Functioning devices for solar to fuel conversion

Abstract

a b s t r a c tThis paper provides a perspective on the technologies capable of converting solar energy, CO 2 and H 2 O into an easy to use fuel. The paper addresses bio-based approaches, but mainly focuses on (i) the combination of photovoltaic (PV) devices and electrocatalysis, (ii) single unit operation by photocatalytic conversion, and (iii) solar thermal conversion. Each option is described in a general manner, including a brief evaluation of the advantages and disadvantages. Also suggestions for future research endeavours are given. Based on the used literature data, for electrocatalytic and photocatalytic technologies, dramatic improvements should be made in material optimization, as well as reactor design and operation. Large efficiency gains are necessary to enable use of these technologies in practice. Solar thermal conversion is more mature, and requires specific optimization in processing, as will be discussed.

Alternative photocatalysts to TiO 2 for the photocatalytic reduction of CO 2

“…The main handicap of all the thermochemical approaches is that they require high temperatures, which means that the cost of heat supply is significantly raised. In other words, by following these thermochemical processes the energy costs are very high, whereas, actual mitigation of the atmospheric CO 2 does not take place [24][25][26].…”

“…The properties of TiO 2 , such as the band-gap energy, were improved when it was loaded with metals or non-metals or when it was modified to form for example nanotube arrays or dispersions in zeolites [26]. Indeed, functionalized titanates have been recently synthesized which exhibited rather high photocatalytic activities under visible light irradiation [37].…”

Photoelectrochemical Hydrogen Production on α‐Fe2O3 (0001): Insights from Theory and Experiments

“…[65] On a microscopic scale, Fe III adatoms are present in nonperiodic sites that are different from those of bulk termination. [57] In short, we considered three different a-Fe 2 O 3 surface terminations, namely, (OH) 3 ÀR termination, which is the most relevant one in aqueous solution, [63] O 3 ÀR termination, which is the most relevant under PEC conditions, [57] and finally FeÀO 3 ÀR termination, which is the stable termination under nonaqueous conditions. [67] Hematite (a-Fe 2 O 3 ) structure and (0001) surface terminations used herein were described in detail earlier.…”

“…[1] At present, there is no clear pathway to satisfy the increasing energy and chemical needs for a growing and prosperous society by using economically and environmentally sustainable processes. If there were abundant and sustainable sources of low-cost hydrogen, then the production of hydrocarbons from CO 2 would be possible by using several well-known thermochemical processes, [3,4] possibly at the sites of the largest CO 2 -emitting sources, such as coal-fired power plants. [2] However, all forms of natural gas, although currently abundant, can be considered nonrenewable and will eventually be consumed.…”

“…[9] However, the growth, harvesting, and processing of biomass for gasification add another dimension in complexity and cost to the sustainable production of hydrogen. Three different a-Fe 2 O 3 surface terminations were investigated, including the predominant surface found in aqueous electrolytes, (OH) 3 ÀR. Among the first industrial processes for producing hydrogen, the reaction of hot reduced iron oxide with steam was used to oxidize iron into the iron oxide and produce hydrogen.…”