Spilling Over: A Noble Route to Green Ammonia

The quest for green ammonia—essential for fertilisers and future fuels—often stumbles on a specific hurdle: consistency. Converting nitrate to ammonia electrochemically requires a precise supply of active hydrogen. Too little, and the reaction stalls; too much, and the system wastes energy generating hydrogen gas. This balance is particularly difficult to maintain when relying on the erratic output of wind or solar power.

A new study presents an elegant solution: the 'hydrogen spillover' strategy. Researchers decorated nanoporous cobalt phosphide with platinum nanoparticles. In this microscopic partnership, the platinum acts as a dedicated generator of active hydrogen. Once formed, these hydrogen atoms migrate—or 'spill over'—onto the cobalt phosphide surface, where they efficiently convert nitric oxide intermediates into ammonia.

The separation of duties works wonders. The catalyst significantly lowers the energy barriers for the reaction, maintaining a Faradaic efficiency above 90 per cent across a wide 600 mV potential window. Essentially, it remains highly selective whether the system is running at low or high power. At industrially relevant currents (approx. 1 A cm^-2), the efficiency approaches 100 per cent.

Crucially, this technique is not limited to platinum; other noble metals show similar benefits. This suggests a universal blueprint for designing catalysts that can turn nitrate pollutants into valuable resources, regardless of how the wind blows.