Light, Water, Hydrogen The Solar Generation of Hydrogen by Water Photoelectrolysis Craig A. Grimes • Oomman K. Varghese • Sudhir Ranjan Light, Water, Hydrogen The Solar Generation of Hydrogen by Water Photoelectrolysis Craig A. Grimes Pennsylvania State University Department of Electrical Engineering Department of Materials Science & Engineering 217 Materials Research Lab. University Park, PA 16802 Oomman K. Varghese Pennsylvania State University Materials Research Institute 208 Materials Research Lab. University Park, PA 16802 Sudhir Ranjan Pennsylvania State University Materials Research Institute 208 Materials Research Lab. University Park, PA 16802 ISBN 978-0-387-33198-0 e-ISBN 978-0-387-6828-9 Library of Congress Control Number: 2007933414 © 2008 Springer Science+Business Media, LLC All rights reserved. This work may not be translated or copied in whole or in part without the written permission of the publisher (Springer Science+Business Media, LLC, 233 Spring Street, New York, NY 10013, USA), except for brief excerpts in connection with reviews or scholarly analysis. Use in connection with any form of information storage and retrieval, electronic adaptation, computer software, or by similar or dissimilar methodology now know or hereafter developed is forbidden. The use in this publication of trade names, trademarks, service marks and similar terms, even if they are not identified as such, is not to be taken as an expression of opinion as to whether or not they are subject to proprietary rights. Printed on acid-free paper. 9 8 7 6 5 4 3 2 1 springer.com Foreword In addition to domestic animals the earliest records of mankind indicate that slavery, until the use of coal became widespread, has always been a significant aspect, or part, of nearly every society. Consider for example ancient Attica (Greece), in which 115,000 out of a total population of 315,000 were slaves [1]. For the lucky rulers slaves represented power, Joule/second or Watt. On a steady state basis a healthy adult generates about 100 Watts, or 100 J/s, while a highly conditioned endurance athlete can generate about 300 W for perhaps an hour. Today we obtain our energy from fossil fuels, that magical brew of latent-heat chemistry that allows us to run the world without having to rely on people or domestic animal power. We owe much if not all of modern civilization to fossil fuels, no more than stored solar energy, which provide the 40-plus Terawatts that annually powers the ≈ 7,000,000,000 people on this planet, with our fossil fuel burn rate growing to accommodate the annual increase of some additional 100,000,000 or so souls. The foundation of modern society is a pile (lake) of priceless, irreplaceable fossil fuel that, by any measure of the energy you get and what you pay, is all intents free, and being virtually free we have and continue to burn our way through it as fast as we possibly can. It is the tragedy of the (fossil fuel) commons. Take away fossil fuels with their life giving energy and for all intents and purposes you are back in the 16th century, with an impact that should be obvious. A gallon of gasoline has an energy equivalent of 121.8 MJ, a remarkable number that is entirely sufficient to explain the modern politics of the Middle East and the vast military presence there of the United States. Converted to 100 W people power, a single gallon of gasoline is equivalent in energy to the fulltime dedication of 14 people for 24-hours. From that perspective gasoline at $100/gallon can be considered a rare bargain. Since fossil fuels are so remarkably energy dense (a single tank of gas can move your fully laden inefficient car hundreds of vi Foreword miles), essentially free (try walking instead), and relatively safe to use its good that they will continue to be freely available to us for the imaginable future, that is the next few years. A couple of decade’s worth of oil remains, at least for the fortunate rulers with the strongest armies. Depending upon the expert, the earth has 80 to 300 years or so of coal, and about 50 years worth of natural gas, with the supply lifetimes dependent upon a variety of factors such as the desire of rich countries to turn their coal into gasoline. However experiencing fossil fuel depletion, today, would be a great thing from the perspective of keeping modern civilization intact, as otherwise we will simply cook ourselves, having set the house on fire and then finding there are no exits, no way out from planet earth. In a collective effort we have succeeded in depositing vast amounts of CO2 in the atmosphere, today reaching the highest concentrations seen on this planet in, at least, the last 500,000 years. As we keep on doing what we are doing (burning fossil fuels) to provide the more