Electrolyzer with hierarchical transition metal sulfide and phosphide towards overall water splitting

Transition metal sulfide (TMS) and phosphide (TMP) have been considered as efficient catalysts for electrochemical water splitting. Here, we have reported an effective strategy to synthesize TMS- and TMP-assembled hierarchical anode ([email protected]2) and cathode (Cu3[email protected]2P) for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER), respectively. It is found that the three-dimensional (3D) hierarchical electrodes not only provide a large number of active sites to promote the apparent catalytic activity, but also present tuned valence state of Co, which enhances the intrinsic activity of the active sites. Therefore, the [email protected]2 anode possesses excellent OER activity with an overpotential of 230 mV at a current density of 10 mA/cm2, and the Cu3[email protected]2P cathode exhibits good HER performance with a low overpotential of 95 mV at a current density of 10 mA/cm2. Impressively, the [email protected]2//Cu3[email protected]2P electrolyzer deliver a current density of 10 mA/cm2 at a cell voltage of 1.55 V for overall water splitting, which is better than most reported TMS and TMP based catalysts.