US-12624466-B1 - Electrocatalytic method for hydrogen production

Abstract

A method of producing hydrogen by an electrochemical ammonia oxidation reaction (AOR) includes disposing an anode and a cathode in an aqueous electrolyte solution including dissolved ammonia and potassium hydroxide, and applying a potential difference between the anode and the cathode. The anode includes, based on the weight of the anode from about 98.0 percent by weight (wt. %) to about 99.5 wt. % of a polycrystalline matrix including copper hydroxide and from about 0.5 wt. % to about 2.0 wt. % of nanoparticles of crystalline platinum (Pt) dispersed in the polycrystalline matrix.

Inventors

• Saheed Ganiyu
• Esraa Ragab Abas Kotob
• Khalid Alhooshani
• Ijaz Hussain

Assignees

• KING FAHD UNIVERSITY OF PETROLEUM AND MINERALS

Dates

Publication Date

20260512

Application Date

20250610

Claims (3)

1. 1 . A method of producing hydrogen by an electrochemical ammonia oxidation reaction, comprising: A. making an anode by a process comprising the following steps performed under an inert atmosphere; 1. Dissolving copper (II) chloride (CuCl 2 ) and polyvinylpyrrolidone (PVP) in water to form a first mixture; 2. Adding ascorbic acid to the first mixture to form a second mixture and allowing the reduction reaction to proceed to completion; 3. Adding sodium borohydride (NaBH 4 ) to the second mixture under agitation at a temperature of about 30° C. to about 90° C. to form a third mixture and produce a solid; 4. Separating the solid from the third mixture to provide copper nanoparticles; 5. Forming a 1 wt. % platinum (Pt) solution derived from a PtCl 3 precursor in 0.5M NaOH and combining it with the solid from the third mixture to form a fourth mixture and agitating the fourth mixture at a temperature of from 10° C. to 80° C. for a duration of from 1 to 10 hours to produce an anodic material; 6. Separating the anodic material from the fourth mixture and forming the anode; wherein the anode comprises: a. from 98.0 wt. % to 99.5 wt. % of a polycrystalline matrix comprising copper hydroxide (CuOH), the polycrystalline matrix further comprising: i. substantially spherical aggregates of nanoparticles of the copper hydroxide, having a mean grain size as determined by High Resolution Transmission Electron Microscopy, of from 50 nm to 100 nm; and ii. Substantially spherical aggregates of elemental copper (Cu) nanoparticles, wherein a fraction of the elemental copper (Cu) nanoparticles have a particle size less than about 10 nm, as determined by High Resolution Transmission Electron Microscopy; and b. from 0.5 wt. % to 2.0 wt. % of nanoparticles of crystalline platinum (Pt) having a mean grain size, as determined by High Resolution Transmission Electron Microscopy, of from 0.5 nm to 5 nm; wherein the nanoparticles of crystalline Pt are uniformly dispersed in the polycrystalline matrix comprising copper hydroxide; B. disposing the anode and a cathode in an aqueous electrolyte solution comprising dissolved ammonia and potassium hydroxide; and C. applying a potential difference between the anode and the cathode to produce hydrogen by the electrochemical ammonia oxidation reaction.
2. 2 . The method of claim 1 , wherein the polycrystalline matrix further comprises single atom Pt.
3. 3 . The method of claim 1 , wherein the anode has a sheet resistance of greater than 15 Ωcm −2 , as determined by electrochemical impedance spectroscopy.

