Heterogeneous catalysis is of paramount importance in chemistry and energy applications. Catalysts that couple light energy into chemical reactions in a directed, orbital-specific manner would greatly reduce the energy input requirements of chemical transformations, revolutionizing catalysis-driven chemistry. Here we report the room temperature dissociation of H(2) on gold nanoparticles using visible light. Surface plasmons excited in the Au nanoparticle decay into hot electrons with energies between the vacuum level and the work function of the metal. In this transient state, hot electrons can transfer into a Feshbach resonance of an H(2) molecule adsorbed on the Au nanoparticle surface, triggering dissociation. We probe this process by detecting the formation of HD molecules from the dissociations of H(2) and D(2) and investigate the effect of Au nanoparticle size and wavelength of incident light on the rate of HD formation. This work opens a new pathway for controlling chemical reactions on metallic catalysts.

Photocatalysis based on optically active, “plasmonic” metal nanoparticles has emerged as a promising approach to facilitate light-driven chemical conversions under far milder conditions than thermal catalysis. However, an understanding of the relation between thermal and electronic excitations has been lacking. We report the substantial light-induced reduction of the thermal activation barrier for ammonia decomposition on a plasmonic photocatalyst. We introduce the concept of a light-dependent activation barrier to account for the effect of light illumination on electronic and thermal excitations in a single unified picture. This framework provides insight into the specific role of hot carriers in plasmon-mediated photochemistry, which is critically important for designing energy-efficient plasmonic photocatalysts.

processes. Biological or land-based forms of CO 2 utilization can generate economic value in the form of, for example, wood products for buildings, increased plant yields from enhanced soil carbon uptake, and even the production of biofuel and bio-derived chemicals. We use this broader definition deliberately; by thinking functionally, rather than narrowly about specific processes, we hope to promote dialogue across scientific fields, compare costs and benefits across pathways, and consider common techno-economic characteristics across pathways that could potentially assist in the identification of routes towards the mitigation of climate change. In this Perspective, we consider a non-exhaustive selection of ten CO 2 utilization pathways and provide a transparent assessment of the potential scale and cost for each one. The ten pathways are as follows: (1) CO 2-based chemical products, including polymers; (2) CO 2-based fuels; (3) microalgae fuels and other microalgae products; (4) concrete building materials; (5) CO 2 enhanced oil recovery (CO 2-EOR); (6) bioenergy with carbon capture and storage (BECCS); (7) enhanced weathering; (8) forestry techniques, including afforestation/reforestation, forest management and wood products; (9) land management via soil carbon sequestration techniques; and (10) biochar. These ten CO 2 utilization pathways can also be characterized as 'cycling', 'closed' and 'open' utilization pathways (Fig. 1, Table 1, Supplementary Materials). For instance, many (but not all) conventional industrial utilization pathways-such as CO 2-based fuels and chemicals-tend to be 'cycling': they move carbon through industrial systems over timescales of days, weeks or months. Such pathways do not provide net CO 2 removal from the atmosphere, but they can reduce emissions via industrial CO 2 capture that displaces fossil fuel use. By contrast, 'closed' pathways involve utilization and nearpermanent CO 2 storage, such as in the lithosphere (via CO 2-EOR or BECCS), in the deep ocean (via terrestrial enhanced weathering) or in mineralized carbon in the built and natural environments. Finally, 'open' pathways tend to be based in biological systems,