Journal of Mineral
and Material
Science (JMMS)
How to cite this article: Suller Garcia MA (2022) Electrochemical Energy Storage and Conversion Systems – A Short Review. J Miner Sci Materials 3: 1041
Introduction
Fossil fu els – oil, coal, a nd gas – are the g lobal prima ry energy s ources, esti mated to be respon sible for 85% of the
total energ y generation [1]. This overdependence on non-ren ewable fuels has resu lted in several envi ronmental issues t hat
are diffic ult to circumve nt, such as cli matic variat ions due to green house gas emiss ions, poor air qu ality, and wate r/soil
contami nation [2]. Thus, efforts hav e been directe d toward replaci ng/complementing t he global ca rbon-based ener gy matrix
with alt ernative sources , e.g., wind, sola r or geothermal [3]; however, thei r unpredictabil ity has considera ble effects on grid
operations , except when use d in small a mounts. In th is scenario, e lectrochem ical energy c onversion technolo gies have
received at tention because the y are not location-spe cific as the other so urces, deliveri ng higher flexibi lity [4]. Nevertheless ,
proper grid i ntegration is re quired to man age supply energy flu ctuations a nd mismatches . Hence, appropriate s torage
technolog ies are essential t o reduce the gap between c onsumption and produc tion, and a myriad of ener gy storage device s
are avail able, includi ng chemical, mec hanical, t hermochemica l, electric al, and elect rochemical s ystems [5]. The last ones are
highl ighted due to thei r simplicity, rela tively low cost, sp eed, and effici ency, and lithiu m-based batt eries are the mo st popular
system. Howe ver, although such bat teries promise to sh ift energy in ti me and store any exces s for future util ization, aim ing
to avoid voltage spi kes, their c ost, environ mental impac ts, and safe ty are severe d rawbacks [6,7]. Thus, e lectrochem ical
capacitors/Supercapacitors a re being improved, a nd new nanoengine ered materials a re being studied to ove rcome their low
energy den sities [8]. Thus, thi s ultra-shor t review wi ll highl ight the fu ndamental pr inciples of al kaline w ater electroly sis, fuel
cells, a nd Supercapacitors, drawing atte ntion to the main mat erials for thei r applications.
Water Electrolysis
Althoug h electrolysi s requires elec tric energ y for its funct ioning, renew able sources are b eing studie d to efficiently
provide the p ower needed for the pro cess as a whole [9]. In the ele ctrolyzer, elec tric energ y is converted into c hemical ener gy;
oxygen is produ ced at the anode, an d hydrogen is obtained at t he cathode (2H2O(l) + 2e - → H2(g) + 2OH-(aq)), in which the
releasing hyd roxide ions go thro ugh the diaphr agm to the anode t o form O2. About 4% of the hydrog en produced worldwide
is derived f rom water elect rolysis [9], either in aci d or alkal ine electroly tes. Although Pro ton Exchange Membr ane, Solid
Oxide, a nd Anion Excha nge Membrane Elec trolysis are h ighly stud ied, alk aline elec trolysis achi eved a more extens ive
commercia l maturity t han the other technol ogies [10]. It can be noticed t hat the method re quires 1.23 V of pote ntial for
the occu rrence of both the oxyg en (OER) and hydrogen evolution (HE R) reactions [3]. However, overpotentia ls are always
needed, a nd reducing such par ameters is essent ial once they affe ct the efficiency of a lkaline el ectrolysis. Thus , the efficiency
of alka line elect rolysis in th is matter is in fluenced by membran e resistivit y, distance be tween elect rodes, bubbles , KOH
concentrat ion, and temperat ure affect su ch overpotentia l [10,11]. Such parame ters are the most c ommon and easy t o
circumvent . However, the electrod es’ material choic e has a significa nt impact on this m atter as well.
One can bea r in mind that p recious counter parts are s tudied due to the ir lower activat ion energy for H de sorption
and optimu m Gibbs free energy of me tal-hydrogen bindi ng [12]. However, due to cost issu es and abundancy, Nickel -based
materia ls are usual ly considered, pre senting sign ificant stabi lity; als o, their deact ivation can b e circumvented by u sing other
metals , such as Iron and Vanad ium [13,14]. Researchers worldwid e are studyi ng non-precious met als for elect rolysis cata lysts
due to their pr ices, and nanoen gineering a spects (controlli ng shape, size, c omposition, and str ucture), doping, a nd alloying
are some str ategies for perform ance improvement [15]. Most studied cat alysts for OER are per ovskite-type a nd spinel-type
oxides, a nd layered oxides/(oxy)hydrox ides, whi le HER counts on tr ansition met al oxides, su lfides, and d ichalcogeni des, and
modified c arbons, among ot hers [11].
Fuel Cells
The process is b ased on generating elec tricity by reducin g oxygen in the cathod e and oxidizing a fu el (e.g., hydroge n,
methanol , ethanol) in the ano de [14]. The components of the fu el cell devices ar e similar to those of t he electrolyzer u nits,
i.e., two ele ctrodes (with t heir surfac es modified wit h the cataly sts) separated by a n electroly te. According to t heir operatin g
conditions , fuel cells ca n be classifie d as Solid Oxide , Proton Exchange Me mbrane, Molten Ca rbonate, Alk aline, Phosphor ic
Acid, Sing le-layered, a nd Direct Me thanol Fuel C ells [16]. Fuel cells ar e high-ener gy densit y power source de vices; t hus, futu re
uses can b e as backup power for reside ntial, commercia l, and industri al areas, but al so to power vehicles, bus es, and train s.
Especia lly, supply chain devel opments integrati ng water electroly zers and fuel cel ls are considered to mee t future demands
for decarb onization goa ls. Also, Dire ct Methanol Fue l Cells promise t o give us complete flex ibility in ou r daily life on ce they
Volume 3 Issue 3, 2022
Article Information
Received date :July 25, 2022
Published date: August 01, 2022
*Corresponding author
Marco Aurélio Suller Garcia,
Departament of Chemistry, Federal
University of Maranhão, Dos
Portugueses Av 1966, São Luís, 65080-
805, Brazil
Keywords
Electrochemical Energy Production;
Energy Storage; Electrolyzers; Fuel
Cells; Supercapacitors
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CC-BY 4.0
Mini Review
Electrochemical Energy Storage and
Conversion Systems – A Short Review
Marco Aurélio Suller Garcia*
Department of Chemistry, Federal University of Maranhão, Dos Portugueses Av 1966, São Luís, 65080-
805, Brazil
Abstract
Electrochemical energy production systems – including fuel cells and electrolyzers – are vital technologies to
address energy security and environmental demands. Also, their combination for improved performance is essential for
future commercial applications. However, their real utilization (and integration with other alternative energy sources) goes
beyond efficiency; large-scale penetration of renewable energy in the existing electrical grid systems is challenging due
to destabilization possibility. Thus, electrochemical energy storage systems (e.g., electrochemical supercapacitors) are
necessary for managing power generation intermittency and grid reliability. Therefore, this ultra-short review provides a
brief overview of some of the most promising electrochemical devices for electrochemical energy production and storage
for future systems in an engagement scenario.
