Insight into the influence of doped oxygen on active sites of molybdenum sulfide materials in hydrogen evolution reaction

Abstract Molybdenum disulfide has received great attention as a promising non-noble catalyst for electro-catalyzed hydrogen evolution reaction. The active sites originated from the limited edge of crystalline molybdenum disulfide is the key to restrict its HER performance. To increase the active sites of molybdenum disulfide through the heteroatom doping with effective synthetic strategy has become the focus of activity improvement. Herein, a facile and efficient strategy was adopted to synthesize oxygen-doped molybdenum sulfide catalyst by utilizing thiourea and sodium molybdate as precursors. It was found that the number of active sites could be regulated by controlling the dosage ratio of thiourea to sodium molybdate. The doped oxygen and abundant S endows molybdenum sulfide a great deal of lattice disorder or defects, thus providing adequate active sites. When the optimized ratio of thiourea to sodium molybdate (40:1), the double layer value of oxygen-doped molybdenum sulfide reached 34.14 mF/cm2 (mass loading on glassy carbon electrode was 0.142 mg/cm2) which is considered to be proportional to the electrochemical active area. Raman spectroscopy and X-ray photoelectron spectroscopy confirmed the presence of Mo–O bond and bridging S22− bonds which endows molybdenum sulfide with a great deal of lattice disorder or defects, thus providing plentiful active sites.