared by droplet shaping cum nonsolvent induced phase separation. Then, they were converted to nitrogen‐doped carbon spheres by two‐step carbonization via preoxidation and pyrolysis. During the pyrolysis step, carbon dioxide was used to reopen the pores of the materials that had been blocked after the preoxidation step. By this way, specific surface area values of carbon spheres of more than 1000 m2/g could be obtained. Best performing carbon materials (C#3) showed high adsorption capacity (e.g., 296 mg/g for methyl orange at solute equilibrium concentration of 24 mg/L in water). The XPS analysis revealed that only quaternary (N‐Q) and pyridinic (N‐6) nitrogen sites were found in these carbon spheres. The best ORR performance was found also for C#3 carbon spheres, with a potential of 0.81 V versus reversible hydrogen electrode (RHE) at −1 mA/cm2 and electron transfer number of 3.5 at 0.6–0.8 V versus RHE, as determined by rotating disk or rotating ring disk electrode tests. In conclusion, all results confirm that these PAN‐derived carbon spheres are potentially valuable materials for both wastewater treatment by adsorption and electrocatalytic oxygen reduction.
Astita Dubey, Ignacio Sanjuán, Corina Andronescu, and Doru C. Lupascu
Wiley
AbstractThe investigation delves into the functionality exhibited by ferroelectric BiFe0.95Mn0.05O3 (BFM) nanoparticles (NPs) concerning the hydrogen evolution reaction (HER). The electrocatalytic activity of BFM NPs undergoes a transformative shift as a consequence of mono‐, di‐, and tri‐valent cation substitution. Notably, the strategic engineering of doping at the Bi site within BFM NPs yields a remarkable outcome, namely the conspicuous reduction of the kinetic overpotential prerequisite for HER. This diminished overpotential in doped BFM NPs arises from the confluence of multifarious factors: diminished charge transfer resistance, augmented specific surface area, a discernible distribution of pore sizes ranging from narrow to broad, particles endowed with a shape boasting abundant active facets, and the integration of dopants as novel active sites on the surface. Furthermore, the presence of surface defects, oxygen vacancies, and amplified microstrain within doped BFM NPs contributes to the reduction in overpotential.
Ignacio Sanjuán, Vaibhav Kumbhar, Vimanshu Chanda, Raíssa R. L. Machado, Bright N. Jaato, Michael Braun, Muhammad A. A. Mahbub, Georg Bendt, Ulrich Hagemann, Markus Heidelmann,et al.
Wiley
AbstractSimultaneous electroreduction of CO2 and H2O to syngas can provide a sustainable feed for established processes used to synthesize carbon‐based chemicals. The synthesis of MOx/M‐N‐Cs (M = Ni, Fe) electrocatalysts reported via one‐step pyrolysis that shows increased performance during syngas electrosynthesis at high current densities with adaptable H2/CO ratios, e.g., for the Fischer–Tropsch process. When embedded in gas diffusion electrodes (GDEs) with optimized hydrophobicity, the NiOx/Ni‐N‐C catalyst produces syngas (H2/CO = 0.67) at −200 mA cm−2 while for the FeOx/Fe‐N‐C syngas production occurs at ≈−150 mA cm−2. By tuning the electrocatalyst's microenvironment, stable operation for >3 h at −200 mA cm−2 is achieved with the NiOx/Ni‐N‐C GDE. Post‐electrolysis characterization revealed that the restructuring of the catalyst via reduction of NiOx to metallic Ni NPs still enables stable operation of the electrode at −200 mA cm−2, when embedded in an optimized microenvironment. The ionomer and additives used in the catalyst layer are important for the observed stable operation. Operando Raman measurements confirm the presence of NiOx during CO formation and indicate weak adsorption of CO on the catalyst surface.
Doris Segets, Corina Andronescu, and Ulf-Peter Apfel
Springer Science and Business Media LLC
Daniel Siegmund, Corina Andronescu, Christof Schulz, Harry Hoster, Doris Segets, and Ulf‐Peter Apfel
Wiley
AbstractAkademische Forschung und industrielle Anwendung – wie die Zusammenarbeit zwischen Industrie und Akademia zu optimieren ist, zeigt ein Blick aus der technischen Elektrochemie auf deren Anwendung in der Industrie. Wichtig ist dabei eine klare Kommunikation auf beiden Seiten.
