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Single atom catalysts (SACs) exhibit desirable catalytic properties in key renewable energy reactions and devices. However, rational design of SACs and boosting their performances for oxygen electrocatalysis and rechargeable Zn–air batteries (ZABs) are still crucial yet challenging. Herein, single Co atoms anchored in ultrathin N, P-codoped porous carbon nanosheets (CoSA/NPC) were prepared by an in situ confinement pyrolysis strategy. The ultrathin nanosheet structure provides an ideal platform for high exposure of the generated Co active sites and extremely shortens the electron transport pathways. Both experimental and theoretical results demonstrate that the N/P coordinated Co sites enable optimized charge distribution and facilitate oxygen intermediate adsorption/desorption. Such a CoSA/NPC catalyst exhibits high oxygen reduction reaction (ORR) activity with a half-wave potential (E1/2) of 0.87 V and oxygen evolution reaction (OER) activity with a low potential of 1.67 V at 10 mA cm−2. As an air electrode in ZABs, it demonstrates a high peak power density of 204.3 mW cm−2 and excellent long-term stability in aqueous ZABs. It also reveals superior flexibility and stability in solid-state ZABs. Thus, CoSA/NPC is a promising bifunctional electrocatalyst for practical applications in aqueous and flexible solid-state ZABs.

Atomically dispersed metal catalysts are promising candidates for the oxygen reduction reaction (ORR) and for achieving efficient energy conversion. However, rational design of single atom catalysts (SACs) with high-efficiency ORR catalytic activity and superior stability is still crucial yet challenging. Herein, an in situ gas-foaming methodology is presented for constructing single Fe atoms dispersed on a N, S-codoped (FeSA/NSC) hierarchically ordered porous carbon (HOPC) framework via one-step pyrolysis of dopamine (DA)/Fe3+ complexes and thiourea in SBA-15 channels. HOPC structures (facilitating active site access and mass transfer) and optimized FeN4S2 catalytic centers make FeSA/NSC exhibit high ORR activity with a half-wave potential (E1/2) of 0.91 V, fuel selectivity and long-term stability (3 mV negative shift after 5000 potential cycles) in 0.1 M KOH. It even shows comparable ORR catalytic activity (E1/2 = 0.78 V) to the Pt/C catalyst in acidic electrolytes. As the air electrode in zinc–air batteries, FeSA/NSC demonstrates superior power density, long-term discharge stability and specific capacity to the commercial Pt/C catalyst. Thus, FeSA/NSC is a promising non-platinum-group metal ORR catalyst for the ORR and application in zinc–air batteries.

Phenolic-metal complexation coatings have been discovered to be a universal route for the deposition of multifunctional coatings. However, most complexation coatings have been prepared by the immersion method, which limits their practical large-scale application. Herein, we describe a facile and green engineering strategy that involves spraying phenolic compound and metal ions on substrate to form in-situ complexation coating with different coordination states. The coating is formed within minutes and it can be achieved in large scale by the spray method. The pyrogallol-FeIII complexation coating is prepared at pH 7.5, which consists predominantly of biscoordination complexation with a small amount of tris-coordination complexation. It displays that the water contact angle is near zero due to the generation of rough hierarchical structures and massive hydroxyl groups. The superhydrophilic cotton resulting from the deposition of the pyrogallol-FeIII complexation can separate oil/water mixtures and surfactant-stabilized oil-in-water emulsions with high separation efficiency. The formation of the phenolic-metal complexation coating by using spray technique constitutes a cost-effective and environmentally friendly, strategy with potential to be applied for large-scale surface engineering processes and green oil/water separation.

The wettability of the coating used in controlled release fertilizers (CRFs) is a crucial parameter for the release behavior of nutrients. However, how to control the wettability of coating to tune nutrient release is a big challenge. Herein, the alkylamine-poly (tannic acid) (APTA) building blocks coatings with controlled wettability were prepared as coating materials for CRFs. Alkylamine (octadecylamine (ODA), hexadecylamine (HDA), dodecylamine (DDA), and hexylamine (HEA)) were applied for the modification of poly (tannic acid) (PTA) coating on the silicon wafer and urea surface. The wettability of coatings on silicon wafers were studied and nutrient release of APTA coated fertilizers were characterized in water and soil. The nitrogen nutrient and water vapor permeability coefficient of coatings were characterisized and the mathematical model for predicting the release of nutrients in soil. The alkyl chain length of alkylamine is demonstrated to play a crucial part in controlling the wettability. The rate of nutrient release increases in the order of ODA-PTA

Polymer coated fertilizer has been designed for gradual release of nutritional content of fertilizer to improve the utilization efficiency. However, the better slow release property of the coated fertilizer and simplified preparation process are still a huge challenge. The hydrophobic ODA-polyphenol film coated urea was prepared by one-step spraying for excellent nutrient release performance. Octadecylamine (ODA) was used to modify poly(tannic acid) (PTA) and poly(pyrogallol) (PPG) coating on substrates and prepare the hydrophobic ODA-PTA and ODA-PPG coated urea granules. The nutrient release rate of ODA-PTA and ODA-PPG coated fertilizers was much slower than PTA and PPG coated fertilizers in water and soil. The N release longevities of ODA-PTA coated fertilizers will be extended from 2 h to 30 days compared with PTA coated fertilizers. Moreover, pot experiments showed that coated fertilizer could effectively promote plant growth. This work will provide one-step spraying co-deposition approach to fabricate hydrophobic ODA-polyphenol film coated urea to improve the N release longevity, which can shine a light on the development of new slow release fertilizers (SRFs).