Electrocatalytic properties of Pt nanoparticles grown on MXene surface

Electrocatalytic properties of Pt nanoparticles grown on MXene surface Sifani Zavahira, Jaroslav Filipb, Khaled A. Mahmoudc, Jan Tkacd Peter Kasaka,* a Center for Advanced Materials, Qatar University, P.O. Box 2713 Doha, Qatar bDepartment of Environmental Protection Engineering, Faculty of Technology, Tomas Bata University in Zlin, Vavreckova 275, 76001 Zlín, Czech Republic c Qatar Environment and Energy Research Institute (QEERI), Hamad Bin Khalifa University (HBKU), P.O. Box 5825, Doha, Qatar d Slovak Academy of Sciences, Institute of Chemistry, Department of Glycobiotechnology, Dubravska cesta 9, Bratislava, SK-84538; It is well known that modification of nanoparticles (NPs) allow precise tailoring of their physical and/or chemical properties. MXenes (Ti3C2TX) are 2D nanomaterials with a unique layered structure, hence are frequently studied in energy transformation and storage applications, especially for supercapacitor development. Metal (Au, Ag, Pd, Pt, Co..) and metal oxide (Mn3O4) modified MXenes, have shown significant increase in their catalytic properties compared to the pristine material, while MXene specifically contributing to the stability of the overall material. In this regard, we hypothesised that using MXene as the support material for Pt NPs will enhance the electrocatalytic water splitting efficiency of Pt catalyst, and this will allow us to use a low weight percentage of the otherwise expensive Pt. Hydrogen generation from water splitting produces clean energy, but the high overpotential hinder the rate of hydrogen evolution reaction (HER). Pt being the most efficient catalyst studied to date that can lower the overpotential of this demanding reaction, it is important to find avenues to minimize the amount of Pt used. In this study two Pt NP on MXene were prepared according to two different synthetic protocols. In the first approach (in-situ) Pt NPs were reduced from a Pt salt solution, and this resulted in partial oxidation of MXene layer in the vicinity of Pt4+ ions. Secondly, two catalysts were synthesised with the aid of NaBH4, external reducing agent for structure and activity comparison reasons. Different times of reaction in combination with loading of 5 % and 25 % of Pt in feed were chosen to further investigate the influence of the preparation conditions on the final NPs. Characterization by XRD, SEM, EDX and XPS revealed substantial differences in structure and composition of Pt/MXene nanohybrids synthesised in-situ and with reducing agent. Pt NPs prepared by reducing agent stacked into clusters and the initial Ti3C2TX MXene remained relatively unchanged after the Pt NP synthesis. Whereas, without NaBH4 the Pt precursor was more intensely reduced by the initial MXene particles, this in turn changed MXene NP structure. It was found that this method provided a nanohybrid with a higher overall concentration of Pt and the observed Pt NPs were assembled into larger clusters. HER was tested using cyclic voltammetry performed in a deaerated 100 mM H2SO4 acid solution. Significant boost in the HER rate was observed after modification of MXene with Pt NPs compared to that of pristine MXene (about 1 mA cm-2) irrespective of the synthetic protocol. Maximum current densities up to 61.4 ± 1.7 and 61.9 ± 9.9 mA cm-2 was achieved. This significant increase in current generation was accompanied with a shift of reaction onset potential. Catalytic performance of Pt NPs was tremendously enhanced in the Pt/MXene nanohybrids, thus these nanohybrides become attractive as HER electrocatalyst. Acknowledgements This contribution was supported by Qatar University Grant QUUG-CAM-2017-1. This work was made possible by NPRP grant No.: 6 - 381 - 1 – 078 and 9 - 219 - 2 - 105 from the Qatar National Research Fund (A Member of The Qatar Foundation).The statements made herein are solely the responsibility of the authors.