Controllable Heteroatom Doping Effects of CrxCo2–xP Nanoparticles: a Robust Electrocatalyst for Overall Water Splitting in Alkaline Solutions

The effect of doping Cr on the electrocatalytic activity of Co 2 P supported on carbon black (Cr x Co 2– x P/CB) for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in alkaline solution was investigated. A beneficial improvement in the performance of Co 2 P toward HER and OER was discovered. For the HER at −200 mV overpotential, the turnover frequency (TOF) increases almost 6-fold from 0.26 to 1.52 electron site Co –1 s –1 when Co 2 P/CB has a small amount of Cr added to form Cr 0.2 Co 1.8 P/CB. Similarly, we estimate an increase from 0.205 to 0.585 electron site Co –1 s –1 for the OER at 1.6 V for the same change in composition. With 10 atom % Cr doping, the Cr 0.2 Co 1.8 P/CB catalyst needed 226 mV overpotential to produce a cathodic current density of −100 A g Co –1 and 380 mV overpotential to produce an anodic current density of 100 A g Co –1 . Based on both experimental results and theoretical calculations, the activity improvement results from optimization of the electronic properties of Co 2 P after Cr doping.