Naslov (eng)

Investigation of the influence of electrolytes and the role of reduced graphene oxide as a support for metal catalysts on the catalytic activity toward the hydrogen evolution reaction : doctoral dissertation

Autor

Gebremariam, Goitom, 1986-

Doprinosi

Pašti, Igor, 1984-
Gavrilov, Nemanja, 1981-
Dobrota, Ana, 1990-
Krstajić Pajić, Mila, 1989-

Opis (srp)

Efficient hydrogen production is crucial due to the global energy crisis and environmental concerns,which necessitates identifying catalytic trends for informed choices in hydrogen generation technologiesand materials. Hydrogen evolution reaction (HER) volcano plots, initially established for acidic solutionsand later adapted for alkaline media, play a crucial role in identifying catalytic trends related to HER.The first part of the thesis focuses on conducting a comprehensive analysis of the HER catalytic trendson nine polycrystalline monometallic surfaces in seven solutions, encompassing a wide pH range fromhighly acidic to highly alkaline.Using theoretically calculated hydrogen binding energies (HBEs) on clean metallic surfaces andexperimentally measured HER overpotentials it is shown, for the first time, that the volcano-likerelationships are predominantly preserved across a broad spectrum of pH values, spanning from acidicto neutral and alkaline solutions. This signifies that HBE can be used as a descriptor for the identificationof active electrocatalysts in a wide pH range, including pH neutral solutions. Accordingly, Cr was foundto have high HER activity in pH-neutral solutions surpassing that of W, Fe, and Co. Furthermore,exposing metallic surfaces to high anodic potentials can lead to either enhanced or suppressed HER,depending on the metal and the electrolyte used. In view of the nontrivial impacts of surface oxidation,its effects might be seen either as a promotion in HER activity or as HER blocking (as in the case of Crand W). The former case is specifically applicable to Ni and Co in alkaline and pH-neutral solutions,which can be attributed to the enhanced dissociation of water at the metal-oxide interface. This effect ismore significant for Ni in NaCl solutions to the extent that, after undergoing oxidation, it becomes moreactive than Pt. Therefore, this section of the research work reveals that the shape of the volcano curve islargely preserved in the entire pH range, indicating that HBE can be employed to identify powerfulcatalysts for the HER regardless of pH.Supporting metal catalysts on various supports is another possible design strategy to boost the catalyticactivity and stability and improve their utilization. Kinetic Monte Carlo (KMC) simulations wereemployed in the second part of the thesis work to illustrate that the HER can be enhanced throughhydrogen spillover to the support material. This effect happens when the catalysts have a high surfacecoverage of adsorbed hydrogen atoms under the reaction conditions. Drawing from the insights obtainedthrough KMC, a range of catalysts supported on reduced graphene oxide were synthesized, and theirperformance in promoting the HER was then compared to their respective pure metal counterparts inalkaline environments. While the support effect is negative for Ag, Au, and Zn, it boosts the HER activityfor Pt, Pd, Fe, Co, and Ni. The HER volcano plot, a plot of calculated HBEs vs measured HER activities,is preserved and demonstrates a positive shift in the strong binding region. Thus, this part of the thesiswork highlights the potential of metal-support interface engineering in making effective catalysts forHER and provides general guidelines for selecting suitable combinations of catalysts and supports forenhanced electrocatalytic hydrogen production.

Opis (srp)

Physical chemistry - Electrochemistry / Fizička hemija - Elektrohemija Datum odbrane: 26.09.2023.

