Investigation of non-stoichiometric tungsten-oxides and carbides as the anode catalysts supports and additives for the proton exchange membrane fuel cells

Gorivne ćelije sa protonski provodnom membranom (PEM) su elektrohemijski sistemi koji iz vodonika (goriva) i kiseonika/vazduha (oksidansa) proizvode ĉistu elektriĉnu energiju, toplotu i vodu. Masovnu proizvodnju i upotrebu gorivnih ćelija ograniĉava cena komponenti, pre svega cena katalizatora. Neĉistoća goriva (prisustvo CO) dovodi do razgradnje i trovanja katalizatora. Stoga, intenzivno se razvijaju jeftiniji i dugotrajniji katalizatori i njihovi interaktivni nosaĉi. U okviru ove doktorske disertacije razvijeni su nestehiometrijski oksidi i karbidi volframa kao nosaĉi/aditivi katalizatora baziranih na Pt i PtRu za PEM gorivne ćelije. Ispitivana je provodljivost, struktura, morfologija i sastav pripremljenih nosaĉa/aditiva i katalizatora. Katalizatori su ispitivani cikliĉnom voltametrijom i voltametrijom na rotirajućoj disk elektrodi. Graniĉne difuzione struje oksidacije vodonika (HOR) dostižu se vrlo brzo i zadržavaju konstantne vrednosti u širokoj oblasti potencijala koji odgovaraju anodnim potencijalima aktivne PEM gorivne ćelije. Posebna pažnja posvećena je ispitivanju tolerancije katalizatora na CO korišćenjem metode elektrooksidacije COads i kinetike HOR u prisustvu CO. Sintetisani katalizatori pokazuju veću katalitiĉku aktivnost i toleranciju na CO u odnosu na komercijalne katalizatore. Pripremljeni katalizatori korišćeni su kao anodni katalizatori u jediniĉnim PEM gorivnim ćelijama. Performanse su ispitivane pri razliĉitim radnim uslovima: H2/O2, H2+CO/vazduh, reformat/vazduh, na razliĉitim temperaturama. Najbolje performanse daje PEM gorivna ćelija sa anodnim katalizatorom 30% PtRu/WxCyOz koja na 70ºC ima ~40% veću iskorišćenost Pt u odnosu na komercijalni katalizator. Veća iskorišćenost implicira moguće smanjenje koliĉine Pt, a time i nižu cenu PEM gorivne ćelije.Proton exchange membrane (PEM) fuel cells are electrochemical systems that produce clean electricity, heat and water from hydrogen (fuel) and oxygen/air (oxidants). Mass production and use of fuel cells is limited by the price of components, primarily the price of catalysts. Fuel impurities (presence of CO) lead to decomposition and poisoning of the catalyst. That is why cheaper and longlasting catalysts and their interactive supports are being intensively developed. Within this doctoral dissertation, non-stoichiometric tungsten-oxides and carbides were developed as supports/additives for catalysts based on Pt and PtRu for PEM fuel cells. The conductivity, structure, morphology and composition of the prepared supports/additives and catalysts were investigated. The catalysts were tested by cyclic voltammetry and rotating disk electrode voltammetry. Limiting diffusion currents were reached very quickly and maintained constant values in a wide range of potentials that corresponding to the anode potentials of the active PEM fuel cell. Special attention was dedicated to the examination of the catalyst CO tolerance , using the method of electro-oxidation of COads and HOR kinetics in the presence of CO. The synthesized catalysts showed higher catalytic activity and CO tolerance compared to commercial catalysts. The prepared catalysts were used as anode catalysts in unit PEM fuel cells. Performance was tested under various operating conditions: H2/O2, H2+CO/air and reformate/air, at different temperatures. The best performance was achieved with a PEM fuel cell employing 30% PtRu/WxCyOz anode catalyst which had ~40% higher Pt utilization compared to a commercial catalyst at 70ºC. Higher utilization implies possible reduction of the Pt loading and thus a lower cost of the PEM fuel cell

Energetska tranzicija i vodonična evolucija

The escalating concerns over climate changes and environmental disturbances resulting from anthropogenic influence have propelled the scientific community to seek efficient models for the energy transition. Hydrogen emerges as a promising energy carrier with the potential to replace fossil fuels and mitigate global warming, a pressing threat to life on Earth. This research paper primarily focuses on the electrolytic production of hydrogen, deemed the environmentally acceptable method for this purpose. The central emphasis lies in enhancing the electrodes utilized in this process to elevate the significance of the Hydrogen Evolution Reaction (HER). By improving HER, a pivotal step in the hydrogen production process, the trajectory of civilization's evolution can be positively influenced.Sve veća zabrinutost zbog klimatskih promena i ekoloških poremećaja koji su rezultat antropogenog uticaja naterali su naučnu zajednicu da traži efikasne modele za energetsku tranziciju. Vodonik se pojavljuje kao perspektivan nosilac energije sa potencijalom da zameni fosilna goriva i ublaži globalno zagrevanje, goruću pretnju životu na Zemlji. Ovaj istraživački rad se prvenstveno fokusira na elektrolitičku proizvodnju vodonika, koja se smatra ekološki prihvatljivom metodom za ovu svrhu. Centralni naglasak je na poboljšanju elektroda koje se koriste u ovom procesu kako bi se podigao značaj reakcije evolucije vodonika (HER). Poboljšanjem HER, ključnog koraka u procesu proizvodnje vodonika, može se pozitivno uticati na putanju evolucije civilizacije

