Synergistically modulating electronic structure of NiS2 hierarchical architectures by phosphorus doping and sulfur-vacancies defect engineering enables efficient electrocatalytic water splitting

The synergistic achievement of heteroatom doping, defect engineering and appropriate structural design is efficient to adjust and boost the catalytic performance of catalysts yet challenging. Herein, phosphorus (P)-doped NiS2 hierarchical architectures with sulfur vacancies are synthesized via a Prussian-blue-analogue-sacrificed strategy followed by a phosphidation process. By modulation of P doping and sulfur vacancies, the optimal catalyst manifests outstanding electrocatalytic activities, affording low overpotentials of 73 mV at 10 mA cm−2 for hydrogen evolution reaction (HER), and 255 mV at 20 mA cm−2 for oxygen evolution reaction (OER), respectively. Density functional theory calculations certify that the P dopant not only serves as the new active sites, but also activates the electrochemical activity of neighboring Ni and S sites. Moreover, the synergistic effect of P-doping and sulfur vacancies further improve electrochemical activities of HER and OER by optimizing the adsorption free energy of hydrogen (ΔGH*) and oxygen-containing intermediates (OH*, O* and OOH*), respectively. This finding provides a directive strategy to achieve efficient non-noble metal catalysts for energy conversion and storage.