Vimanshu Chanda, João R. C. Junqueira, Nivedita Sikdar, Ignacio Sanjuán, Michael Braun, Stefan Dieckhöfer, Sabine Seisel, and Corina Andronescu
Wiley
AbstractElectrochemical conversion of CO2 (CO2RR) has received significant attention since it could provide pathways for renewable energy storage to energy‐dense chemicals and synthetic fuels. We developed a novel CuOx/Cu/C type electrocatalyst via pyrolysis, which we used to convert CO2 at industrially relevantly current densities using gas diffusion electrodes. The influence of the pyrolysis conditions on the electrocatalytic CO2RR activity and selectivity was evaluated. Optimization of the electrode structure to mitigate electrowetting was done by mixing the catalyst with polytetrafluoroethylene (PTFE). We found that mixing the most active catalyst with PTFE in a mass ratio of 1 to 0.25 substantially increased the formation of C2H4 displaying 41% Faradaic efficiency (FE) at –240 mA cm–2. Prolonged CO2RR at different current densities shows that the electrode containing 25 wt.% PTFE in the catalyst layer display FEC2H4 > 40% at –280 mA cm–2 for 2 h.
Moonjoo Kim, Emmanuel Batsa Tetteh, Olga A. Krysiak, Alan Savan, Bin Xiao, Tobias Horst Piotrowiak, Corina Andronescu, Alfred Ludwig, Taek Dong Chung, and Wolfgang Schuhmann
Wiley
AbstractThe vast possibilities in the elemental combinations of high‐entropy alloys (HEAs) make it essential to discover activity descriptors for establishing rational electrocatalyst design principles. Despite the increasing attention on the potential of zero charge (PZC) of hydrogen evolution reaction (HER) electrocatalyst, neither the PZC of HEAs nor the impact of the PZC on the HER activity at HEAs has been described. Here, we use scanning electrochemical cell microscopy (SECCM) to determine the PZC and the HER activities of various elemental compositions of a Pt−Pd−Ru−Ir−Ag thin‐film HEA materials library (HEA‐ML) with high statistical reliability. Interestingly, the PZC of Pt−Pd−Ru−Ir−Ag is linearly correlated with its composition‐weighted average work function. The HER current density in acidic media positively correlates with the PZC, which can be explained by the preconcentration of H+ in the electrical double layer at potentials negative of the PZC.
Swapnil Varhade, Gabriel Meloni, Emmanuel Batsa Tetteh, Monjoo Kim, Simon Schumacher, Thomas Quast, Corina Andronescu, Patrick Unwin, and Wolfgang Schuhmann
Elsevier BV
Alexandra S. M. Wittmar, Marcus Ropertz, Michael Braun, Ulrich Hagemann, Corina Andronescu, and Mathias Ulbricht
Springer Science and Business Media LLC
AbstractCarbon-based electrocatalysts for oxygen reduction reaction (ORR) are prepared by a direct pathway including a two-step thermal treatment process applied to porous spheres of natural biopolymer blends. Cellulose blends with chitosan are first thermally treated at moderate temperatures (e.g., 200 °C), then pyrolyzed at elevated temperature (800–1000 °C), both steps under a constant nitrogen flow. By blending of cellulose with chitosan, the nitrogen content in the final carbon-based catalyst can be considerably increased. The influence of the composition of the precursor biopolymer blend on the ORR electrocatalytic activity is analyzed in correlation with the elemental composition and other structural features of the catalyst. The polymer blend containing cellulose:chitosan = 75:25, thermally treated 1 h at 200 °C and pyrolyzed 1 h at 800 °C under nitrogen atmosphere, shows the highest electrocatalytic ORR activity. This is attributed to an increased surface area combined with relatively high nitrogen content and a higher pyridinic/pyrrolic species ratio.
