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Highlights: Critical strategies for converting wastes to catalysts are summarized. Applications of waste-derived catalysts in hydrogen evolution reaction, oxygen evolution reaction, and overall water electrolysis are comprehensively reviewed. Perspectives in the development of waste-derived catalysts are analyzed.The sustainable production of green hydrogen via water electrolysis necessitates cost-effective electrocatalysts. By following the circular economy principle, the utilization of waste-derived catalysts significantly promotes the sustainable development of green hydrogen energy. Currently, diverse waste-derived catalysts have exhibited excellent catalytic performance toward hydrogen evolution reaction (HER), oxygen evolution reaction (OER), and overall water electrolysis (OWE). Herein, we systematically examine recent achievements in waste-derived electrocatalysts for water electrolysis. The general principles of water electrolysis and design principles of efficient electrocatalysts are discussed, followed by the illustration of current strategies for transforming wastes into electrocatalysts. Then, applications of waste-derived catalysts (i.e., carbon-based catalysts, transitional metal-based catalysts, and carbon-based heterostructure catalysts) in HER, OER, and OWE are reviewed successively. An emphasis is put on correlating the catalysts’ structure–performance relationship. Also, challenges and research directions in this booming field are finally highlighted. This review would provide useful insights into the design, synthesis, and applications of waste-derived electrocatalysts, and thus accelerate the development of the circular economy-driven green hydrogen energy scheme. [ABSTRACT FROM AUTHOR]

The abundant plastic wastes become an imperative global issue, and how to handle these organic wastes gains growing scientific and industrial interest. Recently, converting plastic wastes into hydrogen fuel has been investigated, and the "waste-to-value" practice accelerates the circular economy. To accelerate the development of plastic-to-hydrogen conversion, in this review, recent advances in plastic-to-hydrogen conversion via thermochemical, photocatalytic, and electrocatalytic routes are analyzed. All of the thermo-, photo-, and electrochemical processes can transform different plastic wastes into hydrogen, and the hydrogen production efficiency depends heavily on the selected techniques, operating parameters, and applied catalysts. The application of rational-designed catalysts can promote the selective production of hydrogen from plastic feedstocks. Further studies on process optimization, cost-effective catalyst design, and mechanism investigation are needed. [Display omitted] • Plastic-to-hydrogen conversion can be realized via thermo-, photo-, and electrochemical processes. • Operating factors have obvious effects on H 2 production yield in plastic upcycling. • Catalysts can improve the plastic-to-hydrogen conversion efficiency. [ABSTRACT FROM AUTHOR]

The pervasive presence of plastics in the environment, particularly microplastics, has become a significant global challenge, demanding innovative solutions for their management and upcycling. While traditional methods including landfill and incineration face limitations in environmental impact, emerging technologies offer promising pathways for the conversion of plastics into valuable chemicals and fuels, operating under ambient conditions and often utilizing sustainable energy sources. Considering the current research progress in plastic upgrading, it is necessary to summarize the chemical upcycling of plastic waste. To this end, this review provides an overall examination of current and emerging methodologies for plastic treatment, including pyrolysis, hydrogenolysis, photocatalysis, and electrocatalysis. Existing knowledge gaps and future research directions are then proposed. Overall, this review highlights the potential of these novel plastic management approaches in aligning with the principles of a circular economy. [Display omitted] • Chemical upcycling of plastic provides a sustainable method for plastic waste management. • Pyrolysis and hydrogenolysis show promise in depolymerizing plastic but consuming large amounts of energy. • Photocatalysis and electrocatalysis are emerging technologies that leverage renewable energy sources for plastic upcycling. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel PS activation system is developed for carbon recycle from wastewater. • BPA is selectively degraded via initiating nonradical-induced polymerization. • BPA in wastewater is converted into value-added polymers. • The polymerization process can occur under typical environmental conditions. The selective removal of targeted pollutants from complex wastewater is challenging. Herein, a novel persulfate (PS)-based advanced oxidation system equipped with a series of two-dimensional (2D) bimetallic oxide nanosheets (NSs) catalysts is developed to selectively degrade bisphenol A (BPA) within mixed pollutants via initiating nonradical-induced polymerization. Results indicate that the Ni 0.60 Co 0.40 O x NSs demonstrate the highest catalytic efficiency among all Ni-Co NSs catalysts. Specifically, BPA degradation rate is 47.34, 27.26, and 9.72 times higher than that of 4-chlorophenol, phenol, and 2,4-dichlorophenol in the mixed solution, respectively. The lower oxidative potential of BPA in relation to the other pollutants renders it the primary target for oxidation within the PDS activation system. PDS molecules combine on the surface of Ni 0.60 Co 0.40 O x NSs to form the surface-activated complex, triggering the generation of BPA monomer radicals through H-abstraction or electron transfer. These radicals subsequently polymerize on the surface of the catalyst through coupling reactions. Importantly, this polymerization process can occur under typical aquatic environmental conditions and demonstrates resistance to background matrices like Cl− and humic acid due to its inherent nonradical attributes. This study offers valuable insights into the targeted conversion of organic pollutants in wastewater into value-added polymers, contributing to carbon recycle and circular economy. [ABSTRACT FROM AUTHOR]

