The_Catalyst_Review_December_2023 - 10

SPECIAL FEATURE
properties). The advent of the nanostructuring approach, involving the engineering of nanostructures and meticulous control over
morphology, structure, size, facet, and composition of nanostructured catalysts, has brought numerous advantages for improving
activity and selectivity in CO2
RR on metals (Nguyen et al., 2022).
Diverse transition metals serve as electrocatalysts for CO2
RR, and the binding energy of key intermediate species emerges as a
critical descriptor influencing major products, such as CO, formate, hydrocarbons, and hydrogen. For instance, metals like Au and
Ag demonstrate selective CO production via *COOH intermediate adsorption, while Sn and Bi exhibit high formate selectivity. The
nanostructuring of these metals enhances intrinsic activity without altering the major product (Nguyen et al., 2022).
Another recent approach for electrocatalyst design for CO2
RR is nanostructuring and alloying. There are studies about the use of
nanostructured Pd catalysts in CO oxidation, dehydrogenation of formic acid, formic acid oxidation, HER, and electrochemical reactions
in fuel cells (Nguyen et al., 2022). The strategic use of nanostructuring, alloying, and understanding the reaction mechanism enables
Pd-based electrocatalysts to exclusively produce desired products and enhance intrinsic activity in CO2
electroreduction.
Application of the bimetallic catalysts has also been reported to enhance the catalytic activity by adjusting the coordination and
surface phases, which affect the binding energy of different intermediates. The efficacy of a bimetallic electrocatalyst extends beyond
being a mere average of the properties of its individual metals; instead, it has the capacity to surpass the inherent characteristics of
each component, a capability derived from the strategic design of the bimetallic nanostructure. In particular, the introduction of a
secondary metal with a Pd-based electrocatalyst offers an effective approach to finely control reaction pathways and break scaling
relations of key intermediates. The bimetallic Pd-based electrocatalyst presents intriguing possibilities, with various beneficiary effects
induced by strain, electronic, geometric effects, and structural reconstruction, contributing to the alteration and regulation of the
electronic structure for the formation of desired
final products. Despite notable progress, there
exists a lack of a comprehensive overview for
the electroreduction of CO2
over bimetallic
Pd-containing electrocatalysts, underscoring
the need for further investigation to advance
this promising strategy both fundamentally and
practically.
Factors crucial for the real-world implementation
of CO2
of CO2
electrolysis encompass the origin
Figure 2. Factors for the application of electrochemical CO2
Source: Author
conversion
, be it from atmospheric sources or
specific emission points, and the utilization of
renewable energy sources like solar, wind, and
hydroelectric power. Additionally, the efficiency
and cost considerations of the electrolyzer, the
methods employed for product separation (e.g.,
distillation and pressure swing absorption), and
economic aspects, including the potential for
carbon credits and the marketing of hydrogen
and byproducts, are paramount in practical CO2
electrolysis applications (Figure 2).
Electrochemical Synthesis of
Ammonia
Ammonia (NH3
), a crucial chemical compound
in both agriculture and industry, is traditionally
produced through the energy-intensive
Haber-Bosch process, which involves the
high-temperature and high-pressure reaction
of nitrogen (N2
) and hydrogen (H2
). This
Figure 3. Electrochemical synthesis of ammonia
Source: Author
conventional method accounts for a significant
share of global energy consumption and carbon
dioxide emissions. In recent years, there has
been a growing interest in developing more
sustainable and energy-efficient approaches for
ammonia synthesis.
10
The Catalyst Review
December 2023

The_Catalyst_Review_December_2023

Table of Contents for the Digital Edition of The_Catalyst_Review_December_2023