Sodium borohydride hydrogen generator using Co–P/Ni foam catalysts for 200 W proton exchange membrane fuel cell system
Introduction
Small UAVs (unmanned aerial vehicles) are widely used for reconnaissance missions without the risk of loss of life on the battlefield. Fuel cells have attracted attention in the field of aerospace engineering because the batteries that are currently used as power sources for small UAVs limit the duration of these missions [1], [2], [3], [4], [5], [6], [7], [8], [9], [10], [11]. Fuel cells are suitable for military applications owing to their high efficiency, high energy density, low noise, and low vibration.
The combination of PEMFCs (proton exchange membrane fuel cells) and NaBH4 (sodium borohydride) hydrolysis (Eq. (1)) is a suitable power source for small UAVs [3], [5], [8]. PEMFCs have many advantages, including high power density (300–1000 mW/cm2), high energy density (100–600 Wh/kg), a wide power range (0–100 kW), rapid response characteristics, and simplicity [12], [13], [14], [15], [16], [17]. NaBH4 hydrolysis is a suitable method to supply hydrogen to PEMFCs for the following reasons: hydrogen purity, simple hydrogen generation system, safe fuel storage, and easy refueling.
NaBH4 is stable when stored in alkaline solution, with hydrolysis activated by various catalysts including platinum, rhodium, ruthenium, cobalt, and nickel [18]. Platinum [19], [20], [21], rhodium, and ruthenium [20], [21], [22], [23], [24], [25], [26], [27], [28], [29] are very expensive; therefore, cobalt [30], [31], [32], [33], [34], [35], [36], [37], [38], [39], [40], [41], [42], [43], [44], [45], [46], [47], [48], [49], [50], [51], [52] and nickel [42], [43], [44], [53], [54], [55] are being widely investigated.
A Co/γ–Al2O3 catalyst was used for fuel cell powered UAVs in our previous study, but it was not stable for long periods because of poor durability and adhesion of the catalyst [3], [5]. Consequently, Co–P/Ni foam catalysts were investigated based on studies of Co–P/Cu sheet catalysts [41], [47], [48]. Ni foam was used to improve the durability of the support, and electroless plating was used to improve adhesion of the catalyst. We previously determined appropriate catalyst manufacturing conditions such as the coating conditions [50] and bath composition [51]. The performance of the Co–P/Ni foam catalyst was previously evaluated [52]. The catalyst durability was good, but response characteristics were poor because of low surface area [52]. The response characteristics and catalyst durability are both important for mobile applications, such as in small UAVs. Although a number of catalysts for NaBH4 hydrolysis have been developed by many research groups, to the best of our knowledge, the response characteristics of those catalysts were rarely studied.
Sodium borohydride hydrogen generator using Co–P/Ni foam catalysts with fast response characteristics was investigated for a 200 W PEMFC system in this study. The effect of pore density (pores per inch; PPI) of Ni foam on the properties of the catalyst and catalyst response characteristics was determined. Batch-type hydrogen generators were used in other studies [41], [47], [48], [50], [51], but to evaluate the response characteristics of Co–P/Ni foam catalysts under real operating conditions, a flow-type hydrogen generator was used in this study as well. Moreover, a hydrogen generation test and fuel cell tests for a 200 W PEMFC system were conducted, and the energy density of a 200 W fuel cell system was estimated.
Section snippets
Preparation of Co–P/Ni foam catalyst
Various Ni foams (E2 Tech, South Korea) with 40 PPI and 80 PPI (thickness: 0.5 cm) and 110 PPI (thickness: 0.15 cm) were pretreated using our previous procedure [50], [51]. Ni foams were washed with detergent and then cleaned with ethanol (C2H5OH, OCI, South Korea) in an ultrasonic bath (JAC-1505, Kodo Technical Research, South Korea) for 5 min. Hydrochloric acid (HCl, OCI, South Korea) was used for etching, which was performed in a 10 vol% HCl solution for 1 min. Tin chloride (SnCl2·2H2O,
Effect of Ni foam geometry on properties of electroless-deposited Co–P/Ni foam catalyst
Co–P/Ni foam catalysts with 40 and 80 PPI values were produced to investigate the effect of Ni foam geometry on catalyst properties, and batch hydrogen generation tests were performed. Fig. 2 represents the weight percent, and the hydrogen generation rate per gram, of the deposited catalyst. The weight percent of the Co–P/Ni foam (80 PPI) catalyst was smaller than that of the Co–P/Ni foam (40 PPI) catalyst. It was expected that the weight percent of the Co–P/Ni foam (80 PPI) catalyst would be
Conclusions
A 200 W PEMFC system using Co–P/Ni foam catalysts was developed and the energy density was estimated. The response characteristics of Co–P/Ni foam catalysts were investigated because the response characteristics and catalyst durability are important for mobile applications. The effect of Ni foam geometry on the catalyst properties was determined. The hydrogen generation rate per gram of the deposited catalyst was increased with an increase in the PPI value of the Ni foam due to an increase in
Acknowledgments
This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MEST) (No. 2012R1A2A1A05026398).