than 40 Terawatts of energy we use every year earth’s atmospheric CO2 levels will reach heights never, to our knowledge, seen outside of planet Venus. Since atmospheric CO2 lasts a long time in the atmosphere, and acts as an insulator trapping heat, the logical outcome is a very hot earth for a very long time. Not an ice age, but a steam age. It will be a Saurian hot house for future generations with, finally, the oceans receiving the vast amount of atmospheric CO2 and subsequently becoming acidic. So we can say to future generations, “Sorry for the mess,” and “Good Luck.” To summarize the issue, approximately 7 billion people on the planet the support of whom is virtually all based upon fossil fuels which are: Point {1} rapidly being depleted, and Point {2} when burned in such vast quantities, after a modest time lag, appears likely to make life on earth un-tenable but for a substantially reduced population. Point {3}, there is no backup plan, no Energy Plan B on how we might even begin to provide the vast amounts of energy used by humans on this planet once fossil fuels are either depleted or their use made politically unacceptable due to environmental consequences. In essence modern society is being bet on a Faith- based Energy Policy, that is to say let us hope for a miracle. Point {4}, the discussion here is not of another crisis du jour, of which most of us are familiar and can ignore without consequence, rather Foreword vii an increasingly inescapable grinding reality of our future that was first foretold in 1949 by M. K. Hubbert [2]; since 1949 the story has stayed the same but the ending grown increasingly unpleasant. Perhaps the above noted points are not to be considered a problem. Nature defines good as that which survives, and bad as that which goes under; if we have some intrinsic weakness as a species that allows us to cook ourselves while feasting at the fossil fuel table maybe that’s just how it is, and we shouldn’t dwell upon it. On one point all historians agree, civilizations begin, flourish, decline, and disappear. “They failed as a species since they were unable to look beyond their immediate gratification,” an observer might one day write. Another could pencil “their civilization declined through failure of its intellectual and political leaders to meet the challenges of change. Alas.” Let us consider where the path we are on leads. Notably it appears one that includes the potential for massive wars over the remaining fossil fuel supplies. Whatever the pretences, the real points of interest for the Middle East deserts is the oil that lies beneath them, an interest the United States at least does not take lightly.1 Without a viable Energy Plan B as the energy-noose 1 U. S. Military presence in the Middle East: BAHRAIN: Navy 5th Fleet headquarters - 1,200 sailors; Joint Venture HSV-X1 – 50 troops. DJIBOUTI: Camp Lemonier – 1,300 U.S. troops. HORN OF AFRICA: Elements of Combined Joint Task Force Horn of Africa, 10th Mountain Division, 478th Civil Affairs Division; about 1,300 troops. MEDITERRANEAN: Harry S. Truman Carrier Battle Group/Carrier Air Wing 3 (Marine Fighter-Attack Squadron 115) – 7,610 sailors and Marines; Theodore Roosevelt Carrier Battle Group/Carrier Air Wing 8 – 7,445 sailors; 26th Marine Expeditionary Unit trains aboard Iwo Jima Amphibious Ready Group. PERSIAN GULF: Amphibious Task Force East – 5,000 sailors; Amphibious Task Force West – 4,080 sailors; Tarawa Amphibious Ready Group w/15th Marine Expeditionary Unit – 1,700 sailors, 2,200 Marines; 2nd Marine Expeditionary Brigade returns to ships of Amphibious Task Force East; Echo Company, Battalion Landing Team 2nd Battalion (with Nassau Amphibious Ready Group); Coast Guard cutters (2) and patrol boats (4) - 690 Coast Guardsmen. RED SEA: Attack submarine Boise – 112 sailors; Attack submarine Toledo – 112 sailors; Attack submarine San Juan – 112 sailors. TURKEY: Elements of 1st Infantry Division – 2,000 soldiers; Incirlik Air Base – F-15 and F-16 aircraft, 4,000 airmen. DIEGO GARCIA: AF 20th Bomb Squadron; 917th Bomb Wing Air Force Reserve. EGYPT: 1st Battalion, 180th Infantry Regiment, Oklahoma National Guard - 865 soldiers. GULF OF ADEN: viii Foreword tightens pressures on governments to obtain more of a precious, vitally needed dwindling resource will grow more intense, resulting in ever-larger military establishments and appropriations, with the freedoms of democracy disappearing to the discipline of arms. History indicates time and again such statements to be fully accurate. We compete peacefully when there is enough to go around, but let the mouths out-run the food and it is us-versus-them, and violent. Yet for all that, as climate changes go non-linear a few more wars will probably be the least of our troubles.