In-situ grafting of Fe and Cu nanoparticles on carbon for electrolytic hydrogen production

In order to reduce air pollution by green-house gases released during fossil fuels combustion, hydrogen has been suggested as an alternative, clean fuel [1]. The most promising method of obtaining green hydrogen (and oxygen) is electrolytic water splitting [2]. For splitting process to be efficient, it is necessary to useelectrocatalysts with high activity, but they should also be economically accessible. Ionic liquids are used in the most diverse fields of sciencedue to their unique physical and chemical properties, and in this regard, they can be used for the development of electrocatalystsby direct carbonization [3]. Within this study, carbon catalysts doped with iron and copper (Fe/C, Cu/C and FeCu/C) were prepared by carbonization of ionic liquids containing the corresponding metal and characterized for the hydrogen evolution reaction (HER) in alkaline (8 M KOH) media. Electrochemical measurements were made by cyclic voltammetry (CV), linear cyclic voltammetry (LSV), electrochemical impedance spectroscopy (EIS) and chronoamperometry (CA). All electrocatalysts showed good activity for HER. Tafel slope (b) values of -132, 155 and -151 mV dec-1 (Table 1) were obtained for HER at 25 oC for Fe/C, Cu/C and FeCu/C, respectively. Also, the exchange current density (j0) was determined and the values ranged from 1.28 to 2.94 10-2 mAcm-2. The results (Table 1) show that Fe/C, Cu/C and FeCu/Care promisingelectrocatalysts for hydrogen gas production by water splitting.Ninth Symposium Chemistry and Environmental Protection : June 4-7, Kladovo, 2023

Na zelenom putu inovacija – vodonik iz laserski potpomognute alkalne elektrolize

The dominant problem that needs to be solved today is the issue of energy sources and how to use them, which must be ecological and sustainable - in a word, green. As the best candidate for a global solution to this problem, hydrogen produced electrolytically stood out as a green fuel with no carbon footprint. However, for a hydrogen-based economy to have a realistic and sustainable perspective in the future, it largely depends on its efficient and economically viable production that would meet the market's needs. Special attention in this paper is devoted to the influence of laser radiation on the possibility of improving the process of alkaline electrolysis for obtaining hydrogen, as well as on increasing the amount of separated hydrogen when the electrolytic cell is directly irradiated with a laser beam during the electrolysis process itself. After the experiments, it was determined that the application of direct irradiation of the electrolyte with a green laser at 532 nm wavelength significantly increases the amount of hydrogen produced and reduces the voltage of the electrolytic process, which is directly related to the increase in the energy efficiency of the overall hydrogen production process.Dominantan problem koji danas treba rešiti je pitanje energenata i načina njihove upotrebe koji moraju biti ekološki i održivi – jednom rečju zeleni. Kao najbolji kandidat za globalno rešenje ovog problema istakao se vodonik proizveden elektolitičkim putem, kao zeleno gorivo bez ugljeničnih otisaka. Da bi ekonomija zasnovana na vodoniku imala realnu i održivu perspektivu u budućnosti, u velikoj meri zavisi od njegove efikasne i ekonomski podobne proizvodnje koja bi zadovoljila potrebe tržišta. Posebna pažnja u ovom radu posvećena je uticaju laserskog zračenja na mogućnost poboljšanja procesa alkalne elektrolize za dobijanje vodonika, kao i na povećanje količine izdvojenog vodonika pri direktnom ozračivanju elektrolitičke ćelije laserskim snopom tokom samog procesa elektrolize. Nakon izvršenih eksperimenata utvrđeno je da se primenom direktnog ozračivanja elektrolita zelenim laserom talasne dužine 532 nm u značajnoj meri povećava količina proizvedenog vodonika i smanjuje napon elektrolitičkog procesa, što je u direktnoj vezi sa povećanjem energetske efikasnosti ukupnog procesa dobijanja vodonika

