This study explores the performance degradation mechanism of direct borohydride fuel cells (DBFCs) by investigating the catalyst surface characteristics, electrode structure, and electrode polarization after cell operation. Catalyst erosion from the anode substrate is a major cause of DBFC performance degradation. The depression of hydrogen evolution effectively stabilizes DBFC performance. DBFCs using Ni-Pd/C as the anode catalyst and polypyrrole-modified carbon-supported Co(OH)(2) [Co(OH)(2)-PPy/BP] as the cathode catalyst exhibit high performance stability. The performance stability of Co(OH)(2)-PPy/BP is similar to that of commercial Pt/C, although only a small amount of Co remains after operation. The cooperative interaction among Co, N from polypyrrole, and C from the carbon supporter plays a very important role in the performance stability of a DBFC cathode. (c) 2013 Elsevier B.V. All rights reserved.