The area of non-noble metals based electro-catalysts with electrochemical activity and stability similar or superior to that of noble metal electro-catalyst for efficient hydrogen production from electrolytic and photoelectrochemical (PEC) water splitting is a subject of intense research. In the current study, exploiting theoretical first principles study involving determination of hydrogen binding energy to the surface of the electro-catalyst, we have identified the (Cu0.83Co0.17)(3)P: x at. %S system displaying excellent electrochemical activity for hydrogen evolution reaction (HER). Accordingly, we have experimentally synthesized (Cu0.83Co0.17)(3)P: x at. % S (x = 10, 20, 30) demonstrating excellent electrochemical activity with an onset over potential for HER similar to Pt/C in acidic, neutral as well as basic media. The highest electrochemical activity is exhibited by (Cu0.83Co0.17)(3)P:30 at % S nanoparticles (NPs) displaying overpotential to reach 100 mA cm(-2) in acidic, neutral and basic media similar to Pt/C. The (Cu0.83Co0.22)(3)P:30 at % S NPs also display excellent electrochemical stability in acidic media for long term electrolytic and PEC water splitting process [using our previously reported (Sn0.95Nb0.05) O-2: N-600 nanotubes (NTs) as the photoanode]. The applied bias photon-to current efficiency obtained using (Cu0.83CO0.17)(3)P:30 at % S NPs as the cathode electrocatalyst for HER in an H-type PEC water splitting cell (similar to 4%) is similar to that obtained using Pt/C (similar to 4.1%) attesting to the promise of this exciting non-noble metal containing system. (C) 2018 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.