生物质资源是地球上储量最大、分布最广泛的可再生能源之一。面临日益严峻的能源环境问题，充分合理地利用生物质资源无疑是解决问题的重要途径。光催化重整生物质制氢耦联了太阳能与生物质能两大可再生能源，其应用价值不言而喻。近几年来，关于生物质重整的机理研究不断展开，催化剂以TiO2居多，而生物质主要是简单的模型分子，如甲醇、乙醇、丙三醇、葡萄糖等。我们利用时间分辨红外光谱对甲醇的光催化重整过程进行了研究，发现重整过程中催化剂表面有吸附中间物种CH2O，CH2OO，以及HCOO生成，说明甲醇的重整是通过逐步氧化脱氢进行的。在生物质重整制氢的过程中，获得高产氢活性的同时，CO的产生量却往往被忽视，众所周知，氢能作为未来能源的重要组成，其主要利用技术为燃料电池，而H2中微量的CO就能使燃料电池催化剂中毒，因此，降低催化重整制氢中CO的含量，是一个非常有意义的课题。
我们在研究生物质重整甲醇的实验中发现，在反应体系中加入少量无机阴离子就能在不降低氢气的前提下大幅度降低重整过程中的CO 的含量。 随后，我们以具有较高光催化活性的商品氧化钛（P25）为原料，利用其在高温过程中的相变机制，精细控制焙烧温度得到一系列不同相结构的氧化钛样品，其重整生物质产氢活性较P25可提高至3～5倍。之后，我们进一步改进合成方法，采用浸渍焙烧法，通过控制合成过程中加入硫酸盐的含量实现高温下TiO2相结构的调变。使原本全部转化为金红石相的氧化钛样品在高温下的保持了混相结构。该方法既实现了高温处理下半导体催化剂晶化度的提高，同时又保证了TiO2混相结构的形成，因此明显促进了TiO2样品在光催化重整甲醇制氢反应中的活性，其活性较商品氧化钛（P25）提高至6倍。
Photocatalytic H2 production on Pt/TiO2–SO42- with tuned surface-phase structures: enhancing activity and reducing CO formation， Yi Ma, Qian Xu, Xu Zong, Donge Wang, Guopeng Wu, Xiang Wang and Can Li*，Energy Environ. Sci., 2011
此外，在重整过程中，我们发现P25样品反应产生的CO高至几千ppm（以CO/H2计算），而我们通过焙烧所制备的样品可将CO含量降低两个数量级，最低可达到10 ppm左右。对催化剂的表面酸碱性研究表明，TiO2表面酸碱性对其CO的产生有很大影响，其机理类似传统催化中甲酸的分解反应，即酸性表面有利于CO的产生。此发现对今后设计光催化重整生物质制氢反应催化剂具有很好的借鉴意义采用硫酸钠浸渍后焙烧的方法实现了氧化钛高温下的相变控制。在光催化重整甲醇制氢反应中，该催化剂可以达到6倍于商品P25的产氢活性，所用Pt担载量也较之前工作降低50%，同时其CO/H2也降低2个数量级。表面相结的形成和氧化钛表面酸性的降低被认为是光催化活性提高及CO选择性降低的原因。相关该研究成果近日被Energy & Environmental Science 杂志接收发表。
Photocatalytic Reforming of Biomass
The main research interest in our group is to identify and challenge the key scientific problems for efficient solar to chemical energy conversion, carry out fundamental research for better understanding the solar to chemical energy conversion processes by means of bench-top material synthesis/assembly and various spectroscopic techniques. The ultimate goal of our research is to develop efficient sunlight capturing photocatalysts and assembly functional integrated photocatalytic systems for efficient solar to energy conversion. Throughout the research activities, particular emphasis will be focused on better understanding the energy transfer related processes theoretically and experimentally.
Research activities:
1) Photocatalytic reforming of biomass into gas (hydrogen, methane) and liquid fuels (methanol, ethanol) as well as value-added chemicals.
Current research is focused on the development of photocatalysts/photocatalytic systems by conversion of model biomass compounds, such as methanol, ethanol, glycerol, glucose, etc. Our long term and ultimate goal of biomass research is photocatalytic reforming of polysaccharide, cellulose and hemicelluloses and lignin in environmental friendly and energy and cost effective way using solar energy.
2) Photocatalytic splitting of water.
Current research is mainly focused on the development of visible light absorbing photocatalyst for water oxidation multi-electron transfer catalyst and cheap and abundant proton reduction catalyst. We are exploring the way to assembly of integrated photocatalytic systems with inorganic materials (including semiconductors) as water oxidation catalyst and organic or inorganic materials as proton reduction catalyst. The ultimate goal of this research is to develop efficient photocatalysts, photocatalytic systems, or photoelectrochemical cells for efficient overall water splitting.
This part work is in close collaboration with Group DNL1601 and 1603.
3) Photocatalytic reduction of CO2 to chemical fuels.
Current research is mainly focused on the development water oxidation photocatalyst and searching for CO2 reduction catalyst. The ultimate goal of this research is to develop efficient artificial leaf integrated with photocatalysts, photocatalytic systems, or photoelectrochemical cells for CO2 reduction.
This part work is in close collaboration with Group DNL1601 and 1603
