The trifunctional electrocatalytic activity of hierarchically structured porous carbon derived from environmentally malignant Prosopis juliflora

Abstract

Finding an efficient and affordable multifunctional electrocatalyst with long-term durability has received paramount interest in the recent scenario. The present work attempted to facilitate ecologically threatful invasive biomass – P. juliflora- derived porous carbon as an effectual Pt support for trifunctional electrocatalytic applications. The preparation of Pt decorated P. juliflora -derived porous carbon (Pt/J-600, Pt/J-700, and Pt/J-800) involves simple hydrothermal carbonization, pyrolysis at various temperatures of 600, 700 & 800⁰C and polyol mediated reduction. The obtained XRD results reveal the turbostratic nature of the prepared porous carbon favoring to anchor the Pt NPs. Significantly, the estimated I_D/I_G ratios of Raman profile substantiates the highly defective structure of Pt/J-800. The TEM images disclose the agglomeration-free dispersion of Pt NPs in the Pt/J-800 electrocatalyst. The EIS analysis demonstrates the relatively low solution and charge transfer resistances (R_s = 0.646 Ω & R_ct = 0.312 Ω). The desirable 4e- transfer with an improved limiting current density of -4.44 mA cm^-2 signpost better oxygen reduction reaction (ORR) performance of Pt/J-800 than the other prepared electrocatalysts. Additionally, the high electrochemical surface area (652.72 m² g^-1) and good mass activity (49.09 mA mg_pt^-1) prove the excellent methanol oxidation reaction (MOR) activity. Moreover, a minimal overpotential of 31 mV @ 10 mA/cm², and a lower Tafel slope of 32 mV/dec with 24 hr stable performance proved the efficient hydrogen evolution reaction (HER) performance of Pt/J-800. The remarkable electrochemical performance of Pt/J-800 is attributed to the enhanced surface area created by hierarchically porous carbon support and the uniform dispersion of Pt nanoparticles with optimum loading.