Synergy of Ni dopant and oxygen vacancies in ZnO for efficient photocatalytic depolymerization of sodium lignosulfonate

Oxygen vacancies are efficient to promote the separation of photogenerated electrons and holes, thereby enhancing the photocatalytic performance of the catalyst. In this work, Ni-doped ZnO with oxygen vacancies was successfully synthesized. 3ZnO with 3 wt% of Ni2+ doping has an optimum photocatalytic activity. The optimal depolymerization rate of sodium lignosulfonate (SLS) was 94%, and the optimal yields of vanillic acid and guaiacol were 9.3% and 1.5%, respectively. 3ZnO can effectively depolymerize SLS to valuable products, CO2 and H2O due to proper concentration of surface oxygen vacancies induced by Ni2+ doped, which promotes the formation of •O2–. •O2– is considered to be more conducive to depolymerization of SLS to valuable products. Proper concentration of oxygen vacancies is very necessary for depolymerizing SLS into valuable products. This work will give an innovative vision for efficient depolymerizing biomass to valuable products through photocatalytic reactions.