Mond and Langer

The "new form of gas battery" described by Ludwig Mond and Carl Langer in 1889 was more than an improvement; it was the prototype for the practical fuel cell. These researchers considered their main contribution as being a solution to the problem of electrode flooding, caused by a liquid electrolyte. The sulfuric acid could be held in place by using a matrix:

[Grove], as well as later investigators, overlook one important point, viz., the necessity of maintaining the condensing power of the absorbent unimpaired ... platinum black, the most suitable absorbent for gas batteries, loses its condensing power almost completely as soon as it gets wet, and that it is therefore necessary for our purpose to keep it comparatively dry.

The matrix, also called diaphragm, was a porous, non-conducting solid:

... such as plaster of Paris, earthenware, asbestos, pasteboard, &c., is impregnated by dilute sulphuric acid or another electrolyte, and is covered on both sides with thin perforated leaf of platinum or gold and with a thin film of platinum black.

In continuing to describe their first of two designs, Mond and Langer showed their insight into developing practical hardware to sustain the fuel cell reaction. They realized that internal electrical resistance would reduce the voltage from across the two electrodes:

The platinum or gold leaf, which serves as conductor for the generated electricity (the platinum black being a very bad conductor), is placed in contact at small intervals with strips of lead or other good conductor in order to reduce the internal resistance of the battery to a minimum.

Figure 2.3 shows one of Mond and Langer's designs for a gas battery.

Mond and Langer were concerned about a lower electromotive force (EMF) or open circuit cell voltage, and they realized that it was related to the method used to prepare the platinum black catalyst. Their data, showing the performance of one catalyst, are presented in Fig. 2.4.

Mond and Langer investigated the cause of the lower open circuit voltage, which they reported to be 0.97 V instead of the expected 1.47 V. (The maximum cell voltage that was expected, according to

Mond And Langer

FIGURE 2.3 One design of the gas batteries of Mond and Langer (1889), which used a diaphragm to contain the sulfuric acid electrolyte. The lettering in the diagram denotes A: conducting strips, E: ebonite plates, G: gastight chambers, H: hydrogen, K: rubber frames, O: oxygen, M: earthenware plate, R: ebonite frame, S: electrode.

FIGURE 2.3 One design of the gas batteries of Mond and Langer (1889), which used a diaphragm to contain the sulfuric acid electrolyte. The lettering in the diagram denotes A: conducting strips, E: ebonite plates, G: gastight chambers, H: hydrogen, K: rubber frames, O: oxygen, M: earthenware plate, R: ebonite frame, S: electrode.

Current density [milliamperes/cm2]

FIGURE 2.4 The performance of a gas battery of Mond and Langer (1889). It is unclear whether these data are based on the cathode reactant being pure oxygen or oxygen from the air because Mond and Langer fed their cells with both gases. The electrode area was 42 cm2.

Current density [milliamperes/cm2]

FIGURE 2.4 The performance of a gas battery of Mond and Langer (1889). It is unclear whether these data are based on the cathode reactant being pure oxygen or oxygen from the air because Mond and Langer fed their cells with both gases. The electrode area was 42 cm2.

Liebhafsky and Cairns (1968), was based on the "Thomsen-Berthelot Fallacy" that the heat released in a chemical reaction was a measure of the chemical affinity of the reactants; in other words, the change in enthalpy was thought to be equal to the change in Gibbs energy.) By substituting different electrode materials for both anode and cathode, they identified it to be the PtO as the electrode that caused the loss. These data would be confirmed by Alder Wright and Thompson in a paper (see Section 2.1.5) meant to dispute the originality of Mond and Langer's work.

Mond and Langer calculated that the efficiency of the battery was nearly 50% (based on the expected 1.47 V) and realized that the wasted energy was converted to heat within the cell. To maintain the temperature constant at 40°C, they passed through excess air, which simultaneously removed the water formed at the cathode.

With a useful effect of 50 per cent, one-half of the heat produced by the combination of the H with the O is set free in the battery, and raises its temperature. By passing through the battery a sufficient excess of air, we can keep the temperature of the battery constant at about 40°C, and at the same time carry off the whole of the water formed in the battery by means of the gases issuing from it, so that the platinum black is kept sufficiently dry, and the porous plate in nearly the same state of humidity.

The battery performance degraded by 4 to 10% in a period of an hour. Mond and Langer identified the concentration gradient of the acid, being stronger at the anode than the cathode, as the cause: "Probably this difference of concentration of the acid sets up a counter-current." To reduce the concentration polarization, they switched the gases at the electrodes and therefore the direction of ion flow through the diaphragm once per hour, to return the acid to the weak side.

Ludwig Mond had begun developing this gas battery with the hope of it using more efficiently his "Mond Gas," the product of the reaction of air and steam passed through glowing coal (Cohen, 1956). Originally, Mond had intended to synthesize ammonia with this reaction, but the results showed that no fixation of nitrogen occurred. Instead, the reaction product was rich in hydrogen, and this "smokeless fuel" could be used for power generation and for heating furnaces and kilns. Mond knew that its chemical energy would be more efficiently used by a gas battery to produce electricity, and in 1889, he and Carl Langer reported that the performance of a gas battery was sustainable when fed with Mond Gas containing 30 to 40% H2.

Guide to Alternative Fuels

Guide to Alternative Fuels

Your Alternative Fuel Solution for Saving Money, Reducing Oil Dependency, and Helping the Planet. Ethanol is an alternative to gasoline. The use of ethanol has been demonstrated to reduce greenhouse emissions slightly as compared to gasoline. Through this ebook, you are going to learn what you will need to know why choosing an alternative fuel may benefit you and your future.

Get My Free Ebook


Post a comment