Car­bon Diox­ide: The new Chem­ic­al Feed­stock for Valu­able Con­sumer Products

The work under­taken by Alf­onso and oth­er mem­bers of NETL’s Com­pu­ta­tion­al Mater­i­als and Engin­eer­ing Team focuses on recyc­ling CO₂ gen­er­ated by fossil energy plants and oth­er indus­tri­al sources into chem­ic­als, alco­hols, acids and syn­gas, which are used to man­u­fac­ture fuels, poly­mers and fer­til­izer. ​“For more than a cen­tury, we have used fossil fuels to pro­duce our elec­tri­city and for a vari­ety of oth­er pur­poses. How­ever, when we extract energy from fossil fuels, we cre­ate CO₂, the primary green­house gas emit­ted through human activ­it­ies,” Alf­onso said. ​“We can address this issue by using CO₂ from factor­ies and power plants as a chem­ic­al feed­stock. Waste CO₂ emis­sions can become some­thing you can recycle into valu­able products, provid­ing a strong fin­an­cial incent­ive to reduce the amount of CO₂ released into the atmo­sphere,” he added. Alfonso’s research is ded­ic­ated to advan­cing the devel­op­ment of CO₂ recyc­ling through elec­tro­chem­istry. In the pres­ence of elec­tri­city, CO₂ molecules and pro­tons from split­ting water molecules react on an appro­pri­ate cata­lyst to form chem­ic­al build­ing blocks for hun­dreds of use­ful products. Where­as tra­di­tion­al reac­tion pro­cesses often require high tem­per­at­ures and pres­sures, elec­tro­chem­istry can be con­duc­ted at near room tem­per­at­ure and ambi­ent pres­sure using elec­tri­city from a renew­able energy source such as wind, sol­ar or geo­therm­al, which makes the pro­cess more effi­cient and envir­on­ment­ally benign. NETL research­ers use a vari­ety of cut­ting-edge exper­i­ment­al and com­pu­ta­tion­al tech­niques to under­stand and optim­ize cata­lysts and open new doors to CO₂ con­ver­sion. The type of chem­ic­al build­ing blocks to be pro­duced by recyc­ling CO₂ is also determ­ined by the iden­tity and char­ac­ter­ist­ics of the cata­lyst.
Nano­metal­lic-based cata­lysts are espe­cially effect­ive because their high sur­face area can dra­mat­ic­ally increase cata­lyt­ic activ­ity. The abil­ity to identi­fy low-cost, abund­ant and high-activ­ity cata­lysts that can guide the reac­tion toward mak­ing only the desired product is the chal­lenge that NETL is address­ing through advanced com­puter mod­el­ing and sim­u­la­tions. NETL’s goal is to dis­cov­er pre­cise cata­lyst recipes. Research­ers want to know what types of cata­lysts work best to select­ively and effi­ciently turn CO₂ into spe­cif­ic chem­ic­al com­pounds. A major object­ive of nanocata­lyst research is to cre­ate effi­cient cata­lysts that have high sta­bil­ity and long lifespans by con­trolling the size, shape, sur­face com­pos­i­tion and elec­tron­ic struc­ture. ​“When it comes to improv­ing a catalyst’s per­form­ance, one of the key things is how to make them more select­ive, so they gen­er­ate just the tar­get product and noth­ing else,” Alf­onso said. Tools such as NETL’s Joule 2.0 super­com­puter are used as plat­forms to sim­u­late exper­i­ments and devel­op mod­els to identi­fy act­ive sites and under­stand how the reac­tions pro­ceed. Super­com­put­ing is essen­tial in achiev­ing NETL’s mis­sion to dis­cov­er, integ­rate and mature tech­no­logy solu­tions that enhance the nation’s energy found­a­tion and pro­tect the envir­on­ment for future