logo ISCRE 21
21st International Symposium on Chemical Reaction Engineering
Sunday June 13th - Wednesday June 16th, 2010
Loews Philadelphia Hotel, Philadelphia, PA, USA

CRE: Addressing resource sustainability, environmental and life science challenges

Plenary Lecture

The important roles of chemistry and chemical engineering in solar energy utilizations

Can Li
State Key Laboratory of Catalysis, Dalian Institute of Chemical Physics,
Chinese Academy of Sciences, Dalian 116023, China (canli@dicp.ac.cn)

The concerns about the depletion of fossil fuel reserves and the pollution caused by continuously increasing energy demands renewable and sustainable energy source. Solar energy is the primary source for clean and renewable energy alternative. Currently, the solar energy can be converted to thermal energy, electricity energy via solar cell and chemical energy via chemical and biological processes. Chemistry and chemical engineering play or will play vital roles in these energy conversion processes.

Photocatalytic hydrogen production using solar energy is a promising process for renewable energy production. In the last three decades, a significant effort in photocatalytic hydrogen production has been focused on using UV light which is only less than 5% in solar spectrum on the earth surface. To convert more solar energy into chemical energy, recent research attention has been paid to the photocatalytic hydrogen production utilizing visible light1-4. The photocatalytic hydrogen production can be realized from several possible routes: direct water splitting, biomass reforming5, and reforming of waste compounds6. The most difficult target is the photocatalytic splitting water into hydrogen and oxygen, which requires the photocatalysts not only absorb solar light but also efficiently convert the photon energy into the chemical energy.

Our recent results show that the formation of surface phase junction between anatase and rutile of TiO2 can greatly enhance the photocatalytic activity possibly due to the separation of photoexcited hole-electron by the surface junction structure7. The activity of photocatalytic H2 production can be significantly enhanced when small amount of MoS2 is loaded on CdS as co-catalyst4. The rate of H2 evolution is increased by up to 36 times when CdS was loaded with only 0.2 wt% of MoS2, and the activity of MoS2/CdS is even higher than those of the CdS photocatalysts loaded with different noble metals, such as Pt, Ru, Rh, Pd and Au. The junction formed between MoS2 and CdS and the excellent H2 activation property of MoS2 are supposed to be responsible for the enhanced photocatalytic activity of MoS2/CdS.

Recently, extremely high quantum efficiency (QE) for H2 production has been achieved over Pt–PdS/CdS photocatalysts8. The Pt–PdS/CdS catalyst demonstrates the possibility of realizing visible-light-responsive photocatalytic hydrogen production with a QE approaching the level of natural photosynthesis. The strategy to achieve high QE by co-loading suitable dual cocatalysts, especially those functioning as oxidation and reduction cocatalysts, respectively, will be of considerable importance in the design and preparation of highly active photocatalysts for solar energy conversion.

The photocatalytic hydrogen production remains one of the most attractive and challenging objectives, but also has highest reward in chemistry and chemical engineering.

References:

  1. M. Y. Liu, W. S. You, Z. B. Lei, G. H. Zhou, J. J. Yang, G. P. Wu, G. J. Ma, G. Y. Luan, T. Takata, M. Hara, K. Domen and C. Li, Chem. Comm., (2004) 2192.
  2. M. Matsuoka, M. Kitano, M. Takeuchi, K. Tsujimaru, M. Anpo and J. M. Thomas, Catalysis Today, 122 (2007) 51.
  3. K. Maeda and K. Domen, J. Phys. Chem. C, 111 (2007) 7851.
  4. Z. Xu, H. J. Yan, G. P. Wu, G. J. Ma, F. Y. Wen, L. Wang and C. Li, J. Am. Chem. Soc.130 (2008)7176
  5. G. P. Wu, T. Chen, X. Zong, H. J. Yan, G. J. Ma, X. L. Wang, Q. Xu, D. E. Wang, Z. B. Lei and C. Li, J. Catal., 253 (2008) 225.
  6. J. S. Jang, H. G. Kim, P. H. Borse and J. S. Lee, J. Hydrogen Energy, 32 (2007) 4786.
  7. J. Zhang, Q. Xu, Z. C. Feng, M. J. Li and C. Li, Angew. Chem. Int. Ed. 47 (2008) 1766.
  8. H. J. Yan, J. H. Yang, G. J. Ma, G. P. Wu, X. Zong, Z. B. Lei, J. Y. Shi and C. Li, J. Catal., 266 (2009) 165.

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