Decarbonization Plus Acquisition Corporation III Menlo Park, CA 94025 Re: Initial Public Offering Gentlemen:

Exhibit 10.2

[●], 2021

Decarbonization Plus Acquisition Corporation III

0000 Xxxx Xxxx Xxxx

Menlo Park, CA 94025

Re: Initial Public Offering

Gentlemen:

This letter (this “Letter Agreement”) is being delivered to you in accordance with the Underwriting Agreement (the “Underwriting Agreement”) to be entered into by and among Decarbonization Plus Acquisition Corporation III, a Delaware corporation (the “Company”), and Credit Suisse Securities (USA) LLC and Citigroup Global Markets Inc., as representatives (the “Representatives”) of the several underwriters (each, an “Underwriter” and collectively, the “Underwriters”), relating to an underwritten initial public offering (the “Public Offering”), of [●] of the Company’s units (including up to [●] units that may be purchased to cover over-allotments, if any) (the “Units”), each comprised of one share of the Company’s Class A common stock, par value $0.0001 per share (the “Common Stock”), and one-third of one warrant. Each whole warrant (each, a “Warrant”) entitles the holder thereof to purchase one share of Common Stock at a price of $11.50 per share, subject to adjustment. The Units shall be sold in the Public Offering pursuant to a registration statement on Form S-1 (File No. 333- [●]) and prospectus (the “Prospectus”) filed by the Company with the Securities and Exchange Commission (the “Commission”) and the Company shall apply to have the Units listed on the Nasdaq Capital Market. Certain capitalized terms used herein are defined in paragraph 11 hereof.

In order to induce the Company and the Underwriters to enter into the Underwriting Agreement and to proceed with the Public Offering and for other good and valuable consideration, the receipt and sufficiency of which are hereby acknowledged, Decarbonization Plus Acquisition Sponsor III LLC (the “Sponsor”) and each of the undersigned entities and individuals, each of whom is a member of the Company’s board of directors and/or management team, or an affiliate thereof (each, an “Insider” and collectively, the “Insiders”), xxxxxx agrees with the Company as follows:

1. The Sponsor and each Insider agrees that if the Company seeks stockholder approval of a proposed Business Combination, then in connection with such proposed Business Combination, it, he or she shall (i) vote any shares of Capital Stock owned by it, him or her in favor of any proposed Business Combination and (ii) not redeem any shares of Common Stock owned by it, him or her in connection with such stockholder approval.

2. The Sponsor and each Insider hereby agrees that in the event that the Company fails to consummate a Business Combination within 24 months from the closing of the Public Offering, or such later period approved by the Company’s stockholders in accordance with the Company’s amended and restated certificate of incorporation, the Sponsor and each Insider shall take all reasonable steps to cause the Company to (i) cease all operations except for the purpose of winding up, (ii) as promptly as reasonably possible but not more than 10 business days thereafter, subject to lawfully available funds therefor, redeem 100% of the Common Stock sold

as part of the Units in the Public Offering (the “Offering Shares”), at a per-share price, payable in cash, equal to the aggregate amount then on deposit in the Trust Account, including interest earned on the funds held in the Trust Account and not previously released to the Company to pay its franchise and income taxes (less up to $100,000 of interest to pay dissolution expenses and net of taxes payable), divided by the number of then outstanding Offering Shares, which redemption will completely extinguish all Public Stockholders’ rights as stockholders (including the right to receive further liquidating distributions, if any), subject to applicable law, and (iii) as promptly as reasonably possible following such redemption, subject to the approval of the Company’s remaining stockholders and the Company’s board of directors, dissolve and liquidate, subject in each case to the Company’s obligations under Delaware law to provide for claims of creditors and other requirements of applicable law. The Sponsor and each Insider agrees to not propose any amendment to the Company’s amended and restated certificate of incorporation (A) that would modify the substance or timing of the Company’s obligation to redeem 100% of the Offering Shares if the Company does not complete a Business Combination within 24 months from the closing of the Public Offering or (B) or with respect to any other provision relating to the rights of holders of Common Stock or pre-initial Business Combination activity, unless the Company provides its Public Stockholders with the opportunity to redeem their Offering Shares upon approval of any such amendment at a per-share price, payable in cash, equal to the aggregate amount then on deposit in the Trust Account, including interest earned on the funds held in the Trust Account and not previously released to the Company to pay its franchise and income taxes, divided by the number of then outstanding Offering Shares.

