As the price of renewable electricity continues to plummet, hydrogen (H₂) production via water electrolysis is gaining momentum globally as a route to decarbonize our energy systems. The requirement of high purity water for electrolysis and the widespread availability of seawater have led to significant research efforts in developing direct seawater electrolysis technology for H₂ production. In this perspective, we critically assess the broad-brush arguments on the research and development (R&D) needs for direct seawater electrolysis from energy, cost and environmental aspects. We focus in particular on a process consisting of seawater reverse osmosis (SWRO) coupled to proton exchange membrane (PEM) electrolysis. Our analysis reveals there are limited economic and environmental incentives of pursuing R&D on today's nascent direct seawater electrolysis technology. As commercial water electrolysis requires a significant amount of energy compared to SWRO, the capital and operating costs of SWRO are found to be negligible. This leads to an insignificant increase in levelized cost of H₂ (<0.1 $ per kg H₂) and CO₂ emissions (<0.1%) from a SWRO-PEM coupled process. Our analysis poses the questions: what is the future promise of direct seawater electrolysis? With an urgent need to decarbonize our energy systems, should we consider realigning our research investments? We conclude with a forward-looking perspective on future R&D priorities in desalination and electrolysis technologies.

As renewable electricity prices continue to decline, interest grows in alternative routes for the synthesis of sustainable fuels and chemicals, including ammonia. Considering demand for fertilizers, as well as its future potential as a dispatchable energy vector, sustainable synthesis of ammonia is being explored as an alternative to the capital- and carbon-intensive fossil-fuel-driven Haber–Bosch process. Here we assess stages along a transition to the sustainable synthesis of ammonia, looking at economic feasibility and climate impacts compared to the incumbent Haber–Bosch without and with CO₂ capture. This analysis enables us to suggest technological thresholds for sustainable synthesis of ammonia to become economically and environmentally favourable. When driven by renewable energy sources, the water electrolyzer (near $400 per kW) coupled Haber–Bosch process will reach cost parity near 2.5 cents per kWh electricity. In the case of direct electrochemical ammonia synthesis, achieving cost-parity using the same 2.5 cents per kWh electricity will rely on achieving major advances in performance: an electrolysis full-cell energy efficiency exceeding 40% at a current density of 0.5 A cm⁻². Once this operating performance is reached, electrically-powered ammonia synthesis will bring climate benefits when coupled with low-carbon electricity (<180 gCO_2e per kWh), achievable when over half of today's U.S. electricity generation is supplied by renewable energy sources. We conclude with a forward-looking perspective on the key challenges and opportunities for sustainable ammonia synthesis routes to be competitive with the incumbent Haber–Bosch process in the future.

Hydrogen is a versatile energy vector, pivotal to a NetZero future, but will require the development of technologies for low-carbon hydrogen production like methane pyrolysis and new value chains that connect supply to demand.

Solar to hydrogen (STH) efficiency of photovoltaic-electrolysis (PV-E) setups is a key parameter to lower the cost of green hydrogen produced. Commercial c-Si solar cells have neared saturation, which warrants the need to look at alternative technologies. In this work, we report a concentrator photovoltaic-electrolysis (CPV-E) setup with STH efficiency of 28% at 41 suns; the highest reported efficiency using an alkaline system to date. Using this as a base case, we carried out a detailed techno-economic (TEA) analysis, which showed despite the high cost associated with CPV cells, levelized cost of hydrogen (LCOH) is at $ 5.9/kg, close to that from c-Si solar farms ($ 4.9/kg), primarily due to the high STH efficiency. We also report sensitivity analysis of factors affecting both CPV and alkaline electrolyser systems such as the CPV module efficiency and installed capacity, electrolyser stack lifetime, operating current density, and working hours. Our results indicate that in a scenario where the installed capacity of CPV technology matches that of silicon and with electrolyser operating current density of ~ 0.7 A/cm2, the LCOH from CPV-electrolysis systems can be < $ 2/kg. These results demonstrate the potential of CPV technology for large-scale green hydrogen production to replace that obtained from fossil fuels.