Development of nonprecious metal catalysts for oxygen reduction reaction (ORR) to reduce or eliminate Pt-based electrocatalysts is of great importance for fuel cells. Herein, Co/N-codoped carbon with carbon nanofiber (CNF) interconnected three-dimensional (3D) frameworks and graphitic carbon-encapsulated Co nanoparticles were designed and successfully prepared via the in situ growth of zeolitic imidazolate framework-67 (ZIF67) with biomass nano-microfibrillar cellulose (MFC) and then pyrolysis. The catalyst (Co/N-C@CNFs) exhibited outstanding long-term catalytic durability with 92.7% current retention after 70 000 s, which was much higher than that of commercial Pt/C in alkaline media. The support and connection of CNFs to Co/N-C frameworks and the protection of Co nanoparticles by graphite layers contribute to their impressive long-term catalytic stability. Meanwhile, Co/C-N@CNFs displayed excellent ORR catalytic performance (E 0 = 0.952 V vs RHE, E 1/2 = 0.852 V vs RHE, and n: 4.2) in alkaline media. This strategy provides new insights into developing advanced nonprecious metal carbon-based catalysts for ORR.

Organic-inorganic perovskite solar cells have emerged as a promising photovoltaic technology because of their advantages such as low cost, high efficiency, and solution processability. The performance of perovskite solar cells is highly dependent on the crystallinity and morphology of the perovskite films. Herein, we report a simple, one-step anti-solvent deposition process using di-isopropyl ether as a dripping solvent to obtain extremely uniform and highly crystalline CHNHPbI perovskite films. Compared to toluene, chlorobenzene, chloroform, or diethyl ether, di-isopropyl ether has proven to be a more suitable solvent for an anti-solvent deposition process. The perovskite solar cells fabricated by the anti-solvent deposition process using di-isopropyl ether treatment exhibit an average power conversion efficiency (PCE) of 17.67 ± 0.54% and the highest PCE of 19.07%. Moreover, the higher boiling point of di-isopropyl ether makes the anti-solvent deposition process more tolerant to elevated ambient temperature, which can be carried out at ambient temperatures up to 40 °C. Our results demonstrate that di-isopropyl ether is an excellent dripping solvent in the anti-solvent deposition process for efficient and reproducible perovskite solar cells.

Development of efficient electrocatalysts for oxygen reduction reaction (ORR) from resource-abundant, eco-friendly, and lowcost materials is important for environmental-friendly fuel cells. In this work, N, P, S/Fe-codoped carbon (FBCÀ Fe) with hierarchical porous structure was successfully prepared by the simple pyrolysis of feculae bombycis (FB) in the presence of ferric nitrate and followed by an acid etching process. FBCÀ Fe exhibits an excellent long-term durability and a remarkable methanol-resistance as well as a high electrocatalytic activity (E onset : 0.92 V vs RHE, E 1/2 : 0.81 vs RHE, and electron transfer number: 4.1) comparable to commercial platinum-carbon (Pt/C, 20 wt.%) catalysts for the ORR in alkaline media. This low-cost and simple approach provides a straightforward route to synthesize excellent electrocatalysts for ORR from biomass.

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