Abstract
Tremendous developments in energy storage and conversion technologies urges researchers to develop inexpensive, greatly efficient, durable and metal-free electrocatalysts for tri-functional electrochemical reactions, namely oxygen reduction reactions (ORRs), oxygen evolution reactions (OERs) and hydrogen evolution reactions (HERs). In these regards, this present study focuses upon the synthesis of porous carbon (PC) or N-doped porous carbon (N-PC) acquired from golden shower pods biomass (GSB) via solvent-free synthesis. Raman spectroscopy, X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) studies confirmed the doping of nitrogen in N-PC. In addition, morphological analysis via field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) provide evidence of the sheet-like porous structure of N-PC. ORR results from N-PC show the four-electron pathway (average n = 3.6) for ORRs with a Tafel slope of 86 mV dec−1 and a half-wave potential of 0.76 V. For OERs and HERs, N-PC@Ni shows better overpotential values of 314 and 179 mV at 10 mA cm−2, and its corresponding Tafel slopes are 132 and 98 mV dec−1, respectively. The chronopotentiometry curve of N-PC@Ni reveals better stability toward OER and HER at 50 mA cm−2 for 8 h. These consequences provide new pathways to fabricate efficient electrocatalysts of metal-free heteroatom-doped porous carbon from bio-waste/biomass for energy application in water splitting and metal air batteries.
Highlights
The current global-energy crisis has provoked researchers to investigate alternative energy storage and conversion systems that should be environmentally benign, inexpensive and highly efficient [1]
To conquer the limitations given by metal catalysts, various metal-free catalysts, in specific, graphene, carbon nanotubes and porous carbons, are attracting more attention to use in oxygen reduction reactions (ORRs), oxygen evolution reactions (OERs) and hydrogen evolution reactions (HERs) due to large surface area, high efficiency, good stability, better electrical and electrochemical properties and better tolerance in alkaline and acidic media [23]
We presented the cost-effective synthesis of porous carbon (PC) and N-doped porous carbon (N-PC) from relatively abundant, natural, renewable golden shower pod biomass (GSB) via a solvent-free method
Summary
The current global-energy crisis has provoked researchers to investigate alternative energy storage and conversion systems that should be environmentally benign, inexpensive and highly efficient [1]. The electrochemical oxygen reduction reaction (ORR), oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) are pivotal to next-generation energy production, storage and conversion systems, include water splitting [2,3] fuel cells [4,5,6,7,8] and metal–air batteries [9,10,11] In this regard, it is essential to develop novel electrocatalysts applicable to ORRs, OERs and HERs with the desired catalytic properties, such as more abundance, higher efficiency, long-term durability and eco-friendliness [12,13]. The OER and HER of the N-PC@Ni catalyst shows better over potential values of 314 and 179 mV at 10 mA cm−2, and it shows better stability over 8 h at 50 mA cm−2
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