Development of highly efficient and durable bifunctional electrocatalyst for hydrogen and oxygen evolution reactions (HER and OER) is essential for efficient solar fuel generation. The commercial RuO2 or RuO2-based catalysts are highly active toward OER, but their poor stability under different operating conditions is the main obstacle for their commercialization. Herein, we report growth of one-dimensional highly crystalline RuO2 nanowires on carbon nitride (1D-RuO2-CNx) for their applications in HER and OER at all pH values. The 1D-RuO2-CNx, as an OER catalyst, exhibits a low onset overpotential of ∼200 mV in both acidic and basic media, whereas Tafel slopes are 52 and 56 mV/dec in acidic and basic media, respectively. This catalyst requires a low overpotential of 250 and 260 mV to drive the current density of 10 mA cm-2 in acidic and basic media, respectively. The mass activity of 1D-RuO2-CNx catalyst is 352 mA mg-1, which is ∼14 times higher than that of commercial RuO2. Most importantly, the 1D-RuO2-CNx catalyst has remarkably higher stability compared to commercial RuO2. This catalyst also exhibits superior HER activity with a current density of 10 mAcm-2 at ∼93 and 95 mV in acidic and basic media. The HER Tafel slopes of this catalyst are 40 mV/dec in acidic condition and 70 mV/dec in basic condition. The HER activity of this catalyst is slightly lower than Pt/C in acidic media, whereas in basic media it is comparable or even better than that of Pt/C at higher overpotentials. The HER stability of this catalyst is also better than that of Pt/C in all pH solutions. This superior catalytic activity of 1D-RuO2-CNx composite can be attributed to catalyst-support interaction, enhanced mass and electron transport, one-dimensional morphology, and highly crystalline rutile RuO2 structure.
Keywords: bifunctional; graphitic carbon nitride; hydrogen evolution; one-dimensional RuO2 nanowire; oxygen evolution.