Reconcile the contradictory wettability requirements for the reduction and oxidation half-reactions in overall CO2 photoreduction via alternately hydrophobic surfaces

The overall photocatalytic CO2 reduction reaction (OPCRR) that can directly convert CO2 and H2O into fuels represents a promising renewable energy conversion technology. As a typical redox reaction, the OPCRR involves two half-reactions: the CO2 reduction half-reaction (CRHR) and the water oxidation half-reaction (WOHR). Generally, both half-reactions can be promoted by adjusting the wettability of catalysts. However, there is a contradiction in wettability requirements for the two half-reactions. Specifically, CRHR prefers a hydrophobic surface that can accumulate more CO2 molecules on the active sites, ensuring the appropriate ratio of gas-phase (CO2) to liquid-phase (H2O) reactants. Conversely, the WOHR prefers a hydrophilic surface that can promote the departure of the gaseous product (O2) from the catalyst surface, preventing isolation between active sites and the reactant (H2O). Here, we successfully reconciled the contradictory wettability requirements for the CRHR and WOHR by creating an alternately hydrophobic catalyst. This was achieved through a selectively hydrophobic modification method and a charge-transfer-control strategy. Consequently, the collaboratively promoted CRHR and WOHR led to a significantly enhanced OPCRR with a solar-to-fuel conversion efficiency of 0.186%. Notably, in ethanol production, the catalyst exhibited a 10.64-fold increase in generation rate (271.44 μmol g−1 h−1) and a 4-fold increase in selectivity (55.77%) compared to the benchmark catalyst. This innovative approach holds great potential for application in universal overall reactions involving gas participation.