Temperature dependent electrocatalytic activity of molybdenum-based ZIF-67 nanorods for water splitting.

Several strategies have been adopted to enhance the electrochemical features of metal-organic framework structures for water splitting, however, a suitable conditions can effectively boost the electrocatalytic activity. Herein, molybdenum-based zeolite imidazolate frameworks (Mo 2g ZIF-67 and Mo 4g ZIF-67) have been synthesized by solvothermal process and electrocatalytic activity was examined at various elevating temperatures of 1 M KOH electrolyte. Mo 4g ZIF-67 nanorods showed the overpotential (η 10) of 358 mV at 20 °C, which was improved to 221 mV at 80 °C for the oxygen evolution reaction. Mo 4g ZIF-67 nanorods exhibited the Tafel slope of 77 mV dec−1 at 80 °C and followed the Volmer-Heyrovsky mechanism. LSV curves reveal that Mo 4g ZIF-67 nanorods showed a greater current density and a good turnover frequency (TOF) of 221.0 ms−1 at the fixed V RHE of 0.7 V. Similarly, Mo 4g ZIF-67 nanorods revealed the η 10 of 181 and 93 mV at 20 and 80 °C, respectively for the HER process. Mo 4g ZIF-67 nanorods displayed a Tafel slope of 95 mV dec−1 and TOF of 213.50 ms−1. The enhanced electrocatalytic activity may be due to rising temperatures, enhanced electrical conductivity at rising temperatures, well defined nanorods shape and greater ECSA, which provided the active sites and facile the flow of charge carriers for oxygen and hydrogen evolution reaction. The electrocatalyst, Mo 4g ZIF-67 nanorods exhibited a uniform current density during stability tests for 30 h at 20 °C, which was increased at 80 °C. Temperature elevation remarkably enhanced the HER and OER characteristics of the Mo 4g ZIF-67 nanorods and suggested an effective electrocatalyst for water splitting. • Mo 4 gZIF-67 nanorods have been synthesized by solvothermal treatment. • Mo 4g ZIF-67 nanorods showed the η 10 of 221 mV at 80 °C for the OER process. • Mo 4g ZIF-67 nanorods exhibited a Tafel slope of 77 mV dec−1 at 80 °C for OER process. • Mo 4g ZIF-67 nanorods exposed the η 10 of 93 mV at 80 °C for the HER process. • Mo 4g ZIF-67 nanorods displayed a TOF of 213.50 ms−1. [ABSTRACT FROM AUTHOR]