Michael Braun, Cássia S. Santana, Amanda C. Garcia, and Corina Andronescu
Elsevier BV
Carla Santana Santos, Bright Nsolebna Jaato, Ignacio Sanjuán, Wolfgang Schuhmann, and Corina Andronescu
American Chemical Society (ACS)
Scanning electrochemical probe microscopy (SEPM) techniques can disclose the local electrochemical reactivity of interfaces in single-entity and sub-entity studies. Operando SEPM measurements consist of using a SEPM tip to investigate the performance of electrocatalysts, while the reactivity of the interface is simultaneously modulated. This powerful combination can correlate electrochemical activity with changes in surface properties, e.g., topography and structure, as well as provide insight into reaction mechanisms. The focus of this review is to reveal the recent progress in local SEPM measurements of the catalytic activity of a surface toward the reduction and evolution of O2 and H2 and electrochemical conversion of CO2. The capabilities of SEPMs are showcased, and the possibility of coupling other techniques to SEPMs is presented. Emphasis is given to scanning electrochemical microscopy (SECM), scanning ion conductance microscopy (SICM), electrochemical scanning tunneling microscopy (EC-STM), and scanning electrochemical cell microscopy (SECCM).
Bhawana Kumari, Michael Braun, Steffen Cychy, Ignacio Sanjuán, Gereon Behrendt, Malte Behrens, Martin Muhler, and Corina Andronescu
Wiley
Michael Braun, Mohit Chatwani, Piyush Kumar, Yun Hao, Ignacio Sanjuán, Ariadni-Aikaterini Apostoleri, Ann Cathrin Brix, Dulce M Morales, Ulrich Hagemann, Markus Heidelmann,et al.
IOP Publishing
Abstract A mixed Co and Ni boride precursor was synthesized via chemical reduction and subsequently annealed at 400 or 500 °C with or without prior addition of the monomer benzoxazine (BO). The resulting mixed CoNiB materials were investigated as electrocatalysts for three alcohol oxidation reactions (AOR) in alkaline electrolyte: the oxidation of glycerol (GOR), ethylene glycol (EGOR) and ethanol (EOR). Comparison of the rotating disk electrode (RDE) cyclic voltammograms for the different catalysts revealed that CoNiB annealed at 500 °C without the addition of BO exhibited the lowest overpotentials in AORs at 10 mA cm−2, promoting GOR at 224 ± 6 mV lower potential compared to OER. When pyrolysis was conducted at 400 °C, the BO-containing catalyst showed a significant increase in the electrocatalytic activity for the AORs compared to the CoNiB catalyst only. The product selectivity on the different catalysts was investigated in a batch-type reactor with flow recirculation revealing formate as the main oxidation product during GOR and EGOR with faradaic efficiencies (FE) in a range of 60%–80%, while acetate was obtained during EOR (FE ∼ 85%–90%). The electrode potential, electrolyte composition and the type of ionomer were explored with respect to their influence on the GOR selectivity. The use of different ionomers resulted in significant differences in the activity trends between RDE and the batch-type reactor with flow recirculation measurements, indicating a strong influence of the two different substrates used, namely glassy carbon and carbon paper on the catalyst formation and thus on the recorded electrochemical activity.
Steven Angel, Michael Braun, Baris Alkan, Joachim Landers, Soma Salamon, Heiko Wende, Corina Andronescu, Christof Schulz, and Hartmut Wiggers
American Chemical Society (ACS)
The product properties of mixed oxide nanoparticles generated via spray-flame synthesis depend on an intricate interplay of solvent and precursor chemistries in the processed solution. The effect of two different sets of metal precursors, acetates and nitrates, dissolved in a mixture of ethanol (35 Vol.%) and 2-ethylhexanoic acid (2-EHA, 65 Vol.%) was investigated for the synthesis of LaFexCo1-xO3 (x = 0.2, 0.3) perovskites. Regardless of the set of precursors, similar particle-size distributions (dp = 8-11 nm) were obtained and a few particles with sizes above 20 nm were identified with transmission electron microscopy (TEM) measurements. Using acetates as precursors, inhomogeneous La, Fe, and Co elemental distributions were obtained for all particle sizes according to energy dispersive X-ray (EDX) mappings, connected to the formation of multiple secondary phases such as oxygen-deficient La3(FexCo1-x)3O8 brownmillerite or La4(FexCo1-x)3O10 Ruddlesden-Popper (RP) structures besides the main trigonal perovskite phase. For samples synthesized from nitrates, inhomogeneous elemental distributions were observed for large particles only where La and Fe enrichment occurred in combination with the formation of a secondary La2(FexCo1-x)O4 RP phase. Such variations can be attributed to reactions in the solution prior to injection in the flame as well as precursor-dependent variations in in-flame reactions. Therefore, the precursor solutions were analyzed by temperature-dependent attenuated total reflection Fourier-transform infrared (ATR-FTIR) measurements. The acetate-based precursor solutions indicated the partial conversion of, mainly La and Fe, acetates to metal 2-ethylhexanoates. In the nitrate-based solutions, esterification of ethanol and 2-EHA played the most important role. The synthesized nanoparticle samples were characterized by BET (Brunauer, Emmett, Teller), FTIR, Mössbauer, and X-ray photoelectron spectroscopy (XPS). All samples were tested as oxygen evolution reaction (OER) catalysts, and similar electrocatalytic activities were recorded when evaluating the potential required to reach 10 mA/cm2 current density (∼1.61 V vs reversible hydrogen electrode (RHE)).
