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 Co2P supported on carbon black (CrxCo2-xP/CB) for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in alkaline solution was investigated. A beneficial improvement in the performance of Co2P 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 Co2P/CB has a small amount of Cr added to form Cr0.2Co1.8P/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 Cr0.2Co1.8P/CB catalyst needed 226 mV overpotential to produce a cathodic current density of -100 A gCo(-1) and 380 mV overpotential to produce an anodic current density of 100 Ag-Co(-1). Based on both experimental results and theoretical calculations, the activity improvement results from optimization of the electronic properties of Co2P after Cr doping.