Ultra-deep photocatalytic desulfurization of dibenzothiophene over hollow Core-shell N-doped graphene nanospheres anchored bimetallic single atoms under visible light

[Display omitted] •Hollow core–shell N-doped graphene (HCS-NG) oriented Ni/Cu by a facile method.•The confined space effect improved the synergy between metal active centers and supports.•The hollow microenvironment improved the contact probability between reactants and active centers.•The ultra-thin shell and hollow structure reduced the diffusion resistance of sulfide.•A removal ratio of DBT was>99.1 % over HCS-NG-Ni/Cu under visible light.•Coordination between N and Ni/Cu altered electronic states of Ni/Cu. HCS-NG-Ni/Cu nanospheres composed of the 100–120 nm hollow core- shell N-doped graphene with lattice spacing d = 0.25 nm were prepared by a facile method and their surfaces were decorated with d = 0.14 nm Ni and d = 0.12 nm Cu single atoms. Characterization of HAADF-STEM, XPS, Raman, and photoelectron-chemi- cal showed the morphology of Ni/Cu was a single atomic state on the hollow core- shell N-doped graphene, which could effectively inhibit the photoelectron-hole pair recombination leading to improve the efficiency of photocatalytic desulfurization. The influence of metal loading, Ni:Cu ratios, time, catalyst amount, and different catalysts on the removal of DBT were investigated. Results indicated the hollow core–shell N-doped graphene decorated with Ni/Cu had higher photocatalytic removal ratios (>99.1%) than the others under the mild conditions and had a high activity even after 10 cycles because of the synergism of single Ni/Cu atoms and the hollow core–shell N-doping-graphene under visible light. The energy barrier and the removal rate constant of DBT were 78 kJ/mol and 3.79*10-2, respectively, and the photocatalytic mechanism was assumed. Researches provided not only a high-efficiency desulfurization catalyst to produce clean fuel, but also a new idea on designing bimetallic single-atom catalysts.