▎ 摘　　要

A new hybrid system mainly consisting of a molten hydroxide direct carbon fuel cell (MHDCFC) and a vacuum thermionic energy converter (VTEC) is proposed to improve fuel utilization efficiency. The MHDCFC has different anodic and cathodic reaction compartment heights and uses molten sodium hydroxide as electrolyte. The VTEC with a graphene-based cathode can conveniently convert the waste heat from MHDCFC into electricity. Based on thermodynamic-electrochemical analyses and semi-empirical equations available in literature, multi-irreversibilities within the hybrid system are taken into account to obtain performance parameters. Effects of fuel types, working temperature, reaction compartment width, anodic and/or cathodic compartment heights, cathode to anode pressure ratio, Fermi level and cathode work function on power output, efficiency, exergy destruction rate and exergy efficiency of MHDCFC/VTEC hybrid system are discussed. Optimal regions for the performance param-eters are determined. The results obtained may provide some theoretical bases for designing and operating such an actual MHDCFC/VTEC hybrid system. (c) 2021 Elsevier Ltd. All rights reserved.