Towards photoelectrocatalytic dinitrogen reduction

This thesis presents an investigation into the fabrication and catalytic testing of p-type InP semiconductors with a CoMo alloy electrocatalyst towards dinitrogen reduction in a photoelectrochemical system. To obtain an optically transparent deposit of the bimetallic electrocatalyst on the p- InP surface, a range of metal salt precursor combinations as well as solution compositions were investigated. Furthermore, the effects of additives such as boric acid on the resultant films were also explored. Deposits from a cophotoelectrodeposition of CoMo conducted in the presence of boric acid afforded the crucial morphological and compositional needs hypothesised to be most effective towards nitrogen reduction: the metals were alloyed, with both Mo0 and Co0 present on the electrode surface post deposition. fabricated photoelectrodes were subsequently tested towards dinitrogen reduction in a photoelectrochemical system, which suggested enhanced activity in the presence of alkali metal cations (AMCs), with the highest yield of ammonium achieved in the presence of Cs+(aq) cations. These effects are believed to be due to electrochemical (EC) as well as surface energetics changes induced by the cation. Preliminary investigations were conducted into styrene activation and its potential transformation to 2-phenylaziridine, prompted by the presence of a Mo–Nads species present on the electrode surface, as confirmed by XPS studies. The attempts were not successful however the chapter reports on the useful observations and suggests ideas for future work. Overall, the thesis highlights the importance of research into nitrogen reduction, ammonia synthesis, and C–N bond formation, and the role that photoelectrochemical systems may play in realising the potential of solar energy towards achieving these transformations under ambient conditions.