To test our exfoliated materials as HER catalysts, electrochemical measurements were performed in a three-electrode cell composed of platinum wire, Ag/AgCl and glassy carbon as counter, reference and working electrodes, respectively. The glassy carbon electrode was covered with bulk MnPS 3 , MnPS 3 @H 2 O, MnPS 3 @PVP, or MnPS 3 @PEI, depending on the system under study.