Efficient and stable hydrogen evolution based on earth-abundant SnSe nanocrystals

Tin chalcogenide nanocrystals (NCs) exhibit a wide absorption spectrum with excellent optoelectronic properties. Both Sn and Se are relatively less harmful and less expensive compared to heavy-metals and precious elements. However, it is still a challenge to directly synthesize SnSe NCs without using toxic and sensitive precursors. Here, we use a cation exchange assisted approach to synthesize SnSe NCs that are optically active in the near infrared (NIR). The SnSe NCs have a cuboid shape obtained thorough an orientated growth path. A typical indirect bandgap was found in these NCs ranging from 0.9 to 1.2 eV. As a proof-of-concept, the SnSe NCs were used as light absorbers for photoelectrochemical (PEC) hydrogen evolution, leading to a saturated photocurrent density of 8.2 mA/cm2, a record value for PEC devices using heavy-metal-free NIR NCs. Our results indicate that SnSe NCs of cuboid shape have great potential for use in emerging optoelectronic and photovoltaic devices.