Rational design of photocatalysts for ammonia production from water and nitrogen gas

Abstract

Photocatalytic N2 reduction has emerged as one of the most attractive routes to produce NH3 as a useful commodity for chemicals used in industries and as a carbon-free energy source. Recently, significant progress has been made in understanding, exploring, and designing efficient photocatalyst. In this review, we outline the important mechanistic and experimental procedures for photocatalytic NH3 production. In addition, we review effective strategies on development of photocatalysts. Finally, our analyses on the characteristics and modifications of photocatalysts have been summarized, based on which we discuss the possible future research directions, particularly on preparing more efficient catalysts. Overall, this review provides insights on improving photocatalytic NH3 production and designing solar-driven chemical conversions.

Nontypical Wulff-Shape Silicon Nanosheets with High Catalytic Activity

“…In general, the conversion efficiency depends on the cumulative efficiency of the elementary steps: (i) light absorption, (ii) charge transfer, and (iii) surface reactions. The crystallinity and surface morphology are responsible for charge transfer and surface reactions, respectively. ,,− Given that (i) the grain size effect is minimal (Figure S16) and (ii) the curved surface appearances of all Si nanosheets are similar, the factor that most likely contributed to the considerable H 2 evolution with a T r of 750 °C is light absorption.…”

Photoelectrochemical Nitrate Reduction to Ammonia on Ordered Silicon Nanowire Array Photocathodes

“…[1][2][3] Recently, it has attracted immense attention as a carbon-free energy carrier because of its high content (17.6 wt %) of hydrogen and ease of storage and transportation. [4] Ironically, more than 90 % of global ammonia production relies on the traditional Haber-Bosch process, which releases an enormous amount of CO 2 and requires high energy consumption. [5] This situation has prompted the search for environmentally benign (or "green") NH 3 production techniques.…”

Three Phase Boundary Engineering Using Hydrophilic–Hydrophobic Poly(N-isopropylacrylamide) with Oxygen-Vacant TiO2 Photocatalysts for Photocatalytic N2 Reduction

“…Recently, it is a great potential to use ammonia as hydrogen storage media and renewable fuel itself, enabling energy storage and transportation to be cost effective and environmentally friendly. − However, the ammonia production is mainly relied on the traditional Haber–Bosch process, which requires extensive operation conditions and induces massive emission of greenhouse gases . The photocatalytic N 2 reduction reaction (PNRR), that utilizes solar energy, ideally produces NH 3 using N 2 and H 2 O as a hydrogen source under mild conditions. , The PNRR [N 2 (g) + 6H + + 6e – ⇌ 2NH 3 (g), E 0 = 0.092 eV vs SHE] is proceeded using photoexcited electrons and which is coupled with water oxidation using photoexcited holes on photocatalysts at the same time in aqueous solution. , However, especially, two factors have restricted the application of PNRR: the ineffective adsorption and activation of inert N 2 molecules on catalysts, and the insufficient formation of the three phase boundary (TPB) of N 2 (gas), H 2 O (liquid), and catalyst (solid) . Therefore, it is essential to design the surface of catalysts where N 2 molecules can be adsorbed, activated, and further reduced to NH 3 , while controlling the concentration of N 2 and H 2 O around the catalysts.…”