Light to hydrogen conversion via water splitting is of immense interest as a clean, storable, and renewable energy source (Tachibana and Vayssieres, 2012 [1]; Maeda and Domen, 2010 [2]; van de Krol et al., 2008 [3]; van Dorp et al., 2009 [4]; Kudo and Miseki, 2009 [5]) but efficient materials need to be found. To solve, InGaN has properties ideally suited and we demonstrate here that epitaxial InN quantum dots (QDs) more than double the photoelectrochemical (PEC) water splitting efficiency of an In0.54Ga0.46N photoelectrode. The InN/In0.54Ga0.46N-QDs-photoelectrode reveals a maximum incident-photon-to-current-conversion efficiency (IPCE) of up to 56% at a wavelength of 600 nm with hydrogen generation rate of 133 µmol h−1 cm−2 at zero voltage under white light illumination of a 1000 W Xenon arc lamp. The bare In0.54Ga0.46N-layer-photoelectrode reveals a much lower IPCE of 24% with hydrogen generation rate of 59 µmol h−1 cm−2.