3. During the period commencing on the effective date of the Underwriting Agreement and ending 180 days after such date, the Sponsor and each Insider shall not, without the prior written consent of the Representatives, (i) sell, offer to sell, contract or agree to sell, hypothecate, pledge, grant any option to purchase or otherwise dispose of or agree to dispose of, directly or indirectly, or establish or increase a put equivalent position or liquidate or decrease a call equivalent position within the meaning of Section 16 of the Securities Exchange Act of 1934, as amended, and the rules and regulations of the Commission promulgated thereunder, with respect to any Units, shares of Common Stock, Founder Shares, Warrants or any securities convertible into, or exercisable, or exchangeable for, shares of Common Stock owned by it, him or her, (ii) enter into any swap or other arrangement that transfers to another, in whole or in part, any of the economic consequences of ownership of any Units, shares of Common Stock, Founder Shares, Warrants or any securities convertible into, or exercisable, or exchangeable for, shares of Common Stock owned by it, him or her, whether any such transaction is to be settled by delivery of such securities, in cash or otherwise, or (iii) publicly announce any intention to effect any transaction specified in clause (i) or (ii).

4. In the event of the liquidation of the Trust Account, the Sponsor (which for purposes of clarification shall not extend to any other shareholders, members or managers of the Sponsor) agrees to indemnify and hold harmless the Company against any and all loss, liability, claim, damage and expense whatsoever (including, but not limited to, any and all legal or other expenses reasonably incurred in investigating, preparing or defending against any litigation, whether pending or threatened, or any claim whatsoever) to which the Company may become subject as a result of any claim by (i) any third party (other than the Company’s independent accountants) for services rendered or products sold to the Company or (ii) a prospective target

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business with which the Company has entered into an acquisition agreement (a “Target”); provided, however, that such indemnification of the Company by the Sponsor shall apply only to the extent necessary to ensure that such claims by a third party for services rendered (other than the Company’s independent public accountants) or products sold to the Company or a Target do not reduce the amount of funds in the Trust Account to below (i) $10.00 per share of the Offering Shares or (ii) such lesser amount per share of the Offering Shares held in the Trust Account due to reductions in the value of the trust assets as of the date of the liquidation of the Trust Account, in each case, net of the amount of interest earned on the property in the Trust Account which may be withdrawn to pay taxes, except as to any claims by a third party (including a Target) who executed a waiver of any and all rights to seek access to the Trust Account and except as to any claims under the Company’s indemnity of the Underwriters against certain liabilities, including liabilities under the Securities Act of 1933, as amended. In the event that any such executed waiver is deemed to be unenforceable against such third party, the Sponsor shall not be responsible to the extent of any liability for such third party claims. The Sponsor shall have the right to defend against any such claim with counsel of its choice reasonably satisfactory to the Company if, within 15 days following written receipt of notice of the claim to the Sponsor, the Sponsor notifies the Company in writing that it shall undertake such defense.

5. To the extent that the Underwriters do not exercise their over-allotment option to purchase up to an additional [●] Units within 45 days from the date of the Prospectus (and as further described in the Prospectus), the Sponsor agrees to forfeit, at no cost, a number of Founder Shares in the aggregate equal to the product of [●] multiplied by a fraction, (i) the numerator of which is [●] minus the number of Units purchased by the Underwriters upon the exercise of their over-allotment option, and (ii) the denominator of which is [●]. The forfeiture will be adjusted to the extent that the over-allotment option is not exercised in full by the Underwriters so that the Initial Stockholders will own an aggregate of 20.0% of the Company’s issued and outstanding shares of Capital Stock after the Public Offering.

