Red Bean Pod Derived Heterostructure Carbon Decorated with Hollow Mixed Transition Metals as a Bifunctional Catalyst in Zn‐Air Batteries

Abstract

Design and synthesis of low‐cost and efficient bifunctional catalysts for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) in Zn‐air batteries are essential and challenging. We report a facile method to synthesize heterostructure carbon consisting of graphitic and amorphous carbon derived from the agricultural waste of red bean pods. The heterostructure carbon possesses a large surface area of 625.5 m2 g−1, showing ORR onset potential of 0.89 V vs. RHE and OER overpotential of 470 mV at 5 mA cm−2. Introducing hollow FeCo nanoparticles and nitrogen dopant improves the bifunctional catalytic activity of the carbon, delivering ORR onset potential of 0.93 V vs. RHE and OER overpotential of 360 mV. Electron energy‐loss spectroscopy (EELS) O K‐edge map suggests the presence of localized oxygen on the FeCo nanoparticles, suggesting the oxidation of the nanoparticles. Zn‐air battery with these carbon‐based catalysts exhibits a peak power density as high as 116.2 mW cm−2 and stable cycling performance over 210 discharge/charge cycles. This work contributes to the advancement of bifunctional oxygen electrocatalysts while converting agricultural waste into value‐added material.

Bifunctional Single-Atom Cobalt Electrocatalysts with Dense Active Sites Prepared via a Silica Xerogel Strategy for Rechargeable Zinc–Air Batteries

“…A series of strategies based on co-precipitation, wet impregnation, and metal–organic frameworks (MOFs) [ 25 , 26 , 27 ] have been recently developed for preparing Co-N-C SACs. Furthermore, many advanced biomass-derived electrocatalysts, e.g., nutshell and red bean pod, have shown excellent electrocatalytic performance for metal–air batteries [ 28 , 29 , 30 ]. Despite significant progresses, there are still quite a few challenges to synthesize the well-defined metal–nitrogen co-doped carbon catalysts, including the aggregation of metal atoms at high temperature, harsh reaction conditions, and environmental pollutions.…”

Rechargeable Zinc–Air Batteries with Seawater Electrolyte and Cranberry Bean Shell-Derived Carbon Electrocatalyst

“…A porous and crumpled structure with a smooth surface is observed in the SEM image of C-cranberry (Figure b,c). Carbonization of cranberry bean shells employs a chemical activation using KOH to induce the porosity in the resulting carbon . It occurs via the formation of K 2 O from the dehydration of KOH, which then reacts with CO 2 to form K 2 CO 3 .…”

“…Carbonization of cranberry bean shells employs a chemical activation using KOH to induce the porosity in the resulting carbon. 34 It occurs via the formation of K 2 O from the dehydration of KOH, which then reacts with CO 2 to form K 2 CO 3 . K 2 CO 3 is a porogen that reacts with carbon to produce K and gaseous CO. Metallic potassium (K) will intercalate into carbon and create pores upon its removal by acid washing.…”

“…Carbon-based catalysts are pivotal in the commercialization of zinc–air batteries because of their manifested properties, such as promising catalytic activity, strong stability, excellent conductivity, and adjustable morphologies. − Biomass-derived carbons have captivated considerable interest due to their large availability, ease of synthesis, and environmental benefit. The sources of biomass can vary from agricultural wastes to animal residues or other crops that are rich in carbon and organic components that may benefit their catalytic activity. − In particular, various wastes of agricultural products have been employed as the source of carbon-based catalysts, such as coffee waste, pistachio shells, red bean pods, bamboo, and corn cobs . The edible cranberry bean or dry bean is one of the most cultivated legumes that is widely consumed in almost all continents .…”

“…The sources of biomass can vary from agricultural wastes to animal residues or other crops that are rich in carbon and organic components that may benefit their catalytic activity. 29−31 In particular, various wastes of agricultural products have been employed as the source of carbon-based catalysts, such as coffee waste, 32 pistachio shells, 33 red bean pods, 34 bamboo, 35 and corn cobs. 36 The edible cranberry bean or dry bean is one of the most cultivated legumes that is widely consumed in almost all continents.…”