Advances in the Homogeneously Catalyzed Hydrogen Production from Biomass Derived Feedstocks: A Review

Biomass-derived feedstocks for hydrogen production are crucial as an alternative to fossil fuel especially in those areas where green electricity and clean water are scarce. In this framework the transformation of simple (formic acid, alcohols) and more complex (polyalcohols, sugars and cellulose) bio-derivatives in pure hydrogen is recognized as a promising approach. Parallel to great effort in heterogeneous catalysis, milder molecular systems represent a more selective eye for alternative solutions and mechanistic insights. In the present review the introduction summarizes the challenges in the catalytic utilization of biomass-derived feedstocks, followed by the advances in homogeneously catalyzed hydrogen production from different substrates which will cover formic acid, with oustanding efficiency with noble metals and promising results with earth abundant ones and alcohols and polyalcohols, with particular emphasis to the development of heterogenized systems, ligand assisted catalysts and bi-catalytic synergistic solutions which allow to avoid base and to promote catalyst stability and recyclability. In the last part, description of hydrogen production from more complex substrates, such as sugars and cellulose, will show the role of molecular complexes in main and side reactions. Critical comments on the reported advances are provided along the whole discussion.The review describes recent advances in homogeneously catalysed hydrogen production from biomass derived substrates, such as formic acid, alcohols, polyalcohols, sugars and cellulose. Role of bifunctional catalysts, bi-catalytic systems, catalysts immobilization, and mechanistic investigation is critically analyzed to draw a perspective from both sustainability and possible development on real application. image