US 2014003 0628A1 (19) United States (12) Patent Application Publication (10) Pub. No.: US 2014/0030628 A1 McMahon (43) Pub. Date: Jan. 30, 2014 (54) PHOTOCATALYTICFUEL CELL AND (52) U.S. Cl. ELECTRODE THEREOF CPC ........... H01 M 4/8657 (2013.01); HOIL 29/401 2013.O1 (71) Applicant: Fordham University, Bronx, NY (US) USPC ........................................... 1948: 33 (72) Inventor: John J. McMahon, Yonkers, NY (US) (57) ABSTRACT (73) Assignee: FORDHAM UNIVERSITY, Bronx, The invention provides a novel fuel cell, the output voltage of NY (US) which is pH dependent. The fuel cell comprises a membrane electrode assembly and a light source. In accordance with one (21) Appl. No.: 13/950,424 embodiment, the membrane electrode assembly includes i) an electrolyte; ii) an anode operably coupled to the electro (22) Filed: Jul. 25, 2013 lyte; and iii) a cathode operably coupled to the electrolyte, wherein the cathode is made from an electrically conductive Related U.S. Application Data material and has an unroughened Surface where an adsorbate (60) Provisional application No. 61/676,018, filed on Jul. material is applied. The adsorbate material used herein com 26, 2012. prises a material having semiconductor properties, and the s combination of the electrically conductive material and the Publication Classification adsorbate material is photosensitive and has catalytic proper ties. The invention also provides a novel electrode that can be (51) Int. Cl. used as a cathode in a fuel cell, a novel method for making the HOLM 4/86 (2006.01) electrode, and a novel method of generating electricity using HOIL 29/40 (2006.01) the fuel cell and/or electrode of the invention. hydrogen 1. side ey as o-ring af 4. Pt/carbon cloth anode S). 6. insulator N) insulating band Nafion 115 (PEM) Ag/Agl coated stainless steel Screen Cathode oxygen side Patent Application Publication Jan. 30, 2014 Sheet 1 of 7 US 2014/0030628A1 O E-4 5. O E-5 -5.O E-5 -0.2 OO O2 O.4 O. O.8 1.O 2 Potential (V) FIG. 1 Patent Application Publication Jan. 30, 2014 Sheet 2 of 7 US 2014/0030628A1 Pourbaix Diagram for the Photocatalytic Fuel Cell 5 i mor- -T O T- 8 O, + 4 . m "res II . is m - f2 H.O L + 2 e - 2 I- w Eacil M O c) m 2 2 Hi + 2 r X H.(g). 9O 5 - r--- - O i i i i -- O 2 4 6 8 O 2 pH FIG. 2 Patent Application Publication Jan. 30, 2014 Sheet 3 of 7 US 2014/0030628A1 V s C 4000 : 3000 2000 - r | | was 1000 | Yi'? "..") Wy/w". Y'www.wywww.h- wry. O -- r T 100 150 200 250 Wavenumber (cm) FIG. 3 Patent Application Publication Jan. 30, 2014 Sheet 4 of 7 US 2014/0030628A1 Cell Voltage vs. pH --womem AY-2 -0- E(cell) = 0.0481 pH + 0.6241 (measured) - E(cell) = 0.0591 pH + 0.535 (calculated from Eq. (1)) FIG. 4 Patent Application Publication Jan. 30, 2014 Sheet 5 of 7 US 2014/0030628A1 Polarization Curves 900 800 e 700 r o 600 -- Ag|Agl, light, pH 2.0 O Ag/Agl, dark, pH 2.0 > 300 Ag Agl, light, pH 2.0 200 - 100 0 +------ O 200 400 600 800 Current (uAmp) FIG. 5 Patent Application Publication Jan. 30, 2014 Sheet 6 of 7 US 2014/0030628A1 Patent Application Publication Jan. 30, 2014 Sheet 7 of 7 US 2014/0030628A1 3500 3000 2500 2000 FIG. 7 US 2014/003 0628 A1 Jan. 30, 2014 PHOTOCATALYTCFUEL CELL AND 200°C., and a solid polymer electrolyte fuel cell is operated ELECTRODE THEREOF in the temperature range of 60° C. to 90° C. In order to maintain the temperature of the power generation cells in the CROSS REFERENCE RELATED APPLICATION desirable temperature range, various cooling systems have been adopted. Typically, the power generation cells are 0001. This application claims under 35 U.S.C. S 120 and cooled by Supplying coolant Such as water to a coolant pas S119(e) the benefit of U.S. Provisional Patent Application sage formed in the bipolar plates of the fuel cell stack. No. 61/676,018 filed Jul. 26, 2012, the entire contents of 0008 Generally, fuel cells provide an environmentally which are incorporated herein by reference. clean alternative to energy production from fossil fuel com FIELD OF THE INVENTION bustion. The electrochemical efficiency of a fuel cell (cur rently sG5%) handily exceeds that of internal combustion 0002 The present invention relates to a fuel cell and a engines (<30%). However, in spite of recent increases in the method for producing the fuel cell, the output voltage of prices of crude oil and natural gas, fossil fuel combustion which is pH dependent. Particularly, the present invention is continues to hold a significant economic advantage over fuel directed to a fuel cell comprising a membrane electrode cells. The high cost of fuel cell energy production is attribut assembly which includes an electrolyte; an anode and a cath able to the need for addition of expensive catalysts (platinum) ode coupled to the electrolyte, and a