Volatile fatty acids (VFA) from sewage sludge represent an excellent recovered resource from wastewater treatment. This study investigated four sludge pre-treatments (namely, potassium permanganate - KMnO 4 , initial pH = 10, initial pH = 2.5 and low-temperature thermal hydrolysis) by operating batch reactors under acidogenic fermentation conditions. Results revealed that 0.1 g KMnO 4 /g of total suspended solids represents the best pre-treatment obtaining up to 2713 mgCOD L−1 and 452 mgCOD/g of volatile suspended solids. These results also paralleled metataxonomic analysis highlighting changes in prokaryotic microbial structures of sewage sludge of the batch fermentations subjected to the different pre-treatments. [Display omitted] • Sewage sludge acidogenic fermentation was performed in batch scale reactors. • Potassium permanganate, pH and thermal hydrolysis were applied as pre-treatments. • Potassium permanganate increased VFA production by 45200% compared to control test. • VFA accounted for 95 ± 4 % of the soluble COD produced. • Comamonadaceae and Chlamydiae percentage abundance was reduced by permanganate. [ABSTRACT FROM AUTHOR]

Dealing with the current defaults of environmental toxicity, heating, waste management, and economic crises, exploration of novel non-edible, toxic, and waste feedstock for renewable biodiesel synthesis is the need of the hour. The present study is concerned with Buxus papillosa with seeds oil concentration (45% w/w), a promising biodiesel feedstock encountering environmental defaults and waste management; in addition, this research performed simulation based-response surface methodology (RSM) for Buxus papillosa bio-diesel. Synthesis and application of novel Phyto-nanocatalyst bimetallic oxide with Buxus papillosa fruit capsule aqueous extract was advantageous during transesterification. Characterization of sodium/potassium oxide Phyto-nanocatalyst confirmed 23.5 nm nano-size and enhanced catalytic activity. Other characterizing tools are FTIR, DRS, XRD, Zeta potential, SEM, and EDX. Methyl ester formation was authenticated by FTIR, GC-MS, and NMR. A maximum 97% yield was obtained at optimized conditions i.e., methanol ratio to oil (8:1), catalyst amount (0.37 wt%), reaction duration (180 min), and temperature of 80 °C. The reusability of novel sodium/potassium oxide was checked for six reactions. Buxus papillosa fuel properties were within the international restrictions of fuel. The sulphur content of 0.00090% signified the environmental remedial nature of Buxus papillosa methyl esters and it is a highly recommendable species for biodiesel production at large scale due to a t huge number of seeds production and vast distribution. [Display omitted] • A novel biodiesel feedstock with 45% oil content has been proven to be buxus papillosa. • A novel green bimetallic catalyst with 0.37 wt% yielded 97% BPBD. • Buxus papillosa biodiesel has pollution-free and eco-friendly properties. • Buxus papillosa seed oil's successful conversion to bio-diesel was ascertained by FT-IR, GC/MS. • Buxus papillosa bio-diesel has fuel physical qualities compatible with international fuel restrictions. [ABSTRACT FROM AUTHOR]

• Photocatalytic conversion of biomass to biofuels is firstly and comprehensively reviewed. • Long-chain hydrocarbons can be produced from photocatalytic C-C coupling of biomass-derived compounds. • Photocatalytic decarboxylation reactions are concluded for the generation of diesel-like biofuels. • Photocatalytic (trans)esterification processes are reviewed for the production of biodiesels. • Photocatalytic conversion of biomass to produce syngas or H 2 energy is reviewed. Biofuels derived from abundant biomass are promising alternatives to fossil fuels, which are considered to be green, renewable, and sustainable. Great efforts have been made to explore efficient strategies for converting biomass to biofuels. Although thermal catalytic methods are frequently studied, but the harsh reaction conditions and high energy consumption limit their applications. Alternatively, the solar energy-driven photocatalytic approaches are considered as mild, eco-friendly and energy-saving processes, and recent achievements in the photocatalytic biomass-to-biofuels conversion significantly improve the sustainable development of biofuels. Lignocellulosic biomass and non-edible oil are seen as promising source of materials for future biofuels. In this review, photocatalytic processes for producing liquid biofuels from diverse biomass are systematically concluded, including the C-C coupling of biomass-derived platform compounds to produce diesel-like biofuels, decarboxylation reactions to produce diesel-like biofuels, and (trans)esterification of crude bio-oil to produce biodiesels. Moreover, photocatalytic conversion of biomass to produce gas biofuels is also discussed including the production of hydrogen, carbon monoxide, and syngas. The advances in photocatalysts are emphasized, and efficient photocatalysts for specific reactions and the factors influencing the catalytic performance are outlined. Moreover, perspectives for the photo-reforming of biomass to biofuels are proposed to guide further development of biofuel production. [ABSTRACT FROM AUTHOR]