Synergy of Cu doping and SO42− adsorption in the self-optimized SO42−@Cu doped Co(OH)2 reconstructed from CuCo2S4 towards enhanced oxygen evolution reaction

Catalysts in-situ reconstructed from transition metal sulfides for oxygen evolution reaction (OER) have been regarded as potential alternatives for the noble metal catalysts. Intriguingly, it was found that the self-optimized SO42−@Cu doped Co(OH)2 catalyst was reconstructed from bimetallic sulfide of CuCo2S4. During the OER process, the copper was partially leached and meantime doped into the in-situ generated Co(OH)2 with SO42− adsorption, while only oxides were discovered in counterparts of mono-metal sulfides. As a result, the SO42−@Cu doped Co(OH)2 catalyst exhibited superior OER performances, with low overpotentials of 211/272 mV to achieve the current densities of 10/100 mA cm−2, exceeding the counterparts reconstructed from mono-metal sulfides. Experimental and theoretical results suggested that the in situ generated Cu doped Co(OH)2 possessed thin and loosely layered structure with expanded lattice spacing (lattice spacing expanded from 0.28 nm to 0.46 nm) due to the SO42− adsorption, making the intermediates more accessible to the active centers. In addition, the catalyst surface changed from hydrophobicity to super hydrophilicity, which greatly accelerated the mass transfer. This work indicated that the in-situ reconstruction process was greatly influenced by the interactions between metal sites and sulfide species, directly influencing the OER performances of the reconstructed catalysts.