Synergistic effect of photo-reduced Ni-Ag loaded g-C3N4 nanosheets for efficient visible Light-Driven photocatalytic hydrogen evolution

Abstract

A heterogenous ternary Ni and Ag co-modified g-C3N4 nanocomposite is designed and fabricated using a photoreduction approach for photo-catalytic hydrogen production from methanol-water mixture. Ternary nanocomposite consisting of Ni–Ag co-deposited onto g-C3N4 was successfully fabricated and uniformly distributed, therefore, exhibited strong visible-light absorption and efficient charge carrier separation due to synergistic effect throughout the ternary composite. The nanocomposite with varying amounts of nickel and silver, play an important role to maximize the photoactivity with the optimized 3Ni–1Ag/CN sample delivering H2 of 2137.5 μmolg−1h−1, which is 16.13, 1.42 and 1.52 folds greater than using CN, 3Ni/CN and 3Ag/CN, respectively. This proves that semiconductor composition ratio is important in achieving a successful p-n junction and efficient charge separation and transfer in the ternary composite. The performance of optimized Ni–Ag/CN was further enhanced using photo-reduction method. The highest H2 yield of 5740 μmolg−1 is achieved over the photo-reduced Ni–Ag/CN-R nanocomposite which is 1.25 folds higher than non-photo-reduced composite. This improvement can be accredited to the formation of good p-n junction between the semiconductors in the ternary composite and due to the formation of photo-reduced Ag which acts as electron sinks which leads to improved charge separation. Furthermore, increasing catalyst loading increases the H2 production rate and methanol-water mixture gave the highest H2 production rate. The findings of this study would be beneficial for future hydrogen generation and implementation within newer sustainable systems.