Various oxygen evolution electrocatalysts including cobalt phosphate, FeOOH, Ag+, and metal oxides MOx (M = Co, Mn, Ni, Cu, Rh, Jr, Ru, Pd) were loaded on BiVO4 photoanode for photoelectrochemical water splitting under simulated solar light. In all cases, the electocatalysts increased photocurrent generation and brought cathodic shifts of current onset potential. The screening test led to discovery of a novel PdOx-loaded BiVO4 electrode that showed the best performance in terms of fivefold increase in photocurrent, the largest onset potential shift, and dramatically improved stability, relative to bare BiVO4. To assess the role of the electrocatalyst in a quantitative way, photooxidation of sulfite ion was investigated as a sacrificial agent to obtain charge separation yields in the bulk and on the surface of BiVO4. The analysis clearly demonstrated that electrocatalysts reduced surface charge recombination with no effect on bulk recombination. (C) 2014 Elsevier Inc. All rights reserved.