Make the complex “streamlined hydrogen production from biomass” simple

Make the complex “streamlined hydrogen production from biomass” simple

The paper “streamlined hydrogen production from biomass” in Nature Catalysis is here:

My initial learning about hydrogen production from biomass was during the discussion with Prof. Beller when I did my postdoctoral research in 2012. Prof. Beller said: “If a child puts a piece of sugar in water, then hydrogen bubbles release. That would be very interesting. If you are interested, we can start.”

Then in Prof. Beller’s group, we started the research of hydrogen generation from glycerol, fructose, glucose, disaccharide, cellulose, and lignocellulose.

During the studies of hydrogen generation from fructose and glucose, we met insurmountable difficulties. Although the catalyst TON reached more than 10,000, the yields of hydrogen were 2% (Scheme 1). The only insight is that formic acid acts as one of the possible intermediates accompanying with many unidentified intermediates. The clear understanding of the transformation pathway looked impossible as black sticky gum was all that remained after the reaction.

Scheme 1. Hydrogen production from fructose and glucose. For the details, see: Li, Y.; Sponholz, P.; Nielsen, M.; Junge, H.; Beller, M. ChemSusChem 2015, 8, 804.

Even when I started my independent career in Frontier Institute of Science and Technology in Xi’an Jiaotong University, the black sticky gum always came to my mind. Dr. Ping Zhang’s research background is the analysis of sugars. Thus Dr. Ping Zhang joined our group as a postdoctoral fellow. After a great deal of effort, we could not make any progress to understand the reaction mechanism yet.   

During that period, I felt deeply frustrated: “This project is extremely complex, I cannot overcome”. One day, an idea came to my mind. Is it possible to transform biomass to formic acid via oxidative catalysis and followed by hydrogen release via reductive catalysis (Scheme 2)?

Scheme 2. The initial idea

If possible, the complex project “Streamlined hydrogen production from biomass” would be simple as these two steps are known although the transformation of biomass to formic acid needs improvement.     

  The previous studies were conducted in argon atmosphere. Can the reductive catalysis for the hydrogen release be tolerated after the oxidative catalysis? With these considerations in mind, we started this project.

With efforts of all authors, Ping, Yan-Jun, Jianbin, Yu-Rou, Jun, Henrik and Matthias, we realized “Streamlined hydrogen production from biomass” (Scheme 3).

Scheme 3. Streamlined hydrogen production from biomass 

We thank Ke-Han, Wan-Fa for their help during the experiments. We thank Dr. Lei Wang, Institute of Pulp and Paper Technology, Hubei University of Technology, China for affording various raw biomass and daily waste. We thank Prof. Dr. Hai-Jun Jiao, Leibniz-Institut für Katalyse e. V. an der Universität Rostock,Prof. Dr. Zhang-Jie Shi, Fudan University for helpful discussion. We thank Wattecs Lab Equipment Co., Ltd. for strong support on autoclaves and constant pressure gas collectors.