In this work, bimetallic NiCoP nanoparticles (NPs) were firstly prepared by a solvothermal method using red phosphorus (RP) as P source, and it was combined with RP nanosheets via a physical grinding process. Investigation indicates that NiCoP has better charge transfer ability and faster H₂ releasing kinetics than the corresponding single metal phosphides alone. 6 wt% NiCoP/RP exhibits an excellent H₂ evolution activity in 20 vol.% triethanol-amine/water solution under a 300W Xe-lamp irradiation, and the corresponding H₂ production rate is 1535.6 μmol·g^-1·h^-1, which is 7.4, 3.2 and 2.6 times higher than those of pure RP, 6 wt% Co₂P/RP and 6 wt% Ni₂P/RP, respectively. In addition, we demonstrate that K₂HPO₄ can further enhance the H₂ evolution kinetics by inducing a new H⁺ reduction path, when appropriate K₂HPO₄ is introduced into the reaction solution. The H₂ production rate of 6 wt% NiCoP/RP is boosted from 1535.6 to 2793.9 μmol·g^-1·h^-1 due to the easier combination between H⁺ and electrons with the assistance of HPO₄^2-. It is 13.4 times higher than that of pure RP. This work demonstrates that bimetallic phosphides with suitable electrolytes can greatly enhance the photocatalytic H₂ evolution efficiency.