Ultrathin Pd metallenes as novel co-catalysts for efficient photocatalytic hydrogen production

Photocatalytic hydrogen production as a green and pollution-free technology plays an important role in alleviating the fossil fuel crisis, but remains a great challenge. Herein, an ultrathin two-dimensional (2D) palladium metallene (Pd-ene) is first developed as hydrogen evolution co-catalysts for g-C3N4 nanosheets. The Pd-ene and Pd-ene/g-C3N4 photocatalysts were fabricated by a hydrothermal method and deposition method using acetylacetonate palladium as Pd source, and the Pd-ene with a size of 100 nm uniformly distributed on the surface of g-C3N4 nanosheets forming a 2D/2D structure. The Pd-ene/g-C3N4 with 2 wt% Pd-ene showed the highest photocatalytic hydrogen production rate with 31,292 μmol/h/ g, which was>98 times that of the pure g-C3N4 and superior to the PdNC/g-C3N4 loading with Pd nanocluster. The unique 2D/2D structure of the Pd-ene/g-C3N4 catalyst, which promotes the transfer and separation of photogenerated charge carriers, is credited with the improved photocatalytic performance. In additions, the 2D structure of Pd-ene makes it expose more reaction sites for the photocatalytic reduction reaction, promoting the hydrogen production of the photocatalysts. This study demonstrates that the development of structurally matched 2D metallene co-catalysts for 2D photocatalysts is a promising strategy to obtain the photocatalysts with high hydrogen production performance.