Rational tailoring of spin-polarized photoelectrode for magnetic-assisted overall water splitting
Charge transport
and metal site stability play a critical role in realizing efficient solar
water splitting in photoelectrochemical devices. Here, we investigate BiVO4-based
composite photoanodes
(labelled as NF@PTA/2PACz/BVO) in which
BiVO4, hole transport layers (HTLs) based on self-assembled
monolayers (SAMs), and carboxyl-functionalized NiFeOOH oxygen evolution
cocatalysts (OECs) structurally similar to the OECs in natural photosystem II, were
assembled sequentially. By designing this particular structure, alignment of
energy levels and stabilization of metal sites can be achieved. And the uncoordinated
(?COOH) carboxylate groups can accelerate the proton transfer. Fundamental
investigations reveal that the NF@PTA/2PACz/BVO
photoanodes
exhibit unique properties including passivated surface traps, excellent carrier
density and lifetime, enlarged photovoltage, and smoother hole transport band structure. Consequently,
the optimum NF@PTA/2PACz/BVO
photoanodes
show the PEC performance of 5.43 mA·cm?2 at
1.23 V vs reversible hydrogen electrode (RHE) with an applied bias
photon-to-current efficiency of 1.45% at 0.75 VRHE. And the C?O?Fe
bond coupling between the coordinating carboxylate and the metals inhibits the leaching
of the metal species and maintains a steady photocurrent density over 8 h of
stability testing. Our work paves the way for the development of more efficient
PEC cells with superior charge separation and breakthroughs in the stability of
metal active sites, thus broadening their potential applications.