6. The Sponsor and each Insider hereby agrees and acknowledges that: (i) the Underwriters and the Company would be irreparably injured in the event of a breach by such Sponsor or an Insider of its, his or her obligations under paragraphs 1, 2, 3, 4, 5, 7(a), 7(b), and 9 of this Letter Agreement, (ii) monetary damages may not be an adequate remedy for such breach and (iii) the non-breaching party shall be entitled to injunctive relief, in addition to any other remedy that such party may have in law or in equity, in the event of such breach.

7. (a) The Sponsor and each Insider agrees that it, he or she shall not Transfer any Founder Shares (or shares of Common Stock issuable upon conversion thereof) until the earlier of (A) one year after the completion of the Company’s initial Business Combination or (B) subsequent to the Business Combination, (x) if the last sale price of the Common Stock equals or exceeds $12.00 per share (as adjusted for stock splits, stock dividends, reorganizations, recapitalizations and the like) for any 20 trading days within any 30-trading day period commencing at least 150 days after the Company’s initial Business Combination or (y) the date on which the Company completes a liquidation, merger, capital stock exchange, reorganization or other similar transaction that results in all of the Company’s stockholders having the right to

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exchange their shares of Common Stock for cash, securities or other property (the “Founder Shares Lock-up Period”).

(b) The Sponsor and each Insider agrees that it, he or she shall not Transfer any Private Placement Warrants (or shares of Common Stock issued or issuable upon the exercise of the Private Placement Warrants) until 30 days after the completion of a Business Combination (the “Private Placement Warrants Lock-up Period” and, together with the Founder Shares Lock-up Period, the “Lock-up Periods”).

(c) Notwithstanding the provisions set forth in paragraphs 7(a) and (b), Transfers of the Founder Shares, Private Placement Warrants and shares of Common Stock issued or issuable upon the exercise or conversion of the Private Placement Warrants or the Founder Shares and that are held by the Sponsor, any Insider or any of their permitted transferees (that have complied with this paragraph 7(c)), are permitted (a) to the Company’s officers or directors, any affiliates or family members of any of the Company’s officers or directors, any members of the Sponsor, or any affiliates of the Sponsor; (b) in the case of an individual, transfers by gift to a member of the individual’s immediate family, to a trust, the beneficiary of which is a member of the individual’s immediate family or an affiliate of such person, or to a charitable organization; (c) in the case of an individual, transfers by virtue of laws of descent and distribution upon death of the individual; (d) in the case of an individual, transfers pursuant to a qualified domestic relations order; (e) transfers by private sales or transfers made in connection with the consummation of a Business Combination at prices no greater than the price at which the securities were originally purchased; (f) transfers in the event of the Company’s liquidation prior to the completion of an initial Business Combination; (g) transfers by virtue of the laws of the State of Delaware or the Sponsor’s limited liability company agreement upon dissolution of the Sponsor; and (h) in the event of the Company’s liquidation, merger, capital stock exchange, reorganization or other similar transaction which results in all of the Company’s stockholders having the right to exchange their shares of Common Stock for cash, securities or other property subsequent to the completion of the Company’s initial Business Combination; provided, however, that in the case of clauses (a) through (e) and (g), these permitted transferees must enter into a written agreement agreeing to be bound by the restrictions herein.