Lars Banko, Emmanuel Batsa Tetteh, Aleksander Kostka, Tobias Horst Piotrowiak, Olga Anna Krysiak, Ulrich Hagemann, Corina Andronescu, Wolfgang Schuhmann, and Alfred Ludwig
Wiley
Polyelemental material systems, specifically high‐entropy alloys, promise unprecedented properties. Due to almost unlimited combinatorial possibilities, their exploration and exploitation is hard. This challenge is addressed by co‐sputtering combined with shadow masking to produce a multitude of microscale combinatorial libraries in one deposition process. These thin‐film composition spreads on the microscale cover unprecedented compositional ranges of high‐entropy alloy systems and enable high‐throughput characterization of thousands of compositions for electrocatalytic energy conversion reactions using nanoscale scanning electrochemical cell microscopy. The exemplary exploration of the composition space of two high‐entropy alloy systems provides electrocatalytic activity maps for hydrogen evolution and oxygen evolution as well as oxygen reduction reactions. Activity optima in the system Ru–Rh–Pd–Ir–Pt are identified, and active noble‐metal lean compositions in the system Co–Ni–Mo–Pd–Pt are discovered. This illustrates that the proposed microlibraries are a holistic discovery platform to master the multidimensionality challenge of polyelemental systems.
Swapnil Varhade, Emmanuel Batsa Tetteh, Sascha Saddeler, Simon Schumacher, Harshitha Barike Aiyappa, Georg Bendt, Stephan Schulz, Corina Andronescu, and Wolfgang Schuhmann
Wiley
The electrocatalytic activity for the oxygen evolution reac-tion in alkaline electrolyte of hexagonal spinel Co3O4 nanoparticles derived using scanning electrochemical cell microscopy (SECCM) is correlated with scanning electron microscopy and atomic force microscopy images of the droplet landing sites. A unique way to deconvolute the intrinsic catalytic activity of individual crystal facets of the hexagonal Co3O4 spinel particle is demonstrated in terms of the turnover frequency (TOF) of surface Co atoms. The top surface expo-sing 111 crystal planes displayed a thickness-dependent TOF with a TOF of about 100 s-1 at a potential of 1.8 V vs RHE and a particle thickness of 100 nm. The edge of the particle exposing (110) planes, however, showed an average TOF of 270 ± 68 s-1 at 1.8 V vs RHE and no correlation with particle thickness. However, the higher atomic density of Co atoms on the edge surface (2.5 times of the top) renders the overall catalytic activity of the edge planes significantly higher than that of the top planes. The use of a free-diffusing Os- complex in the alkaline electrolyte revealed the low electrical conductivity through individual particles which explains the thickness-dependent TOF of the top planes and could be a reason for the low activity of the top (111) planes.
Baris Alkan, Michael Braun, Gautier Landrot, Olaf Rüdiger, Corina Andronescu, Serena DeBeer, Christof Schulz, and Hartmut Wiggers
Springer Science and Business Media LLC
AbstractLa1–xSrxCoO3 (x = 0, 0.1, 0.2) and LaCo0.8Fe0.2O3 perovskite nanoparticles were synthesized by spray-flame synthesis, and their electrocatalytic water oxidation activity was evaluated in the prepared state. Highly crystalline, rhombohedrally distorted cubic structures of the cobaltite perovskites were confirmed by STEM and XRD analyses. The decreased JT distortions were observed in the cobaltite perovskite structure upon substitution with Sr, while orthorhombic distortions in Fe-substituted perovskites could explain the changes in their Raman spectra. Debye–Waller factors and coordination numbers from fitted EXAFS data indicate more disordered crystalline structures upon Sr substitution and a lower Co–O coordination number at 20 at% Sr. Thermal characterization of the catalysts by STA coupled with QMS shows higher mass losses in Sr-substituted catalysts, and these results were associated with a higher concentration of carbonate species in these catalysts, which was also confirmed by XPS measurements. Both Fe and Sr substitution lead to higher catalytic OER activity of the cobaltite perovskites with lower overpotentials of about 30–50 mV. The cobaltite perovskite catalyst substituted with 20 at% Sr exhibited the highest OER activity and stable electrocatalytic performance at moderate conditions.
