Ni-based phosphides (NiP_x) composed of earth-abundant elements are promising cocatalysts to replace noble metals for photocatalytic H₂ evolution reaction (HER). A safe, energy-saving, and composition-controllable synthesis of NiP_x is still highly desired. A facile and mild solvothermal process was developed for the first time for selective synthesis of a series of NiP_x, including Ni, Ni₁₂P₅, Ni₂P/Ni₁₂P₅, Ni/Ni₂P and Ni₂P, through controlling the dosage of NaBH₄ and NaH₂PO₂. The phosphidation process was mainly composed of (1) a sequential reduction of Ni²⁺ to Ni⁰ and (H₂PO₂)⁻ to P (around the formed Ni⁰) triggered by NaBH₄, and (2) a final phosphidation between Ni⁰ and the in situ generated P atoms. The photocatalytic HER performance of g-C₃N₄ can be substantially improved with the decoration of NiP_x (3 wt%) as the separation of photoinduced charge carriers can be promoted and some active sites with low over-potential for HER can be introduced. The cocatalytic efficiency of NiP_x is mainly determined by P content. Ni₂P with a high ratio of P consequently exhibits the highest HER performance (215.1 µmol g⁻¹ h⁻¹), which is almost six times higher than that of the pristine g-C₃N₄ (35.6 µmol g⁻¹ h⁻¹). Thus, as for the cocatalyst based on Ni phosphides, Ni₂P is the preferable crystal phase and more efforts should be devoted to Ni₂P to further optimize its structure, texture, and morphology in future works.

由丰富的地球元素组成的镍基磷化物（NiP _x）是有前途的助催化剂，可以代替贵金属进行光催化H ₂析出反应（HER）。仍然非常需要安全，节能且可控制组成的NiP _x合成。一种简便并温和溶剂热过程的第一次的一系列辊隙的选择性合成开发_X，包括镍，镍₁₂ P ₅，镍₂ P /镍₁₂ P ₅，镍/镍₂ P与Ni ₂ P，通过控制NaBH ₄和NaH ₂ PO ₂的剂量。磷化过程主要由（1）由NaBH ₄触发将Ni ²⁺依次还原为Ni ⁰和将（H ₂ PO ₂）^-还原为P（在形成的Ni ^0附近），以及（2） Ni ⁰和原位生成P原子。通过修饰NiP _x（3 wt％），可以促进gC ₃ N ₄的光催化HER性能，因为可以促进光诱导电荷载流子的分离，并且可以引入一些对HER过低电势的活性位点。NiP _x的共催化效率主要由P含量决定。因此，具有高比例P的Ni ₂ P表现出最高的HER性能（215.1 µmol g ^-1  h ^-1），几乎是原始gC ₃ N ₄（35.6 µmol g ^-1  h ^-1）的六倍。）。因此，对于基于Ni磷化物的助催化剂，Ni ₂ P是优选的晶相，在今后的工作中应更加努力地使Ni ₂ P进一步优化其结构，织构和形态。