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J. Zhu et al.
oxygen reduction catalyst for the first time by heat treatment at 800°C with a mixture
of nonmacrocyclic polyacrylonitrile, ferrous acetate (or cobalt acetate) and charcoal
powder. The catalyst showed high oxygen reduction activity in acidic solutions,
with a peak potential of about 0.90 V (vs RHE) in 0.05 mol/L sulfuric acid solution. In 2011, Gang Wu et al. [21] from Los Alamos National Laboratory obtained
nitrogen-stable PANI-Fe–C and PANI-FeCo-C catalysts by heat-treating polyaniline
and Fe-N x (Co-N x ) complexes. The peak potential of oxygen reduction in perchloric
acid solution at 0.1 mol/L reached 0.93 V (vs RHE), which was comparable to that of
Pt/C (E-TEK) catalyst under the same conditions. M-Nx/C non-noble metal oxygen
reduction catalysts have been extensively studied, and the oxygen reduction activity
and peak potential of the catalysts have been optimized by adjusting different experimental conditions such as nitrogen source precursor, metal source and heat treatment
process.
Palladium (Pd), in the same group as platinum, often exhibits similar chemical
properties to platinum and has recently attracted great attention due to its obvious
advantages in reserves and price over platinum [22]. After various structural modification and enhancement, the oxygen reduction activity of Pd-based electrocatalysts
in acidic media has been significantly improved, showing a peak potential equivalent to platinum. In 2007, Mustain et al. successfully synthesized cobalt palladium
(CoPd x ) bimetallic electrocatalyst [23], and CoPd 3 showed the highest oxygen reduction activity and peak potential of 0.9 V versus NHE in 0.5 mol/L acid sulfuric
acid electrolyte. In CoPd 3 , Co atom has played the role of adsorption of oxygen
molecules and rapid electron transfer, so that CoPd 3 bimetallic electrocatalyst acid
oxygen reduction performance improved, thus showing a higher peak potential. In
the same year, Yang Hui et al., from Chinese academy of sciences, confirmed that
CoPd of high temperature heat treatment has higher oxygen reduction activity and
peak potential in 0.1 mol/L chloric acid solution [24]. In 2008, Solorza-Feria found
that PdNi alloy also had good oxygen reduction performance in 0.5 mol/L sulfuric
acid solution, and the introduction of Ni greatly reduced the oxygen reduction overpotential of Pd, making it 110 mV more positive than the peak potential of Pd [25]. In
2011, professor Shen Peikang’s research group from Sun Yat-sen university reported
that tungsten carbide (WC) enhanced PdFe bimetallic catalyst (PdFe-WC/C) had the
same oxygen reduction peak potential as commercial Pt/C in 0.5 mol/L sulfuric acid
solution, and the introduction of methanol in electrolyte had almost no impact on
the oxygen reduction peak potential of PdFe-WC/C [26]. This work has attracted
extensive attention to the oxygen reduction performance of Pd-based nonplatinum
electrocatalysts in acidic environment. In 2014, professor Shen’s group in Sun Yat-sen
university once again reported that tungsten carbide cobalt (WC) enhanced Pd metal
catalyst (Pd/Co 3 W 3 C) had the same oxygen reduction peak potential as commercial
Pt/C in 0.1 mol/L chloric acid solution, reaching 0.98 V versus RHE.
Platinum, the most widely used oxygen reduction electrocatalyst for fuel cell,
has the best electrocatalytic activity. The peak potential of oxygen reduction of
platinum/carbon catalyst in acidic medium is generally considered to be around
1.0 V versus RHE [27, 28]. The oxygen reduction peak potential of platinum can be
improved by carrier synergy and electron effect.
J. Zhu et al.
oxygen reduction catalyst for the first time by heat treatment at 800°C with a mixture
of nonmacrocyclic polyacrylonitrile, ferrous acetate (or cobalt acetate) and charcoal
powder. The catalyst showed high oxygen reduction activity in acidic solutions,
with a peak potential of about 0.90 V (vs RHE) in 0.05 mol/L sulfuric acid solution. In 2011, Gang Wu et al. [21] from Los Alamos National Laboratory obtained
nitrogen-stable PANI-Fe–C and PANI-FeCo-C catalysts by heat-treating polyaniline
and Fe-N x (Co-N x ) complexes. The peak potential of oxygen reduction in perchloric
acid solution at 0.1 mol/L reached 0.93 V (vs RHE), which was comparable to that of
Pt/C (E-TEK) catalyst under the same conditions. M-Nx/C non-noble metal oxygen
reduction catalysts have been extensively studied, and the oxygen reduction activity
and peak potential of the catalysts have been optimized by adjusting different experimental conditions such as nitrogen source precursor, metal source and heat treatment
process.
Palladium (Pd), in the same group as platinum, often exhibits similar chemical
properties to platinum and has recently attracted great attention due to its obvious
advantages in reserves and price over platinum [22]. After various structural modification and enhancement, the oxygen reduction activity of Pd-based electrocatalysts
in acidic media has been significantly improved, showing a peak potential equivalent to platinum. In 2007, Mustain et al. successfully synthesized cobalt palladium
(CoPd x ) bimetallic electrocatalyst [23], and CoPd 3 showed the highest oxygen reduction activity and peak potential of 0.9 V versus NHE in 0.5 mol/L acid sulfuric
acid electrolyte. In CoPd 3 , Co atom has played the role of adsorption of oxygen
molecules and rapid electron transfer, so that CoPd 3 bimetallic electrocatalyst acid
oxygen reduction performance improved, thus showing a higher peak potential. In
the same year, Yang Hui et al., from Chinese academy of sciences, confirmed that
CoPd of high temperature heat treatment has higher oxygen reduction activity and
peak potential in 0.1 mol/L chloric acid solution [24]. In 2008, Solorza-Feria found
that PdNi alloy also had good oxygen reduction performance in 0.5 mol/L sulfuric
acid solution, and the introduction of Ni greatly reduced the oxygen reduction overpotential of Pd, making it 110 mV more positive than the peak potential of Pd [25]. In
2011, professor Shen Peikang’s research group from Sun Yat-sen university reported
that tungsten carbide (WC) enhanced PdFe bimetallic catalyst (PdFe-WC/C) had the
same oxygen reduction peak potential as commercial Pt/C in 0.5 mol/L sulfuric acid
solution, and the introduction of methanol in electrolyte had almost no impact on
the oxygen reduction peak potential of PdFe-WC/C [26]. This work has attracted
extensive attention to the oxygen reduction performance of Pd-based nonplatinum
electrocatalysts in acidic environment. In 2014, professor Shen’s group in Sun Yat-sen
university once again reported that tungsten carbide cobalt (WC) enhanced Pd metal
catalyst (Pd/Co 3 W 3 C) had the same oxygen reduction peak potential as commercial
Pt/C in 0.1 mol/L chloric acid solution, reaching 0.98 V versus RHE.
Platinum, the most widely used oxygen reduction electrocatalyst for fuel cell,
has the best electrocatalytic activity. The peak potential of oxygen reduction of
platinum/carbon catalyst in acidic medium is generally considered to be around
1.0 V versus RHE [27, 28]. The oxygen reduction peak potential of platinum can be
improved by carrier synergy and electron effect.