The introduction of microstructure to the metal-free graphitic carbon nitride (g-CN) photocatalyst holds promise in enhancing its catalytic performance. However, producing such microstructured g-CN remains technically challenging due to a complicated synthetic process and high cost. In this study, we develop a facile and in-air chemical vapor deposition (CVD) method that produces onion-ring-like g-CN microstructures in a simple, reliable, and economical manner. This method involves the use of randomly packed 350 nm SiO microspheres as a hard template and melamine as a CVD precursor for the deposition of a thin layer of g-CN in the narrow space between the SiO microspheres. After dissolution of the microsphere template, the resultant g-CN exhibits uniquely uniform onion-ring-like microstructures. Unlike previously reported g-CN powder morphologies that show various degrees of agglomeration and irregularity, the onion-ring-like g-CN is highly dispersed and uniform. The calculated band gap for onion-ring-like g-CN is 2.58 eV, which is significantly narrower than that of bulk g-CN at 2.70 eV. Experimental characterization and testing suggest that, in comparison with bulk g-CN, onion-ring-like g-CN facilitates charge separation, extends the lifetime of photoinduced carriers, exhibits 5-fold higher photocatalytic hydrogen evolution, and shows great potential for photocatalytic applications.

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Urbanization and population growth have contributed to a tripling of building material consumption from 2000 to 2017. Building materials have a range of environmental impacts throughout their life cycle, from extraction, processing, and transport of raw materials to building construction, use, and eventual demolition and waste. Mitigation measures that target specific materials or value chain stages may therefore have incremental or even adverse net environmental effects. In this perspective, we develop a framework for applying life cycle thinking to identify key impacts and corresponding mitigation approaches, inform building design and material selection, and ensure effective treatment and recycling of construction and demolition wastes. Life cycle evaluation can also be used to assess and avoid environmental trade-offs among life cycle stages. Challenges for implementing these life cycle principles include collecting and integrating inventory data for products, managing multiple stakeholders within the construction industry, and monitoring end-of-life impacts; measures for overcoming such challenges are discussed.

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