Solar energy driven processes with H₂O and CO₂ as basic feedstocks can produce “solar fuels” that could substitute their fossil based counterparts. This article summarizes the main findings of a techno-economic analysis of systems that can generate different types of fuels with renewable energy as starting point. These “renewable fuels” could potentially play a key role in future energy systems, both as a storage medium in the power sector and as an energy carrier in e.g. the transport sector, or deliver fundamental building blocks for the chemical industry. We determine whether, how, and when renewable fuels might become competitive alternatives for fossil fuels. The technologies required to produce renewable fuels are analyzed by the application of learning curves associated with individual system components. We thereby make projections for possible decreases in investment costs and reductions in fuel production costs. In an optimistic scenario we find that competitivity could be reached between 2025 and 2048 for all renewable energy production pathways that we investigate, for hydrogen, syngas, methanol, and diesel. Two techniques yield break-even costs before 2050 even in a conservative base case scenario: H₂ production through electrolysis and diesel production by Fischer–Tropsch synthesis. Both processes use solid oxide electrolysis, which profits from rapid cost reductions and high efficiency.

The current status and prospects of six routes to electrochemically convert CO₂ into different products are investigated. The study includes for each of these routes an analysis of the costs and of the emissions related to electricity use.

This work reports an aqueous dye‐sensitized photoelectrochemical cell (DSPEC) capable of oxidizing glycerol (an archetypical biobased compound) coupled with H₂ production. We employed a mesoporous TiO₂ photoanode sensitized with the high potential thienopyrroledione‐based dye AP11, encased in an acetonitrile‐based redox‐gel that protects the photoanode from degradation by aqueous electrolytes. The use of the gel creates a biphasic system with an interface at the organic (gel) electrode and aqueous anolyte. Embedded in the acetonitrile gel is 2,2,6,6‐tetramethylpiperidine‐1‐oxyl (TEMPO), acting as both a redox‐mediator and a catalyst for oxidative transformations. Upon oxidation of TEMPO by the photoexcited dye, the in situ generated TEMPO⁺ shuttles through the gel to the acetonitrile–aqueous interface, where it acts as an oxidant for the selective conversion of glycerol to glyceraldehyde. The introduction of the redox‐gel layer affords a 10‐fold increase in the conversion of glycerol compared to the purely aqueous system. Our redox‐gel protected photoanode yielded a stable photocurrent over 48 hours of continuous operation, demonstrating that this DSPEC is compatible with alkaline aqueous reactions.

In this article we analyze how syngas produced in a renewable way can replace fossil‐fuel based syngas production and thereby play an essential role in the decarbonization of industry. We show that in essentially all industrial applications renewable H₂ and/or CO can replace syngas from fossil fuel feedstocks, and quantify the flows of these chemical building blocks required for the transformation of industry towards a net‐zero emitting sector. We also undertake a techno‐economic analysis, in which we demonstrate that under specific assumptions for the learning rates of some of the key process components, renewable syngas can become cost‐competitive with that produced from fossil fuels. Cost competitiveness, however, only materializes for four of the five routes when natural gas prices are at least around 3 €/GJ and carbon taxes increase from 90 €/tCO₂ today to 300 €/tCO₂ in 2050.

Water oxidation catalysis plays a pivotal role in the context of the worldwide interest for sustainable energy. Finding cost-effective and robust catalysts to replace the state-of-the-art noble metal materials is hence urgent. In this work, we develop a molecular iridium complex that selectively and uniformly anchors on the surface of manganese oxide which is interconnected with a nitrogen-doped carbon forming a nanorod material. In the subsequent pyrolysis step, isolated Ir atoms are created on the manganese oxide surface and they strongly interact with the adjacent Mn. Through physicochemical characterization and computational studies, we demonstrate that the incorporation of Ir single-atom species in the MnO_x/N–C composite promotes the electrochemical water oxidation catalysis. The new material shows excellent activity in the oxygen evolution reaction in 0.1 M KOH with an overpotential of 250 mV at 10 mA cm⁻². Importantly, compared to a sample conventionally prepared with H₂IrCl₆, the novel Ir–MnO_x/N–C catalyst not only is more efficient, but also demonstrates improved redox stability without suffering from Ir leaching. Our approach opens up new opportunities for the rational design of site-isolated materials for catalysis in the field of energy applications.