Enhanced Catalytic Activity of a Vanadium-Doped Mesoporous Octahedral Molecular Sieve-2 (K-OMS-2) toward Hydrogen Evolution Reaction

Hydrogen evolution reaction (HER) is the cathodic reaction in electrochemical water splitting that produces H2 in a renewable pathway, primarily to be used in fuel cells. K-OMS-2, a manganese octahedral molecular sieve, has the potential to replace Pt as a catalyst for HER due to its redox and electrochemical properties, which can be further improved by doping metal cations into the K-OMS-2 framework. In this work, we synthesized 1, 5, and 10% vanadium- (V) doped mesoporous K-OMS-2 under mild acidic reaction conditions. The mesoporous nature of the samples was confirmed by BET analysis. X-ray photoelectron spectroscopy confirmed that Mn has 2+, 3 +, and 4+ oxidation states, and V is present as V4+ in V-K-OMS-2 samples. HER performance of 1% V-K-OMS-2 in an acidic medium shows the best activity with −0.32 V overpotential. The overpotential was lowered by 0.56 V upon doping 1% V into the K-OMS-2 framework. The 1% V-K-OMS-2 material has a Tafel slope of 129 mV/decay and an electrochemically active surface area (ECSA) of 127.5 cm2ECSA.