References (56)
- et al.
Efficiency and weight trade-off analysis of regenerative fuel cells as energy storage for aerospace applications
Int J Hydrog Energy
(2005) - et al.
Development and experimental characterization of a fuel cell powered aircraft
J Power Sour
(2007) - et al.
Fuel cell system with sodium borohydride as hydrogen source for unmanned aerial vehicles
J Power Sour
(2011) A 100-W class regenerative fuel cell system for lunar and planetary missions
J Power Sour
(2011)- et al.
Design and development of a fuel cell-powered small unmanned aircraft
Int J Hydrog Energy
(2012) - et al.
The hydrogen value chain: applying the automotive role model of the hydrogen economy in the aerospace sector to increase performance and reduce costs
Acta Astronaut
(2013) - et al.
Micro space power system using MEMS fuel cell for nano-satellites
Acta Astronaut
(2014) NaBH4 (sodium borohydride) hydrogen generator with a volume-exchange fuel tank for small unmanned aerial vehicles powered by a PEM (proton exchange membrane) fuel cell
Energy
(2014)- et al.
Performance evaluation of direct borohydride–hydrogen peroxide fuel cells with electrocatalysts supported on multiwalled carbon nanotubes
Energy
(2014) - et al.
Electrocatalysts supported on multiwalled carbon nanotubes for direct borohydride–hydrogen peroxide fuel cell
Int J Hydrog Energy
(2014)
Effect of heat treatment of electrodes on direct borohydride–hydrogen peroxide fuel cell performance
J Power Sour
Exergy analysis of PEM fuel cells for marine applications
Energy
Design of experiment study of the parameters that affect performance of three flow plate configurations of a proton exchange membrane fuel cell
Energy
Modeling and control of a portable proton exchange membrane fuel cell–battery power system
J Power Sour
Water droplet accumulation and motion in PEM (proton exchange membrane) fuel cell mini-channels
Energy
Development of a continuous hydrogen generator fueled by ammonia borane for portable fuel cell applications
J Power Sour
Development and testing of a hybrid system with a sub-kW open-cathode type PEM (proton exchange membrane) fuel cell stack
Energy
Hydrogen generation using sodium borohydride solution and metal catalyst coated on metal oxide
Int J Hydrog Energy
PtRu-LiCoO2–an efficient catalyst for hydrogen generation from sodium borohydride solutions
J Power Sour
Pt and Ru dispersed on LiCoO2 for hydrogen generation from sodium borohydride solutions
J Power Sour
A safe, portable, hydrogen gas generator using aqueous borohydride solution and Ru catalyst
Int J Hydrog Energy
An ultrasafe hydrogen generator: aqueous, alkaline borohydride solutions and Ru catalyst
J Power Sour
Feasibility study of hydrogen generation from sodium borohydride solution for micro fuel cell applications
J Power Sour
Kinetics of Ru-catalyzed sodium borohydride hydrolysis
J Power Sour
Ru-based bimetallic alloys for hydrogen generation by hydrolysis of sodium tetrahydroborate
J Alloys Compd
Hydrogen generation from sodium borohydride solution using a ruthenium supported on graphite catalyst
Int J Hydrog Energy
Development of Al2O3 carrier-Ru composite catalyst for hydrogen generation from alkaline NaBH4 hydrolysis
Energy
Hydrogen generator system using Ru catalyst for PEMFC (proton exchange membrane fuel cell) applications
Energy
Cited by (43)
Solid-state hydrogen generation from NaBH<inf>4</inf> using mannitol as a bi-functional additive
2023, International Journal of Hydrogen EnergyExploring the technological maturity of hydrogen production by hydrolysis of sodium borohydride
2023, International Journal of Hydrogen EnergyEffect of anode conditions on the performance of direct borohydride–hydrogen peroxide fuel cell system
2023, International Journal of Hydrogen EnergyApplication-oriented hydrolysis reaction system of solid-state hydrogen storage materials for high energy density target: A review
2022, Journal of Energy ChemistryCo–Fe–B as an effective catalyst for hydrogen production from NaBH<inf>4</inf> hydrolysis
2021, Materials Letters: XCitation Excerpt :Consequently, recent strategies have been focused on prohibiting the agglomeration, containing designing catalyst structure, optimizing synthetic methods, adjusting reaction conditions, and utilizing substrate substances. Among them, the way of utilizing substrate substances and electroless plating method can deposit nanoparticles on the surface of substrates and obtain catalyst materials [5,6]. Electroless plating has been widely used as a convenient method to prepare supported metal based thin films.