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

Abstract

Pt catalysts in proton exchange membrane fuel cells (PEMFC) typically use carbon blacks like Vulcan® 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. In this study, a Pt catalyst derived from HTC of coconut shells is developed for catalysis of O2 reduction in acidic media. Thermal activation enlarges the specific surface area by factor of 7 to 546 m2 g-1, and generates electrical conductivity making the material suitable for catalysis. 1.8±0.5 nm Pt particles are well-distributed on the activated carbon. Cyclic and CO stripping voltammetry show an electrochemical surface area (ECSA) of 69±21 m2 gPt -1, being almost identical to that of the commercial catalyst using Vulcan® (69±6 m2 gPt-1). Although ECSAs are highly comparable, the activity for O2 reduction is lower compared to 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.