000K utf8 1100 2017$c2017-10-13 1500 eng 2050 urn:nbn:de:hbz:464-20171117-152721-7 2051 10.1038/s41598-017-13333-z 3000 Waag, Friedrich 3010 Barcikowski, Stephan 3010 Behrens, Malte 3010 Bendt, Georg 3010 Gökce, Bilal 3010 Hagemann, Ulrich 3010 Hartmann, Nils 3010 Heidelmann, Markus 3010 Kalapu, Chakrapani 3010 Landers, Joachim 3010 Salamon, Soma 3010 Schulz, Stephan 3010 Wende, Heiko 4000 Adjusting the catalytic properties of cobalt ferrite nanoparticles by pulsed laser fragmentation in water with defined energy dose [Waag, Friedrich] 4209 Highly active, structurally disordered CoFe2O4/CoO electrocatalysts are synthesized by pulsed laser fragmentation in liquid (PLFL) of a commercial CoFe2O4 powder dispersed in water. A partial transformation of the CoFe2O4 educt to CoO is observed and proposed to be a thermal decomposition process induced by the picosecond pulsed laser irradiation. The overpotential in the OER in aqueous alkaline media at 10 mA cm−2 is reduced by 23% compared to the educt down to 0.32 V with a Tafel slope of 71 mV dec−1. Importantly, the catalytic activity is systematically adjustable by the number of PLFL treatment cycles. The occurrence of thermal melting and decomposition during one PLFL cycle is verified by modelling the laser beam energy distribution within the irradiated colloid volume and comparing the by single particles absorbed part to threshold energies. Thermal decomposition leads to a massive reduction in particle size and crystal transformations towards crystalline CoO and amorphous CoFe2O4. Subsequently, thermal melting forms multi-phase spherical and network-like particles. Additionally, Fe-based layered double hydroxides at higher process cycle repetitions emerge as a byproduct. The results show that PLFL is a promising method that allows modification of the structural order in oxides and thus access to catalytically interesting materials. 4950 https://doi.org/10.1038/s41598-017-13333-z$xR$3Volltext$534 4950 https://nbn-resolving.org/urn:nbn:de:hbz:464-20171117-152721-7$xR$3Volltext$534 4961 https://duepublico2.uni-due.de/receive/duepublico_mods_00044879 5010 54 5051 540