In the future we will be phasing out the use of fossil fuels in favour of more sustainable forms of energy, especially solar derived forms such as hydroelectric, wind and photovoltaic. However, due to the variable nature of the latter sources which depend on time of day, and season of the year, we also need to have a way of storing such energy at peak production times for use in times of low production. One way to do this is to convert such energy into chemical energy, and the principal way considered at present is the production of hydrogen. Although this may be achieved directly in the future via photocatalytic water splitting, at present it is electrolytic production which dominates thinking. In turn, it may well be important to store this hydrogen in an energy dense liquid form such as methanol or ammonia. In this brief review it is emphasised that CO₂ is the microscopic carbon source for current industrial methanol synthesis, operating through the surface formate intermediate, although when using CO in the feed, it is CO which is hydrogenated at the global scale. However, methanol can be produced from pure CO₂ and hydrogen using conventional and novel types of catalysts. Examples of such processes, and of a demonstrator plant in construction, are given, which utilize CO₂ (which would otherwise enter the atmosphere directly) and hydrogen which can be produced in a sustainable manner. This is a fast‐evolving area of science and new ideas and processes will be developed in the near future.

Hydrogen production by water splitting is a holy grail of science, being one route to a non-fossil fuel and a potential source of clean energy. It is essential to use a non-polluting energy source to drive the reaction and one way is to utilise sunlight energy, combined with a way to overcome the kinetic limitations of the reaction. The production of hydrogen by the photocatalytic cleavage of water can overcome these energetic hurdles. This area of science is briefly reviewed here, focussing on two routes, namely i) the use of sacrificial agents such as alcohols to act as oxygen scavengers and liberate hydrogen only and ii) by direct water splitting to produce both hydrogen and oxygen. The factors which are important in determining the characteristics of effective photocatalytic water splitting systems are elucidated.

Zn substituted cobalt ferrite spinels with the general formula Zn_xCo_1−xFe₂O₄ (with x varying from 0 to 0.5) were synthesized by a co-precipitation method and calcined at 500 °C and 800 °C. It was found that Zn substitution has a big effect in decreasing the Curie temperature (T_c), from around 440 °C for the undoped sample to ∼180 °C with x = 0.5. However, these values were also strongly affected by the pre-calcination temperature of the samples, thus T_C shifts from ∼275 °C for the x = 0.3 sample to ∼296 °C after calcination at 500 °C and 800 °C respectively. These effects are due to facilitation of demagnetisation by substitution of the non-magnetic Zn ions and by production of very small nanoparticles. The latter are removed by higher temperature calcinations and so T_C increases.

The formation of PdZn bimetallic alloys on ZnO, TiO ₂ and Al ₂ O ₃ supports was investigated, together with the effect of alloy formation on the CO ₂ hydrogenation reaction. The chemical vapour impregnation (CVI) method produced PdZn nanoparticles with diameters of 3–6 nm. X-ray photoelectron spectroscopy and X-ray diffraction revealed the changes in the structure of the PdZn alloy that help stabilise formate intermediates during methanol synthesis. PdZn supported on TiO ₂ exhibits high methanol productivity of 1730 mmol kg _cat ⁻¹ h ⁻¹ that is associated with the high dispersion of the supported PdZn alloy.

Here, we report a method for sustainable hydrogen production using sunlight and biomass. It is shown that cellulose can be photoreformed to produce hydrogen, even in solid form, by use of metal-loaded titania photocatalysts. The experiments performed verified that the process is enabled by initial hydrolysis via glucose, which itself is shown to be efficiently converted to produce hydrogen by photocatalysis. Importantly, it is shown that not only precious metals such as Pt, Pd and Au can be used as the metal component, but also much more economic and less environmentally damaging Ni is effective. Even more importantly, we show for the first time, to the best our knowledge, that fescue grass as raw biomass can be effective for hydrogen production without significant pre-treatment. This provides additional benefits for the efficiency of biomass hydrogen production, because fewer processing steps for the raw material are required than in the production of purer forms of cellulose, for example.

In this tutorial review I discuss the significant impact that surface science has had on our understanding of the catalytic phenomena associated with automobile exhaust depollution catalysis. For oxidation reactions it has generally been found that reactions are self-poisoned at low temperatures by the presence of strongly adsorbed reactants (such as molecular CO and NO), and that the rapid acceleration in rate at elevated temperatures (often called ‘light-off’) is due to the desorption of such adsorbates, which then frees up sites for dissociation and hence for oxidation reactions. In some circumstances such autocatalytic phenomena can then manifest themselves as oscillatory reactions which can vary in rate in both space and time. For NO reduction, the efficiency of depollution (by production of molecular nitrogen) is strongly affected by the nature of the metal used. Rh is extremely effective because it can dissociate NO much more readily than metals such as Pd and Pt, enabling oxygen removal (by reaction with CO to CO₂) even at room temperature. Rh is also very selective in producing predominantly N₂, rather than N₂O. NO_x storage and reduction (NSR) is an important recent development for removal of NO_x under the highly oxidising conditions of a lean-burn engine exhaust, and the strategy involves storing NO_x on BaO under oxidising conditions followed by the creation of reducing conditions to de-store and reduce it to nitrogen. By the use of STM it has been shown that this storage process is extremely facile, occurring fast even under UHV conditions, and that the storage occurs on BaO in the vicinity of Pt, with most of the oxide being converted to nitrate.