Improved hydrogen evolution with SnS₂ quantum dot-incorporated black Si photocathode

Black silicon (bSi), possessing appealing light-trapping properties and large specific surface area, ranks high among many other photocathode materials. However, the insufficient dynamics towards HER seriously bother black Si. Herein, a novel photoelectrode with ultrasmall size tin sulfide quantum dot (SnS₂ QD) incorporated black silicon was employed. Nanosized SnS₂ possesses numerous active sites for electrochemical reactions. Impressively, benefiting from SnS₂ QDs, the downward band bending of the Si Fermi level at the interface of electrolyte becomes higher, which remarkably suppresses the recombination of photo-generated carriers, thereby facilitating the participation of photo-generated electrons in PEC-HER. As a result, the thus-designed SnS₂/bSi reveals an exceptional PEC-HER activity with a positive onset potential of 0.235 V vs. reversible hydrogen electrode (RHE), a high photocurrent of 1.23 mA cm^-2 at 0 V vs. RHE, and long-term stability. Besides, the saturated photocurrent of ∼41 mA cm^-2 is achieved at about -0.51 V vs. RHE.