The Hole-Tunneling Heterojunction of Hematite-Based Photoanodes Accelerates Photosynthetic Reaction.

Single-atom metal-insulator-semiconductor (SMIS) heterojunctions based on Sn-doped Fe O nanorods (SF NRs) were designed by combining atomic deposition of an Al O overlayer with chemical grafting of a RuO hole-collector for efficient CO -to-syngas conversion. The RuO -Al O -SF photoanode with a 3.0 nm thick Al O overlayer gave a >5-fold-enhanced IPCE value of 52.0 % under 370 nm light irradiation at 1.2 V vs. Ag/AgCl, compared to the bare SF NRs. The dielectric field mediated the charge dynamics at the Al O /SF NRs interface. Accumulation of long-lived holes on the surface of the SF NRs photoabsorber aids fast tunneling transfer of hot holes to single-atom RuO species, accelerating the O -evolving reaction kinetics. The maximal CO-evolution rate of 265.3 mmol g  h was achieved by integration of double SIMS-3 photoanodes with a single-atom Ni-doped graphene CO -reduction-catalyst cathode; an overall quantum efficiency of 5.7 % was recorded under 450 nm light irradiation.