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Hydrodeoxygenation (HDO) of various bio oil oxygenated model compounds in low H2 pressure has been discussed in this study. Because of the high yield of aromatic mixtures in bio-oil, they carry great potential for fuel efficiency. Nevertheless, due to its high viscosity, abundance of Abstract……………………………………………………………………………………………………………………………………. 1 Keywords…………………………………………………………………………………………………………………………………... 2 1-Introduction………………………………………………………………………………………………………………………….. 2 2-Bio-oil characteristics and its upgrading techniques……………………………………………………………………….………. 5 3-Low H2 pressure HDO………………………………………………………………………………………………………………. 8 3-1 Catalysts……………………………………………………………………………………………………………………. 14 3-1-1 Molybdenum……………………………………………………………………………………………………………………... 14 3-1-2 Platinum………………………………………………………………………………………………………………………….. 15 3-1-3 Other metals……………………………………………………………………………………………………………………... 16 3-1-4 Bi-functional active sites………………………………………………………………………………………………………… 17 3 _ 1-5 Supports…………………………………………………………………………………………………………………………... 19 3-2 Deactivation……………………………………………………………………………………………………………………. 20 3-3 Reaction network and Kinetics of guaiacol HDO at atmospheric pressure…………………………………………………. 21 3-4 Overall aspects and prospects…………..……………………………………………………………………………………. 25 Conclusion………………………………………………………………………………………………………………………………….

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To achieve the requirements of rechargeable Zn–air batteries (ZABs), designing efficient, bifunctional, stable, and cost-effective electrocatalysts is vital for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER), which still are struggling with unsolved challenges. The present research provides a concept based on the nanoscale composites which were engineered by using MnO2@C, CoO@C, and CoO:MnO2@C bifunctional electrocatalysts for fabrication of uniform carbon cloth (CC)-based electrodes. The CoO:MnO2@C electrocatalyst represented more efficient electrochemical properties through ORR and OER processes with superior positive half-wave potential (E 1/2 = 0.78 V) and better limiting current density (i = 1.10 mA cm–2) in comparison with MnO2@C (E 1/2 = 0.71 V, i = 0.92 mA cm–2) and CoO@C (E 1/2 = 0.69 V, i = 0.86 mA cm–2) electrocatalysts. For the rechargeable ZABs fabricated by using CoO:MnO2@C–CC as an O2-breathing cathode, the specific capacity (SC), peak power density (P), open-circuit voltage (E OCV), and gap of charge/discharge voltage resulted in values of 520 mAh gZn –1, 210.0 mW cm–2, and 1.45 and 0.45 V, respectively, that afforded greater electrochemical characters than what was obtained for ZABs based on MnO2@C–CC (410 mAh gZn –1, 195.0 mW cm–2, 1.38 and 0.44 V) and CoO@C–CC (440 mAh gZn –1, 165.0 mW cm–2, 1.15 and 0.54 V). At the same time, lower E i=10 (= 1.45 V) implied a more efficient OER in alkaline electrolyte solution for CoO:MnO2@C than MnO2@C (E i=10 = 1.50 V) and CoO@C (E i=10 = 1.39 V). Based on cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), linear sweep voltammetry (LSV), and X-ray photoelectron spectroscopy (XPS) results, it could be stated that the CoO:MnO2@C catalytic surface could experience 30 and 32% lower charge transfer resistance (R ct = 13.9 Ω) than MnO2@C (R ct = 20.1 Ω) and CoO@C (R ct = 29.7 Ω), respectively, which empowers an enhancement in ORR/OER performance. Prominently, the design concept of proposed electrocatalysts could suggest clear horizon for the synthesis and development paradigms of bifunctional catalysts for energy storage materials and devices.