light source. to accelerate the oxidation of the fuel (hydrogen) at the anode and the reduction of oxygen at the cathode. The slow oxygen BACKGROUND OF THE INVENTION reduction reaction alone accounts for the largest limitation to 0003) A variety of fuel cell devices are known in the art for the fuel cell efficiency, even in the presence of platinum generating electric power. Of Such devices, most include catalyst. graphite anodes and cathodes comprising a finely dispersed 0009. The demand by dioxygen molecules (O) for elec platinum catalyst. trons during reduction at electropositive metal electrodes 0004 For example, a phosphoric acid fuel cell (PAFC) is a forces the electrostatic potential of the metal to wander nega power generation cell which employs a porous electrolyte tively (referred to as a large negative overVoltage) before layer of silicon carbide matrix for retaining concentrated giving up the electrons needed by oxygen. Because the output phosphoric acid. The electrolyte layer is interposed between power of a fuel cell is defined by the product of the cell carbon-based electrodes (an anode and a cathode) to forman potential (V) and current (I), i.e., P=VI, a drop in the potential electrolyte electrode assembly, sometimes referred to as a lowers the power output and the cell efficiency linearly. Typi membrane electrode assembly (“MEA). The membrane cally, a platinum-catalyzed hydrogen fuel cell operates at electrode assembly is then interposed between electrically moderate current levels at cell voltages close to +0.75 volts conductive bipolar plates. The membrane electrode assembly instead of the thermodynamic equilibrium cell voltage of and the bipolar plates form a single fuel cell for generating +1.23 volts. This amounts to an overvoltage of -0.48 volts electricity by reacting a fuel Such as hydrogen with oxygen below the thermodynamic voltage, thus limiting the effi across the electrolyte. A single fuel cell as described generally ciency to near 60%. Experiments probing alternatives to plati herein has an output voltage of about 0.8 volts. To raise the num catalysis of the electroreduction of oxygen continue to voltage of the electrical output, a fuel cell stack can beformed define a vigorous area of research. Nonetheless, platinum by arranging any desired number of fuel cells in electrical remains the best known electrocatalyst of the oxygen reduc series on top of one another. Since the bipolar plates are tion reaction. In recent years, advances in fuel cell utility have electrically conductive, current flows through the stack via relied upon improved methods for dispersing the platinum the end plates. catalyst only at the active sites of graphite electrodes. The 0005. Another type of fuel cell device is a solid polymer total amount of platinum needed to Sustain operational cur electrolyte fuel cell which employs a membrane electrode rents was thereby reduced, along with the overall cost of fuel assembly including electrodes separated by a polymer ion cells. However, the fundamental limitation caused by the exchange membrane (proton exchange membrane or PEM). overvoltage problem still persists. Similarly, the membrane electrode assembly and the bipolar 0010 Thus, there remains a compelling need in the art for plates make up a unit of the power generation cell. Once a fuel cell that is more electrochemically efficient than known again, a predetermined number of the power generation cells fuel cells. There is also a continuing need for a fuel cell can be stacked together to form a fuel cell stack having a system that can be operated economically at lower tempera desired output Voltage. tures, such as at room temperature. The present invention 0006. In the fuel cell stacks, a fuel gas such as a hydrogen provides a solution for these problems. containing gas is Supplied to the anode. The anode includes a catalyst that induces a chemical reaction of the fuel gas to split SUMMARY OF THE INVENTION the hydrogen molecule into hydrogen ions (protons) and elec 0011. The purpose and advantages of the present invention trons. The hydrogen ions move toward the cathode through will be set forth in and become apparent from the description the electrolyte, and the electrons flow through an external that follows, as well as will be learned by practice of the circuit to the cathode, creating a DC electric current. invention. Additional advantages of the invention will be 0007. The fuel cell should be operated at or near an opti realized and attained by the methods and systems particularly mum temperature for the performance of power generation. pointed out in the written description and claims hereof, as Generally, fuel cells known in the art operate attemperatures well as from the appended drawings.