Aqueous‐phase hydrodeoxygenation (APH) of bioderived feedstocks into useful chemical building blocks is one the most important processes for biomass conversion. However, several technological challenges, such as elevated reaction temperature (220–280 °C), high H2 pressure (4–10 MPa), uncontrollable side reactions, and intensive capital investment, have resulted in a bottleneck for the further development of existing APH processes. Catalytic transfer hydrogenation (CTH) under much milder conditions with non‐fossil‐based H2 has attracted extensive interest as a result of several advantageous features, including high atom efficiency (≈100 %), low energy intensity, and green H2 obtained from renewable sources. Typically, CTH can be categorized as internal H2 transfer (sacrificing small amounts of feedstocks for H2 generation) and external H2 transfer from H2 donors (e.g., alcohols, formic acid). Although the last decade has witnessed a few successful applications of conventional APH technologies, CTH is still relatively new for biomass conversion. Very limited attempts have been made in both academia and industry. Understanding the fundamentals for precise control of catalyst structures is key for tunable dual functionality to combine simultaneous H2 generation and hydrogenation. Therefore, this Review focuses on the rational design of dual‐functionalized catalysts for synchronous H2 generation and hydrogenation of bio‐feedstocks into value‐added chemicals through CTH technologies. Most recent studies, published from 2015 to 2018, on the transformation of selected model compounds, including glycerol, xylitol, sorbitol, levulinic acid, hydroxymethylfurfural, furfural, cresol, phenol, and guaiacol, are critically reviewed herein. The relationship between the nanostructures of heterogeneous catalysts and the catalytic activity and selectivity for C−O, C−H, C−C, and O−H bond cleavage are discussed to provide insights into future designs for the atom‐economical conversion of biomass into fuels and chemicals.

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Selective synthesis of lactic acid from bioderived substrates still remains a grand challenge. We reported a series of unique bimetallic Pt–Co/CeO x catalysts, prepared by fractional precipitation method. Strong electronic coupling for Pt–Co is found to enhance activity toward dehydrogenation (C–H bond cleavage) of glycerol, as evidenced from X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM) studies of the catalysts. Detectable electroaffinity of PtCo trends to gain electrons from CeO x support; thus some side reactions (such as C–C and C–O bond cleavage) are largely restrained. Such hybridized structures lead to remarkable activity (turnover frequency (TOF) = 1533.9 h–1) with good selectivity toward lactic acid (87.7%) and total organic acids (>95%) at 200 °C. In addition, the effect of reaction temperature and substrate concentration on the initial reaction rate reveals that dehydrogenation of glycerol possibly follows a dual-site mechanism, where both glycerol and base need to be activated on the bimetallic Pt–Co surface. Furthermore, the plausible reaction pathway is discussed in detail.

Catalytic transfer hydrogenolysis, using liquid H‐donors in the absence of pressurized H2 under mild temperatures, is regarded as the most important technology to substitute traditional hydrogenation processes in industry. Despite decade development with several breakthroughs in catalyst design, the reaction mechanism involved in H2 generation and subsequent hydrogenolysis reactions is still under debate. In this review, transfer hydrogenolysis of glycerol, as a representative example, on metallic catalysts is revised critically with respect to surface reaction mechanism and catalyst design. The detailed reaction pathways for propanol, methanol, formic acid and ethanol for H2 generation have been discussed systematically. In particular, reaction mechanism for catalytic C−H cleavage, H spillover/transfer and C−O cleavage reaction steps will be critically revised with experimental and theoretical results in literature. Insights into reaction pathways, mechanism and H2 transfer efficiency and structure‐performance relation for Pd, Cu and Ni catalysts will be provided for future development of catalyst manufacture and process development. The outcome of this work is useful for successful implementation of bio‐refinery.