A pseudo-metal-free strategy for constructing high performance photoelectrodes

One of the obvious merits of graphitic carbon nitride (g-CN), which has been considered a promising candidate for photoelectrochemical (PEC) applications, is its metal-free nature; but it suffers from low PEC performance. Metal-containing semiconductors generally exhibit high PEC performance, but their applications are restricted by their high cost. In this study, we put forward for the first time a pseudo-metal-free strategy to combine the advantages of metal-free g-CN and metal-containing semiconductor materials with high PEC performance. A new g-CN precursor of sulfur-rich poly thiourea formaldehyde (PTF) is adopted to react with part of the fluorine-doped tin dioxide (FTO) layer deposited on glass in a closed reaction system at high temperature to in situ form g-CN/SnS₂ composite films which are fabricated by using a multiple-step thermal vapor condensation (MSTVC) approach. It is noticeable that metal-containing compounds are not added to the precursor; the metal element is from the FTO layer which is almost indispensable for fabricating photoelectrodes. The photocurrent density of the as-prepared g-CN/SnS₂ composite photoelectrode is as high as 844.6 μA cm⁻² at 1.23 V vs. RHE under AM 1.5G illumination without sacrificial agents. This novel pseudo-metal-free strategy opens a new field to stimulate further studies on fabricating composite photoelectrodes.