Description

BACKGROUND Technical Field The present disclosure relates to the field of electrochemical energy conversion and electrocatalysis and more particularly, pertains to a method for producing hydrogen via electrochemical ammonia oxidation. Description of Related Art The “background” description provided herein is for the purpose of generally presenting the context of the disclosure. The work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description which may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present invention. The need for plentiful energy has led to the looming depletion of fossil fuel reserves and energy security concerns caused by rapid population growth and technological advancement. Environmental challenges include global warming-induced phenomena such as rising sea levels and extreme climatic events. In response to the aforementioned exigencies, the global community has established multiple policy targets. The Paris Agreement, adopted at COP21 on Dec. 12, 2015, aims to cap the rise in global mean temperatures to below 2° C. and pursue efforts to restrict it to 1.5° C. above pre-industrial levels. The European Green Deal has committed the EU to net-zero greenhouse gas emissions by 2050, while similar declarations have been made by China (by 2060, Japan and Korea (by 2050), and India (by 2070). In view of these climate imperatives, considerable global efforts have been channelled toward the development of clean, efficient, and renewable energy technologies. Hydrogen has emerged as a potent candidate in future energy infrastructure due to high energy density, abundance, and environmentally benign combustion profile. However, the widespread adoption of hydrogen is hampered by significant technical obstacles, particularly in storage and transport. Hydrogen has inherently low volumetric energy density and high diffusivity, which makes hydrogen prone to leakage, flammability hazards, and elevated compression or liquefaction energy requirements [See: Li Y, Li X, Pillai H S, Lattimer J, Mohd Adli N, Karakalos S, and coworkers. Ternary PtIrNi catalysts for efficient electrochemical ammonia oxidation, ACS Catal 2020; 10:3945-57]. The aforementioned issues have collectively impeded large-scale industrial application of hydrogen and raised the need for a viable hydrogen carrier. Among the alternatives investigated, ammonia (NH3) has attracted significant interest due to its favourable thermophysical properties and hydrogen content. As a hydrogen-rich chemical, ammonia possesses an energy density of approximately 3000 Wh kg−1 and a hydrogen content of about 17.7 wt. % (120 g L−1), surpassing that of methanol, synthesis gas, and other hydrogen-containing compounds [See: Lan R, Irvine J T S, Tao S. Ammonia and related chemicals as potential indirect hydrogen storage materials, Int J Hydrogen Energy 2012; 37:1482-94]. Furthermore, ammonia decomposition generates only nitrogen and hydrogen, without the emission of carbon oxides (COX), facilitating clean fuel production [See: García-Bordejé E, Armenise S, Roldán L. Toward practical application of H2generation from ammonia decomposition guided by rational catalyst design, Catal Rev Sci Eng 2014; 56:220-37]. Ammonia is advantageous in terms of transportability, as ammonia liquefies under mild conditions (about 25° C. and about 3 atm), enabling safer and more efficient logistics [See: Wan Z, Tao Y, Shao J, Zhang Y, You H. Ammonia as an effective hydrogen carrier and a clean fuel for solid oxide fuel cells, Energy Convers Manag 2021; 228]. Moreover, the decomposition of ammonia produces only nitrogen and hydrogen, ensuring high selectivity and process simplicity when compared to systems involving liquid organic hydrogen carriers [See: Lee S, Kim T, Han G, Kang S, Yoo Y S, Jeon S Y, and coworkers, Comparative energetic studies on liquid organic hydrogen carrier: A net energy analysis. Renewable and sustainable energy reviews, Renewable and Sustainable Energy Reviews 2021; 150]. Ammonia electrolysis offers further promise as a method for hydrogen generation, producing clean hydrogen without COX emissions and requiring less energy input than conventional water electrolysis. The anode and cathode reactions in alkaline ammonia electrolysis are represented as follows: Anode: 2NH3+6OH−→N2+6H2O+6e−E°=−0.77 V vs SHE  (1) Cathode: 6H2O+6e−→3H2+6OH−E°=−0.83 V vs SHE  (2) Overall Reaction: 2NH3→N2+3H2 E° Cell=0.06 V vs SHE  (3) As demonstrated by equations (1)-(3), ammonia electrolysis operates at a thermodynamic cell voltage of just 0.06 V, significantly lower than the 1.23 V required for water splitting [See: Palaniappan R, Botte G G. Effect of ammonia on Pt, Ru, Rh, and Ni cathodes during the alkaline hydrogen evolution reaction, Journal of Physical Chemistry C 2013; 117:17429-41]. This implies a theoretical energy cons