Rational design of Pd-TiO2/g-C3N4 heterojunction with enhanced photocatalytic activity through interfacial charge transfer

A hybrid heterojunction-based photocatalyst is synthesized by an electrostatic self-assembly strategy including surface modification and controlled metal deposition. The interfacial contact was made by mixing negatively charged anatase TiO2 nanoparticles with positively charged g-C3N4. Visible-light deposition of Pd nanoparticles largely on TiO2 was made possible due to the charge transfer from C3N4 (excited by visible light) to the conduction band of TiO2 reducing Pd ions on contact with its surface. In order to further test the efficiency of this cascade of electron transfer across the conduction bands of the two semiconductors, photocatalytic H2 production from water was studied. Upon optimizing the ratio of the two semiconductors, increased H2 production rates were observed and attributed to enhanced charge separation. Catalysts were studied by a variety of techniques in order to probe into their properties and link them to activity. The reaction rate, under visible-light excitation, of the best sample showed an 8-fold enhancement when compared to that of Pd-C3N4 in identical conditions and the highest apparent quantum yield of 31% was achieved by a 0.1%Pd/20%TiO2/C3N4 sample in a 420- to 443-nm range.