Carbon-coated nickel phosphide enhances efficiently electron transfer of cadmium sulfide for photocatalytic hydrogen production

The capacitance of a co-catalyst can be likened to a "double-edged sword". Α co-catalysts with high capacitance can store photoexcited electrons, thereby facilitating charge separation within the host catalyst. However, this property simultaneously restricts electron release. Both effects are enhanced with an increasing capacitance value, implying that excessively high capacitance can significantly hinder the photocatalytic hydrogen (H₂) production reaction. Herein, we have designed a metal-organic framework (MOF) -derived carbon-coated nickel phosphide (C-Ni₅P₄) as the co-catalyst of cadmium sulfide (CdS). When C-Ni₅P₄ and CdS are closely interconnected, electrons spontaneously migrate from CdS to C-Ni₅P₄ under irradiation due to the higher work function (WF) of C-Ni₅P₄ compared to CdS. Most importantly, although the WF of C-Ni₅P₄ is 0.1 eV lower than that of Ni₅P₄, its specific capacitance (1.2 mF/cm²) is also lower than that of Ni₅P₄ (1.3 mF/cm²). This difference dramatically promotes electron release. Thereby exerting a strong positive effect on capacitance catalysis. Therefore, 7% C-Ni₅P₄/CdS exhibits exceptional cyclic stability and has a remarkably high activity level of 12283 μmol/h/g and 3.8 times as many as 3.0 %Ni₅P₄/CdS. This study provides a theoretical basis for the advancement of photocatalysts with high efficiency in H₂ production and is expected to be applied in other fields of photocatalysis.