Ab Initio Study of Graphene Interaction with O-2, O, and O-

A systematic ab initio (DFT-GGA) study of adsorption of various oxygen species on graphene has been performed in order to find out general trends and provide a good starting point to analyze the oxidation of more complex carbon materials. Particular attention was paid to finding an appropriate supercell model. According to our findings, atomic O is characterized by stable adsorption on graphene and very strong adsorption on defective graphene. On the other hand, O-2 does not adsorb on graphene and is allowed to diffuse freely to the defect, where it is expected to dissociate into two strongly adsorbed O atoms. The obtained results were compared with available theoretical data in the literature and good agreement was achieved

Investigation of non-stoichiometric tungsten-oxides and carbides as the anode catalysts supports and additives for the proton exchange membrane fuel cells

Gorivne ćelije sa protonski provodnom membranom (PEM) su elektrohemijski sistemi koji iz vodonika (goriva) i kiseonika/vazduha (oksidansa) proizvode ĉistu elektriĉnu energiju, toplotu i vodu. Masovnu proizvodnju i upotrebu gorivnih ćelija ograniĉava cena komponenti, pre svega cena katalizatora. Neĉistoća goriva (prisustvo CO) dovodi do razgradnje i trovanja katalizatora. Stoga, intenzivno se razvijaju jeftiniji i dugotrajniji katalizatori i njihovi interaktivni nosaĉi. U okviru ove doktorske disertacije razvijeni su nestehiometrijski oksidi i karbidi volframa kao nosaĉi/aditivi katalizatora baziranih na Pt i PtRu za PEM gorivne ćelije. Ispitivana je provodljivost, struktura, morfologija i sastav pripremljenih nosaĉa/aditiva i katalizatora. Katalizatori su ispitivani cikliĉnom voltametrijom i voltametrijom na rotirajućoj disk elektrodi. Graniĉne difuzione struje oksidacije vodonika (HOR) dostižu se vrlo brzo i zadržavaju konstantne vrednosti u širokoj oblasti potencijala koji odgovaraju anodnim potencijalima aktivne PEM gorivne ćelije. Posebna pažnja posvećena je ispitivanju tolerancije katalizatora na CO korišćenjem metode elektrooksidacije COads i kinetike HOR u prisustvu CO. Sintetisani katalizatori pokazuju veću katalitiĉku aktivnost i toleranciju na CO u odnosu na komercijalne katalizatore. Pripremljeni katalizatori korišćeni su kao anodni katalizatori u jediniĉnim PEM gorivnim ćelijama. Performanse su ispitivane pri razliĉitim radnim uslovima: H2/O2, H2+CO/vazduh, reformat/vazduh, na razliĉitim temperaturama. Najbolje performanse daje PEM gorivna ćelija sa anodnim katalizatorom 30% PtRu/WxCyOz koja na 70ºC ima ~40% veću iskorišćenost Pt u odnosu na komercijalni katalizator. Veća iskorišćenost implicira moguće smanjenje koliĉine Pt, a time i nižu cenu PEM gorivne ćelije.Proton exchange membrane (PEM) fuel cells are electrochemical systems that produce clean electricity, heat and water from hydrogen (fuel) and oxygen/air (oxidants). Mass production and use of fuel cells is limited by the price of components, primarily the price of catalysts. Fuel impurities (presence of CO) lead to decomposition and poisoning of the catalyst. That is why cheaper and longlasting catalysts and their interactive supports are being intensively developed. Within this doctoral dissertation, non-stoichiometric tungsten-oxides and carbides were developed as supports/additives for catalysts based on Pt and PtRu for PEM fuel cells. The conductivity, structure, morphology and composition of the prepared supports/additives and catalysts were investigated. The catalysts were tested by cyclic voltammetry and rotating disk electrode voltammetry. Limiting diffusion currents were reached very quickly and maintained constant values in a wide range of potentials that corresponding to the anode potentials of the active PEM fuel cell. Special attention was dedicated to the examination of the catalyst CO tolerance , using the method of electro-oxidation of COads and HOR kinetics in the presence of CO. The synthesized catalysts showed higher catalytic activity and CO tolerance compared to commercial catalysts. The prepared catalysts were used as anode catalysts in unit PEM fuel cells. Performance was tested under various operating conditions: H2/O2, H2+CO/air and reformate/air, at different temperatures. The best performance was achieved with a PEM fuel cell employing 30% PtRu/WxCyOz anode catalyst which had ~40% higher Pt utilization compared to a commercial catalyst at 70ºC. Higher utilization implies possible reduction of the Pt loading and thus a lower cost of the PEM fuel cell

Pt/C catalyst impregnated with tungsten-oxide – Hydrogen oxidation reaction vs. CO tolerance

