Boosting photocatalytic overall water splitting over single-layer graphene coated metal cocatalyst

Cocatalyst plays a critical role in photocatalytic overall water splitting (POWS). However, the typical metal cocatalysts aimed at promoting hydrogen evolution are also highly active for H2-O2 recombination. Here we report a new strategic approach of coating single-layer graphene selectively on metal cocatalyst by chemical vapor deposition to effectively suppress the backward reaction for efficient POWS. Pt@C/SrTiO3 demonstrates steady POWS activity in contrast to the rapid activity decline by 65% in 5 h of Pt/SrTiO3, and no obvious H2 and O2 consumption is observed over Pt@C/SrTiO3 during dark reaction. Experimental and theoretical calculation results indicate that the graphene prevents O2 from contacting Pt and the O2 dissociation as the rate-determining step of backward reaction is retarded. Moreover, this method demonstrates good universality and similar suppressing effect is also achieved over Rh, Pd@C. These findings may open a new pathway for developing effective cocatalysts with suppressed backward reaction for efficient POWS.