Scientists from the Institute of Metal Research, Chinese Academy of Sciences (IMR, CAS), have developed an ordered patterning strategy that integrates p-type and n-type BiVO4 stripes on a conductive substrate, enabling efficient Z-scheme charge separation and significantly enhanced photocatalytic overall water splitting.
Solar-driven water splitting is a promising route to green hydrogen, but photogenerated electrons and holes tend to recombine, and surface reverse reactions severely limit efficiency. Solid-state Z-scheme heterojunctions, which connect two semiconductors through a conductive mediator, can provide high driving force for water splitting while directing high energetic electrons and holes to different components. However, conventional particle-based Z-scheme systems rely on random interparticle contacts, making charge-transfer pathways uncontrollable and often exacerbating recombination.
To address this, the team from the Division of Solar and Hydrogen Energy Materials at IMR’s Shenyang National Laboratory for Materials Science proposed an ordered patterning strategy. Using photolithography, they fabricated alternating stripes of p-type tetragonal zircon BiVO4 (t-BVO) and n-type monoclinic scheelite BiVO4 (m-BVO) on an FTO conductive glass substrate. The FTO layer serves as a conductive mediator, establishing Z-scheme charge-transfer channels between adjacent stripes: photogenerated electrons accumulate on the p-type t-BVO stripes, while photogenerated holes accumulate on the n-type m-BVO stripes. This spatial separation effectively suppresses charge recombination and reverse reactions.
The patterned panel was fabricated by first depositing an m-BVO film on FTO via metal-organic decomposition, then patterning it by photolithography and wet etching, and finally hydrothermally growing t-BVO epitaxially on the exposed FTO regions. The resulting t-BVO//m-BVO alternating stripes were approximately 15 μm wide. Photochemical deposition, surface photovoltage imaging, Kelvin probe force microscopy and surface photovoltage measurements confirm the Z-scheme charge-transfer behavior.
The team further selectively photodeposited Rh@CrOx as a hydrogen-evolution cocatalyst on the t-BVO stripes and MnOx as an oxygen-evolution cocatalyst on the m-BVO stripes, spatially separating oxidation and reduction sites and further suppressing charge recombination and reverse reactions.
Under full-spectrum illumination, the patterned panel achieves stoichiometric overall water splitting, producing 1.77 mmol m−2 of hydrogen and 0.84 mmol m−2 of oxygen within one hour, about four times higher than the unpatterned control. The work demonstrates that ordered semiconductor patterning combined with a conductive-substrate-mediated Z-scheme is an effective strategy for improving photocatalytic overall water splitting and provides a new approach for scalable photocatalytic panel design.
Fabrication of patterned t-BVO//m-BVO semiconductor photocatalytic panels. (Image by IMR)
Photochemical deposition tracing reveals spatial separation of photogenerated charges. (Image by IMR)
