Preface

World demand for energy continues to increase. Based on figures in BPs 2012Statistical Review of World Energy,1 global primary energy consumption in2011 was equivalent to a thermal power output of 16.35 TW, an increase of2.5% on the previous year and around 30% compared with a decade earlier.87% of this energy was generated from carbon-based fuels. BPs World EnergyOutlook 20302 predicts that global power output will rise to over 22 TW by2030, and looking further, other growth models predict that energy con-sumption will at least double by 2050.3,4 In the short term, shale gas will fill thegap in terms of carbon-based energy resources, but renewable energy resourceswill have to play an increased role if there is to be any hope of pegging globalCO2 emissions at a level that will reduce the impact of global climate change.

At present, renewables (including biofuels) account for only 2% of globalprimary energy consumption, but in reference 2 they are predicted to expandtheir share to around 6% by 2030. Since the potential for increases in thecontribution from hydro and nuclear may be limited, this still leaves a hugeincrease in the consumption of oil, gas and coal. In the absence of viable carboncapture and storage technologies, this implies a massive increase in CO2emissions, even if the replacement of coal and oil by gas leads to lower CO2emissions per unit of energy generated.

Rapid expansion of terrestrial photovoltaics will go some way to addressingCO2 emissions from electricity generation. Scenarios considered by the Inter-governmental Panel on Climate Change estimate the potential for power gen-eration by photovoltaics (PV) at around 600-800 GW in 2050, but still thisrepresents only around 2% of the total primary power required.5 The mainproblem with photovoltaic power generation is intermittency. Large-scale de-ployment of PV will require the development of suitable electrical and chemicalstorage methods. Transport, which accounts for around 30% of primary

RSC Energy and Environment Series No. 9

Photoelectrochemical Water Splitting: Materials, Processes and Architectures

Edited by Hans-Joachim Lewerenz and Laurence Peter

r The Royal Society of Chemistry 2013

Published by the Royal Society of Chemistry, www.rsc.org

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energy consumption, is likely to remain based on liquid (or increasingly gas)fuels, although electric vehicles will of course have some impact.

The development of methods of storing solar energy in chemical fuels hastherefore become an important research priority, and countries are beginningto react to the problem by establishing large programmes of research into solarfuels. In the United States, the Joint Center for Artificial Photosynthesis(JCAP) was established in 2010. It is the worlds largest research programmedevoted to the development of an artificial solar fuel generation technology.Other centres in the United States include the Center for Bio-Inspired SolarFuel Production at Arizona State University and the Research Triangle SolarFuels Institute involving Duke, NC State and UNC Chapel Hill. Europe hasbeen slower to address the issues, and the scale of funding is smaller than in theUS. However, a new Solar Fuels programme has been started at the HelmholtzCentre in Berlin, and there are several initiatives elsewhere in Europe includingthe Nordic initiative for solar fuel development and The European ScienceFoundations EuroSolarFuels programme. At the same time, Japan, Korea andSingapore are starting advanced artificial photosynthesis centres. In the UK,the Royal Society of Chemistry has published a helpful booklet that introducesthe topic of solar fuels to a non-specialist audience and identifies some of thekey strategic issues.6

The Editors felt that the recent rapid expansion of light-driven generation ofsolar fuels provided the raison detre for a new book to reflect current progressand to highlight some of the key issues that need to be addressed by the re-search community. Although work on light-driven water splitting has con-tinued since the much-cited work of Fujishima and Honda,7 the recent upsurgeof activity has brought new people and new ideas and methodologies. In thisvolume, we have tried to capture some of the energy and enthusiasm that isrevitalizing this important research area. The chapters in the book cover a widerange of experimental and theoretical aspects that relate to the light-inducedsplitting of water and reduction of CO2, such as materials science, interfaces,heterogeneous catalysts and (photo)electrochemical processes. In addition, newdevelopments related to photonics, light management, excitation energytransfer and third generation approaches have been included in order to em-phasize the potential for innovation in the field. We are grateful to the con-tributing authors, who are all experts in their respective fields and scientificdisciplines, and we hope that the book will not only provide an authoritativeoverview of some of the most important current research directions but alsostimulate debate and critical assessment of research priorities.

Hans-Joachim LewerenzPasadena, California, USA

Laurie PeterBath, UK

April 2013

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References

1. BP Statistical Review of World Energy June 2012. Available on the web atbp.com/statisticalreview.

2. BP Energy Outlook 2030. Available on the web at http://www.bp.com.3. World Energy Technology Outlook 2050: WETO-H2. 2006, European

Commission, Brussels. Available on the web at http://www.ec.europa.eu/research/energy/pdf/weto-h2_en.pdf.

4. World Energy Consumption - What might the Future Look Like? 2008.Shell International BV. Available on the web at http://www.shell.com.

5. IPCC, 2011: IPCC Special Report on Renewable Energy Sources andClimate Change Mitigation. Prepared by Working Group III of the Inter-governmental Panel on Climate Change: [O. Edenhofer, R. Pichs-Madruga,Y. Sokona, K. Seyboth, P. Matschoss, S. Kadner, T. Zwickel,P. Eickemeier, G. Hansen, S. Schlomer, C. von Stechow (eds)]. CambridgeUniversity Press, Cambridge, United Kingdom and New York, NY, USA,p. 1075.

6. Solar Fuels and Artificial Photosynthesis. Science and innovation to changeour future energy options. Royal Society of Chemistry, Cambridge 2012.Available on the web at http://www.rsc.org/ScienceAndTechnology/Policy/Documents/solar-fuels.asp.

7. A. Fujishima and K. Honda, Electrochemical Photolysis of Water atSemiconductor Electrode, Nature, 1972, 238, 3738.

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