Laser synthesis of amorphous CoS nanospheres for efficient hydrogen evolution and nitrogen reduction reactions

Transition metal sulfides (TMSs) have been demonstrated to be excellent electrode materials for various applications of electrochemical energy conversion and storage. However, the synthesis of TMSs through conventional approaches commonly suffers from toxic or environmentally unfriendly reagents as well as time consuming procedures, high thermal power and energy loss. Herein, CoS x nanospheres with uniform distribution and strong adhesion on carbon fiber cloths (CoS x /CC-L) are synthesized via the confined laser temperature field under a H 2 S atmosphere under normal temperature and pressure conditions. It is demonstrated that the high pressure field induced by a laser yields amorphous CoS x containing numerous S vacancies, which could provide more active sites for enhancing the hydrogen evolution reaction (HER) and nitrogen reduction reaction (NRR). The as-prepared CoS x /CC-L exhibits a low overpotential of ∼87 mV at 10 mA cm −2 for the HER in 0.5 M H 2 SO 4 aqueous electrolyte and maintains a stable catalytic performance for 15 h with a high current density of 650 mA cm −2 . In addition, a high ammonia (NH 3 ) production rate (12.2 μg h −1 cm cat −2 ) and Faraday efficiency (10.1%) of CoS x /CC-L at −0.2 V vs. RHE in a neutral 0.05 M Na 2 SO 4 electrolyte were obtained. The good proton activation and nitrogen adsorption abilities arising from the sulfur vacancies contribute to the active nitrogen association/hydrogenation process during the NRR. The laser synthesis provides an alternative process to produce efficient amorphous catalysts, which are expected to be promising HER and NRR electrocatalysts for energy conversion applications. Laser-induced amorphous CoS x nanospheres anchored on carbon fiber cloths are reported. Profiting from the amorphous nature of CoS x , the enhanced electrocatalytic HER and NRR performance with good proton activation and nitrogen adsorption abilities were obtained.