Compositional and Microstructural Engineering of Transition Metal Phosphides for Improved Electrocatalytic Performance

Abstract

Water splitting has been proposed to be a promising approach to renewable energy storage through converting the off-peak solar or wind energy to hydrogen fuels. Presently, one of major challenges facing widespread deployment of water splitting devices is their high cost, which primarily results from the use of precious and scarce noble metal catalysts. In this talk, I will present our recent efforts towards compositional and microstructural engineering of transition metal phosphide (TMP) electrocatalysts, with an aim to improve their electrocatalytic performance for the oxygen evolution reaction (OER). I will showcase two examples: 1) Trends in the OER activity of TMP nanoparticles [1]. We have investigated the alkaline OER electrolysis of a series of TMP catalysts and observed a notable trend in OER activity which follows the order of FeP < NiP < CoP < FeNiP < FeCoP < CoNiP < FeCoNiP. Our results show that the introduction of a secondary metal(s) to a mono-metallic TMP can remarkably boost the OER performance. This promotional effect can be ascribed to the enhanced oxidizing power of bi- and tri-metallic TMPs. 2) Hollow CoP octahedron (OCH) nanostructures with well-defined exposed crystal facets [2]. The hollow CoP OCH NPs were prepared by solution phase synthesis of CoO OCH precursors, followed by a post-phosphorization treatment and subsequent chemical etching process. They show excellent intrinsic electrocatalytic performance for the OER, substantially outperforming CoP nanospheres without any preferentially exposed facets and many other non-precious OER catalysts reported in the literature. Acknowledgements Financial support from the EU Horizon2020 project “CritCat” (grant no. 686053) and the Portuguese Foundation of Science and Technology (IF/01595/2014) is acknowledged. REFERENCES J.Y. Xu, J. J. Li, D.H. Xiong, B.S. Zhang, Y.F. Liu, K.H. Wu, I. Amorim, W. Li, L.F. Liu, Chem. Sci. 9 (2018) 3470J.Y. Xu, Y.F. Liu, J.J. Li, I. Amorim, B.S. Zhang, D.H. Xiong, N. Zhang, S.M. Thalluri, J.P. Sousa, L.F. Liu, J. Mater. Chem. A 6 (2018) 20646.