Two-dimensional transition metal dichalcogenides (2D TMDCs) have attracted tremendous interest as one prominent material group promising inexpensive electrocatalysts for hydrogen evolution reaction (HER). In the present study, using monolayer MoTe2...

The carbon-neutral synthesis of syngas from CO 2 and H 2 O powered by solar energy holds grand promise for solving critical issues such as global warming and the energy crisis. Here we report photochemical reduction of CO 2 with H 2 O into syngas using core/shell Au@Cr 2 O 3 dual cocatalyst–decorated multistacked InGaN/GaN nanowires (NWs) with sunlight as the only energy input. First-principle density functional theory calculations revealed that Au and Cr 2 O 3 are synergetic in deforming the linear CO 2 molecule to a bent state with an O-C-O angle of 116.5°, thus significantly reducing the energy barrier of CO 2 RR compared with that over a single component of Au or Cr 2 O 3 . Hydrogen evolution reaction was promoted by the same cocatalyst simultaneously. By combining the cooperative catalytic properties of Au@Cr 2 O 3 with the distinguished optoelectronic virtues of the multistacked InGaN NW semiconductor, the developed photocatalyst demonstrated high syngas activity of 1.08 mol/g cat /h with widely tunable H 2 /CO ratios between 1.6 and 9.2 under concentrated solar light illumination. Nearly stoichiometric oxygen was evolved from water splitting at a rate of 0.57 mol/g cat /h, and isotopic testing confirmed that syngas originated from CO 2 RR. The solar-to-syngas energy efficiency approached 0.89% during overall CO 2 reduction coupled with water splitting. The work paves a way for carbon-neutral synthesis of syngas with the sole inputs of CO 2 , H 2 O, and solar light.

Upcycling of carbon dioxide towards fuels and value-added chemicals poses an opportunity to overcome challenges faced by depleting fossil fuels and climate change. Herein, combining highly controllable molecular beam epitaxy growth of gallium nitride (GaN) under a nitrogen-rich atmosphere with subsequent air annealing, a tunable platform of gallium oxynitride (GaN1-xOx) nanowires is built to anchor rhodium (Rh) nanoparticles for carbon dioxide hydrogenation. By correlatively employing various spectroscopic and microscopic characterizations, as well as density functional theory calculations, it is revealed that the engineered oxynitride surface of GaN works in synergy with Rh to achieve a dramatically reduced energy barrier. Meanwhile, the potential-determining step is switched from *COOH formation into *CO desorption. As a result, significantly improved CO activity of 127 mmol‧gcat−1‧h−1 is achieved with high selectivity of >94% at 290 °C under atmospheric pressure, which is three orders of magnitude higher than that of commercial Rh/Al2O3. Furthermore, capitalizing on the high dispersion of the Rh species, the architecture illustrates a decent turnover frequency of 270 mol CO per mol Rh per hour over 9 cycles of operation. This work presents a viable strategy for promoting CO2 refining via surface engineering of an advanced support, in collaboration with a suitable metal cocatalyst.

Light-driven hydrogen evolution from liquid hydrogen carriers offers an innovative solution for the realization of safe storage and transportation of hydrogen. The exploration of efficient and cost-effective cocatalysts is highly desirable for constructing an affordable light-driven catalytic architecture. In this work, nickel–iron bimetal (NiFe) is rationally designed and then supported by gallium nitride nanowires (GaN NWs)/Si for light-driven hydrogen generation from methanol aqueous solution. Under optimized conditions, the H2 evolution rate of NiFe is even comparable to noble metals, e.g., Pt, Ru. By correlative operando spectroscopy characterizations, with density functional theory calculations, it is discovered that Fe is cooperative with Ni for dramatically lowering the energy barrier of the potential-limiting step of *CHO → *CO. What is more, by coordination of photoexcited charge carriers with photothermal effect, the production of hydrogen from CH3OH/H2O is evidently improved via the evolving track of *CH3O > *CH2O/*CHO > *CO > *CO2, in concurrent H2O dissociation toward ·OH. Combined with the superior optical and electronic attributes of the GaN NWs/Si semiconductor platform, NiFe bimetal enables the achievement of a marked hydrogen activity of 61.2 mmol g–1 h–1 by the only input of light under ambient conditions. This study presents a promising strategy for hydrogen release from liquid hydrogen carriers by using earth-abundant materials under mild conditions.