(P, W)-codoped MoO2 nanoflowers on nickel foam as an efficient bifunctional electrocatalyst for overall water splitting

Abstract

Due to the rapid consumption of fossil fuels and serious environmental pollution from nonrenewable energy, developing highly efficient, stable and earth-abundant bifunctional electrocatalysts for overall water splitting is thereby an urgent need but remains a significant challenge. Heteroatom doping is regarded as an effective tactic to facilitate electron interactions, and thereby enhance the electrocatalytic activity. In this work, (P, W)-codoped MoO2 nanoflowers were successfully assembled on a nickel foam (NF) substrate (marked as (P, W)-MoO2/NF) by hydrothermal and phosphorization processes. The as-prepared catalyst (P, W)-MoO2/NF exhibits excellent catalytic activities with lower overpotentials of 308 mV and 89 mV to deliver 40 mA cm−2 for oxygen evolution reaction (OER) and 10 mA cm−2 for hydrogen evolution reaction (HER), respectively. More significantly, when directly assembled in the electrolyzer as a bifunctional electrocatalyst for overall water splitting, it only requires a cell voltage of 1.65 V to deliver a current density of 30 mA cm−2. The as-prepared catalyst (P, W)-MoO2/NF also displays splendid long-term stability over 20 h without a visible decrease in an alkaline solution. The blooming flower-like architecture can afford abundant active sites, and the doping of heteroatoms can tune the electronic transfer, which are both responsible for the enhancement in the electrocatalytic properties. This work provides a unique direction to the rational design and synthesis of highly efficient and stable non-noble metal molybdenum-based bifunctional electrocatalysts for overall water splitting.