8. The Sponsor and each Insider represents and warrants that it, he or she has never been suspended or expelled from membership in any securities or commodities exchange or association or had a securities or commodities license or registration denied, suspended or revoked. Each Insider’s biographical information furnished to the Company (including any such information included in the Prospectus) is true and accurate in all respects and does not omit any material information with respect to the Insider’s background. The Sponsor and each Insider’s questionnaire furnished to the Company is true and accurate in all respects. The Sponsor and each Insider represents and warrants that: it, he or she is not subject to or a respondent in any legal action for, any injunction, cease-and-desist order or order or stipulation to desist or refrain from any act or practice relating to the offering of securities in any jurisdiction; it, he or she has never been convicted of, or pleaded guilty to, any crime (i) involving fraud, (ii) relating to any financial transaction or handling of funds of another person, or (iii) pertaining to any dealings in any securities and it, he or she is not currently a defendant in any such criminal proceeding.

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9. Except as disclosed in the Prospectus, neither the Sponsor nor any Insider nor any affiliate of the Sponsor or any Insider, nor any director or officer of the Company, shall receive from the Company any finder’s fee, reimbursement, consulting fee, monies in respect of any repayment of a loan or other compensation prior to, or in connection with any services rendered in order to effectuate the consummation of the Company’s initial Business Combination (regardless of the type of transaction that it is), other than the following, none of which will be made from the proceeds held in the Trust Account prior to the completion of the initial Business Combination: repayment of a loan and advances up to an aggregate of $300,000 made to the Company by the Sponsor; payment to an affiliate of the Sponsor for office space, utilities and secretarial and administrative support for a total of $10,000 per month; reimbursement for any out-of-pocket expenses related to identifying, investigating, negotiating and completing an initial Business Combination; and repayment of loans, if any, and on such terms as to be determined by the Company from time to time, made by the Sponsor or any of the Company’s officers or directors to finance transaction costs in connection with an intended initial Business Combination, provided, that, if the Company does not consummate an initial Business Combination, a portion of the working capital held outside the Trust Account may be used by the Company to repay such loaned amounts so long as no proceeds from the Trust Account are used for such repayment. Up to $1,500,000 of such loans may be convertible into warrants at a price of $1.50 per warrant at the option of the lender. Such warrants would be identical to the Private Placement Warrants, including as to exercise price, exercisability and exercise period.

10. The Sponsor and each Insider has full right and power, without violating any agreement to which it is bound (including, without limitation, any non-competition or non-solicitation agreement with any employer or former employer), to enter into this Letter Agreement and, as applicable, to serve as a director on the board of directors of the Company and hereby consents to being named in the Prospectus as a director of the Company.

11. As used herein, (i) “Business Combination” shall mean a merger, capital stock exchange, asset acquisition, stock purchase, reorganization or similar business combination, involving the Company and one or more businesses; (ii) “Capital Stock” shall mean, collectively, the Common Stock and the Founder Shares; (iii) “Founder Shares” shall mean the [●] shares of the Company’s Class B common stock, par value $0.0001 per share, (or [●] shares if the over-allotment option is not exercised by the Underwriters) initially held by the Sponsor; (iv) “Initial Stockholders” shall mean the Sponsor and any other holder of Founder Shares immediately prior to the Public Offering; (v) “Private Placement Warrants” shall mean the warrants to purchase up to [●] shares of Common Stock of the Company (or [●] shares of Common Stock if the over-allotment option is exercised in full) that the Sponsor, Xxxxx XX XxXxxxxxx, Xxxxxxx Xxxxxx, Dr. Xxxxxxxx Xxxxx, Xxxx Xxxxxx and Xxxxxxx Xxxxxx have agreed to purchase for an aggregate purchase price of $[●] in the aggregate (or $[●] in the aggregate if the over-allotment option is exercised in full by the Underwriters), or $1.50 per warrant, in a private placement that shall occur simultaneously with the consummation of the Public Offering; (vi) “Public Stockholders” shall mean the holders of shares of Common Stock issued in the Public Offering; (vii) “Trust Account” shall mean the trust fund into which a portion of the net proceeds of the Public Offering and the sale of the Private Placement Warrants shall be deposited; and (viii) “Transfer” shall mean the (a) sale or assignment of, offer to sell, contract or agreement to sell, hypothecate, pledge, grant of any option to purchase or otherwise dispose of or

