Due to the multiple electron and proton transfer processes involved, the photogenerated charges are easily recombined during the photocatalytic reduction of CO2, making the generation of the eight-electron product CH4 kinetically more difficult. Herein, Ni3B nanoparticles modulated by p-block element were combined with TiO2 nanosheets to construct a novel Schottky junction photocatalyst (Ni3B/TiO2) for the selective photocatalytic conversion of CO2 to CH4. The formed Ni3B/TiO2 photocatalyst with Schottky junction ensures a transfer pathway of photogenerated electrons from TiO2 to Ni3B, which facilitates the accumulation of electrons on the surface of Ni3B and subsequently improves the activity of photocatalytic CO2 reduction to CH4. The optimized Ni3B/TiO2 Schottky junction shows an improved CH4 yield of 30.03 μmol g-1 h-1, which was much higher than those of TiO2 (1.62 μmol g-1 h-1), NiO/TiO2 (2.44 μmol g-1 h-1), and Ni/TiO2 (4.3 μmol g-1 h-1). This work demonstrated that the introduction of p-block elements can alleviate the scaling relationship effect of pure metal cocatalysts to a certain extent, and the modified Ni3B can be used as a promising new cocatalyst to effectively improve the selective photocatalytic of CO2 to CH4.