Journal
ACS APPLIED MATERIALS & INTERFACES
Volume 8, Issue 8, Pages 5327-5334Publisher
AMER CHEMICAL SOC
DOI: 10.1021/acsami.5b12093
Keywords
NiSe2; CoSe2; water splitting; bifunctional; Si nanowire; photoelectrochemical cell
Funding
- NRF [2014R1A6A1030732]
- MOST
- POSTECH
- National Research Foundation of Korea [2014R1A6A1030732, 10Z20130012349] Funding Source: Korea Institute of Science & Technology Information (KISTI), National Science & Technology Information Service (NTIS)
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Catalysts for oxygen evolution reactions (OER) and hydrogen evolution reactions (HER) are central to key renewable energy technologies, including fuel cells and water splitting. Despite tremendous effort, the development of low-cost electrode catalysts with high activity remains a great challenge. In this study, we report the, synthesis of CoSe2 and NiSe2, nanocrystals (NCs) as excellent bifunctional catalysts for simultaneous generation of H-2 and O-2 in water-splitting reactions. NiSe2 NCs exhibit superior electrocatalytic efficiency in OER, with a Tafel slope (b) of 38 mV dec(-1) (in 1 M KOH), and HER, with b = 44 mV dec(-1) (in 0.5 M H2SO4). In comparison, CoSe2 NCs are less efficient for OER (b = 50 mV dec(-1)), but more efficient for HER (b = 40 mV dec(-1)). It was found that CoSe2 NCs contained more metallic metal ions than NiSe2, which could be responsible for their improved performance in HER. Robust evidence for surface oxidation suggests that the surface oxide layers are the actual active sites for OER, and that CoSe2 (or NiSe2) under the surface act as good conductive layers. The higher catalytic activity of NiSe2 is attributed to their oxide layers being more active than those of CoSe2. Furthermore, we fabricated a Si-based photoanode by depositing NiSe2 NCs onto an n-type Si nanowire array, which showed efficient photoelectrochemical water oxidation with a low onset potential (0.7 V versus reversible hydrogen electrode) and high durability. The remarkable catalytic activity, low cost, and scalability of NiSe2 make it a promising candidate for practical water-splitting solar cells.
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