Synthesis and characterization of a photosensitive interface for hydrogen generation: Chemically modified p-type semiconducting silicon photocathodes

摘要

p-Si photocathodes functionalized first with an N,N′-dialkyl-4,4′-bipyridinium redox reagent, (PQ^2+/+-)surf, and then with a Pt precursor, PtCl6^2-, give significant efficiency (up to 5%) for photoelectrochemical H2 generation with 632.8-nm light. Naked p-Si photocathodes give nearly zero efficiency, owing to poor H2 evolution kinetics that are improved by the (PQ^2+/+-)surf/Pt modification. The mechanism of H2 evolution from p-Si/(PQ^2+/+-)surf/Pt is first photoexcitation of electrons to the conduction band of Si followed by (PQ²⁺)surf → (PQ^+-)surf reduction. The dispersion of Pt then catalyzes H2O reduction to give H2 and regeneration of (PQ²⁺)surf. The overall energy conversion efficiency rivals the best direct optical to chemical conversion systems reported to date.