Melamine formaldehyde metal organic gel interpenetrating networks for heteroporous Fe–N-doped carbon.

Herein, we present Metal‐Organic Gel intercalated with chitosan, a “green” precursor for the synthesis of intrinsic N‐doped Fe entrenched (CHI‐TMA−Fe‐CW) and Fe distributed mesoporous graphitic carbon structures (CHI‐TMA−Fe‐CW−M1) with appreciable Oxygen Reduction Reaction (ORR) activity in alkaline medium. Modulation of the synthetic protocol as a function of reaction kinetics and gelation time while maintaining identical pyrolysis conditions (900 °C, flowing N2 atmosphere) improves the microstructure, surface area and Fe distribution of the graphitic structures (CHI‐TMA−Fe‐CW−M1). CHI‐TMA−Fe‐CW has a Fe entrenched graphitic nanocapsule like morphology while Fe distributed mesoporous graphitic carbon sheets, with a specific surface area value of 565 m2g−1 obtained by modulating the synthesis chemistry in CHI‐TMA−Fe‐CW−M1. The higher percentage of graphitic N in CHI‐TMA−Fe‐CW−M1 apparent from the XPS data validate that the modified synthetic method favours creation of more graphitic N sites contributing for better catalytic performance. CHI‐TMA‐Fe‐CW−M1 catalyst exhibited comparable electrocatalytic activity with that of the commercially available Pt/C via an efficient four‐electron‐dominant ORR pathway with a positive onset potential value of 0.925 V vs RHE. Good durability of CHI‐TMA−Fe‐CW−M1 after 5000 cycles further confirm the prospects of MOG‐chitosan and the feasibility to be used as a potential catalyst for ORR.

Ni,N co-doped porous carbon derived from nickel containing ZIF-8 frameworks for enhanced ORR performance in alkaline medium.

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Direct borohydride fuel cells are a particular class of alkaline direct liquid fuel cells that show interesting performances for mobile applications owing to the use of sodium borohydride (NaBH4) as fuel. The complete electrooxidation of NaBH4 proceeds via an eight-electron pathway. However, due to the inevitable hydrolysis of borohydride at the electrode, the released electrons are usually less than 8. The use of anode catalysts with good performance and high utilization of BH4 – is therefore imperative for practical applications. In this work, we report the development of an anode catalyst derived from trimetallic zeolitic imidazolate framework (ZIF) with M–N x active centers. The trimetallic ZIF precursor (FeCoZn-ZIF) was derived by the codoping of Fe and Co on ZIF-8 synthesized through a fast, aqueous synthesis under ambient conditions. Subsequently, carbonization yielded a carbon alloy catalyst (FeCo-ZNC) with enhanced porosity. The nanotubular structure of the formed carbon assisted in faster electron transport, and the oxidation current density of FeCo-ZNC reached 56.5 mA cm–2 at 0.61 V during electrocatalytic NaBH4 oxidation under alkaline conditions. The enhanced electrocatalytic performance induced by the morphological and textural features of FeCo-ZNC along with active reaction centers such as pyridinic N, graphitic N, and Co–N x enabled NaBH4 electrooxidation via an eight-electron transfer, indicating its potential as a promising catalyst for borohydride oxidation reactions (BORs).

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