Highly Dispersed Nickel Oxide Nanoparticles Anchored on a Tubular Biochar Framework for Selective Photocatalytic CO2 Reduction to CH4

Photocatalytic reduction of CO₂ is considered as a promising approach to achieving carbon neutrality and producing value-added chemicals in a sustainable way, utilizing CO₂ as a feedstock and solar energy as the driving force. Constructing novel photocatalysts with sufficient active sites and efficient charge separation efficiency is crucial for optimizing CO₂ conversion. Herein, the activated pinecone-derived biochar (APC) possesses a porous tubular carbon framework, a high degree of graphitization, and abundant oxygen-containing functional groups. NiO nanoparticles were successfully embedded in the APC supporter to manufacture NiO/APC composites. The obtained NiO/APC sample demonstrates remarkably enhanced photocatalytic properties and high selectivity (95.6%) for CH₄ production with respect to pure NiO. The coupling of APC and NiO can fully expose NiO nanoparticles, regulate the band structure of NiO, and establish a close interfacial interaction, which can significantly increase CO₂ adsorption, improve light absorption, prohibit charge recombination, and accelerate separation and migration of photoexcited charge carriers. Especially, the tubular APC framework not only serves as a supporter to inhibit the aggregation of NiO nanoparticles and as electron shuttles to accelerate the charge separation but also as a reactive site to realize the efficient conversion of CO₂ to CH₄. This work affords a paragon for the construction of highly efficient photocatalysts, which pave the way for practical applications in photocatalysis.