gen­er­a­tions. By exped­it­ing tech­no­logy devel­op­ment through com­pu­ta­tion­al sci­ence and engin­eer­ing, Joule 2.0 helps NETL cut costs and save time. ​“Joule is our work­horse,” Alf­onso said. A pat­ent developed by Alf­onso, a co-invent­or, and NETL research­ers Douglas Kauff­man, Chris­toph­er Mat­ranga, Paul Ohod­nicki, Xingyi Deng, Rajan Siva, Rongchao Jin and Chenjie Zeng defined a meth­od to con­trol and isol­ate dif­fer­en­tially charged gold (Au25) nanocata­lyst clusters from a mixed solu­tion. The inven­tion (USPN 10,385,726) was sig­ni­fic­ant because charge spe­cif­ic Au25 clusters have demon­strated the abil­ity to con­vert CO₂ to car­bon monox­ide (CO) with 99-plus per­cent effi­ciency. CO is a feed­stock in the pro­duc­tion of chem­ic­als ran­ging from acet­ic acid, which is used in many house­hold clean­ing products, polycar­bon­ate plastics and meth­an­ol, which is used in thou­sands of every­day products, includ­ing fuels, paints, adhes­ives, fer­til­izers and wind­shield flu­id. Gold is one of the most select­ive cata­lysts for elec­tro­chem­ic­ally con­vert­ing CO₂ into CO, but its expense is a major draw­back. Mean­while, cheap­er cop­per cata­lysts typ­ic­ally show poor product selectiv­ity and pro­duce a lar­ger vari­ety of chem­ic­als with lower effi­ciency. In a research study, NETL’s gold-cop­per alloy nanocata­lysts demon­strated four to eight times high­er per­form­ance than state-of-the-art gold nanocata­lysts on a pre­cious met­al basis. NETL research com­bined effect­ive expert­ise in exper­i­ment­al cata­lyst test­ing, com­pu­ta­tion­al mod­el­ing and syn­chro­tron-based X‑ray char­ac­ter­iz­a­tion to obtain an atom­ic-level under­stand­ing about how the cata­lyst struc­ture and sur­face groups sus­tained select­ive CO₂ con­ver­sion. ​“The bot­tom line is we are pav­ing the way to devel­op­ing less-expens­ive CO₂ util­iz­a­tion cata­lysts that can con­vert CO₂ into use­ful products soci­ety needs while dra­mat­ic­ally redu­cing the amount of car­bon emit­ted into the atmo­sphere,” Alf­onso said. DOE’s Car­bon Util­iz­a­tion Pro­gram aspires to devel­op tech­no­lo­gies to trans­form CO₂ and oth­er car­bon byproducts and wastes into valu­able products in an effi­cient, eco­nom­ic­al and envir­on­ment­ally friendly man­ner. Research and devel­op­ment activ­it­ies address the chal­lenges and poten­tial oppor­tun­it­ies asso­ci­ated with integ­rat­ing a CO₂ util­iz­a­tion sys­tem with vari­ous power and indus­tri­al plants or car­bon cap­ture sys­tems, such as waste heat integ­ra­tion, wastewa­ter reduc­tion, flue gas con­tam­in­ant reduc­tion and reduced energy demand. The suc­cess of car­bon cap­ture, car­bon recyc­ling and car­bon util­iz­a­tion ini­ti­at­ives, which NETL has advanced in part­ner­ships with industry and top research uni­ver­sit­ies, is crit­ic­al to ensure a clean­er envir­on­ment while con­tinu­ing to use the nation’s abund­ant coal and nat­ur­al gas resources to pro­duce reli­able and afford­able elec­tri­city. The U.S. Depart­ment of Energy’s Nation­al Energy Tech­no­logy Labor­at­ory devel­ops and com­mer­cial­izes advanced tech­no­lo­gies that provide reli­able and afford­able solu­tions to America’s energy chal­lenges. NETL’s work sup­ports DOE’s mis­sion to advance the nation­al, eco­nom­ic and energy secur­ity of the United States. Source: NETL, Press Release, 26.10.2020