Order engineering on the lattice of intermetallic PdCu co-catalysts for boosting the photocatalytic conversion of CO2 into CH4

Photocatalytic conversion of CO2 to CH4, a promising approach to reduce the depletion of fossil fuels and concomitant global warming, is greatly limited by the production of CO and H-2 by side reactions. Rational design of co-catalysts holds promise to address this grand challenge. In this paper, via the transformation from a random A1 alloy phase to an ordered B2 intermetallic phase, order engineering is performed on PdCu co-catalysts to realize enhanced photocatalytic activity and selectivity in reduction of CO2 with H2O to CH4. Based on the experimental results of PdCu co-catalysts with different ordered degrees of atomic arrangement obtained through tuning the annealing temperatures and Pd/Cu molar ratios, two effects are proposed to contribute to this enhancement: (1) the strong electronic interaction between Pd and Cu atoms in the periodic structure increases the electron trapping ability of ordered PdCu co-catalysts; (2) the periodic structure increases the number of isolated Cu atoms in the ordered PdCu co-catalysts, which act as highly active catalytic sites in the reduction of CO2 to CH4. This work represents a step toward the design of high-performance photocatalysts through lattice engineering of the co-catalysts with atomic precision.