With the increasing urgency of both energy crisis and environmental pollution,there is an urgent need to find a kind of alternative fuel source which is clean,environmental-friendly and reproducible.

• 随着环境污染问题的日益严重和能源危机的日益紧迫,迫使人们急需寻找一种不仅清洁的、对环境友好的、而且可再生的能源。