Hydrogen Oxidation Reaction (HOR) is anode reaction in Proton exchange membrane fuel cells (PEMFCs) and it has very fast kinetics. However, the purity of fuel (H 2 ) is very important and can slow down HOR kinetics, affecting the overall PEMFC performance. The performance of commercial Pt/C catalyst impregnated with WO x, as a catalyst for HOR, was investigated using a set of electrochemical methods (cyclic voltammetry, linear scan voltammetry and rotating disk electrode voltammetry). In order to deepen the understanding how WO x species can contribute CO tolerance of Pt/C, a particular attention was paid to CO poisoning. In the absence of CO, HOR is under diffusion limitations and HOR kinetics is not affected by WO x species. Appreciable HOR current on the electrodes pre-saturated with CO ads at potentials above 0.3 V vs. RHE, which is not observed for pure Pt/C, was discussed in details. HOR liming diffusion currents for higher concentrations of W are reached at high anodic potentials. The obtained results were explained by donation of OH ads by WO x phase for CO ads removal in the mid potential region and reduced reactivity of Pt surface sites in the vicinity of the Pt|WO x interface. The obtained results can provide guidelines for development of novel CO tolerant PEMFC anode catalysts. © 2019 Hydrogen Energy Publications LL

Novel Non-Stoichiometric Tungsten Oxide Based Catalyst Support for the Increased CO Tolerance in PEMFC

Cost and durability are two major factors that delay large-scale production and commercialization of PEMFC's. One of the technologically ready application of the proton exchange membrane fuel cells (PEMFC) is in the combined heat and power systems (µCHP), which are used in the individual households or buildings. The performance of the µCHP systems greatly depends on the purity of the hydrogen stream, which is produced via methane reforming process. To overcome low CO tolerance of the commercially used Pt electrocatalyst and to lower the catalyst content we have prepared non-stoichiometric tungsten oxide as a Pt based catalyst support. We have prepared several catalysts designated as 10% Pt/WO3-C, 20% Pt/WO3-C, 40% Pt/WO3-C. The structure and morphology characteristics of the prepared catalysts were investigated using XRD, TEM and SEM/EDX techniques. Investigations concerning electroactivity of these catalysts towards the hydrogen oxidation reaction (HOR) were performed using cyclic voltammetry, linear sweep voltammetry, forming an ultra thin catalyst layer onto RDE. Mechanism and the kinetics of the prepared catalysts towards HOR were evaluated and if was found that increased mass activity of the 10% Pt/WO3-C could be attributed to the interactive naure of the WO3 catalyst support. Obtained results clearly show increased CO tolerance of Pt/WO3-C catalyst compared to commercial Pt/C, which was confirmed by lowering the stripping potential of the CO, adsorbed on the surface of the 10% Pt/WO3-C. catalyst is more facile than that on commercial 40% Pt/C. These catalysts were employed as anode catalyst in the MEA, and the performance of single cell PEMFC were compared to commercial catalyst

Experimental and DFT study of CoCuMo ternary ionic activator for alkaline HER on Ni cathode

In this work, nickel (Ni) cathode for hydrogen evolution reaction (HER) in alkaline medium, was modified by a combination of in situ ionic activators, based on three d-metals (Co, Cu and Mo). Catalytic performance of new Co-Cu-Mo cathode was improved compared to pure Ni in view of both increased HER reaction rate and improved energy efficiency - reduction of energy consumption of a model electrolytic cell by 15%. We discussed obtained results in comparison with previously investigated similar systems (Ni-Co-Mo and Ni-Cu-Mo). In addition, we perform a detailed surface characterization by a series of experimental techniques (XRF, XRD, SEM, profilometry and EIS) and employ DFT calculations to provide a more detailed discussion of the origin of obtained catalytic performance. © 2019 Elsevier B.V

Non-stoichiometric tungsten-carbide-oxide-supported Pt–Ru anode catalysts for PEM fuel cells – From basic electrochemistry to fuel cell performance

Durability and cost of Proton Exchange Membrane fuel cells (PEMFCs) are two major factors delaying their commercialization. Cost is associated with the price of the catalysts, while durability is associated with degradation and poisoning of the catalysts, primarily by CO. This motivated us to develop tungsten-carbide-oxide (WxCyOz) as a new non-carbon based catalyst support for Pt–Ru–based anode PEMFC catalyst. The aim was to improve performance and obtain higher CO tolerance compared to commercial catalysts. The performance of obtained PtRu/WxCyOz catalysts was investigated using cyclic voltammetry, linear scan voltammetry and rotating disk electrode voltammetry. Particular attention was given to the analysis of CO poisoning, to better understand how WxCyOz species can contribute to the CO tolerance of PtRu/WxCyOz. Improved oxidation of COads at low potentials (E 0.5 V vs. RHE) CO removal proceeds dominantly via OH provided from the oxidized metal sites. The obtained catalyst with the best performance (30% PtRu/WxCyOz) was tested as an anode catalyst in PEM fuel cell. When using synthetic reformate as a fuel in PEMFC, there is a significant power drop of 35.3 % for the commercial 30% PtRu/C catalyst, while for the PtRu/WxCyOz anode catalyst this drop is around 16 %