Babajide Patrick Ajayi

A low-noble-metal W1−xIrxO3−δ water oxidation electrocatalyst for acidic media via rapid plasma synthesis

Acid-based electrolysis has many advantages, but to achieve simultaneous activity and stability, commercial water oxidation catalysts rely on noble metal oxides that are expensive and too rare for the global scale. Here, earth-abundant tungsten was used as a structural metal to dilute the noble metal iridium content while maintaining high activity and stability in acid. Mixed-metal oxide catalysts were synthesized using rapid plasma oxidation in which the non-equilibrium reaction environment permitted better formation of a homogenous W1−xIrxO3−δ phase. With an Ir metal content as low as 1%, a competitive and durable overpotential for oxygen evolution was achieved. Relative to high Ir content, low Ir compositions consisted of a more highly crystalline, phase-pure iridium polytungstate which was more catalytically active per Ir content. Moreover, the plasma-synthesized material had a sharp electrocatalytic improvement over an equivalent composition synthesized via standard thermal oxidation, demonstrating the value of non-equilibrium synthesis to find new catalysts.

Unravelling the energy transfer mechanism in bismuth co-activation of LaInO3:Sm3+/Ho3+ nanophosphor for color-tunable luminescence

A series of single-phased and color tunable LaInO3:Bi3+,Ho3+/Sm3+ nano phosphors were synthesized via a cost effective and low temperature chemical route. The crystal structure, morphology, photoluminescence (PL) and energy transfer mechanism between Bi3+ to Ho3+/Sm3+ were investigated in detail. The considerable spectral overlap between the broad emission band of Bi3+ around 400–500 nm and the excitation band of Ho3+ and Sm3+ supports the efficient energy transfer from Bi3+ to Ho3+/Sm3+, which enhances the PL intensity remarkably. The energy transfer efficiency between Bi3+ and Ho3+/Sm3+ in LaInO3 was also calculated and the efficiency increased linearly with increasing concentration of Ho3+ and Sm3+. The emission hue can be tuned from blue to green and pink by varying the content of Ho3+/Sm3+. This investigation will extend an understanding of interactions between Bi3+ and rare earth ions in semiconducting host LaInO3 and show the potential applications of Bi3+, Ho3+/Sm3+ co-doped nanophosphors in displays and light emitting diodes.