ABSTRACT
The awareness concerning carbon dioxide emissions and the depletion of fossil fuel reserves motivates the development of innovative processes to take advantage from renewable energy sources (Grätzel, 2005). The world power consumption is currently about 13 TW and it is expected to increase up to 23 TW by 2050 (Dobran, 2010). With approximately 120 PW of solar energy continuously striking the earth at any given moment, the challenge in converting sunlight into electricity via photovoltaic (PV) cells is to reduce the cost per watt of delivered solar electricity (Krol et al., 2008 and Nathan, 2005), which is already approximately 0.65 a/Wp for crystalline silicon modules. The solar PV technology has greatly evolved in the last decade and it is now a well-established way to convert solar energy into electric energy, which accounts presently more than 21 GW installed worldwide (The Energy Report, 2011). Nevertheless, this technology only works on a daily basis and it largely depends on the amount of solar radiation available. Thus, an effective method to store energy for later dispatch is still needed (Trieb, 2005). A practical way to convert sunlight into a storable energy form is using a photoelectrochemical (PEC) cell that splits water into hydrogen and oxygen by light-induced electrochemical processes (Grimes et al., 2008).
