The development of efficient and robust electrocatalyst has been the central of the solar water splitting based hydrogen fuel acquisition. In this work, we reported the use of cow milk, with addition of tetraethyl orthosilicate (TEOS) and melamine, for the synthesis of nitrogen-doped mesoporous carbon micro spheres. Due to the large surface and enhanced charge transport behavior, the obtained samples enabled low overpotentials and a small Tafel slope toward oxygen evolution reaction, which were close or comparable to the best OER catalysts of carbon materials reported previously. Further incorporation of this catalyst and a Pt wire to a commercial solar cell, the direct solar-to-hydrogen conversion was realized, with a stability of over 30 h. (C) 2016 Elsevier Inc. All rights reserved.