Ni3B as p-Block Element-Modulated Cocatalyst for Efficient Photocatalytic CO2 Reduction

Enhancing photocatalytic CO2 reduction with TiO2-based materials: Strategies, mechanisms, challenges, and perspectives

The concentration of atmospheric CO2 has exceeded 400 ppm, surpassing its natural variability and raising concerns about uncontrollable shifts in the carbon cycle, leading to significant climate and environmental impacts. A promising method to balance carbon levels and mitigate atmospheric CO2 rise is through photocatalytic CO2 reduction. Titanium dioxide (TiO2), renowned for its affordability, stability, availability, and eco-friendliness, stands out as an exemplary catalyst in photocatalytic CO2 reduction. Various strategies have been proposed to modify TiO2 for photocatalytic CO2 reduction and improve catalytic activity and product selectivity. However, few studies have systematically summarized these strategies and analyzed their advantages, disadvantages, and current progress. Here, we comprehensively review recent advancements in TiO2 engineering, focusing on crystal engineering, interface design, and reactive site construction to enhance photocatalytic efficiency and product selectivity. We discuss how modifications in TiO2's optical characteristics, carrier migration, and active site design have led to varied and selective CO2 reduction products. These enhancements are thoroughly analyzed through experimental data and theoretical calculations. Additionally, we identify current challenges and suggest future research directions, emphasizing the role of TiO2-based materials in understanding photocatalytic CO2 reduction mechanisms and in designing effective catalysts. This review is expected to contribute to the global pursuit of carbon neutrality by providing foundational insights into the mechanisms of photocatalytic CO2 reduction with TiO2-based materials and guiding the development of efficient photocatalysts.

Construction synergetic adsorption and activation surface via confined Cu/Cu2O and Ag nanoparticles on TiO2 for effective conversion of CO2 to CH4

High-performance photocatalysts for catalytic reduction of CO2 are largely impeded by inefficient charge separation and surface activity. Reasonable design and efficient collaboration of multiple active sites are important for attaining high reactivity and product selectivity. Herein, Cu-Cu2O and Ag nanoparticles are confined as dual sites for assisting CO2 photoreduction to CH4 on TiO2. The introduction of Cu-Cu2O leads to an all-solid-state Z-scheme heterostructure on the TiO2 surface, which achieves efficient electron transfer to Cu2O and adsorption and activation of CO2. The confined nanometallic Ag further enhances the carrier's separation efficiency, promoting the conversion of activated CO2 molecules to •COOH and further conversion to CH4. Particularly, this strategy is highlighted on the TiO2 system for a photocatalytic reduction reaction of CO2 and H2O with a CH4 generation rate of 62.5 μmol∙g-1∙h-1 and an impressive selectivity of 97.49 %. This work provides new insights into developing robust catalysts through the artful design of synergistic catalytic sites for efficient photocatalytic CO2 conversion.

Synergistic Effects of the Ni3B Cocatalyst and N Vacancy on g-C3N4 for Effectively Enhanced Photocatalytic N2 Fixation

The photocatalytic fixation of N₂ is a promising technology for sustainable production of ammonia, while the unsatisfactory efficiency resulting from the low electron-transfer rate, narrow light absorption range, and limited active sites of the photocatalyst seriously hinder its application. Herein, we designed a noble metal-free Schottky junction photocatalyst constructed by g-C₃N₄ nanosheets with N vacancies (V_N-CN) and metallic Ni₃B nanoparticles (Ni₃B/V_N-CN) for N₂ reduction to ammonia. The ammonia yield rate over the optimized Ni₃B/V_N-CN is 7.68 mM g^-1 h^-1, which is 6.7 times higher than that of pristine CN (1.15 mM g^-1 h^-1). The superior photocatalytic N₂ fixation performance of Ni₃B/V_N-CN can be attributed not only to the formation of Schottky junctions between Ni₃B and V_N-CN, which facilitates the migration and separation of photogenerated electrons, but also to the incorporation of V_N into g-C₃N₄, which enhances visible light absorption and improves electrical conductivity. More importantly, Ni₃B nanoparticles can act as the cocatalyst, which provide more active sites for the adsorption and activation of N₂, thereby improving the N₂ reduction activity. This work provides an effective strategy of designing noble metal-free-based cocatalyst photocatalyst for sustainable and economic N₂ fixation.