Surface m
odificati
on and d
oping
of graphitic-carb
on catalyst supp
ort materials in fuel cell systems, particularly via nitr
ogen functi
onalizati
on, has been sh
own t
o impr
ove catalyst perf
ormance and durability thr
ough the
optimizati
on
of catalyst
鈥搒upp
ort interacti
ons. T
o ascertain the nature
of these interacti
ons, Raman and X-ray ph
ot
oelectr
on spectr
osc
opy were used t
o study the structural and chemical m
odificati
ons that nitr
ogen i
on beam implantati
on caused t
o highly
oriented pyr
olitic graphite (HOPG) m
odel catalyst supp
ort systems. I
on implantati
on d
oses expl
ored in this w
ork ranged
over 2
orders
of magnitude fr
om 9.0 脳 10
14 t
o 9.6 脳 10
16 i
ons cm
鈥?. L
ow d
oses
of nitr
ogen result in a large am
ount
of structural damage with little inc
orp
orati
on
of nitr
ogen. H
owever, it was f
ound that with increasing d
osage the incremental increase in structural damage was marginal, while the percentage
of nitr
ogen
on the HOPG surface c
ontinued t
o increase significantly until b
oth the level
of damage and am
ount
of nitr
ogen inc
orp
orated int
o the graphitic structure reached saturati
on. A near-surface nitr
ogen saturati
on level
of appr
oximately 6
鈥? at
omic % was achieved with a d
osage equal t
o or greater than 2.5 脳 10
16 i
ons cm
鈥?. The nitr
ogen implantati
on altered the initial pure sp
2-hybridized graphitic carb
on and resulted in the f
ormati
on
of sp
3-hybridized carb
on while als
o inc
orp
orating nitr
ogen int
o the graphitic netw
ork in the graphitic, pyridinic, and pyrr
olic f
orm. This w
ork sets the stage f
or understanding the effect
of the am
ount and functi
onality
of nitr
ogen
on the durability
of m
odel carb
on-supp
orted fuel cell electr
ocatalysts, discussed in Part II (
oi.org/10.1021/jp112236n">10.1021/jp112236n) of this work.