Hydrothermal Carbonization-Derived Carbon from Waste Biomass as Renewable Pt Support for Fuel Cell Applications: Role of Carbon Activation

Pt catalysts in proton exchange membrane fuel cells (PEMFCs) typically use carbon blacks such as Vulcan (Vulcan is a registered trademark of the company Cabot Corporation) based on fossil sources. Thus, an important research task is using sustainable supports in PEMFCs. Hydrothermal carbonization (HTC) converts biomasses into chars, which are possible substitutes for fossil-based carbons. Herein, a Pt catalyst derived from HTC of coconut shells is developed for catalysis of O-2 reduction in acidic media. Thermal activation enlarges the specific surface area by factor of 7 to 546 m(2) g(-1) and generates electrical conductivity making the material suitable for catalysis. Pt particles of 1.8 +/- 0.5 nm are distributed well on the activated carbon. Cyclic and CO stripping voltammetry show an electrochemical surface area (ECSA) of 69 +/- 21 m(2) g(Pt)(-1), almost identical to that of the commercial catalyst using Vulcan (69 +/- 6 m(2) g(Pt)(-1)). Although ECSAs are highly comparable, the activity for O-2 reduction is lower compared with the commercial catalyst. HTC-derived carbon has a lower degree of graphitization, less functional oxygen groups on its surface, and a lower electrical conductivity than Vulcan. This suggests different Pt-support interactions.