Tungsten–Cobalt Oxalate with Multiple Catalytic Sites as Efficient Electrocatalyst for Boosting Overall Water Splitting

Bimetallic oxalates are highly desirable for the hydrogen evolution reaction (HER). However, poor oxygen evolution reaction (OER) catalytic activities are a challenge. Herein, tungsten cobalt oxalate (WCoC2O4) was reported as an efficient bifunctional electrocatalyst which provides more reactive sites to assist rapid mass as well charge transfer. Moreover, synergy between cobalt and tungsten atoms effectively tailored the electronic structure of oxalate and optimized the adsorption/desorption of intermediates with hydrogen-binding energy. Thus, WCoC2O4 exhibits superior bifunctional efficiency with low overpotential (η10) of 172 mV (HER) and 251 mV (OER). The optimized WCoC2O4 exhibits higher TOF than CoC2O4 with Faradaic efficiency of 99% at 1.57 V implying exceptional selectivity of WCoC2O4. The long-term stable nature of WCoC2O4 over 100 h at 1.57 V inferred its robustness. The kinetic study through operando EIS reveals enhanced OER kinetics, less resistance, and more conductivity of WCoC2O4. The improved OER activity was further sustained by a Bode study at various potentials. The activation energy of WCoC2O4 (4.1 kJ mol–1) is reduced more than pristine CoC2O4 (15.2 kJ mol–1) at 1.57 V, signifying the impact of tungstenization. The higher rate constant derived from a trumpet plot reveals that WCoC2O4 at various pH values compared to WCoC2O4 inferred rapid formation of gas bubbles. The water splitting device with self-supported WCoC2O4 enables overall water splitting and requires a low cell voltage of 1.57 V with great catalytic durability. All the results lead to a key step to construct high-performance and low-cost bimetallic oxalate as a bifunctional catalyst toward total water splitting.