Searching photocatalysts for efficient hydrogen production has been a challenging issue for solar-energy harvesting. Using co-catalyst is proved to be an effective approach to improve the efficiency of photocatalyst in water-splitting. In this thesis, we developed four efficient co-catalysts for photocatalytic hydrogen evolution through the combination of experiments and theoretical calculations. The graphitic carbon nitride (g-C3N4) and CdS were selected as the host-photocatalysts due to their narrowband gap for visible-light harvesting and suitable band structure. Firstly, a novel MXene, Ti2C, was used as a co-catalyst for photocatalytic hydrogen generation over g-C3N4. The as-synthesized Ti2C/g-C3N4 with 0.4 wt % Ti2C showed significantly enhanced hydrogen generation rate of 47.5 μmol/h, which was much higher than that of pure g-C3N4 (only about 3.3 μmol/h ). Moreover, the Ti2C/g-C3N4 also displayed excellent stability and reproducibility, as its photocatalytic activity kept almost unchanged after 10 cycles of testing. Secondly, we designed the VS2-decorated g-C3N4 (VS2/g-C3N4) as a photocatalyst for water splitting, in which the VS2 displayed high hydrogen evolution reaction (HER) activity both in its basal and edges. The VS2/g-C3N4 showed a super-high photocatalytic hydrogen production rate of 87.4 μmol/h, which was about 26 times higher than pristine g-C3N4. Thirdly, we compared the catalytic activity of different W-compounds as the co-catalysts for g-C3N4, including transition metal carbide (W2C), sulfide (WS2) and nitride (W2N). We found that the three W-compounds loaded g-C3N4 all displayed enhanced photocatalytic performance compared with the pristine g-C3N4, among which the W2C/g-C3N4 showed highest photocatalytic hydrogen evolution rate about 98 μmol/h, which was nearly 4 times as high as the WS2 or W2N loaded one. Fourthly, we theoretically investigated the potential of carbonized MoS2 (MoS2/Mo2C) as a co-catalyst for photocatalytic hydrogen production, and experimentally synthesized the MoS2/Mo2C by a facile chemical vapor carbonization process. When CdS and g-C3N4 loaded with the MoS2/Mo2C, their photocatalytic activities were both improved by 112 and 16 times, respectively. Our combined experimental and computational studies revealed that the excellent efficiency of our designed photocatalysts were attributed to: (1) efficient separation and transfer of photo-induced electrons-holes, resulting from the optimal band alignment between the g-C3N4 (or CdS) and our designed co-catalysts; (2) fast hydrogen evolution on the surface due to the excellent HER activity of Ti2C, VS2, W2Cand MoS2/Mo2C. We expect our designed Ti2C, VS2, W2C and MoS2/Mo2C loaded photocatalysts can be applicable in practical solar-driven water splitting and replace the noble-metal loaded photocatalysts.