Interference mechanism of electrolyte cations on vanadium-oxygen binary doped carbon nitride for hydrogen evolution from artificial seawater splitting: Coupling experiments, DFT calculations and machine learning

Photocatalytic H 2 production from seawater splitting is a promising method for sustainable energy conversion technology. The vanadium-oxygen binary doped carbon nitride (VO X -CN) is successfully prepared for H 2 production. Benefiting from the electronic structure alteration, the maximum H 2 yield on VO X -CN in artificial seawater reaches 4475.74 μmol h −1 g −1 , 10 times higher than that of CN in deionized water. The impact of ions on the photocatalytic activity of VO 2 -CN is followed by Na + > Mg 2+ > K + > Ca 2+ . The adsorption of electrolyte ions promotes the formation of delocalized electron clouds on the surface of VO 2 -CN, facilitating more electrons to participate in H + reduction. Screening based on six machine models, the decision tree regression algorithm is used to reveal the interaction between cation type, their concentration and H 2 yield. Pearson heatmap indicates that Na + , Mg 2+ , and K + ions are positively correlated with H 2 yield, whereas Ca 2+ shows a negative correlation. The interactions among Na + , Mg 2+ and K + atoms facilitate H 2 production in multi-ion system, whereas Ca 2+ ions do the opposite, especially for high concentration. This work proposes new insights into the interference on H 2 yield between the structure alteration of CN framework and the change of ion type and concentration.