Catalytic reforming of liquid hydrocarbons to produce H-2-enriched fuel in an auxiliary power unit is essential to the operation of fuel cell on board. This study explored ceria-supported nickel borate [Ni-3(BO3)(2)] catalyst for conducting the above reaction under autothermal reforming (ATR) condition. In the present catalytic system operating at 750 degrees C and under purge stream of feed, nickel borate undergoes partial degradation whose degree depends on the type of support used to release catalytically reactive tiny Ni-0 metal crystallite and B2O3. To achieve a high fuel conversion (>95%), it is crucial to maintain a dominant ratio of nickel borate versus Ni nanocrystallites as the reactive site. Typically, more than 90% nickel borate remains on the Y-doped ceria (CYO) while almost all nickel borate degrade to Ni and B2O3 on the Gd-doped ceria (CGO) after 24 h ATR of the proxy fuel comprising dodecane, naphthalene (10 wt%) and thiophene (containing 100 pm S). In consequence, the former catalyst shows a higher fuel conversion profile than the latter by 15-20%. It is proposed that nickel borate itself is a cocatalyst to induce cracking of fuel molecules, which provides smaller hydrocarbon species for the reforming on Ni crystallites, and promotes sulfur tolerance of Ni crystallites to a large extent on CYO according to the XPS and NMR characterizations. (C) 2015 Elsevier B.V. All rights reserved.