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agreement to dispose of, directly or indirectly, or establishment or increase of a put equivalent position or liquidation with respect to or decrease of a call equivalent position within the meaning of Section 16 of the Securities Exchange Act of 1934, as amended, and the rules and regulations of the Commission promulgated thereunder with respect to, any security, (b) entry into any swap or other arrangement that transfers to another, in whole or in part, any of the economic consequences of ownership of any security, whether any such transaction is to be settled by delivery of such securities, in cash or otherwise, or (c) public announcement of any intention to effect any transaction specified in clause (a) or (b).

12. This Letter Agreement constitutes the entire agreement and understanding of the parties hereto in respect of the subject matter hereof and supersedes all prior understandings, agreements, or representations by or among the parties hereto, written or oral, to the extent they relate in any way to the subject matter hereof or the transactions contemplated hereby. This Letter Agreement may not be changed, amended, modified or waived (other than to correct a typographical error) as to any particular provision, except by a written instrument executed by all parties hereto.

13. No party hereto may assign either this Letter Agreement or any of its rights, interests, or obligations hereunder without the prior written consent of the other parties. Any purported assignment in violation of this paragraph shall be void and ineffectual and shall not operate to transfer or assign any interest or title to the purported assignee. This Letter Agreement shall be binding on the Sponsor and each Insider and their respective successors, heirs and assigns and permitted transferees.

14. This Letter Agreement shall be governed by and construed and enforced in accordance with the laws of the State of New York, without giving effect to conflicts of law principles that would result in the application of the substantive laws of another jurisdiction. The parties hereto (i) all agree that any action, proceeding, claim or dispute arising out of, or relating in any way to, this Letter Agreement shall be brought and enforced in the courts of New York City, in the State of New York, and irrevocably submit to such jurisdiction and venue, which jurisdiction and venue shall be exclusive and (ii) waive any objection to such exclusive jurisdiction and venue or that such courts represent an inconvenient forum.

15. Any notice, consent or request to be given in connection with any of the terms or provisions of this Letter Agreement shall be in writing and shall be sent by express mail or similar private courier service, by certified mail (return receipt requested), by hand delivery or facsimile transmission.

16. This Letter Agreement shall terminate on the earlier of (i) the expiration of the Lock-up Periods or (ii) the liquidation of the Company; provided, however, that this Letter Agreement shall earlier terminate in the event that the Public Offering is not consummated and closed by March 31, 2022; provided further that paragraph 4 of this Letter Agreement shall survive such liquidation.

[Signature Page Follows]

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Sincerely,

DECARBONIZATION PLUS ACQUISITION SPONSOR III LLC

By: _______________________________

Name: Xxxxx Xxxxxxxxxxx

Title: Authorized Person

By: _______________________________

Name:Dr. Xxxxxxxx Xxxxx

By: _______________________________

Name: Xxxx Xxxxxxxx

By: _______________________________

Name: Xxxxx Xxxxxxxxxxx

By: ________________________________

Name:Xxxx Xxxxxx

By: _______________________________

Name: Xxxxxx Xxxxxxx, Xx.

By: _______________________________

Name: Xxxxx Xxxxxxxx

By: _______________________________

Name: Xxxxx XX XxXxxxxxx

By: _______________________________

Name:Xxxxxxx X. Xxxxxx

By: _______________________________

Name:Xxxxxx Xxxxxx

By: _______________________________

Name: Xxxxxxx Xxxxxx

[Signature Page to Letter Agreement]

Acknowledged and Agreed:

DECARBONIZATION PLUS ACQUISITION CORPORATION III

By: _________________________________________

Name: Xxxxx Xxxxxxxxxxx

Title:   Chief Financial Officer, Chief Accounting Officer and Secretary

[Signature Page to Letter Agreement]