Simon Schumacher, Lukas Madauß, Yossarian Liebsch, Emmanuel Batsa Tetteh, Swapnil Varhade, Wolfgang Schuhmann, Marika Schleberger, and Corina Andronescu
Wiley
Abstract The electrocatalytic activity concerning the hydrogen evolution reaction (HER) of micrometer‐sized MoS2 layers transferred on a glassy carbon surface was evaluated by scanning electrochemical cell microscopy (SECCM) in a high‐throughput approach. Multiple areas on single or multiple MoS2 layers were assessed using a hopping mode nanocapillary positioning with a hopping distance of 500 nm and a nanopipette size of around 55 nm. The locally recorded linear sweep voltammograms revealed a high lateral heterogeneity over the MoS2 sheet regarding their HER activity, with currents between −40 and −60 pA recorded at −0.89 V vs. reversible hygrogen electrode over about 4400 different measured areas on the MoS2 sheet. Stacked MoS2 layers did not show different electrocatalytic activity than the single MoS2 sheet, suggesting that the interlayer resistance influences the electrocatalytic activity less than the resistances induced by possible polymer residues or water layers formed between the transferred MoS2 sheet and the glassy carbon electrode.
Michael Braun, Gereon Behrendt, Moritz L. Krebs, Patricia Dimitri, Piyush Kumar, Ignacio Sanjuán, Steffen Cychy, Ann Cathrin Brix, Dulce M. Morales, Jennifer Hörlöck,et al.
Wiley
Emmanuel Batsa Tetteh, Lars Banko, Olga A. Krysiak, Tobias Löffler, Bin Xiao, Swapnil Varhade, Simon Schumacher, Alan Savan, Corina Andronescu, Alfred Ludwig,et al.
Wiley
Olga A. Krysiak, Simon Schumacher, Alan Savan, Wolfgang Schuhmann, Alfred Ludwig, and Corina Andronescu
Springer Science and Business Media LLC
AbstractDespite outstanding accomplishments in catalyst discovery, finding new, more efficient, environmentally neutral, and noble metal-free catalysts remains challenging and unsolved. Recently, complex solid solutions consisting of at least five different elements and often named as high-entropy alloys have emerged as a new class of electrocatalysts for a variety of reactions. The multicomponent combinations of elements facilitate tuning of active sites and catalytic properties. Predicting optimal catalyst composition remains difficult, making testing of a very high number of them indispensable. We present the high-throughput screening of the electrochemical activity of thin film material libraries prepared by combinatorial co-sputtering of metals which are commonly used in catalysis (Pd, Cu, Ni) combined with metals which are not commonly used in catalysis (Ti, Hf, Zr). Introducing unusual elements in the search space allows discovery of catalytic activity for hitherto unknown compositions. Material libraries with very similar composition spreads can show different activities vs. composition trends for different reactions. In order to address the inherent challenge of the huge combinatorial material space and the inability to predict active electrocatalyst compositions, we developed a high-throughput process based on co-sputtered material libraries, and performed high-throughput characterization using energy dispersive X-ray spectroscopy (EDS), scanning transmission electron microscopy (SEM), X-ray diffraction (XRD) and conductivity measurements followed by electrochemical screening by means of a scanning droplet cell. The results show surprising material compositions with increased activity for the oxygen reduction reaction and the hydrogen evolution reaction. Such data are important input data for future data-driven materials prediction.
Ieva A. Cechanaviciute, Tim Bobrowski, Daliborka Jambrec, Olga A. Krysiak, Ann Cathrin Brix, Michael Braun, Thomas Quast, Patrick Wilde, Dulce M. Morales, Corina Andronescu,et al.
Wiley
Ann Cathrin Brix, Maik Dreyer, Adarsh Koul, Moritz Krebs, Anna Rabe, Ulrich Hagemann, Swapnil Varhade, Corina Andronescu, Malte Behrens, Wolfgang Schuhmann,et al.
Wiley