S omething for N othing : S olid -O xide F uel C ells B S J Karthik Gururangan Fuel cells have been a popular contender for the usage. Recently, scientists have proposed using solid-state gateway to the hydrogen economy for some time. Indeed, diffusion of hydrogen and oxygen ions through an oxide today we can see zero-emission buses and cars powered by electrolyte to make the hydration reaction (Park, 2000). These a hydrogen fuel cell. Generally speaking, a fuel cell is an fuel cells are called solid-oxide fuel cells, or SOFCs. At high electrochemical system that drives the transferred electron enough temperatures, SOFC diffusion can quickly outpace occurring in redox reactions through an external circuit to regular chemical kinetics, give us greater fuel choice flexibility, power something. It is really and eliminate harmful carbon the most straightforward way monoxide by-products of At high enough temperatures, to convert chemical energy into common liquid fuel cells (Park, electrical energy, and provided SOFC diffusion can quickly outpace 2000). that the reactants remain in a regular chemical kinetics, give us Diffusion is a temperature- steady supply, a fuel cell can controlled exponential law based greater fuel choice flexibility, and on two things: the diffusivity of indefinitely supply a steady eliminate harmful carbon monoxide by- a particular electrolyte and the current. By referring to Figure activation energy of diffusion products of common liquid fuel cells. 1 we can understand the setup for that particular solute. of a hydrogen fuel cell. At the The activation energy can be blue side (anode), hydrogen loses decomposed into the energy electrons and the resultant protons migrate into a reaction needed to move around through the solid and the energy chamber. The green side (cathode) is very often an opening associated with moving around through holes called vacancies or simple air reservoir. The electrons flow through the circuit in the solid. Figure 2 gives an intuitive idea of what this and reach the oxygen, completing the chemical reaction to means. produce water. Using the hydration electrochemical reaction is the basis of our intended hydrogen economy. In reality, one cell of this type hardly produces 1 volt so we combine single cells in series into what is called a fuel cell stack for applications. The main drawback of classical gas or liquid hydrogen fuel cells is that they require a platinum catalyst to speed up the reaction process to usable values (Minh, 2004). In Figure 1, the middle plate is the platinum – this is an expensive metal and is one of the main obstacles of widespread hydrogen fuel cell Figure 1. : Simple schematic of a single hydrogen fuel cell An atom can either push its way past two others to move to another position or it can move through the existing gap defects. By choosing a solid oxide electrolyte, the much larger oxygen ions have an easier time migrating through the lattice, making the overall diffusion rate much faster than it 12 • B erkeley S cientific J ournal • W aste • S pring 2015 • V olume 19 • I ssue 2