Opis (eng)

Efikasna proizvodnja vodonika je ključna zbog globalne energetske krize i zabrinutosti za životnusredinu, što zahteva identifikaciju katalitičkih trendova za informisane izbore u tehnologijama imaterijalima za proizvodnju vodonika. Vulkanske krive reakcije izdvajanja vodonika (HER), prvobitnouspostavljene za kisele rastvore, a kasnije prilagođene za alkalne medije, igraju ključnu ulogu uidentifikaciji katalitičkih trendova povezanih sa HER. Prvi deo ove doktorske disertacije fokusira se nasprovođenje sveobuhvatne analize HER katalitičkih trendova na devet polikristalnih monometalnihpovršina u sedam rastvora, obuhvatajući širok pH opseg od visoko kiselih do visoko alkalnih.Koristeći teorijskiizračunate energije vezivanja vodonika (HBE) na čistim metalnim površinama ieksperimentalno izmerene HER nadnapone, po prvi put je pokazanoda su relacije vulkanskog tipapretežno očuvane u širokom spektru pH vrednosti, od kiselih do neutralnih i alkalnih rastvora. Ovo značida se HBE može koristiti kao deskriptor za identifikaciju aktivnih elektrokatalizatora u širokom pHopsegu, uključujući pH neutralne rastvore. Shodno tome, otkriveno je da Cr ima visoku HER aktivnostu pH-neutralnim rastvorima, koja nadmašuje aktivnostV, Fe i Co. Štaviše, izlaganje metalnih površinavisokim anodnim potencijalima može dovesti do pojačane ili potisnute HER, u zavisnosti od metala ikorišćenog elektrolita. S obzirom na netrivijalne uticaje oksidacije površine, njeni efekti se moguposmatrati ili kao promocija HER aktivnosti ili kao HER blokiranje (kao u slučaju Cr i V). Prvi slučaj jeposebno primenljiv na Ni i Co u alkalnim i pH-neutralnim rastvorima, što se može pripisati pojačanojdisocijaciji vode na granici fazametal-oksid. Ovaj efekat je značajniji za Ni u rastvorima NaCl, do temere da posle oksidacije postaje aktivniji od Pt. Stoga, ovaj deo istraživačkog rada otkriva da je oblikvulkanske krive u velikoj meri očuvan u čitavom pH opsegu, što ukazuje da se HBE može koristiti zaidentifikaciju pogodnih katalizatora za HER bez obzira na pH.Postavljanje metalnih katalizatora na različite nosače je još jedna moguća strategija dizajna za povećanjekatalitičke aktivnosti i stabilnosti i poboljšanje njihovog korišćenja. Kinetičke Monte Karlo (KMC)simulacije su korišćene u drugom delu teze da bi se ilustrovalo da se HER može pospešitiprelivanjemvodonika na potporni materijal. Ovaj efekat se dešava kada katalizatori imaju visoku površinskupokrivenost adsorbovanih atoma vodonika u uslovima reakcije. Na osnovu uvida dobijenih putem KMC-a, sintetisanje niz katalizatora podržanih na redukovanom grafen–oksidu, a njihov učinak u promovisanjuHER je zatim upoređen sa odgovarajućim čistim metalima u alkalnim sredinama. Dok je efekatnosačanegativan za Ag, Au i Zn, on povećava HER aktivnost za Pt, Pd, Fe, Co i Ni. HER vulkanskakriva, dijagram izračunatih HBE u odnosu na izmerene HER aktivnosti, je očuvana i pokazuje pozitivanpomak u regionu jakog vezivanja. Stoga, ovaj deo teze naglašava potencijal inženjeringa granicafazametal-podloga u pripremiefikasnih katalizatora za HER i pruža opšte smernice za odabirodgovarajućih kombinacija katalizatora i nosača za poboljšanu elektrokatalitičku proizvodnju vodonika.

Jezik

srpski

Datum

2023

Licenca

Ovo delo je licencirano pod uslovima licence
Creative Commons CC BY-NC-ND 3.0 AT - Creative Commons Autorstvo - Nekomercijalno - Bez prerada 3.0 Austria License.

http://creativecommons.org/licenses/by-nc-nd/3.0/at/legalcode

Predmet

Reakcija izdvajanja vodonika, elektrokataliza, vulkanske krive, redukovani grafen-oksid, nosač katalizatora

Hydrogen evolution reaction, electrocatalysis, volcano plots, reduced graphene oxide, catalyst support