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Improving The Efficiency Of Ammonia Electrolysis For Hydrogen Production

Palaniappan, Ramasamy
http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1386341476

Abstract Details

2013, Doctor of Philosophy (PhD), Ohio University, Chemical Engineering (Engineering and Technology).
Given the abundance of ammonia in domestic and industrial wastes, ammonia electrolysis is a promising technology for remediation and distributed power generation in a clean and safe manner. Efficiency has been identified as one of the key issues that require improvement in order for the technology to enter the market phase. Therefore, this research was performed with the aim of improving the efficiency of hydrogen production by finding alternative materials for the cathode and electrolyte. 1. In the presence of ammonia the activity for hydrogen evolution reaction (HER) followed the trend Rh>Pt>Ru>Ni. The addition of ammonia resulted in lower rates for HER for Pt, Ru, and Ni, which have been attributed to competition from the ammonia adsorption reaction. 2. The addition of ammonia offers insight into the role of metal-hydrogen underpotential deposition (M-Hupd) on HER kinetics. In addition to offering competition via ammonia adsorption it resulted in fewer and weaker M-Hupd bonds for all metals. This finding substantiates the theory that M-Hupd bonds favor HER on Pt electrocatalyst. However, for Rh results suggest that M-Hupd bond may hinder the HER. In addition, the presence of unpaired valence shell electrons is suggested to provide higher activity for HER in the presence of ammonia. 3. Bimetals PtxM1-x (M = Ir, Ru, Rh, and Ni) offered lower overpotentials for HER compared to the unalloyed metals in the presence of ammonia. The activity of HER in the presence of ammonia follows the trend Pt-Ir>Pt-Rh>Pt-Ru>Pt-Ni. The higher activity of HER is attributed to the synergistic effect of the alloy, where ammonia adsorbs onto the more electropositive alloying metal leaving Pt available for Hupd formation and HER to take place. Additionally, this supports the theory that the presence of a higher number of unpaired electrons favors the HER in the presence of ammonia. 4. Potassium polyacrylate (PAA-K) was successfully used as a substitute for aqueous KOH for ammonia electrolysis. PAA-K allowed for a wider operating potential for the electrolytic cell while increasing the rate for HER at lower cell voltages. The conversion of ammonia improved from 16 % to 25 %, while the current efficiency for the consumption of ammonia increased from 92 ± 1 % to 97 ± 2 % by using PAA-K in lieu of KOH. The use of PAA-K also prevented the crossover of the hydrogen produced to the anode side, unlike aqueous KOH.
Gerardine Botte, Ph.D. (Advisor)
Howard Dewald, Ph.D. (Committee Member)
David Ingram, Ph.D. (Committee Member)
Valerie Young, Ph.D. (Committee Member)
Kevin Crist, Ph.D. (Committee Member)
173 p.
Chemical Engineering; Chemistry; Energy; Engineering
Ammonia Electrolysis; Hydrogen; Electrolysis; Electrodeposition; Hydrogen Underpotential Depositions; Platinum; Ruthenium; Rhodium; Nickel; Alkaline Polymer Gel Electrolyte; Poly Acrylic Acid

Recommended Citations

Citations

  • Palaniappan, R. (2013). Improving The Efficiency Of Ammonia Electrolysis For Hydrogen Production [Doctoral dissertation, Ohio University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1386341476

    APA Style (7th edition)

  • Palaniappan, Ramasamy. Improving The Efficiency Of Ammonia Electrolysis For Hydrogen Production. 2013. Ohio University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1386341476.

    MLA Style (8th edition)

  • Palaniappan, Ramasamy. "Improving The Efficiency Of Ammonia Electrolysis For Hydrogen Production." Doctoral dissertation, Ohio University, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1386341476

    Chicago Manual of Style (17th edition)

ohiou1386341476
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This open access ETD is published by Ohio University and OhioLINK.