Study on effect of vanadium doping in cesium tungsten bronze system and application in HER

Increasing demand for energy and the crisis of fossil fuels have led researchers to search for an alternative energy source. Hydrogen is the cleanest energy source producing water as fuel cells exhaust. However, producing hydrogen could be crucial as only some active catalysts produce pure hydrogen. The expense due to the scarcity of the state-of-the-art catalyst (platinum) for the Hydrogen Evolution Reaction (HER) is the main reason for the higher price of pure hydrogen as a fuel. In our present research, we chose the less expensive cesium tungsten bronzes (CTB) doped with various percentages of vanadium (5 mol% -20 mol%) to study their HER performance. The materials were prepared hydrothermally at 180 degrees C at different reaction times. XRD revealed that, upon increasing the vanadium amount, the hexagonal phase of the CTB is transformed to the cubic phase at a higher reaction time. However, the hexagonal phase was retained after vanadium introduction with a lower reaction time. FT-IR, Raman, EDX, SIMS, XPS, and XRF spectroscopy confirmed the incorporation of vanadium into the bronze system. Vanadium-doped samples showed enhanced HER activity compared to the pure CTB. The 20% vanadium-doped hexagonal bronze showed the best HER performance in 0.5 M H2SO4 among all the vanadium -doped materials, which lowered the HER potential of the pure CTB (-0.665 V vs RHE) to-0.288 V vs RHE at-10 mA cm-2. This increase in activity was correlated with a higher surface area, higher electrochemical surface area, faster reaction kinetics with a lower Tafel slope, and a small charge-transfer resistance of the samples after V5+ incorporation compared to the pure CTB.

Automated summary

Researchers studied the performance of vanadium-doped cesium tungsten bronzes as catalysts for the Hydrogen Evolution Reaction (HER). The vanadium-doped samples showed higher activity compared to pure cesium tungsten bronzes, with the 20% vanadium-doped hexagonal bronze exhibiting the best performance.