Core–Shell Structured MXene@Carbon Nanodots as Bifunctional Catalysts for Solar-Assisted Water Splitting

The design of nonprecious bifunctional electrocatalysts with high activity and prolonged durability in a wide pH range is essential for the development of the highly efficient, cost-effective, and simplified overall water splitting systems. Here, we report core–shell structured [email protected] ( [email protected] ) nanodot hybrids with high bifunctional activity, where N-doped carbon shells are grown in a heteroepitaxial manner strongly interacting with the MXene core. The resulting [email protected] nanodot hybrids show enhanced catalytic activity for electrochemical hydrogen evolution reaction (HER) in various pH media from 0 to 14. At pH 14, [email protected] achieves the low onset potential of 134 mV at 10 mA/cm 2 and reduced Tafel slope of 32 mV/dec due to the facilitated charge transfer along the recombination reaction. For the oxygen evolution reaction (OER), [email protected] nanodots are incorporated onto the surface of molybdenum-doped bismuth vanadate (Mo:BiVO 4 ) as a cocatalyst of the photoanode, thereby achieving 1.5 times higher photocurrent density than pristine Mo:BiVO 4 at 1.23 V ( vs reversible hydrogen electrode) due to the enhanced light absorption and charge transfer efficiency. The superiority of this hybrid catalyst is demonstrated implementing the solar-assisted overall water splitting cells based on the [email protected] cathode and [email protected] /Mo:BiVO 4 photoanode. These cells show the enhancement of current density from 0.78 to 1.23 mA/cm 2 with long-term durability over 8 h. These results are attributed to the facile surface catalytic kinetics of the chemically and electronically coupled [email protected] hybrid at the heterointerface for both OER and HER.