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

Anoble metal-free Schottky junction photocatalyst is constructedusing g-C3N4 nanosheets with N vacancies andNi(3)B nanoparticles (denoted as Ni3B/V-N-CN) for photocatalytic N-2 fixation. The ammonia yieldrate of the optimal Ni3B/V-N-CN sample reached7.68 mM g(-1) h(-1), demonstratingthat V-N and Ni3B could synergistically increasethe photocatalytic N-2 fixation performance. The photocatalytic fixation of N-2 is a promising technologyfor sustainable production of ammonia, while the unsatisfactory efficiencyresulting from the low electron-transfer rate, narrow light absorptionrange, and limited active sites of the photocatalyst seriously hinderits application. Herein, we designed a noble metal-free Schottky junctionphotocatalyst constructed by g-C3N4 nanosheetswith N vacancies (V-N-CN) and metallic Ni3B nanoparticles(Ni3B/V-N-CN) for N-2 reduction toammonia. 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 photocatalyticN(2) fixation performance of Ni3B/V-N-CN can be attributed not only to the formation of Schottky junctionsbetween Ni3B and V-N-CN, which facilitates themigration and separation of photogenerated electrons, but also tothe incorporation of V-N into g-C3N4, which enhances visible light absorption and improves electricalconductivity. More importantly, Ni3B nanoparticles canact as the cocatalyst, which provide more active sites for the adsorptionand activation of N-2, thereby improving the N-2 reduction activity. This work provides an effective strategy ofdesigning noble metal-free-based cocatalyst photocatalyst for sustainableand economic N-2 fixation.