Controlled Design of Functional Nano-Coatings: Reduction of Loss Mechanisms in Photoelectrochemical Water Splitting Steve Landsmann Yuri Surace Matthias Trottmann Stefan Dilger Anke Weidenkaff Simone Pokrant 10.1021/acsami.6b01129.s002 https://acs.figshare.com/articles/media/Controlled_Design_of_Functional_Nano_Coatings_Reduction_of_Loss_Mechanisms_in_Photoelectrochemical_Water_Splitting/3363388 Efficient water splitting with photoelectrodes requires highly performing and stable photoactive materials. Since there is no material known which fulfills all these requirements because of various loss mechanisms, we present a strategy for efficiency enhancement of photoanodes via deposition of functional coatings in the nanometer range. Origins of performance losses in particle-based oxynitride photoanodes were identified and specifically designed coatings were deposited to address each loss mechanism individually. Amorphous TiO<sub>2</sub> located at interparticle boundaries enables high electron conductivity. A thin layer of amorphous Ta<sub>2</sub>O<sub>5</sub> can be used as protection layer for photoanodes because of its hole conductivity and thermal and chemical stability. An amorphous layer of NiO<sub><i>x</i></sub> and Co­(OH)<sub>2</sub> reduces photocorrosion or increases water oxidation kinetics because they act as a hole-capture material or water oxidation catalyst, respectively. Crystalline CoO<sub><i>x</i></sub> nanoparticles increase photocurrent and reduce the onset potential due to enhanced charge separation. The combination of all coatings deposited by a scalable, mild, and reproducible step-by-step approach leads to high-performance oxynitride-based photoanodes providing a maximum photocurrent of 2.52 mA/cm<sup>2</sup> at 1.23 V<sub>RHE</sub> under AM1.5G illumination. 2016-05-09 15:34:09 protection layer water oxidation catalyst chemical stability Photoelectrochemical Water Splitting Efficient water splitting loss mechanism hole conductivity Ta 2 O 5 photoactive materials performance losses 1.23 V RHE Loss Mechanisms Controlled Design electron conductivity nanometer range charge separation NiO x coating Amorphous TiO 2 AM 1.5G illumination photoanode Crystalline CoO x nanoparticles increase photocurrent interparticle boundaries loss mechanisms increases water oxidation kinetics efficiency enhancement