Highly efficient Pt-Co alloy hollow spheres with ultra-thin shells synthesized via Co-B-O complex as intermediates for hydrogen evolution reaction

Abstract Improving utilization of precious metals is one of the crucial challenges for electrochemical energy catalysis. Tuning precious metal structure to expose active sites is an effective strategy to reduce mass loading in the practical application. Herein, Pt-Co hollow nanospheres were synthesized via a sequential reduction strategy using amorphous Co-B-O complex as the key spheres-forming intermediates. The modulation mechanism of Pt-Co hollow nanospheres formation was established by investigating critical factors of addition sequence of reducing agent, the type of reducing agents and the ratio of Pt and Co precursors. The optimized Pt-Co hollow nanospheres with the Pt/Co molar ratio of 1:1 by this method is characterized by the average diameter of around 30 nm and the shell thickness of 2.3 nm. They displays superior performance for enhanced hydrogen evolution reaction (HER) in the aspect of activity and stability in 0.5 M H2SO4, in which the mass activity of the Pt-Co hollow spheres exhibits 2.82 times higher than that of commercial Pt/C and its stability also has a significant enhancement. The outstanding activity of the Pt-Co hollow nanospheres for HER is mainly attributed to its highly accessible electron/mass transport path, expose active sites on the ultra-thin shells and strain effect induced by the hollow sphere structure. This hollow nanospheres with ultra-thin shell provides a promising way to develop highly efficient precious metal based electrocatalysts.