Mechanistic insights into the promotional effect of Ni substitution in non-noble metal carbides for highly enhanced water splitting

We elucidate real-time mechanistic insights into the promotional effect of Ni substitution on the bifunctional overall water splitting (OWS) activity of molybdenum and tungsten carbides (Ni-MoC/WC@NGC) supported on N-doped graphitic carbon (NGC). Ni substitution yields multi-fold improvement in OWS over the pristine systems that are comparable to commercial Pt/C for hydrogen evolution reaction (HER) and better than IrO2 for oxygen evolution reaction (OER). Ni-MoC@NGC champions in HER activity exhibiting an onset overpotential of 65 mV and current density of 140 mA/cm(2) at -370 mV (v RHE) in acidic media. An H2O electrolyzer constructed with Ni-MoC@NGC shows a comparable cell voltage to the Pt parallel to IrO2 pair and could split water aided by 1.5 V AAA commercial battery. First principle calculations and in-situ probing through quick-XAS during electrochemical processes provide valuable insights into how the adsorption energies of intermediates and reaction kinetics are modulated at different catalytic sites with the promotional electronic effect of Ni.

Automated summary

The promotion effect of Ni substitution on the bifunctional overall water splitting activity of Ni-MoC/WC@NGC supported on N-doped graphitic carbon is elucidated. Ni substitution significantly improves the OWS performance, especially in the hydrogen evolution reaction. In acidic media, Ni-MoC@NGC exhibits lower onset overpotential and higher current density, enabling water splitting with the assistance of a commercial battery.